Windows Printing with C++Builder using VCL and FMX

Do you need to add printer support to your C++ applications using the Visual Component Library (VCL) or FireMonkey (FMX) GUI ? In this blog post I’ll show you how to build Windows applications that support printing image bitmaps using the VCL and FMX frameworks. One of my favorite C++Builder RTL features is that both frameworks provide similar printer components and ways of programming with only a few subtle differences.

Build VCL and FMX Application Projects

Use the “File | New | Windows VCL Application – C++Builder” menu item and create a starting C++ VCL application. Save the product to a folder.

File | New | Windows VCL Application – C++Builder

Next, in the Project Window, right mouse click on the ProjectGroup node and select the “Add New Project…” menu item.

Add New Project to the Project Group

In the popup dialog choose to create a Multi-Device Application.

Add New Multi-Device Application

Click the OK button and on the next screen choose to create a “Blank Application”.

Multi-Device Project templates list – choose Blank Application

Use the File | Save All menu item (or type Shift+Ctrl+S) to save both starting projects and the project group to a folder.

Project Group with VCL and FMX Starting Projects

Each of the VCL and FMX projects have a main form (.dfm and .fmx extensions respectively). While most of the IDE will look the same, if you select each form’s unit you will see different looks for each of their form designers.

VCL Form Designer
FMX Form Designer

There are many videos, articles and help files that describe the details of each designer (check out links in the reference section below). For now, let’s dig into the VCL and FMX printer examples I’ve created.

A Simple UI for each Printer Test Project

On each of the VCL and FMX main forms you’ll see the following components.

VCL form’s components in the Structure Window
FMX form’s components in the Structure Window

Each project’s main menu contains a File and Destination menu. The Destination menu item allows the user to choose to override the printing destination (Printer or File).

The File menu provides an OpenPictureDialog (VCL) or OpenDialog (FMX), PrintPicture dialog for choosing the printer and other printing options, PrinterSetup dialog to set additional printer setup options, Panel (aligned to the top of the form)with a label and ComboBox which will list the available printer device names, and an Image component (aligned to the client area) to contain the picture bitmap.

The VCL and FMX forms look like the following.

VCL app form with components
FMX app form with components

Right mouse click on the form and choose “View as Text” from the popup menu. Now you can see all of the form and component properties and sub-properties that have been set from their default values. You can also make changes in this text form mode but be careful to not make any errors.

To switch back to the form mode click the right mouse button (or hit Alt-F12) and choose “View as Form” from the popup menu.

VCLPrintUnit.dfm (View as Text)

object MainVCLForm: TMainVCLForm
  Left = 0
  Top = 0
  Caption = 'Printer Test (C++, VCL)'
  ClientHeight = 473
  ClientWidth = 667
  Color = clBtnFace
  Font.Charset = DEFAULT_CHARSET
  Font.Color = clWindowText
  Font.Height = -11
  Font.Name = 'Tahoma'
  Font.Style = []
  Menu = MainMenu1
  OldCreateOrder = False
  OnShow = FormShow
  PixelsPerInch = 96
  TextHeight = 13
  object Image1: TImage
    Left = 0
    Top = 41
    Width = 667
    Height = 432
    Align = alClient
    Proportional = True
    ExplicitLeft = 104
    ExplicitTop = 102
    ExplicitWidth = 424
    ExplicitHeight = 317
  end
  object Panel1: TPanel
    Left = 0
    Top = 0
    Width = 667
    Height = 41
    Align = alTop
    TabOrder = 0
    object Label1: TLabel
      Left = 10
      Top = 12
      Width = 41
      Height = 13
      Caption = 'Printers:'
    end
    object PrintersComboBox: TComboBox
      Left = 57
      Top = 9
      Width = 250
      Height = 21
      TabOrder = 0
      Text = 'PrintersComboBox'
    end
  end
  object PrintDialog1: TPrintDialog
    Options = [poPrintToFile]
    Left = 176
    Top = 56
  end
  object PrinterSetupDialog1: TPrinterSetupDialog
    Left = 304
    Top = 64
  end
  object OpenPictureDialog1: TOpenPictureDialog
    DefaultExt = 'bmp'
    InitialDir = 'c:\temp'
    Left = 56
    Top = 56
  end
  object MainMenu1: TMainMenu
    Left = 424
    Top = 64
    object File1: TMenuItem
      Caption = 'File'
      object File2: TMenuItem
        Caption = 'Open Picture'
        OnClick = File2Click
      end
      object PrintPicture1: TMenuItem
        Caption = 'Print Picture'
        Enabled = False
        OnClick = PrintPicture1Click
      end
      object PrinterSetup1: TMenuItem
        Caption = 'Printer Setup'
        Enabled = False
        OnClick = PrinterSetup1Click
      end
      object PrintPicture2: TMenuItem
        Caption = 'Exit'
        OnClick = PrintPicture2Click
      end
    end
    object Destination1: TMenuItem
      Caption = 'Destination'
      object PrintToPrinterDestinationMenuItem: TMenuItem
        Caption = 'Print to Printer'
        Checked = True
        OnClick = PrintToPrinterDestinationMenuItemClick
      end
      object PrintToFileDestinationMenuItem: TMenuItem
        Caption = 'Print to File'
        OnClick = PrintToFileDestinationMenuItemClick
      end
    end
  end
end

FMXPrintUnit.fmx (View as Text)

object MainFMXForm: TMainFMXForm
  Left = 0
  Top = 0
  Caption = 'Printer Test (C++, FMX)'
  ClientHeight = 380
  ClientWidth = 640
  Position = Designed
  WindowState = wsMaximized
  FormFactor.Width = 320
  FormFactor.Height = 480
  FormFactor.Devices = [Desktop]
  OnShow = FormShow
  DesignerMasterStyle = 0
  object Image1: TImage
    MultiResBitmap = <
      item
      end>
    Align = Client
    Size.Width = 640.000000000000000000
    Size.Height = 339.000000000000000000
    Size.PlatformDefault = False
  end
  object PrintDialog1: TPrintDialog
    Options = [poPrintToFile]
    Left = 68
    Top = 40
  end
  object PrinterSetupDialog1: TPrinterSetupDialog
    Left = 190
    Top = 42
  end
  object OpenDialog1: TOpenDialog
    DefaultExt = 'bmp'
    Filter = '*.bmp'
    InitialDir = 'c:\temp'
    Left = 312
    Top = 44
  end
  object MainMenu1: TMainMenu
    Left = 418
    Top = 46
    object FileMenu: TMenuItem
      Text = 'File'
      object OpenBitmapMenuItem: TMenuItem
        Locked = True
        Text = 'Open Bitmap'
        OnClick = OpenBitmapMenuItemClick
      end
      object PrintMenuItem: TMenuItem
        Enabled = False
        Locked = True
        Text = 'Print'
        OnClick = PrintMenuItemClick
      end
      object PrinterSetupMenuItem: TMenuItem
        Enabled = False
        Locked = True
        Text = 'Printer Setup'
        OnClick = PrinterSetupMenuItemClick
      end
      object ExitMenuItem: TMenuItem
        Locked = True
        Text = 'Exit'
        OnClick = ExitMenuItemClick
      end
    end
    object DestinationMenu: TMenuItem
      Text = 'Destination'
      object PrintToPrinterDestinationMenuItem: TMenuItem
        Locked = True
        IsChecked = True
        Text = 'Print to Printer'
        OnClick = PrintToPrinterDestinationMenuItemClick
      end
      object PrintToFileDestinationMenuItem: TMenuItem
        Locked = True
        Text = 'Print to File'
        OnClick = PrintToFileDestinationMenuItemClick
      end
    end
  end
  object Panel1: TPanel
    Align = Top
    Size.Width = 640.000000000000000000
    Size.Height = 41.000000000000000000
    Size.PlatformDefault = False
    object PrintersComboBox: TComboBox
      Position.X = 72.000000000000000000
      Position.Y = 8.000000000000000000
      Size.Width = 233.000000000000000000
      Size.Height = 22.000000000000000000
      Size.PlatformDefault = False
    end
    object Label1: TLabel
      Position.X = 8.000000000000000000
      Position.Y = 9.000000000000000000
      Size.Width = 57.000000000000000000
      Size.Height = 17.000000000000000000
      Size.PlatformDefault = False
      Text = 'Printers:'
    end
  end
end

Additional comments about component properties and event handlers are included in the source code for the projects.

The Source Code

Below you will find the header files for the VCL and FMX form units. The header files will show the component declarations, event handlers and any public/private declarations.

