Redrawing

**maxorator** · 10-27-2005

I want my program to draw a rectangle on the screen(HWND_DESKTOP), but when I make it redraw it in a while:

Code:

while(1==1){
Rectangle(hdc,48,48,102,77);
}

With this code the borders like flash a bit. But how I can make it redraw my rectangle on the screen only when it is necessary(if something overdraws it).

**rockytriton** · 10-27-2005

put your drawing code in a WM_PAINT handler, if you are doing the paint handler for a window in another process, you may need to write a windows hook DLL and insert it into that process, I assume that's what you mean when you say you are drawing on HWND_DESKTOP.

**maxorator** · 10-28-2005

Well, I don't really know how to make a windows hook DLL...
And it flashes even worse, when I use it in a normal window in a wm_paint:

Code:

#include <windows.h>
LRESULT CALLBACK WindowProcedure (HWND, UINT, WPARAM, LPARAM);
HDC hdc;
RECT rc;
char szClassName[ ] = "WindowsApp";
int WINAPI WinMain (HINSTANCE hThisInstance,
                    HINSTANCE hPrevInstance,
                    LPSTR lpszArgument,
                    int nFunsterStil)

{
    HWND hwnd;
    MSG messages;
    WNDCLASSEX wincl;

    wincl.hInstance = hThisInstance;
    wincl.lpszClassName = szClassName;
    wincl.lpfnWndProc = WindowProcedure;
    wincl.style = CS_DBLCLKS;
    wincl.cbSize = sizeof (WNDCLASSEX);

    wincl.hIcon = LoadIcon (NULL, IDI_APPLICATION);
    wincl.hIconSm = LoadIcon (NULL, IDI_APPLICATION);
    wincl.hCursor = LoadCursor (NULL, IDC_ARROW);
    wincl.lpszMenuName = NULL;
    wincl.cbClsExtra = 0;
    wincl.cbWndExtra = 0;
    wincl.hbrBackground = (HBRUSH) COLOR_BACKGROUND;

    if (!RegisterClassEx (&wincl))
        return 0;

    hwnd = CreateWindowEx (
           0,
           szClassName,
           "Windows App",
           WS_OVERLAPPEDWINDOW,
           CW_USEDEFAULT,
           CW_USEDEFAULT,
           544,
           375, 
           HWND_DESKTOP,
           NULL,
           hThisInstance,
           NULL
           );

    ShowWindow (hwnd, nFunsterStil);
    while (GetMessage (&messages, NULL, 0, 0))
    {
        TranslateMessage(&messages);
        DispatchMessage(&messages);
    }
    return messages.wParam;
}

LRESULT CALLBACK WindowProcedure (HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
    switch (message)
    {
        case WM_PAINT:
            hdc = GetDC(hwnd);
            rc.left = 51;
            rc.top = 53;
            rc.right = 137;
            rc.bottom = 76;
            Rectangle(hdc,48,48,140,77);
            DrawText(hdc,"Garfield rules",14,&rc,DT_CENTER|DT_NOCLIP);
            ReleaseDC(hwnd, hdc);
            break;
        case WM_DESTROY:
            PostQuitMessage (0);
            break;
        default:
            return DefWindowProc (hwnd, message, wParam, lParam);
    }

    return 0;
}

My actual code was:

Code:

#include <windows.h>
HDC hdc;
RECT rc;
int WINAPI WinMain (HINSTANCE hThisInstance,
                    HINSTANCE hPrevInstance,
                    LPSTR lpszArgument,
                    int nFunsterStil)

{
hdc = GetDC(HWND_DESKTOP);
rc.left = 51;
rc.top = 53;
rc.right = 137;
rc.bottom = 76;
while(1==1){
Rectangle(hdc,48,48,140,77);
DrawText(hdc,"Garfield rules",14,&rc,DT_CENTER|DT_NOCLIP);
Sleep(1);
}
ReleaseDC(HWND_DESKTOP, hdc);
return 0;
}

**bithub** · 10-28-2005

Change code to:

Code:

LRESULT CALLBACK WindowProcedure (HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
	switch (message)
	{
	case WM_PAINT:
	{
		PAINTSTRUCT ps;
		hdc = BeginPaint(hwnd,&ps);
		rc.left = 51;
		rc.top = 53;
		rc.right = 137;
		rc.bottom = 76;
		Rectangle(hdc,48,48,140,77);
		DrawText(hdc,"Garfield rules",14,&rc,DT_CENTER|DT_NOCLIP);
		EndPaint(hwnd,&ps);
		break;
	}
	// ...

**maxorator** · 11-04-2005

But does anybody have a good link for a hook dll example?

**cdave** · 11-05-2005

Originally Posted by maxorator

But does anybody have a good link for a hook dll example?

This looks like a good (simple) tutorial, although I have not run the code.

Tutorial - Keyboard Hook
http://www.ragestorm.net/tutorial?id=10

**maxorator** · 11-05-2005

Thanks

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