I try paint on overlapped and child windows using WinApi. For overlapped is OK, but for WS_CHILD dirty/invalidate rect ps.rcPaint is always (0,0,0,0)
I add WS_OVERLAPPEDWINDOW to WS_CHILD window to better seeing. Pivotal is "if ((style & WS_CHILD) != 0) "
It is a Windows error?
#include <windows.h>
LRESULT CALLBACK WndProc(HWND hWnd,
UINT message,
WPARAM wParam,
LPARAM lParam);
int RegClass(HINSTANCE hInstance,LPCTSTR lpszClassName)
{
WNDCLASS wc;
wc.style = CS_HREDRAW | CS_VREDRAW | CS_DBLCLKS | CS_OWNDC;
wc.cbClsExtra = 0;
wc.cbWndExtra = 0;
wc.hInstance = hInstance;
wc.lpfnWndProc = WndProc;
wc.lpszClassName = (LPCTSTR)lpszClassName;
wc.lpszMenuName = (LPCTSTR)NULL;
wc.hbrBackground = (HBRUSH)(COLOR_WINDOW);
wc.hCursor = (HCURSOR)LoadCursor(NULL,IDC_CROSS);
wc.hIcon = (HICON)LoadIcon(NULL,IDI_APPLICATION);
return RegisterClass(&wc);
}
int WINAPI WinMain(HINSTANCE hInstance,
HINSTANCE hPrevInstance,
LPSTR lpCmdLine,
int nShowCmd)
{
HWND hWnd0, hWnd1;
MSG message;
static LPCTSTR lpszClName = L"Wnd Class";
static LPCTSTR lpszCl0Name = L"Child Class";
if(!RegClass(hInstance,lpszClName))
exit(0);
if(!RegClass(hInstance,lpszCl0Name))
exit(0);
hWnd0 = CreateWindow(
lpszClName,
L"Overlapped",
WS_OVERLAPPEDWINDOW | WS_VISIBLE,
CW_USEDEFAULT,
CW_USEDEFAULT,
800,
600,
0,
0,
hInstance,
NULL
);
hWnd1 = CreateWindow(
lpszClName,
L"Child",
WS_OVERLAPPEDWINDOW | WS_VISIBLE | WS_CHILD,
100,
100,
80,
60,
hWnd0,
0,
hInstance,
NULL
);
ShowWindow(hWnd0,SW_SHOWNORMAL);
UpdateWindow(hWnd0);
ShowWindow(hWnd1,SW_SHOWNORMAL);
UpdateWindow(hWnd1);
while (GetMessage(&message,0,0,0))
{
TranslateMessage(&message);
DispatchMessage(&message);
}
return message.wParam;
}
LRESULT CALLBACK WndProc(HWND hWnd,
UINT message,
WPARAM wParam,
LPARAM lParam)
{
switch (message) /* handle the messages */
{
case WM_DESTROY:
PostQuitMessage(0); /* send a WM_QUIT to the message queue */
break;
case WM_ERASEBKGND:
{
if (true)
{
PAINTSTRUCT ps;
HDC hdc = BeginPaint(hWnd, &ps);
HBRUSH hBrush = CreateSolidBrush(RGB(255, 0, 0));
unsigned style = GetWindowLong(hWnd, GWL_STYLE);
if ((style & WS_CHILD) != 0)
FillRect((HDC)wParam, &ps.rcPaint, hBrush);
DeleteObject(hBrush);
EndPaint(hWnd, &ps);
}
}
break;
default: /* for messages that we don't deal with */
return DefWindowProc(hWnd, message, wParam, lParam);
}
return 0;
}