VCLPrintUnit.h

//---------------------------------------------------------------------------

#ifndef VCLPrintUnitH
#define VCLPrintUnitH
//---------------------------------------------------------------------------
#include <System.Classes.hpp>
#include <Vcl.Controls.hpp>
#include <Vcl.StdCtrls.hpp>
#include <Vcl.Forms.hpp>
#include <Vcl.Dialogs.hpp>
#include <Vcl.ExtCtrls.hpp>
#include <Vcl.ExtDlgs.hpp>
#include <Vcl.Menus.hpp>
#include <Vcl.WinXCtrls.hpp>
//---------------------------------------------------------------------------
class TMainVCLForm : public TForm
{
__published:	// IDE-managed Components
	TPrintDialog *PrintDialog1;
	TPrinterSetupDialog *PrinterSetupDialog1;
	TImage *Image1;
	TOpenPictureDialog *OpenPictureDialog1;
	TMainMenu *MainMenu1;
	TMenuItem *File1;
	TMenuItem *File2;
	TMenuItem *PrintPicture1;
	TMenuItem *PrintPicture2;
	TMenuItem *Destination1;
	TMenuItem *PrintToPrinterDestinationMenuItem;
	TMenuItem *PrintToFileDestinationMenuItem;
	TMenuItem *PrinterSetup1;
	TPanel *Panel1;
	TLabel *Label1;
	TComboBox *PrintersComboBox;
	void __fastcall File2Click(TObject *Sender);
	void __fastcall FormShow(TObject *Sender);
	void __fastcall PrintToPrinterDestinationMenuItemClick(TObject *Sender);
	void __fastcall PrintToFileDestinationMenuItemClick(TObject *Sender);
	void __fastcall PrintPicture1Click(TObject *Sender);
	void __fastcall PrinterSetup1Click(TObject *Sender);
	void __fastcall PrintPicture2Click(TObject *Sender);
private:	// User declarations
    bool PictureLoaded;  // boolean for whether a picture is loaded or not
public:		// User declarations
	__fastcall TMainVCLForm(TComponent* Owner);
};
//---------------------------------------------------------------------------
extern PACKAGE TMainVCLForm *MainVCLForm;
//---------------------------------------------------------------------------
#endif

FMXPrintUnit.h

//---------------------------------------------------------------------------

#ifndef FMXPrintUnitH
#define FMXPrintUnitH
//---------------------------------------------------------------------------
#include <System.Classes.hpp>
#include <FMX.Controls.hpp>
#include <FMX.Forms.hpp>
#include <FMX.Controls.Presentation.hpp>
#include <FMX.StdCtrls.hpp>
#include <FMX.Types.hpp>
#include <FMX.Objects.hpp>
#include <FMX.Dialogs.hpp>
#include <FMX.Printer.hpp>
#include <FMX.Menus.hpp>
#include <FMX.ListBox.hpp>
//---------------------------------------------------------------------------
class TMainFMXForm : public TForm
{
__published:	// IDE-managed Components
	TImage *Image1;
	TPrintDialog *PrintDialog1;
	TPrinterSetupDialog *PrinterSetupDialog1;
	TOpenDialog *OpenDialog1;
	TMainMenu *MainMenu1;
	TMenuItem *FileMenu;
	TMenuItem *OpenBitmapMenuItem;
	TMenuItem *PrintMenuItem;
	TMenuItem *PrinterSetupMenuItem;
	TMenuItem *ExitMenuItem;
	TPanel *Panel1;
	TComboBox *PrintersComboBox;
	TLabel *Label1;
	TMenuItem *DestinationMenu;
	TMenuItem *PrintToPrinterDestinationMenuItem;
	TMenuItem *PrintToFileDestinationMenuItem;
	void __fastcall PrintMenuItemClick(TObject *Sender);
	void __fastcall OpenBitmapMenuItemClick(TObject *Sender);
	void __fastcall ExitMenuItemClick(TObject *Sender);
	void __fastcall PrinterSetupMenuItemClick(TObject *Sender);
	void __fastcall FormShow(TObject *Sender);
	void __fastcall PrintToPrinterDestinationMenuItemClick(TObject *Sender);
	void __fastcall PrintToFileDestinationMenuItemClick(TObject *Sender);
private:	// User declarations
	BOOL PictureLoaded;  // boolean for whether a picture is loaded or not
public:		// User declarations
	__fastcall TMainFMXForm(TComponent* Owner);
};
//---------------------------------------------------------------------------
extern PACKAGE TMainFMXForm *MainFMXForm;
//---------------------------------------------------------------------------
#endif

Below you will find the source code for the VCL and FMX form units.

VCLPrinterUnit.cpp

//---------------------------------------------------------------------------

#include <vcl.h>
#include <Vcl.Imaging.GIFImg.hpp>
#include <Vcl.Imaging.jpeg.hpp>
#include <Vcl.Imaging.pngimage.hpp>
#include <Vcl.Printers.hpp>

#pragma hdrstop

#include "VCLPrintUnit.h"
//---------------------------------------------------------------------------
#pragma package(smart_init)
#pragma resource "*.dfm"
TMainVCLForm *MainVCLForm;
//---------------------------------------------------------------------------
__fastcall TMainVCLForm::TMainVCLForm(TComponent* Owner)
	: TForm(Owner)
{
}
//---------------------------------------------------------------------------
void __fastcall TMainVCLForm::File2Click(TObject *Sender)
{
	if (OpenPictureDialog1->Execute()) {
		Image1->Picture->LoadFromFile(OpenPictureDialog1->FileName);
		PictureLoaded = true;
		PrintPicture1->Enabled = true;
        PrinterSetup1->Enabled = true;
	}
}
//---------------------------------------------------------------------------
void __fastcall TMainVCLForm::FormShow(TObject *Sender)
{

	PictureLoaded = false;
	PrintToPrinterDestinationMenuItem->Checked = true;
	PrintToFileDestinationMenuItem->Checked = false;

	// get printers list and put in combobox
	PrintersComboBox->Items = Printer()->Printers;

	// make the currently selected printer the Item in the ComboBox
	PrintersComboBox->ItemIndex = 0;
	for (int i = 0; i < Printer()->Printers->Count-1; i++) {
		if (Printer()->Printers->Strings[Printer()->PrinterIndex] == PrintersComboBox->Items->Strings[i]) {
			PrintersComboBox->ItemIndex = i;
		}
	}

}
//---------------------------------------------------------------------------
void __fastcall TMainVCLForm::PrintToPrinterDestinationMenuItemClick(TObject *Sender)
{
	// set menu item checked for print to printer
	PrintToPrinterDestinationMenuItem->Checked = true;
	PrintToFileDestinationMenuItem->Checked = false;
	// set PrintDialog PrintToFile checkbox off
	// Note: to allow user to override the menu item - make sure
	//   PrintDialog Options poPrintToFile is set to true
	//   so that the PrintToFile checkbox appears in the dialog
	PrintDialog1->PrintToFile = false;
}
//---------------------------------------------------------------------------
void __fastcall TMainVCLForm::PrintToFileDestinationMenuItemClick(TObject *Sender)
{
	// set menu item checked for print to file
	PrintToPrinterDestinationMenuItem->Checked = false;
	PrintToFileDestinationMenuItem->Checked = true;
	// set PrintDialog PrintToFile checkbox on
	// Note: to allow user to override the menu item - make sure
	//   PrintDialog Options poPrintToFile is set to true
	//   so that the PrintToFile checkbox appears in the dialog
	PrintDialog1->PrintToFile = true;
}
//---------------------------------------------------------------------------
void __fastcall TMainVCLForm::PrintPicture1Click(TObject *Sender)
{

	// check if a picture is loaded
	if (PictureLoaded) {
		if (PrintDialog1->Execute()) {

			// Call BeginDoc - to get the dimensions for selected printer
			Printer()->BeginDoc();

			try {
				// use StretchDraw to do full size bitmap printing
				// notes:
				//   printer settings can be made using the
				//     PrintDialog and PrinterSetupDialog
				//   you can also control page layout in code:
				//     Property is Orientation:
				//       poPortrait
				//       poLandscape
				Printer()->Canvas->StretchDraw(
					Rect(0, 0, Printer()->PageWidth,Printer()->PageHeight),
					Image1->Picture->Graphic);
			}
			__finally {
				// end the document and the printing will begin
				Printer()->EndDoc();
			}
		}
	}

}
//---------------------------------------------------------------------------
void __fastcall TMainVCLForm::PrinterSetup1Click(TObject *Sender)
{
	// Printer Setup
    PrinterSetupDialog1->Execute();
}
//---------------------------------------------------------------------------
void __fastcall TMainVCLForm::PrintPicture2Click(TObject *Sender)
{
    Application->Terminate();
}
//---------------------------------------------------------------------------

FMXPrinterUnit.cpp

//---------------------------------------------------------------------------

#include <fmx.h>
#include "FMX.Printer.hpp"
#include "System.SysUtils.hpp"
#pragma hdrstop

