Thread: SetTimer().. WM_TIMER window flickers

If you want to fix the flickering by using double-buffering, then you can try just using the WS_EX_COMPOSITED flag during window creation.

Decided to write a much smaller program to test my double buffering experience learnt in the past few days to test whether or not am doing things wrong. To my amusement i managed to write a code which works 100% using off-screen DC (double buffering). The program rotates a line in a circle at a high speed... So this uses the timer & InvalidateRect. This program was flickering like the other without using double buffering....

Code:

// Rotate.c :
//

#include <windows.h>
#include <math.h>

#pragma hdrstop

#define IDT_ROTATER 101

//---------------------------------------------------------------------------
const char *ClsName = "RADAR_01";
const char *WndName = "Rotate Line";

POINT SetPOINT(LONG radius);
long ErrorHandler(char errorMessage[]);
void Win32APIGDICircle (HDC hdc, LONG radius, int R, int G, int B);
HDC MemoryDCForArea (HDC hdc, int iAreaWidth, int iAreaHeight, int iCommandWhatToDo );
LRESULT CALLBACK WndProcedure(HWND hWnd, UINT uMsg,WPARAM wParam, LPARAM lParam);

// Globals
int	angle=0;
HICON		hIcon1;		
POINT		ptOld;       
UINT_PTR	uResult;    
POINT		coord, ptCenter = {450,300};

//---------------------------------------------------------------------------
INT WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow)
{
	MSG        Msg;
	HWND       hWnd;
	WNDCLASSEX WndClsEx;

	// Create the application window
	WndClsEx.cbSize        = sizeof(WNDCLASSEX);
	WndClsEx.style         = CS_HREDRAW | CS_VREDRAW;
	WndClsEx.lpfnWndProc   = WndProcedure;
	WndClsEx.cbClsExtra    = 0;
	WndClsEx.cbWndExtra    = 0;
	WndClsEx.hIcon		   = LoadIcon(hInstance, MAKEINTRESOURCE(400)); 
	WndClsEx.hCursor	   = LoadCursor(hInstance, MAKEINTRESOURCE(200)); 
	WndClsEx.hbrBackground = (HBRUSH)(COLOR_BTNFACE+1);
	WndClsEx.lpszMenuName  = NULL;
	WndClsEx.lpszClassName = ClsName;
	WndClsEx.hInstance     = hInstance;
	WndClsEx.hIconSm       = LoadIcon(NULL, IDI_APPLICATION);

	// Register the application
	RegisterClassEx(&WndClsEx);

	// Create the window object
	hWnd = CreateWindowEx(0,
		ClsName,
		WndName,
		WS_OVERLAPPEDWINDOW,
		CW_USEDEFAULT,
		CW_USEDEFAULT,
		CW_USEDEFAULT,
		CW_USEDEFAULT,
		NULL,
		NULL,
		hInstance,
		NULL);


	if( !hWnd ) 
		return FALSE; 

	// Display the window to the user
	ShowWindow(hWnd, nCmdShow);
	UpdateWindow(hWnd);

	while( GetMessage(&Msg, NULL, 0, 0) )
	{
		TranslateMessage(&Msg);
		DispatchMessage(&Msg);
	}

	return (int) Msg.wParam;
}

//---------------------------------------------------------------------------
LRESULT CALLBACK WndProcedure(HWND hWnd, UINT Msg,
							  WPARAM wParam, LPARAM lParam)
{
	PAINTSTRUCT		ps;
	HPEN			pen, oldPen;
	HDC				hdc;
	HDC				MemDC;
	HBRUSH			hbrBkGnd;
	HBITMAP			hBitmap, hOldBitmap;
	RECT			rec;
	long			radius=150;

	double	xLimit = sqrt ((double) (radius * radius) / 2);

	// Handle messagse
	switch(Msg)
	{
	case WM_CREATE:

		// Set the timer 
		uResult = SetTimer(hWnd, IDT_ROTATER, (UINT) 0.015,(TIMERPROC) NULL); 

		break;

	case WM_PAINT:
		{		
			hdc = BeginPaint(hWnd, &ps);

			/* Retrieve the client's area width and height */
			GetClientRect(hWnd, &rec);

			MemDC = CreateCompatibleDC (hdc);

			hBitmap = CreateCompatibleBitmap (
				hdc, rec.right-rec.left, rec.bottom-rec.top
				);

			hOldBitmap = SelectObject (MemDC, hBitmap);

