Redrawing

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).

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.

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:

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#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;
}

---

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;
        }
        // ...

---

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

Quote:

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Originally Posted by maxorator

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

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

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

Thanks