Disabling redraw in WinForms app
- by Ryan
I'm working on a C#.Net application which has a somewhat annoying bug in it. The main window has a number of tabs, each of which has a grid on it. When switching from one tab to another, or selecting a different row in a grid, it does some background processing, and during this the menu flickers as it's redrawn (File, Help, etc menu items as well as window icon and title).
I tried disabling the redraw on the window while switching tabs/rows (WM_SETREDRAW message) at first. In one case, it works perfectly. In the other, it solves the immediate bug (title/menu flicker), but between disabling the redraw and enabling it again, the window is "transparent" to mouse clicks - there's a small window (<1 sec) in which I can click and it will, say, highlight an icon on my desktop, as if the app wasn't there at all. If I have something else running in the background (Firefox, say) it will actually get focus when clicked (and draw part of the browser, say the address bar.)
Here's code I added.
m = new Message();
m.HWnd = System.Windows.Forms.Application.OpenForms[0].Handle; //top level
m.WParam = (IntPtr)0; //disable redraw
m.LParam = (IntPtr)0; //unused
m.Msg = 11; //wm_setredraw
WndProc(ref m);
<snip - Application ignores clicks while in this section (in one case)
m = new Message();
m.HWnd = System.Windows.Forms.Application.OpenForms[0].Handle; //top level
m.WParam = (IntPtr)1; //enable
m.LParam = (IntPtr)0; //unused
m.Msg = 11; //wm_setredraw
WndProc(ref m);
System.Windows.Forms.Application.OpenForms[0].Refresh();
Does anyone know if a) there's a way to fix the transparent-application problem here, or b) if I'm doing it wrong in the first place and this should be fixed some other way?