#include "FMXPrintUnit.h"
//---------------------------------------------------------------------------
#pragma package(smart_init)
#pragma resource "*.fmx"
TMainFMXForm *MainFMXForm;
//---------------------------------------------------------------------------
__fastcall TMainFMXForm::TMainFMXForm(TComponent* Owner)
	: TForm(Owner)
{
}
//---------------------------------------------------------------------------
void __fastcall TMainFMXForm::PrintMenuItemClick(TObject *Sender)
{
	TRectF SrcRect, DestRect;

	if (PrintDialog1->Execute()) {
		// Set the default DPI for the printer. The SelectDPI routine defaults
		//	 to the closest available resolution as reported by the driver.
		// Printer->ActivePrinter->SelectDPI(1200, 1200);

		// Printer->ActivePrinter->ActiveDPIIndex = 1; // you can also the DPI index

		// Set canvas filling style
		// Printer->Canvas->Fill->Color = claBlack;
		// Printer->Canvas->Fill->Kind = TBrushKind(1);

		// Start printing
		Printer::Printer()->BeginDoc();

		// Set the Source and Destination TRects

		SrcRect = TRectF(0, 0, Image1->Bitmap->Width, Image1->Bitmap->Height);
		DestRect = TRectF(0, 0, Printer::Printer()->PageWidth, Printer::Printer()->PageHeight);

		// Print the picture, on all the surface of the page and all opaque.
		Printer::Printer()->Canvas->DrawBitmap(Image1->Bitmap, SrcRect, DestRect, 1);

		// Finish the printing job
		Printer::Printer()->EndDoc();
	}

}
//---------------------------------------------------------------------------

void __fastcall TMainFMXForm::OpenBitmapMenuItemClick(TObject *Sender)
{
	// open a bitmap for printing
	if (OpenDialog1->Execute()) {
		Image1->Bitmap->LoadFromFile(OpenDialog1->FileName);
		PrintMenuItem->Enabled = true;
		PrinterSetupMenuItem->Enabled = true;
        PictureLoaded = true;
	}
}
//---------------------------------------------------------------------------

void __fastcall TMainFMXForm::ExitMenuItemClick(TObject *Sender)
{
	// exit the application
    Application->Terminate();
}
//---------------------------------------------------------------------------

void __fastcall TMainFMXForm::PrinterSetupMenuItemClick(TObject *Sender)
{
	// use the Printer Setup dialog box
	PrinterSetupDialog1->Execute();
}
//---------------------------------------------------------------------------

void __fastcall TMainFMXForm::FormShow(TObject *Sender)
{
	// on form show event handler

	PictureLoaded = false;
	PrintToPrinterDestinationMenuItem->IsChecked = true;
	PrintToFileDestinationMenuItem->IsChecked = false;

	// populate the ComboBox with the printer device names
	PrintersComboBox->ItemIndex = 0;
	for (int i = 0; i < Printer::Printer()->Count-1; i++) {
		PrintersComboBox->Items->Add(Printer::Printer()->Printers[i]->Title);
		// set the ComboBox ItemIndex to the active printer
		if (Printer::Printer()->Printers[i]->Title == Printer::Printer()->ActivePrinter->Title) {
			PrintersComboBox->ItemIndex = i;
		}
	}
}
//---------------------------------------------------------------------------

void __fastcall TMainFMXForm::PrintToPrinterDestinationMenuItemClick(TObject *Sender)
{
	// set menu item checked for print to printer
	PrintToPrinterDestinationMenuItem->IsChecked = true;
	PrintToFileDestinationMenuItem->IsChecked = false;
	// set PrintDialog PrintToFile checkbox off
	// Note: to allow user to override the menu item - make sure
	//   PrintDialog Options poPrintToFile is set to true
	//   so that the PrintToFile checkbox appears in the dialog
	PrintDialog1->PrintToFile = false;
}
//---------------------------------------------------------------------------

void __fastcall TMainFMXForm::PrintToFileDestinationMenuItemClick(TObject *Sender)
{
	// set menu item checked for print to file
	PrintToPrinterDestinationMenuItem->IsChecked = false;
	PrintToFileDestinationMenuItem->IsChecked = true;
	// set PrintDialog PrintToFile checkbox on
	// Note: to allow user to override the menu item - make sure
	//   PrintDialog Options poPrintToFile is set to true
	//   so that the PrintToFile checkbox appears in the dialog
	PrintDialog1->PrintToFile = true;
}
//---------------------------------------------------------------------------

The VCL and FMX applications in Action

VCL app in action
FMX app in action

References

VCL Printing

Printing in VCL Applications
Vcl.Printers

FMX Printing

Printing from a FireMonkey Application
FMX.Printer

YouTube Videos

Creating your First VCL Application for Windows with C++Builder
Creating Your First C++ Windows App
Why C++Builder?

Source Code

Source Code for VCL and FMX printing projects (zip file)

About C++Builder

C++Builder Product Page – Native Apps that Perform. Build Windows C++ Apps 10x Faster with Less Code

C++Builder Product Editions – C++Builder is available in four editions – Professional, Enterprise, Architect and Community (free). C++Builder is also available as part of the RAD Studio development suite.

Using the Eigen C++ Template Library with C++Builder and VCL

It’s been almost 50 years since I took a Linear Algebra and Matrices course as one of my Computer Science electives at Cal Poly San Luis Obispo, CA. The textbook for the course was “Mathematics Of Matrices: First Book Of Matrix Theory And Linear Algebra” by Philip J Davis. While I have used arrays and vectors in many programming projects, I have to be honest and say that I have not used a lot of matrix math in my code.

Now that the Eigen C++ Template Library is available for download inside the C++Builder IDE using the GetIt Package Manager, I decided to re-introduce myself to matrix math, manipulations and linear algebra (not bad for a 69 year old software engineer). This blog post will show C++ developers how to download, install and use the Eigen C++ library using C++Builder and VCL.

Installing Eigen via the GetIt Package Manager

Inside the C++Builder IDE, use the Tools | GetIt Project Manager menu item to bring up the list of available add-on components, libraries and demos. Type “Eigen” in the search box to see what is available.

Click the Install button to download, install, build and run tests the Eigen C++ library with your release of C++Builder (I used C++Builder version 10.4.1). As part of the Eigen installation you will see two additional windows.

Dependency notice about minimal changes made to allow Eigen to work with C++Builder
Eigen Installation Window showing progress of the download, installation and tests

Once the download and installation is completed, you can start using Eigen in your applications. To learn more about the Eigen C++ Template Library I’ve included some reference links at the end of this post. To dust off my matrix and linear algebra cobwebs and learn a little bit about Eigen, I created three sample C++Builder VCL applications using Eigen.

Simple Eigen Test C++ VCL Application

This first example Button onClick event handler displays the Eigen version number, creates a 3×3 matrix, populates it with random floating point numbers (between -1 and 1) and uses the addition, subtraction and multiplication operators.

The VCL Form containing a button and memo
Application Output using addition, subtraction and multiplication

The Source Code

MainUnit.h

//---------------------------------------------------------------------------

#ifndef MainUnitH
#define MainUnitH
//---------------------------------------------------------------------------
#include <System.Classes.hpp>
#include <Vcl.Controls.hpp>
#include <Vcl.StdCtrls.hpp>
#include <Vcl.Forms.hpp>
//---------------------------------------------------------------------------
class TForm1 : public TForm
{
__published:	// IDE-managed Components
	TButton *Button1;
	TMemo *MatrixOutputMemo;
	TMemo *DemoCodeMemo;
	TLabel *Label1;
	TLabel *Label2;
	TLabel *EigenVersionLabel;
	void __fastcall Button1Click(TObject *Sender);
private:	// User declarations
public:		// User declarations
	__fastcall TForm1(TComponent* Owner);
};
//---------------------------------------------------------------------------
extern PACKAGE TForm1 *Form1;
//---------------------------------------------------------------------------
#endif

MainUnit.cpp

//---------------------------------------------------------------------------

#include <vcl.h>
#pragma hdrstop

#include <Eigen/Dense>
using Eigen::MatrixXd;
using Eigen::IOFormat;

#include "MainUnit.h"
//---------------------------------------------------------------------------
#pragma package(smart_init)
#pragma resource "*.dfm"
TForm1 *Form1;

// create string stream from Eigen Matrix
  static std::string ConvertToString(const Eigen::MatrixXd& mat){
	std::stringstream ss;
	IOFormat CleanFmt(Eigen::FullPrecision, 0, ", ", "\n", "[", "]");
	ss << mat.format(CleanFmt);
	return ss.str();
}

//---------------------------------------------------------------------------
__fastcall TForm1::TForm1(TComponent* Owner)
	: TForm(Owner)
{
}
//---------------------------------------------------------------------------
void __fastcall TForm1::Button1Click(TObject *Sender)
{
	// first sample app adapted from Eigen documentation and put in VCL app

	// display Eigen version number
	EigenVersionLabel->Caption = "Eigen version: "
		+ IntToStr(EIGEN_WORLD_VERSION)
		+ "."
		+ IntToStr(EIGEN_MAJOR_VERSION)
		+ "."
		+ IntToStr(EIGEN_MINOR_VERSION);

	// define a 3x3 matrix of doubles
	MatrixXd m(3,3);
	// Fill matrix with random numbers between -1 and +1
	m.setRandom(3,3);
	// Change three matrix items using + - and *
	m(0,2) = m(0,0) + m(0,1);
	m(1,2) = m(1,0) - m(1,1);
	m(2,2) = m(2,0) * m(2,1);

	// output matrix using strings
	MatrixOutputMemo->Lines->Clear();
	MatrixOutputMemo->Lines->Text = ConvertToString(m).c_str();
}
//---------------------------------------------------------------------------

Matrix Operations C++ VCL Application

The second Eigen C++ VCL application exercises several Eigen operations including adding and subtracting two matricies, multiplying and dividing a matrix by a scalar, multiplying two matricies, transposing a matrix, invert a matrix and sum all elements of a matrix. There are many additional features to explore in Eigen for vector and matrix operations.

