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Win32 Button Commands

Started by captacha Aug 11, 2012 at 1:54 AM 4 replies 1.5k views

Original Post

Aug 11, 2012 at 1:54 AM

In my code the WM_COMMAND segment causes my program to exit when I click on a button. Why is this? Shouldn't it do nothing?


 LRESULT CALLBACK WndProc(HWND hwnd, UINT msg, WPARAM wparam, LPARAM lparam)
 {
 switch(msg)
 {
 case WM_CREATE:
 CreateWindow("button", "Button 1", WS_VISIBLE | WS_CHILD, (width/2)-40, (height/2)-12, 80, 25, hwnd, (HMENU)1, NULL, NULL);
 CreateWindow("button", "Button 2", WS_VISIBLE | WS_CHILD, (width/2)-40, ((height/2)-12)-45, 80, 25, hwnd, (HMENU)2, NULL, NULL);
 break;
 case WM_COMMAND:
 if(LOWORD(wparam) == 1)
 {
 }
 case WM_CLOSE:
 DestroyWindow(hwnd);
 break;
 case WM_DESTROY:
 PostQuitMessage(0);
 break;
 default:
 return DefWindowProc(hwnd, msg, wparam, lparam);
 break;
 }
 }

ApochPiQ

Aug 11, 2012 at 2:52 AM

You seem to have left out a break; just above case WM_CLOSE.

Endurion

Aug 11, 2012 at 4:29 AM

Not the problem here, but you don't return anything for any handled message. In most cases you also want to call DefWindowProc for handled messages.

dilyan_rusev

Aug 11, 2012 at 4:40 PM

And also you should return 0 for handled messages. I don't know if this is the full code, but I can't see a "return 0" statement. Returning 0 is important.

Endurion

Aug 12, 2012 at 4:35 AM

And also you should return 0 for handled messages. I don't know if this is the full code, but I can't see a "return 0" statement. Returning 0 is important.

You cannot generally return 0. Look up the handled message and see what you should return (if you should do so).

SiCrane

Aug 12, 2012 at 6:23 AM

In particular, a common mistake is to return 0 from WM_NCCREATE, which indicates that window creation shouldn't proceed and causes CreateWindow()/CreateWindowEx() to return a NULL handle. Confusingly, WM_CREATE does the opposite: 0 indicates success.

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