Thread: SetTimer().. WM_TIMER window flickers

How do i avoid this?

Code:

	case WM_CREATE:
		{
			/* Create timer to refresh screen */ 
			SetTimer(hwnd, IDT_REFRESH, (UINT)0.005,(TIMERPROC) NULL); 

        ............
        ............

	case WM_TIMER: 
		{
			// Refresh screen
			InvalidateRect (hwnd, NULL, TRUE);
			UpdateWindow(hwnd);
		}
		break;

My whole window is flickering and when selecting menu, sometimes menu is black (wont see text on menu) until i move mouse over menu then text clears out.. Lets just say the window operations would not function properly if i use timer as shown... I just wanna refresh screen every milliseconds

Originally Posted by matsp

Are you SURE that you want t a time of 0? (UINT)0.005 will turn into zero, as UINT is an integer, and 0.005 is less than 1.0. And although it gets changed to USER_TIMER_MINIMUM, you probably want to do something else in the first place.

--
Mats

increasing the value doesn't really make much difference... made it 5 with no difference

Originally Posted by matsp

5 milliseconds is 200 times a second - do you REALLY need to update your screen that often (by the way, I _THINK_ USER_TIMER_MINIMUM is 10, so setting it to less than that would clamp it to 10).

Try something like 20 or 50, and see if that makes a difference.

--
Mats

made it 1000, well much better but can see there's something happening on the screen every second... I'm sure there must be something to smooth out the flickering completely.. Anywayz, suppose i can leave with that minimal flickering

Originally Posted by Elysia

Are these rectangles windows? If not, it's best to make them labels.
Then just invalidate those labels and it will redraw.

No they not, they are drawn on one window... How do you make them labels?

Originally Posted by vart

You can also actually try to draw what you need on the invisible dc - and then just copy it - when whole buffer is ready - onto the screen dc

Just read through some tutorial... Is this Double buffering you talking about? If so, i'm busy adding some code... Not sure how it works but will update you on my progress...

The idea is...

1. Create a DC on buffer
2. Add/draw rectangles on Buffer DC
3. Copy back to DC to client area using BitBlt()...

Originally Posted by Elysia

You would just add labels to your window. They're called "static," I think. Create them just like any other windows. Labels are made to contain text and appears invisible to the dialog.

So you could make labels and seeing as they are windows, draw upon them and invalidate them.

Will check this later.. now am busy wif double buffering....

Yep, it's double buffer and the general idea you have is correct.
Basically, it's to avoid drawing anything on the window until you've finished drawing at which time you copy the data over to the window.
It's similar to games which also tend to use some double buffering technique.

Q. Is it essential to first delete the DC on buffer only after you copied it to client area DC? Thing is i have about 5 rectangles. Currently i draw each on DC created by BegingPaint(), then delete after drawing it, draw next Rec, then delete until i finish drawing all... The example i have draws object(s) on Memory DC on a buffer, then copies the buffer DC to Client DC, then only after copying deletes the Buffer DC.... To clear my question, is it safe to draw all five rectangles without deleting each separately on Buffer DC, then delete all after copying back to Client DC... (Hope this question is clear)

You might try overriding WM_ERASEBKGRND and just return non zero.

Originally Posted by DaveH

You might try overriding WM_ERASEBKGRND and just return non zero.

The examples of this i've seen only in MFC

Code:

 
  BOOL CRecordList::OnEraseBkgnd(CDC* pDC)
   {
      return FALSE;
   }

How would one do this in WinAPI C? how do u override functions in C