In the UI for the application you’ll see a RadioGroup for selecting one of the operations, three StringGrids to display matrix contents, an EditBox for inputing a scalar (I used Pi), and a Label for the summing result.

The Matrix Operations example VCL form
Example Output after subtracting the x and y matrices giving z

The Source Code

MainUnit.h

//---------------------------------------------------------------------------

#ifndef MainUnitH
#define MainUnitH
//---------------------------------------------------------------------------
#include <System.Classes.hpp>
#include <Vcl.Controls.hpp>
#include <Vcl.StdCtrls.hpp>
#include <Vcl.Forms.hpp>
#include <Vcl.Grids.hpp>
#include <Vcl.ExtCtrls.hpp>
#include <Vcl.Samples.Spin.hpp>

//---------------------------------------------------------------------------
class TForm1 : public TForm
{
__published:	// IDE-managed Components
	TStringGrid *StringGridX;
	TStringGrid *StringGridY;
	TStringGrid *StringGridZ;
	TLabel *Label1;
	TLabel *Label2;
	TLabel *Label3;
	TRadioGroup *RadioGroup1;
	TButton *Button1;
	TLabel *Label4;
	TEdit *ScalarEdit;
	TLabel *ResultLabel;
	void __fastcall FormShow(TObject *Sender);
	void __fastcall Button1Click(TObject *Sender);
private:	// User declarations
    void __fastcall displayMatricies();
public:		// User declarations
	__fastcall TForm1(TComponent* Owner);
};
//---------------------------------------------------------------------------
extern PACKAGE TForm1 *Form1;
//---------------------------------------------------------------------------
#endif

MainUnit.cpp

//---------------------------------------------------------------------------

#include <vcl.h>
#pragma hdrstop

#include <Eigen/Dense>
using Eigen::MatrixXd;

#include <System.SysUtils.hpp>
#include "MainUnit.h"
//---------------------------------------------------------------------------
#pragma package(smart_init)
#pragma resource "*.dfm"
TForm1 *Form1;

MatrixXd x(3,3);
MatrixXd y(3,3);
MatrixXd z(3,3);

void TForm1::displayMatricies() {
	// display contents of x, y and z matricies
	int numberRows = x.rows();
	int numberColumns = y.cols();
	for (int r=0 ; r < numberRows ; r++) {
		for (int c = 0; c < numberColumns; c++) {
			StringGridX->Cells[r][c] = FloatToStrF(x(r,c),ffFixed,5,3);
			StringGridY->Cells[r][c] = FloatToStrF(y(r,c),ffFixed,5,3);
			StringGridZ->Cells[r][c] = FloatToStrF(z(r,c),ffFixed,5,3);
		}
	}
}

//---------------------------------------------------------------------------
__fastcall TForm1::TForm1(TComponent* Owner)
	: TForm(Owner)
{
}
//---------------------------------------------------------------------------
void __fastcall TForm1::FormShow(TObject *Sender)
{
	// populate x and y matricies and their string grids with random numbers
	x.setRandom(5,5);
	y.setRandom(5,5);
	z.setZero(5,5);

	// clear selections in the string grids
	TGridRect gr;

	gr.Left = StringGridX->ColCount;
	gr.Top = StringGridX->RowCount;
	StringGridX->Canvas->Brush->Color = clWindow;
	StringGridX->Canvas->FillRect(Rect(StringGridX->Left,StringGridX->Width,StringGridX->Top,StringGridX->Height));

	gr.Left = StringGridY->ColCount;
	gr.Top = StringGridY->RowCount;
	StringGridY->Canvas->Brush->Color = clWindow;
	StringGridY->Canvas->FillRect(Rect(StringGridY->Left,StringGridY->Width,StringGridY->Top,StringGridY->Height));

	gr.Left = StringGridZ->ColCount;
	gr.Top = StringGridZ->RowCount;
	StringGridZ->Canvas->Brush->Color = clWindow;
	StringGridZ->Canvas->FillRect(Rect(StringGridZ->Left,StringGridZ->Width,StringGridZ->Top,StringGridZ->Height));

	// display current values of matricies
	displayMatricies();
}
//---------------------------------------------------------------------------

void __fastcall TForm1::Button1Click(TObject *Sender)
{
	// do the operation that is currently selected in the Radio Button Group
	// 0 = addition, 1= subtraction, 2 = multiplication,
	// 3 = division, 4 = dot product
	switch(RadioGroup1->ItemIndex) {
		case 0: // addition
			z = x + y;
			break;
		case 1: // subtraction
			z = x - y;
			break;
		case 2: // multiply x by scalar and save result in z
			z = x * StrToFloat(ScalarEdit->Text);
			break;
		case 3: // divide x by scalar and save result in z
			z = x / StrToFloat(ScalarEdit->Text);
			break;
		case 4:  // multiply x * y and save result in z
			z.noalias() = x * y;
			break;
		case 5: // transpose x and save result in z
			z = x.transpose();
			break;
		case 6: // invert x and save result in z
			z = x.inverse();
			break;
		case 7: // sum all elements of x and save in result
			ResultLabel->Caption = "Result: "+FloatToStr(x.sum());
			break;
	}

	// display current values of matricies
	displayMatricies();
}
//---------------------------------------------------------------------------

Shopping Linear Algebra C++ VCL Application

I wanted to use a “real world” linear algebra example to showcase a few additional features of the Eigen C++ template library. There are many matrix and linear algebra courses and examples out on the Internet. After a quick search I decided to use “Real-world Applications of Linear Algebra Tools” by E. Ulrychova, postgradual student at the University of Economics, Department of Mathematics, Prague, Czech Republic.

The scenario has three people who want to each shop for baked goods at only one of two stores. Each person has a quantity of rolls, buns, cakes and breads that they want to purchase. Each store has a list of prices that they charge for each of the baked goods. This linear algebra example calculates a spending analysis for each person at each store to show where each person should shop.

The user interface includes a button to run code that calculates the lowest shopping cost for each person, a StringGrid for the baked goods demand matrix for each person, a StringGrid for the store pricing for each baked good, and a StringGrid for the results of the optimal spending analysis for each person.

The VCL Form for the UI
The demand matrix of baked goods for each person, the prices for each baked good by shop and the resulting optimal shop spending for each person

The Source Code

ShoppingUnit.h

//---------------------------------------------------------------------------

#ifndef ShoppingUnitH
#define ShoppingUnitH
//---------------------------------------------------------------------------
#include <System.Classes.hpp>
#include <Vcl.Controls.hpp>
#include <Vcl.StdCtrls.hpp>
#include <Vcl.Forms.hpp>
#include <Vcl.Grids.hpp>
//---------------------------------------------------------------------------
class TForm1 : public TForm
{
__published:	// IDE-managed Components
	TButton *Button1;
	TStringGrid *DemandMatrixStringGrid;
	TLabel *Label1;
	TStringGrid *PriceMatrixStringGrid;
	TLabel *Label2;
	TStringGrid *ResultStringGrid;
	TLabel *Label3;
	void __fastcall Button1Click(TObject *Sender);
private:	// User declarations
public:		// User declarations
	__fastcall TForm1(TComponent* Owner);
};
//---------------------------------------------------------------------------
extern PACKAGE TForm1 *Form1;
//---------------------------------------------------------------------------
#endif

ShoppingUnit.cpp

//---------------------------------------------------------------------------

#include <vcl.h>
#pragma hdrstop

#include <Eigen/Dense>
using Eigen::MatrixXd;
using Eigen::VectorXd;
using Eigen::IOFormat;


#include "ShoppingUnit.h"
//---------------------------------------------------------------------------
#pragma package(smart_init)
#pragma resource "*.dfm"
TForm1 *Form1;
//---------------------------------------------------------------------------
__fastcall TForm1::TForm1(TComponent* Owner)
	: TForm(Owner)
{
}
//---------------------------------------------------------------------------
void __fastcall TForm1::Button1Click(TObject *Sender)
{

