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SendMessage Function and Windows Message: WM_LBUTTONDOWN
SendMessage Function and Windows Message: WM_LBUTTONDOWN

Description

This example illustrates how to press the left button of the mouse cyclically on each control contained on Form1 through software.

This is achieve with a loop and the SendMessage function which sends the WM_LBUTTONDOWN message to the control specified by the corresponding handle (Control->Handle)

       SendMessage(pControl->Handle, WM_LBUTTONDOWN , 0, 0);

A delay of 1 Second is intoduced between iterations with the call

       Sleep(1000);

Form1 has the following components: a TTimer, a TEdit, a TMemo and four TButtons.

Files

SendMessageLBUTTONDOWN.cpp

#include <vcl.h>
#pragma hdrstop

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

void __fastcall TForm1::Timer1Timer(TObject *Sender)
{
// Scan all components derived from TWinControl
// on Form1 and click on each component with the
// Left Button of the mouse by sending the WM_LBUTTONDOWN
// Windows message.

    HWND hwnd;

    if((hwnd = FindWindow(NULL, "Form1")))
    {
        //Loop though all the controls on Form1
        //
        for( int i=0; i < this->ControlCount; i++ )
        {
            // Get the pointer to the next control on Form1
            TWinControl* pControl = dynamic_cast <TWinControl*>(this->Controls[i]);
            
            //Send Windows Message WM_LBUTTONDOWN
            SendMessage(pControl->Handle, WM_LBUTTONDOWN , 0, 0);

            // Pause for 1 second
            Sleep(1000);
        }
    }
    else
    {
        ShowMessage("Error: Cannot find the window caption");
    }  
}
//---------------------------------------------------------------------------

SendMessageLBUTTONDOWN.h

#ifndef SendMessageLBUTTONDOWNH
#define SendMessageLBUTTONDOWNH
//---------------------------------------------------------------------------
#include <Classes.hpp>
#include <Controls.hpp>
#include <StdCtrls.hpp>
#include <Forms.hpp>
#include <ExtCtrls.hpp>
#include <Buttons.hpp>
//---------------------------------------------------------------------------
class TForm1 : public TForm
{
__published:	// IDE-managed Components
        TTimer *Timer1;
        TEdit *Edit1;
        TMemo *Memo1;
        TButton *Button1;
        TButton *Button2;
        TButton *Button3;
        TButton *Button4;
        void __fastcall Timer1Timer(TObject *Sender);
private:	// User declarations
public:		// User declarations
        __fastcall TForm1(TComponent* Owner);
};
//---------------------------------------------------------------------------
extern PACKAGE TForm1 *Form1;
//---------------------------------------------------------------------------
#endif

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