[ros-dev] [gvg] 19895: Make sure that WM_NCPAINT messages aregenerated by calling BeginPaint

[Ge van Geldorp]

> From: Thomas Weidenmueller
> 
> Filip Navara wrote:
> > I overlooked that the code used GetUpdateRect with the last 
> > parameter set to FALSE, it should be set to TRUE. In that
> > case GetUpdateRect is responsible for sending the WM_NCPAINT
> > message and cleaning the update region.
> 
> No, that shouldn't be a problem. The last parameter just 
> specifies if the update region is supposed to be erased (by 
> sending a WM_ERASEBKGND message). It doesn't affect the 
> validation of update region at all.

According to MSDN, you're right, it doesn't mention GetUpdateRect sending a
WM_NCPAINT message. According to the attached test program (gcc -o
gurtest.exe gurtest.c -lgdi32, click inside the window to invalidate the
whole window), Filip is right and a WM_NCPAINT is actually sent from within
GetUpdateRect.

GvG
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#include <windows.h>
#include <stdio.h>
#include <tchar.h>

static LRESULT CALLBACK
MainWndProc(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam)
{
  PAINTSTRUCT ps;
  HDC hDC;
  LRESULT Result;
  RECT rc;

  switch(msg)
    {
    case WM_DESTROY:
      PostQuitMessage(0);
      Result = 0;
      break;

    case WM_NCPAINT:
      printf("received WM_NCPAINT\n");
      Result = DefWindowProc(hWnd, msg, wParam, lParam);
      break;

    case WM_PAINT:
      printf("Before GetUpdateRect\n");
      GetUpdateRect(hWnd, &rc, TRUE);
      printf("After GetUpdateRect\n");
      hDC = BeginPaint(hWnd, &ps);
      EndPaint (hWnd, &ps);
      Result = 0;
      break;

    case WM_LBUTTONDOWN:
      RedrawWindow(hWnd, NULL, NULL, RDW_INVALIDATE | RDW_FRAME);
      Result = 0;
      break;

    default:
      Result = DefWindowProc(hWnd, msg, wParam, lParam);
      break;
    }

  return Result;
}

int WINAPI
WinMain(HINSTANCE hInstance,
	HINSTANCE hPrevInstance,
	LPSTR lpszCmdLine,
	int nCmdShow)
{
  WNDCLASS wc;
  MSG msg;
  HWND hWnd;

  wc.lpszClassName = "GurTestClass";
  wc.lpfnWndProc = MainWndProc;
  wc.style = CS_VREDRAW | CS_HREDRAW;
  wc.hInstance = hInstance;
  wc.hIcon = LoadIcon(NULL, (LPCTSTR) IDI_APPLICATION);
  wc.hCursor = LoadCursor(NULL, (LPCTSTR) IDC_ARROW);
  wc.hbrBackground = (HBRUSH) GetStockObject(GRAY_BRUSH);
  wc.lpszMenuName = NULL;
  wc.cbClsExtra = 0;
  wc.cbWndExtra = 0;
  if (RegisterClass(&wc) == 0)
    {
      fprintf(stderr, "RegisterClass failed (last error 0x%lX)\n",
	      GetLastError());
      return(1);
    }

  hWnd = CreateWindow(_T("GurTestClass"),
                      _T("ReactOS test"),
                      WS_OVERLAPPEDWINDOW,
                      0, //Position; you can use CW_USEDEFAULT, too
                      0,
                      600, //height
                      400,
                      NULL,
                      NULL,
                      hInstance,
                      NULL);
  if (hWnd == NULL)
    {
      fprintf(stderr, "CreateWindow failed (last error 0x%lX)\n",
	      GetLastError());
      return(1);
    }

  ShowWindow(hWnd, nCmdShow);

  while(GetMessage(&msg, NULL, 0, 0))
  {
    TranslateMessage(&msg);
    DispatchMessage(&msg);
  }

  return msg.wParam;
}