	// Calculate results of spending analysis by person by store
	//    R = PQ
	// from:
	// Real-world Applications of Linear Algebra Tools
	// by E. Ulrychova, postgradual student
	// University of Economics, Department of Mathematics, Prague, Czech Republic
	// https://www.mff.cuni.cz/veda/konference/wds/proc/pdf06/WDS06_106_m8_Ulrychova.pdf


	int r,c;  // row and column indexes used throughout this event handler

	// matricies used for spending analysis
	MatrixXd DemandMatrix(4,3);   // Q
	MatrixXd PriceMatrix(2,4);    // P
	MatrixXd ResultMatrix(2,3);   // R

	// vectors used for dot product analysis of spending by person by shop
	VectorXd DemandVector(4);
	VectorXd PriceVector(4);


	// Demanded quantity of foodstuffs per person (3 people, 4 foodstuffs)
	DemandMatrix <<  // Q
		6,3,3,  // foodstuff quantities for rolls for each of the 3 people
		5,6,4,  // foodstuff quantities for buns for each of the 3 people
		3,2,3,  // foodstuff quantities for cakes for each of the 3 people
		1,2,1;  // foodstuff quantities for breads for each of the 3 people

	// Prices for each foodstuff in each shop (4 foodstuffs, 2 shops)
	PriceMatrix <<  //P
		1.50,2.00,5.00,16.00,  // prices for foodstuffs at Shop 1
		1.00,2.50,4.50,17.00;  // prices for foodstuffs at Shop 2


	// Calculate results of spending analysis by person by store
	//    R = PQ

	int ResultMatrixNumberRows = ResultMatrix.rows();
	int ResultMatrixNumberColumns = ResultMatrix.cols();

	for (r=0 ; r < ResultMatrixNumberRows ; r++) {
		for (c = 0; c < ResultMatrixNumberColumns; c++) {
			// create price and demand vectors
			DemandVector = DemandMatrix.col(c);
			PriceVector = PriceMatrix.row(r);
			// use dot product of demand and price to get a result
			ResultMatrix(r,c) = DemandVector.dot(PriceVector);
		}
	}

	// set heading and column strings for Demand Matrix rows and columns
	DemandMatrixStringGrid->Cells[1][0] = "roll";
	DemandMatrixStringGrid->Cells[2][0] = "bun";
	DemandMatrixStringGrid->Cells[3][0] = "cake";
	DemandMatrixStringGrid->Cells[4][0] = "bread";
	DemandMatrixStringGrid->Cells[0][1] = "p1";
	DemandMatrixStringGrid->Cells[0][2] = "p2";
	DemandMatrixStringGrid->Cells[0][3] = "p3";

	// set heading and column strings for Price Matrix rows and columns
	PriceMatrixStringGrid->Cells[1][0] = "s1";
	PriceMatrixStringGrid->Cells[2][0] = "s1";
	PriceMatrixStringGrid->Cells[0][1] = "roll";
	PriceMatrixStringGrid->Cells[0][2] = "bun";
	PriceMatrixStringGrid->Cells[0][3] = "cake";
	PriceMatrixStringGrid->Cells[0][4] = "bread";

	// set heading and column strings for Result Matrix String Grid rows and columns
	ResultStringGrid->Cells[1][0] = "s1";
	ResultStringGrid->Cells[2][0] = "s1";
	ResultStringGrid->Cells[0][1] = "p1";
	ResultStringGrid->Cells[0][2] = "p2";
	ResultStringGrid->Cells[0][3] = "p3";

	int DemandMatrixNumberRows = DemandMatrix.rows();
	int DemandMatrixNumberColumns = DemandMatrix.cols();

	// populate string grid with the Demand Data
	for (r=1 ; r <= DemandMatrixNumberRows ; r++) {
		for (c = 1; c <= DemandMatrixNumberColumns; c++) {
			DemandMatrixStringGrid->Cells[r][c] = FloatToStrF(DemandMatrix(r-1,c-1),ffFixed,5,3);
		}
	}

	int PriceMatrixNumberRows = PriceMatrix.rows();
	int PriceMatrixNumberColumns = PriceMatrix.cols();

	// populate string grid with the Price Data
	for (r=1 ; r <= PriceMatrixNumberRows ; r++) {
		for (c = 1; c <= PriceMatrixNumberColumns; c++) {
			PriceMatrixStringGrid->Cells[r][c] = FloatToStrF(PriceMatrix(r-1,c-1),ffFixed,5,3);
		}
	}


	// With the supplied data this program shows it is optimal
	//  for person p1 to buy in the shop s2,
	//  for person p2 to buy in shop s1
	//  and person p3 will pay the same price in shop s1 and s2

	int ResultNumberRows = ResultMatrix.rows();
	int ResultNumberColumns = ResultMatrix.cols();

	// populate string grid with the results
	for (r=1 ; r <= ResultNumberRows ; r++) {
		for (c = 1; c <= ResultNumberColumns; c++) {
			ResultStringGrid->Cells[r][c] = FloatToStrF(ResultMatrix(r-1,c-1),ffFixed,5,3);
		}
	}

}
//---------------------------------------------------------------------------

References

C++Builder DocWiki information

GetIt Package Manager

C++ Libraries in GetIt

Eigen C++ Template Library information

Eigen C++ Template Library main page

Eigen Library Documentation (version 3.3.7 as of this posting)

Eigen Quick Reference Guide

Eigen latest development version documentation (ver 3.3.90 as of this posting)

Eigen Advanced Initialization

Eigen IOFormat Class Reference

Eigen and Linear Algebra Tutorials and Information

Real-world Applications of Linear Algebra Tools by E. Ulrychova, postgradual student University of Economics, Department of Mathematics, Prague, Czech Republic (PDF)

Eigen Tutorial – CS2240 Interactive Computer Graphics (PDF) by Daniel Ritchie, Assistant Professor of Computer Science at Brown University

Eigen Library for Matrix Algebra in C++ by The Quantcademy

C++Builder Product Information

C++Builder Product Page – Native Apps that Perform. Build Windows C++ Apps 10x Faster with Less Code

C++Builder Product Editions – C++Builder is available in four editions – Professional, Enterprise, Architect and Community (free). C++Builder is also available as part of the RAD Studio development suite.

My C++Builder Eigen VCL Example Applications

Source Code zip file for all 3 examples

Two VCL Example Applications that Use C++Builder and the C++ Boost Libraries

Boost is a set of open source C++ libraries that build on the ISO C++ programming language. In some cases, the Boost library functionality has become part of recent ISO C++ standards. RAD Studio allows you to install a subset of Boost that has been fully tested and preconfigured specifically for C++Builder. Use the GetIt Package Manager to install the Boost libraries for the Win32 classic C++ compiler, Win32 Clang-enhanced C++ compiler and Win64 Clang-enhanced compiler.

Boost libraries available in C++Builder’s GetItPackage Manager

boost::filesystem and std:filesystem VCL example

The ISO C++ std::filesystem evolved from the Boost filesystem library. The Filesystem library started in Boost, then became an ISO C++ Technical Specification and was finally merged into the ISO C++17 standard. The first example shows how to create a C++Builder VCL application using the Boost filesystem and the ISO C++ filesystem.

The VCL form contains two TButton, one TEdit and two TMemo components. The TEdit is used to set a path to files and directories on your hard drive. One button OnClick event handler will use the boost::filesystem functions to display the contents of the path. The other button OnCLick event handler will use the std::filesystem functions to display the contents of the same path. Why use both libraries? You may have an application and compiler than does not support the latest C++17 filesystem library standard. There are additional boost library versions available to support a wider range of platform filesystem operations.

