How can I detect key combinations?

Applies To: C++Builder 1 or higher
Category: Knowledge Base

The Key parameter shows me which key has been pressed. But if I use key combinations such as Ctrl + A, Key contains only A.

 

1.

  Start a new project using File | New Application.

 

2.

  Double-click the OnKeyDown event:

 

void __fastcall TForm1::FormKeyDown(TObject *Sender, WORD &Key,

    TShiftState Shift)

{

    if(Shift.Contains(ssCtrl) && Key == 'A')

        ShowMessage("You pressed Ctrl + A");

}

 

TShiftState indicates the state of the Alt, Ctrl, and Shift keys and the mouse buttons.

 

TShiftState seems easy to use but it supports only Alt, Ctrl, and Shift. How can I detect special key combinations such us left arrow button + up arrow button?

 

1.

  Start a new project using File | New Application.

 

2.

  Double-click the OnKeyDown event:

 

void __fastcall TForm1::FormKeyDown(TObject *Sender, WORD &Key,

    TShiftState Shift)

{

    if(GetAsyncKeyState(VK_LEFT) < 0 &&< 0 &&

       GetAsyncKeyState(VK_UP) < 0)< 0)

    {

        ShowMessage("Left arrow + Up arrow");

    }

}

 

The GetAsyncKeyState Win32 API function determines whether a key is up or down.

C++Builder Developer's Network
Copyright © Yoto Yotov