Question

I want to invalidate the window when it’s created. How can I do that? calling InvalidateRect during WM_CREATE doesn’t work.

The thing is I call SetWindowLongPtr in WM_CREATE and set GWLP_USERDATA. WM_PAINT looks for some pointer in USER_DATA but the first time I receive WM_PAINT the data isn’t apparently still there so it doenst paint my stuff.

Also tried this:

#define MyDefinedMsg (WM_APP+1) //...// case WM_CREATE:   //...//   SetWindowLongPtr(hWnd,GWLP_USERDATA,ptr);   PostMessage(hWnd,MyDefinedMsg,0,0);    break; case MyDefinedMsg:    InvalidateRect(hWnd,NULL,TRUE);   break; 

but did not work.

Thanks in advance

Answer 1

1. Your window is already invalid when it is created
2. PostMessage puts a message in the queue so is likely to arrive after the regular creation messages (WM_CREATE/WM_SIZE/WM_PAINT etc).

If your painting is failing due to GWLP_USERDATA being NULL then something else is happening…