VCL form for Boost and Std filesystem libraries application

C++Builder VCL application after using the boost and std filesystem library buttons

Filesystem VCL app mainunit.h:

//---------------------------------------------------------------------------

#ifndef MainUnitH
#define MainUnitH
//---------------------------------------------------------------------------
#include <System.Classes.hpp>
#include <Vcl.Controls.hpp>
#include <Vcl.StdCtrls.hpp>
#include <Vcl.Forms.hpp>
//---------------------------------------------------------------------------
class TForm1 : public TForm
{
__published:	// IDE-managed Components
	TButton *BoostButton;
	TEdit *Edit1;
	TMemo *Memo1;
	TButton *Cpp17Button;
	TMemo *Memo2;
	void __fastcall BoostButtonClick(TObject *Sender);
	void __fastcall Cpp17ButtonClick(TObject *Sender);
private:	// User declarations
public:		// User declarations
	__fastcall TForm1(TComponent* Owner);
};
//---------------------------------------------------------------------------
extern PACKAGE TForm1 *Form1;
//---------------------------------------------------------------------------
#endif

Filesystem VCL App MainUnit.cpp:

//---------------------------------------------------------------------------

#include <vcl.h>

/*
	https://en.cppreference.com/w/cpp/filesystem
	The filesystem library was originally developed as boost.filesystem,
	was published as the technical specification ISO/IEC TS 18822:2015,
	and finally merged to ISO C++ as of C++17.

	https://www.boost.org/doc/libs/1_70_0/libs/filesystem/doc/index.htm
*/

#include <boost/filesystem.hpp>
namespace Boostfs = boost::filesystem;

#include <filesystem>
namespace Cpp17fs = std::filesystem;

#pragma hdrstop

#include "MainUnit.h"
//---------------------------------------------------------------------------
#pragma package(smart_init)
#pragma resource "*.dfm"
TForm1 *Form1;

//---------------------------------------------------------------------------
__fastcall TForm1::TForm1(TComponent* Owner)
	: TForm(Owner)
{
}
//---------------------------------------------------------------------------
void __fastcall TForm1::BoostButtonClick(TObject *Sender)
{

	// Boost Filesystem verion

	Memo1->Lines->Clear();
	// use the Boost FileSystem to get directories and files using path in editbox
	Boostfs::path directoryPath = Edit1->Text.c_str();
	for (const auto& entry : Boostfs::directory_iterator(directoryPath)) {
		Boostfs::path p = entry.path();
		// test if the path is a file
		if (is_regular_file(p)) {
			int fsize = file_size(p);
			std::string s = p.string() + " : size = ";
			Memo1->Lines->Add(s.c_str() + IntToStr(fsize));
		}
		// test if the path is a directory
		else if (is_directory(p)) {      // is p a directory?
			std::string s = p.string() + " : directory";
			Memo1->Lines->Add(s.c_str());
		}
		// otherwise it is something else :)
		else {
			std::string s = p.string() + " not a file or directory";
			Memo1->Lines->Add(p.c_str());
		}
	}
}
//---------------------------------------------------------------------------
void __fastcall TForm1::Cpp17ButtonClick(TObject *Sender)
{
	// C++17 FileSystem version

	Memo2->Lines->Clear();
	// use C++17 std FileSystem library to get directories given a path in the editbox
	Cpp17fs::path directoryPath = Edit1->Text.c_str();
	for (const auto& entry : Cpp17fs::directory_iterator(directoryPath)) {
		Cpp17fs::path p = entry.path();
		if (Cpp17fs::is_directory(p)) {
			std::string s = p.string() + " : directory";
			Memo2->Lines->Add(s.c_str());
		}
		else if (Cpp17fs::is_regular_file(p)) {
			int fsize = Cpp17fs::file_size(p);
			std::string s = p.string() + " : size = ";
			Memo2->Lines->Add(s.c_str() + IntToStr(fsize));
		}
		else {
			std::string s = p.string() + " not a file or directory";
			Memo2->Lines->Add(p.c_str());
		}
	}
}
//---------------------------------------------------------------------------

boost::circular_buffer VCL example

The boost circular buffer (also known as a ring or cyclic buffer) library allows for the storing of data. The boost is designed to support fixed capacity storage. When the buffer is full, additional elements will overwrite existing elements at the front and back of the buffer (depending on the operations used).

The VCL form contains three TButton, one TSpinEdit and one TMemo components. One TButton OnClick event handler shows the contents of the circular buffer (originally populated by the Form’s OnShow event handler. The other two TButton OnClick event handlers use the boost circular buffer push_front and push_back public member functions.

Boost circular buffer C++Builder VCL form
C++Builder VCL form with Circular Buffer populated by OnShow event handler
Application showing contents of Circular Buffer after Add to front button is clicked
Application showing contents of Circular Buffer after Add to back button is clicked
Circular Buffer VCL app mainunit.h:

//---------------------------------------------------------------------------

#ifndef MainUnitH
#define MainUnitH
//---------------------------------------------------------------------------
#include <System.Classes.hpp>
#include <Vcl.Controls.hpp>
#include <Vcl.StdCtrls.hpp>
#include <Vcl.Forms.hpp>
#include <Vcl.Samples.Spin.hpp>
//---------------------------------------------------------------------------
class TForm1 : public TForm
{
__published:	// IDE-managed Components
	TButton *AddToCircularQueueFrontButton;
	TSpinEdit *SpinEdit1;
	TMemo *Memo1;
	TButton *ShowCircularBufferButton;
	TButton *AddToCircularQueueBackButton;
	void __fastcall FormShow(TObject *Sender);
	void __fastcall ShowCircularBufferButtonClick(TObject *Sender);
	void __fastcall AddToCircularQueueFrontButtonClick(TObject *Sender);
	void __fastcall AddToCircularQueueBackButtonClick(TObject *Sender);
private:	// User declarations
public:		// User declarations
	__fastcall TForm1(TComponent* Owner);
};
//---------------------------------------------------------------------------
extern PACKAGE TForm1 *Form1;
//---------------------------------------------------------------------------
#endif

Circular Buffer VCL app mainunit.cpp:

//---------------------------------------------------------------------------

#include <vcl.h>
#include <boost/circular_buffer.hpp>
#pragma hdrstop

#include "MainUnit.h"
//---------------------------------------------------------------------------
#pragma package(smart_init)
#pragma resource "*.dfm"
TForm1 *Form1;

// Create a circular buffer with a capacity for 3 integers.
boost::circular_buffer<int> cb(3);

//---------------------------------------------------------------------------
__fastcall TForm1::TForm1(TComponent* Owner)
	: TForm(Owner)
{
}
//---------------------------------------------------------------------------
void __fastcall TForm1::FormShow(TObject *Sender)
{
	// initialize circular buffer with 3 integers
	cb.push_back(1);
	cb.push_back(2);
	cb.push_back(3);
}
//---------------------------------------------------------------------------
void __fastcall TForm1::ShowCircularBufferButtonClick(TObject *Sender)
{
	int circularbuffersize = cb.size();
	Memo1->Lines->Clear();
	Memo1->Lines->Add("Circular Buffer Size = "+IntToStr(circularbuffersize));
	Memo1->Lines->Add("Items:");
	// display items in the circular buffer
	for (int i : cb)
		Memo1->Lines->Add("  "+IntToStr(i));
}
//---------------------------------------------------------------------------

void __fastcall TForm1::AddToCircularQueueFrontButtonClick(TObject *Sender)
{
	cb.push_front(SpinEdit1->Value);
}
//---------------------------------------------------------------------------

void __fastcall TForm1::AddToCircularQueueBackButtonClick(TObject *Sender)
{
	cb.push_back(SpinEdit1->Value);
}
//---------------------------------------------------------------------------

References

Boost C++Builder DocWiki

Boost C++ Libraries home page

Boost version 1.70

Converting from Boost to std::filesystem by Scott Furry as a guest post on Bartlomiej Filipek (Bartek) blog.

boost::filesystem library documentation

C++ std::filesystem documentation

boost::circular_buffer documentation

boost and std filesystem VCL app source code project (zip file)

boost circular buffer VCL app source code project (zip file)

C++Builder Product Information

C++Builder Product Page – Native Apps that Perform. Build Windows C++ Apps 10x Faster with Less Code
C++Builder Product Editions – C++Builder is available in four editions – Professional, Enterprise, Architect and Community (free). C++Builder is also available as part of the RAD Studio development suite.

Building a C++Builder RSS Feeds VCL Application with XMLDocument, NetHTTPClient, NetHTTPRequest and WebBrowser Components

I have many favorite prebuilt components that are included with C++Builder 10.4 Sydney. In this blog post I’ll show you how to create an RSS Feeds VCL (you can also use the same approach for a FireMonkey FMX) application using the XMLDocument, NetHTTPClient, NetHTTPRequest and WebBrowser components.

Start by creating a C++Builder VCL application. Set the form’s WindowState property to wsMaximized. Add a Panel, Button, ListBox (used to hold the list of RSS feed URLs to process) and a few labels and align them to the top of the form. Add Memo (to display the Feed XML), ListBox (to contain the title and URL for each article found in the feeds) and WebBrowser (to display the web page when you click on an item in the articles list box) components to the rest of the form.

Main Form
The RSS Feed application’s main form.

To populate the Panel’s listbox, I use a text file, “FeedsList.txt”, which contains a number of RSS feed URLs. The panel listbox is populated in the Form’s OnShow event handler.

Clicking on the button will process all of the RSS feed URLs and add each article and URL item found into the list box of articles found.

The XMLDocument component has a DOMVendor property to select the DOM implementation to use for parsing and manipulating the XML document.

DOMVendor choices

Clicking on an item in the articles list box uses the OnClick event handler to call the WebBrowser Navigate method  for the selected article URL. In C++Builder 10.4 Sydney there is a new property added to the WebBrowser component that lets you choose which browser engine will be used on Windows. I’ve chosen the EdgeIfAvailable engine.

