Thread: New to Windows & C++ - InvalidateRect Problem

OK,
I'm making little excersizes for myself just to explore programming C++ in windows. I made a little app to show the mouse coordinates next to the cursor as I moved it but didn't like the way it made the entire screen flicker. So I decided to try giving InvalidateRect an hRgn. (type RECT)

The code below has been adjusted for testing. A rectangle appears at the mouse pointer. BUT it only seems to appear when the x and y coordinates are close to the same. So you get unearased fragments of the box from 0,0 and continuing 0+1, 0+1... etc in a diaginal line down the window?!?!

I read the technote on normalization of RECT and tried that with no positive results. Can anyone tell me what I'm missing?

Code:

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

		MoveToEx(hdc,0,0,NULL);
		LineTo(hdc,639,429);
		MoveToEx(hdc,300,0,NULL);

		LineTo(hdc,50,300);
		TextOut(hdc,120,30,"<- a few lines ->",17);

		Ellipse(hdc,250,250,450,450);
		TextOut(hdc,345,330,"Ellipse",7);

		Chord(hdc,550,20,630,80,555,25,625,70);
		TextOut(hdc,470,30," A Chord ->",11);

		Pie(hdc,300,50,400,150,300,50,300,100);
		TextOut(hdc,350,80,"<- A Pie Wedge", 14);

		Rectangle(hdc,550,300,700,400);
		TextOut(hdc,710,350,"<- A Rectangle",14);

		Rectangle(hdc,x,y,x+50,y+50);
//		TextOut(hdc,x+20,y,"X-",2);
//		TextOut(hdc,x+35,y,convertedX,(int)strlen(convertedX));
//		TextOut(hdc,x+20,y+20,"Y-",2);
//		TextOut(hdc,x+35,y+20,convertedY,(int)strlen(convertedY));

		ValidateRect(hWnd,NULL);
		EndPaint(hWnd,&ps);
		break;
	case WM_MOUSEMOVE:
		x=LOWORD(lParam);
		y=HIWORD(lParam);
		itoa(x,convertedX,10);
		itoa(y,convertedY,10);

// coords is of type RECT
		coords.left = y;
		coords.top = x;
		coords.bottom = x+40;
		coords.right = y+40;

		InvalidateRect(hWnd,&coords,TRUE);
		UpdateWindow(hWnd);
		break;

Is the RECT a static? (or it will have lost its value before the paint)

Don't need the ValidateRect(), BiginPaint() does that by default. Could use GetUpdateRect() before the BeginPaint().

Try setting the flag to FALSE in InvalidateRect() and not calling for a paint again straight after wards.

Or returning true to WM_ERASEBKGRD msg's.