			// Force background color to grey 
			hbrBkGnd = CreateSolidBrush( RGB(0xD3, 0xD3, 0xD3) );
			FillRect(MemDC, &rec, hbrBkGnd);
			DeleteObject(hbrBkGnd);

			// Draw a circle
			Win32APIGDICircle (MemDC, radius, 0, 255, 128);

			// Create pen
			pen = CreatePen(PS_SOLID, 2, RGB(128, 255, 128));	
			oldPen = (HPEN)SelectObject(MemDC, pen);		

			// Draw line
			SetPOINT(radius);
			MoveToEx(MemDC, ptCenter.x,ptCenter.y, NULL);		
			LineTo(MemDC, coord.x, coord.y);
			
			// Delete Pen
			SelectObject(MemDC, oldPen);
			DeleteObject(pen);

			/* Render circle to screen from memory DC */
			BitBlt(hdc,0,0,rec.right,rec.bottom,MemDC,0,0,SRCCOPY);

			// Delete & Release DCs
			SelectObject(MemDC, hOldBitmap);
			DeleteObject(hBitmap);
			DeleteDC(MemDC);

			EndPaint(hWnd, &ps);
		}
		break; 

	case WM_TIMER: 
		angle-=2;
		InvalidateRect (hWnd, NULL, TRUE);
		UpdateWindow(hWnd);

		break;

	case WM_DESTROY:
		
		KillTimer(hWnd, IDT_ROTATER); 
		PostQuitMessage(WM_QUIT);
		break;

	case WM_ERASEBKGND:
		{
			return (LRESULT)1;
		}

	default:
		// Process the left-over messages
		return DefWindowProc(hWnd, Msg, wParam, lParam);
	}
	// If something was not done, let it go
	return 0;
}

// Win32API GDI circle:
void Win32APIGDICircle (HDC hdc, LONG radius,int R, int G, int B)
{
	HBRUSH hBrush = CreateSolidBrush (RGB (R,G,B));
	HGDIOBJ hOldBrush = SelectObject (hdc, hBrush);

	Ellipse (hdc, 
		ptCenter.x - radius, 
		ptCenter.y + radius,
		ptCenter.x + radius,
		ptCenter.y - radius);

	SelectObject (hdc, hOldBrush);
	DeleteObject (hBrush);
}

/* Calculate the line points */
POINT SetPOINT(LONG radius)
{
	const double Deg2Rad = 0.017453292;
	double degInRad;

	degInRad = angle*Deg2Rad;   // Convert degrees to radians

	// Finds the adjacent value
	coord.x = (long)(ptCenter.x + (cos(degInRad)*radius));	

	// Finds the hypotenuse value
	coord.y = (long)(ptCenter.y - (sin(degInRad)*radius));	

	return coord;
}

This is how the rendering on memory DC is done and it works 100% (no flickering at all)

Now, i have tried to update my other project following the same steps... Still in vain, i think this may have to do with how i have used my variables (global vs local or memory related issues) which causes the flickering on edit controls as well (which is strange cause they not part of repaint)

Originally Posted by csonx_p

Now, i have tried to update my other project following the same steps... Still in vain, i think this may have to do with how i have used my variables (global vs local or memory related issues) which causes the flickering on edit controls as well (which is strange cause they not part of repaint)

I'm going to assume you didn't read the link I posted about the WS_EX_COMPOSITED flag. Seriously, it will do the double-buffering for you!
That one tiny little change and then it'll be smooth, like magic - piece of cake!

Originally Posted by csonx_p

Code:

: error C2065: 'WS_EX_COMPOSITED' : undeclared identifier

Wow, you give up easily. Here's it's definition in the winuser.h header file:

Code:

#if(_WIN32_WINNT >= 0x0501)
#define WS_EX_COMPOSITED        0x02000000L
#endif /* _WIN32_WINNT >= 0x0501 */

So all you have to do is define _WIN32_WINNT as 0x0501 or greater. All this means is that WS_EX_COMPOSITED only works on XP and later.

Try defining
NTDDI_VERSION = NTDDI_WINXP
Or
_WIN32_WINNT = 0x0501
WINVER = 0x0501

Hopefully that should make it compile for XP+ only, without the need to copy the macros out of the header.

You need #define, since they are defines.
Like
#define NTDDI_VERSION NTDDI_WINXP