SelectedEngine

Here is the contents of the FeedsList.txt file:

https://isocpp.org/blog/rss
https://herbsutter.com/feed/
http://feeds.hanselman.com/scotthanselman
http://feeds.dzone.com/home
https://news.ycombinator.com/rss
http://www.odbms.org/feed/
https://www.techmeme.com/feed.xml
https://techcrunch.com/feed/
http://feeds.feedburner.com/oreilly/radar/atom
http://feeds.feedburner.com/appdevelopermagazine
https://www.infoworld.com/index.rss
https://newsroom.ibm.com/announcements?pagetemplate=rss
https://www.computerworld.com/index.rss
https://techxplore.com/rss-feed/
https://sdtimes.com/feed/
https://www.geeksforgeeks.org/feed/
https://feeds.feedburner.com/venturebeat/SZYF
http://feeds.feedburner.com/ProgrammableWeb

Here is a bitmap of the running application:

Finally here is the source code for the application:

//---------------------------------------------------------------------------

#include <vcl.h>
#include <fstream>
#pragma hdrstop

#include "MainFeedUnit.h"
//---------------------------------------------------------------------------
#pragma package(smart_init)
#pragma resource "*.dfm"
TForm2 *Form2;
//---------------------------------------------------------------------------
__fastcall TForm2::TForm2(TComponent* Owner)
	: TForm(Owner)
{
}
//---------------------------------------------------------------------------
void __fastcall TForm2::ArticlesFoundListBoxClick(TObject *Sender)
{
	// for the ListBox item clicked - get the URL and Browse to the article
	LabelStatus->Caption = ArticlesFoundListBox->Items->Names[ArticlesFoundListBox->ItemIndex];
	ArticleWebBrowser->Navigate(ArticlesFoundListBox->Items->Values[ArticlesFoundListBox->Items->Names[ArticlesFoundListBox->ItemIndex]]);
}
//---------------------------------------------------------------------------
void __fastcall TForm2::Button1Click(TObject *Sender)
{
	// Find and save Title and URL for items found
	std::ofstream fs (AnsiString(FormatDateTime("yyyy-mm-dd-hhnnss",Now())+"_RSSFound.txt").c_str());
	fs << AnsiString("RSS Feed for: "+ NetHTTPRequest1->URL).c_str() << std::endl;
	fs << AnsiString(FormatDateTime("dddd mmmm dd, yyyy @ hh:nn:ss",Now())).c_str() << std::endl;
	fs << std::endl;

	// Clear the Articles Found List Box to prepare for the title and URL of articles
	ArticlesFoundListBox->Clear();
	FeedsItemsCountLabel->Caption = "Items Found = 0";

	// get all articles and URLs in all feeds
	for (int i = 0; i < FeedsListBox->Count; i++) {
		// Get the RSS feed URL string from the ListBox
		NetHTTPRequest1->URL = FeedsListBox->Items->Strings[i];

		UrlLabel->Caption = "Feed URL: "+NetHTTPRequest1->URL;
        UrlLabel->Update();

		// Use NetHTTPRequest Execute method to get the RSS Feed XML
		UnicodeString FeedString = NetHTTPRequest1->Execute()->ContentAsString();

		// copy the XML string to the Memo
		MemoFeedXML->Lines->Clear();
		MemoFeedXML->Lines->Text = FeedString;
		MemoFeedXML->Update();

		// load the RSS Feed XML into the XMLDocument
		XMLDocument1->LoadFromXML(FeedString);
		XMLDocument1->Active = True;

		LabelStatus->Caption = "Processing RSS for "+NetHTTPRequest1->URL;
		LabelStatus->Update();

		// find the RSS feed channel node
		_di_IXMLNode ChannelNode = XMLDocument1->DocumentElement->ChildNodes->FindNode ("channel");
		// test to make sure the ChannelNote is found
		if (ChannelNode != NULL) {
			for (int I=0;I<ChannelNode->ChildNodes->Count;I++) {
				// iterate through child nodes
				_di_IXMLNode ItemNode = ChannelNode->ChildNodes->Get(I);
				// if child node is an item then get the title, pubDate and URL
				if (ItemNode->NodeName == "item") {
					LabelStatus->Caption = "Processing Node " + IntToStr(I);
					LabelStatus->Update();
					UnicodeString title = ItemNode->ChildValues ["title"];
					UnicodeString pubDate = ItemNode->ChildValues ["pubDate"];
					// author := ItemNode.ChildValues ['author'];    // could be nil
					UnicodeString url = ItemNode->ChildValues ["link"];

					// populate the articles found ListBox with the pair of title and URL
					ArticlesFoundListBox->Items->AddPair(title,url);
					ArticlesFoundListBox->Update();
					FeedsItemsCountLabel->Caption = "Items Found = "+IntToStr(ArticlesFoundListBox->Count);
					FeedsItemsCountLabel->Update();

					// write the Title, pubDate and URL to the text file
					fs << AnsiString(title).c_str() << std::endl;
					fs << AnsiString(pubDate).c_str() << std::endl;
					fs << AnsiString(url).c_str() << std::endl;
					fs << std::endl;
				}
			}
		}

	}

	fs << std::endl;
	fs << AnsiString("Items Found = "+IntToStr(ArticlesFoundListBox->Count)).c_str() << std::endl;
	fs << "end of file" << std::endl;
	fs.close();   // close the text file
	LabelStatus->Caption = "RSS Processing Done!";
    UrlLabel->Caption = "";
}
//---------------------------------------------------------------------------
void __fastcall TForm2::FormShow(TObject *Sender)
{
	// load RSS Feeds ListBox with the "FeedsList.txt" text file
    // I put the text file in the same folder as the app .EXE file
	FeedsListBox->Items->Clear();
	FeedsListBox->Items->LoadFromFile("FeedsList.txt");
	LabelStatus->Caption = "RSS Feed Urls Loaded = "+IntToStr(FeedsListBox->Count);
	LabelStatus->Update();

}
//---------------------------------------------------------------------------

References

Using TXMLDocument

Using the Document Object Model

Using an HTTP Client

System.Net.HttpClientComponent.TNetHTTPClient

System.Net.HttpClientComponent.TNetHTTPRequest

Using TEdgeBrowser Component and Changes to the TWebBrowser Component

RSS 2.0 Specification

Download Source Code ZipFile for RSSFeedListsUsingTextFileVCLCpp

C++Builder Product Information

C++Builder Product Page – Native Apps that Perform. Build Windows C++ Apps 10x Faster with Less Code
C++Builder Product Editions – C++Builder is available in four editions – Professional, Enterprise, Architect and Community (free). C++Builder is also available as part of the RAD Studio development suite.

Using C++Builder to list all available VCL styles in a ComboBox and apply a selected style using the ComboBoxChange event

Back in June a developer asked a C++Builder question on StackOverflow. The question was “How can I list all the available VCL styles in a combo box and in the ComboBoxChange event, apply that style in C++ Builder?” I answered the question and gave the example code.

One of my favorite RTL features for the VCL and FMX frameworks is the ability to customize the look and feel of your applications using Styles. The first step is to create a C++Builder VCL project and select a few of the VCL Styles in the Project | Options | Application | Appearance settings. The C++Builder 10.4 Sydney DocWiki explains that “the VCL Styles architecture has been significantly extended to support High-DPI graphics and 4K monitors. In 10.4 Sydney all graphical elements are automatically scaled for the proper resolution of the monitor the element is displayed on. This means that the scaling depends on the DPI resolution of the target computer or the current monitor, in case of multi-monitor systems.”

The C++ Application User Interface

For the application user interface I have a TButton (has code to populate the ComboBox with selected application styles) and a TComboBox (to display and allow selection of a style).

The C++ code

//---------------------------------------------------------------------------

#include <vcl.h>
#pragma hdrstop

#include "Unit1.h"
#include <Vcl.Themes.hpp>
//---------------------------------------------------------------------------
#pragma package(smart_init)
#pragma resource "*.dfm"
TForm1 *Form1;
//---------------------------------------------------------------------------
__fastcall TForm1::TForm1(TComponent* Owner)
	: TForm(Owner)
{
}
//---------------------------------------------------------------------------
void __fastcall TForm1::Button1Click(TObject *Sender)
{
	// populate the ComboBox with VCL styles that are selected
	//    in Project | Options | Application | Appearance
	ComboBox1->Items->BeginUpdate();
    try
    {
		ComboBox1->Items->Clear();

		DynamicArray<String> styleNames = Vcl::Themes::TStyleManager::StyleNames;

        for(int i = 0; i < styleNames.Length; ++i)
        {
            String styleName = styleNames[i];
			ComboBox1->Items->Add(styleName);
        }
    }
    __finally
    {
		ComboBox1->Items->EndUpdate();
	}
}
//---------------------------------------------------------------------------
void __fastcall TForm1::ComboBox1Change(TObject *Sender)
{
	// set the style for the selected combobox item

	Vcl::Themes::TStyleManager::TrySetStyle(ComboBox1->Items->Strings[ComboBox1->ItemIndex],false);
}
//---------------------------------------------------------------------------

The Application in Action

TComboBox populated with VCL styles selected
Application Style Changed by TComboBox selection

References

VCL Styles Overview

Project Options Application Appearance

VCL Styles Support for High-DPI Graphics

C++Builder Product Information

C++Builder Product Page – Native Apps that Perform. Build Windows C++ Apps 10x Faster with Less Code
C++Builder Product Editions – C++Builder is available in four editions – Professional, Enterprise, Architect and Community (free). C++Builder is also available as part of the RAD Studio development suite.

