Win32 - cannot trigger WM_PAINT message with RedrawWindow() - c++

Question

I am trying to trigger a WM_PAINT message form WM_TIMER; the timer works, but RedrawWindow() function does not seem to do anything. What am I doing wrong?
Here is my Callback function:
LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
int wmId, wmEvent;
PAINTSTRUCT ps;
HDC hdc;
PAINTSTRUCT Ps;
COLORREF clrBlue = RGB(25, 55, 200);
RECT Recto = { 20, 28, 188, 128 };
COLORREF clrAqua = RGB(128, 255, 255);
COLORREF clrRed = RGB(255, 25, 5);
static bool x = true;
switch (message)
{
case WM_COMMAND:
wmId = LOWORD(wParam);
wmEvent = HIWORD(wParam);
// Parse the menu selections:
switch (wmId)
{
case IDM_ABOUT:
DialogBox(hInst, MAKEINTRESOURCE(IDD_ABOUTBOX), hWnd, About);
break;
case IDM_EXIT:
DestroyWindow(hWnd);
break;
default:
return DefWindowProc(hWnd, message, wParam, lParam);
}
break;
case WM_TIMER:
//InvalidateRect(hWnd ,NULL , FALSE);
//RedrawWindow(hWnd , NULL , NULL , RDW_INVALIDATE);
RedrawWindow(hWnd,NULL,NULL,RDW_INTERNALPAINT);
break;
case WM_PAINT:
if(x)
{
hdc = BeginPaint(hWnd, &ps);
SetTextColor(hdc, clrRed);
TextOut(hdc, 50, 42, L"Some text", 13);
EndPaint(hWnd, &ps);
toggle(x);
}
else
{
hdc = BeginPaint(hWnd, &ps);
SetTextColor(hdc, clrRed);
TextOut(hdc, 50, 42, L"Another text", 13);
EndPaint(hWnd, &ps);
toggle(x);
}
break;
case WM_DESTROY:
PostQuitMessage(0);
break;
default:
return DefWindowProc(hWnd, message, wParam, lParam);
}
return 0;
}

Answer 1

As x is defined as a local variable in your function, it always gets the value true when the function is called. That is, the code in WM_PAINT never gets to the else branch of the if.
Try, for example, changing the definition of x to static bool x = true; to get the toggling work.
Additionally, you need to invalidate the window's contents to get it redrawn:
RedrawWindow(hWnd,NULL,NULL,RDW_INVALIDATE | RDW_INTERNALPAINT);