Multithreaded Sorting with C++Builder and the Parallel Programming Library (PPL)

The Parallel Programming Library (PPL) is one of my favorite features in C++Builder runtime library. PPL allows developers to create tasks that run in parallel to take advantage of multi-core processors.

Using the PPL, you can: 1) speed up loops with a Parallel For, 2) run multiple tasks in parallel using TTask, and 3) use Future Objects to allow a process run with your program focused on other work until the future value is set.

To showcase the TTask feature of the PPL, I’ve created a C++Builder VCL application (build and tested using the C++Builder 10.4 Sydney release) that runs three sort algorithms in separate tasks – Bubble Sort, Shell Sort and the ISO C++ standard Sort (which implements the Quicksort algorithm).

The User Interface

The VCL user interface for my application includes a TButton, two TMemos, and four TLabels. The TButton onClick event handler creates a vector of integers, creates three TTasks (for the sort algorithms) and waits for the sort tasks to complete using the TTask::WaitForAll method.

The Code

MainUnit.h:

#ifndef MainUnitH
#define MainUnitH
//---------------------------------------------------------------------------
#include <System.Classes.hpp>
#include <Vcl.Controls.hpp>
#include <Vcl.StdCtrls.hpp>
#include <Vcl.Forms.hpp>
#include <Vcl.ExtCtrls.hpp>
//---------------------------------------------------------------------------
class TForm1 : public TForm
{
__published:	// IDE-managed Components
	TButton *Button1;
	TLabel *SortingStatusLabel;
	TLabel *BubbleSortLabel;
	TMemo *Data_Memo;
	TMemo *SortResult_Memo;
	TLabel *ShellSortLabel;
	TLabel *STDSortLabel;
	void __fastcall Button1Click(TObject *Sender);
private:	// User declarations
public:		// User declarations
	__fastcall TForm1(TComponent* Owner);
};
//---------------------------------------------------------------------------
extern PACKAGE TForm1 *Form1;
//---------------------------------------------------------------------------
#endif

MainUnit.cpp:

//---------------------------------------------------------------------------

#include <vcl.h>
#include <System.Threading.hpp>
#include <vector>
#include <algorithm>
#pragma hdrstop

#include "MainUnit.h"
//---------------------------------------------------------------------------
#pragma package(smart_init)
#pragma resource "*.dfm"
TForm1 *Form1;
//---------------------------------------------------------------------------
__fastcall TForm1::TForm1(TComponent* Owner)
	: TForm(Owner)
{
}
//---------------------------------------------------------------------------
void __fastcall TForm1::Button1Click(TObject *Sender)
{

	_di_ITask My_Tasks[3];
	const int max_data = 15000;   // number of random numbers to create

	int LoopValue = 0;

	Button1->Enabled = false;
	Button1->Update();
	BubbleSortLabel->Caption = "Bubble Sort";
	BubbleSortLabel->Update();
	ShellSortLabel->Caption = "Shell Sort";
	ShellSortLabel->Update();
	STDSortLabel->Caption = "std::sort";
	STDSortLabel->Update();

	SortingStatusLabel->Caption = "Sorting "+IntToStr(max_data)+" integers!";
	SortingStatusLabel->Update();

	// Windows GetTicks() start and stop for each sort method
	int StartBubble,StopBubble;
	int StartShell,StopShell;
	int StartSTD,StopSTD;

	Data_Memo->Lines->Clear();
	SortResult_Memo->Lines->Clear();

	// create a vector of data that all sort algorithms will use
	std::vector<int> my_data;

	// populate the vector with integers
	for (int i = 1; i <= max_data; i++) {
		int random_value = Random(max_data);
		my_data.push_back(random_value);
		// Data_Memo->Lines->Add(IntToStr(random_value));
	}

	// copy data vector to sort vectors
	std::vector<int> bubble_data = my_data;
	std::vector<int> shell_data = my_data;
	std::vector<int> std_data = my_data;

	// First Task - Bubble Sort
	My_Tasks[0] = TTask::Create([&](){
		// Set Bubble Sort Windows GetTickCount()
		StartBubble = GetTickCount();
		// body of Bubble Sort
		bool swapp = true;
		while(swapp){
			swapp = false;
			for (size_t i = 0; i < bubble_data.size()-1; i++) {
				if (bubble_data[i]>bubble_data[i+1] ){
					bubble_data[i] += bubble_data[i+1];
					bubble_data[i+1] = bubble_data[i] - bubble_data[i+1];
					bubble_data[i] -=bubble_data[i+1];
					swapp = true;
				}
			}
		}
		// Set the Bubble Sort Stop GetTicks()
		StopBubble = GetTickCount();
	});
	// Start the Bubble Sort Task
	My_Tasks[0]->Start();


	// Second Task - Shell Sort
	My_Tasks[1] = TTask::Create([&](){
		// Set Shell Sort Windows GetTickCount()
		StartShell = GetTickCount();
		// body of the Shell Sort
		for (int gapSize = shell_data.size() / 2; gapSize > 0; gapSize /= 2) {
			for (int currentIndex = gapSize; currentIndex < shell_data.size(); currentIndex++) {
				// save the currentIndex
				int currentIndexCopy = currentIndex;
				// save the value of the currentIndex
				int item = shell_data[currentIndex];
				while (currentIndexCopy >= gapSize && shell_data[currentIndexCopy - gapSize] > item) {
					shell_data[currentIndexCopy] = shell_data[currentIndexCopy - gapSize];
					currentIndexCopy -= gapSize;
				}
				shell_data[currentIndexCopy] = item;
			}
		}
		// Set the Shell Sort Stop GetTicks()
		StopShell = GetTickCount();
	});
	// Start the Shell Sort
	My_Tasks[1]->Start();


	// Third Task - std::sort
	My_Tasks[2] = TTask::Create([&](){
		// Set std::sort Windows GetTickCount()
		StartSTD = GetTickCount();
		// Body of the std::sort
		std::sort(std_data.begin(),std_data.end());
		// Set the std::sort Stop GetTicks()
		StopSTD = GetTickCount();
	});
	// Start the Shell Sort
	My_Tasks[2]->Start();

	// wait until all of the sorting tasks complete
	TTask::WaitForAll(My_Tasks, sizeof(My_Tasks)/sizeof(My_Tasks[0])-1);

	SortingStatusLabel->Caption = "Sorting All done!";

	BubbleSortLabel->Caption = "Bubble Sort Time: "
		+ IntToStr(StopBubble - StartBubble)
		+ " ms";
	BubbleSortLabel->Update();

	ShellSortLabel->Caption = "Shell Sort Time: "
		+ IntToStr(StopShell - StartShell)
		+ " ms";
	ShellSortLabel->Update();

	STDSortLabel->Caption = "std::sort: "
		+ IntToStr(StopSTD - StartSTD)
		+ " ms";
	STDSortLabel->Update();

	// if you want to see the sort results un-comment
	// one of the for loops and the sort result memo statement
	// for(int n : std_data) {
	// for(int n : bubble_data) {
	// for(int n : shell_data) {
		// SortResult_Memo->Lines->Add(IntToStr(n));
	// }

	// clear the vectors
	my_data.clear();
	bubble_data.clear();
	shell_data.clear();
	std_data.clear();

	Button1->Enabled = true;
}
//---------------------------------------------------------------------------

The form after sorting 15,000 integers

References

PPL – Parallel Programming Library – http://docwiki.embarcadero.com/RADStudio/Sydney/en/Using_the_Parallel_Programming_Library

Using TTask – http://docwiki.embarcadero.com/RADStudio/Sydney/en/Using_TTask_from_the_Parallel_Programming_Library

Using TParallel::For – http://docwiki.embarcadero.com/RADStudio/Sydney/en/Using_TParallel.For_from_the_Parallel_Programming_Library

Using TTask::IFuture – http://docwiki.embarcadero.com/RADStudio/Sydney/en/Using_TTask.IFuture_from_the_Parallel_Programming_Library

Algorithms Library – https://en.cppreference.com/w/cpp/algorithm

std::sort – https://en.cppreference.com/w/cpp/algorithm/sort

C++Builder Product Information

C++Builder Product Page – Native Apps that Perform. Build Windows C++ Apps 10x Faster with Less Code
C++Builder Product Editions – C++Builder is available in four editions – Professional, Enterprise, Architect and Community (free). C++Builder is also available as part of the RAD Studio development suite.