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ShadowAtNight
01-07-2016, 02:10 AM
'm using Windows XP with a pretty old Intel video adapter (82945G). It supports OpenGL 1.1.
There is a simple OpenGL application. It processes WM_PAINT message and draws the scene.
The problem is that when I press the Start button the window gets completely erased. Some rubbish appears there. The same situation is happening when I hover cursor on close button and a tooltip appears.
I have checked that the application receives no messages during that. Something makes me think that windows just repaints desktop and erases my window. How could I avoid that?
Run the application. Make sure that window is on the desktop. Resize it a bit. the press start button or hover cursor over close button and waint until tooltip appear.
Here is a source code:



#include <stdio.h>
#include <windows.h>
#include <gl\gl.h>
#include <gl\glu.h>

HDC hDC=NULL;
HGLRC hRC=NULL;
HWND hWnd=NULL;
HINSTANCE hInstance;

bool keys[256];
bool active=TRUE;
bool fullscreen=TRUE;

LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);

GLvoid ReSizeGLScene(GLsizei width, GLsizei height)
{
if (height==0)height=1;

glViewport(0,0,width,height);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluPerspective(45.0f,(GLfloat)width/(GLfloat)height,0.1f,100.0f);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
}

int InitGL(GLvoid)
{
glShadeModel(GL_SMOOTH);
glClearColor(0.0f, 0.0f, 0.0f, 0.5f);
glClearDepth(1.0f);
glEnable(GL_DEPTH_TEST);
glDepthFunc(GL_LEQUAL);
glHint(GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST);
return TRUE;
}

int DrawGLScene(GLvoid)
{
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glLoadIdentity();
return TRUE;
}

BOOL CreateGLWindow(char* title, int width, int height, int bits, bool fullscreenflag)
{
GLuint PixelFormat;
WNDCLASS wc;
DWORD dwExStyle;
DWORD dwStyle;
RECT WindowRect;
WindowRect.left=(long)0;
WindowRect.right=(long)width;
WindowRect.top=(long)0;
WindowRect.bottom=(long)height;
fullscreen=fullscreenflag;

hInstance = GetModuleHandle(NULL);
wc.style = CS_HREDRAW | CS_VREDRAW | CS_OWNDC;
wc.lpfnWndProc = (WNDPROC) WndProc;
wc.cbClsExtra = 0;
wc.cbWndExtra = 0;
wc.hInstance = hInstance;
wc.hIcon = LoadIcon(NULL, IDI_WINLOGO);
wc.hCursor = LoadCursor(NULL, IDC_ARROW);
wc.hbrBackground = NULL;
wc.lpszMenuName = NULL;
wc.lpszClassName = "OpenGL";

if (!RegisterClass(&wc))
{
MessageBox(NULL,"Failed To Register The Window Class.","ERROR",MB_OK|MB_ICONEXCLAMATION);
return FALSE;
}

dwExStyle=WS_EX_APPWINDOW | WS_EX_WINDOWEDGE;
dwStyle=WS_OVERLAPPEDWINDOW;

AdjustWindowRectEx(&WindowRect, dwStyle, FALSE, dwExStyle);

// Create The Window
if (!(hWnd=CreateWindowEx( dwExStyle,"OpenGL", title,dwStyle |
WS_CLIPSIBLINGS |WS_CLIPCHILDREN,0, 0,WindowRect.right-WindowRect.left,
WindowRect.bottom-
WindowRect.top,NULL,NULL,hInstance,NULL)))return FALSE;

static PIXELFORMATDESCRIPTOR pfd=
{
sizeof(PIXELFORMATDESCRIPTOR),
1,
PFD_DRAW_TO_WINDOW |
PFD_SUPPORT_OPENGL |
PFD_DOUBLEBUFFER,
PFD_TYPE_RGBA,
bits,
0, 0, 0, 0, 0, 0,
0,
0,
0,
0, 0, 0, 0,
16,
0,
0,
PFD_MAIN_PLANE,
0,
0, 0, 0
};

if (!(hDC=GetDC(hWnd))) return FALSE;
if (!(PixelFormat=ChoosePixelFormat(hDC,&pfd))) return FALSE;
if(!SetPixelFormat(hDC,PixelFormat,&pfd))return FALSE;
if (!(hRC=wglCreateContext(hDC)))return FALSE;
if(!wglMakeCurrent(hDC,hRC))return FALSE;
ShowWindow(hWnd,SW_SHOW);
SetForegroundWindow(hWnd);
SetFocus(hWnd);
ReSizeGLScene(width, height);
if (!InitGL())return FALSE;
return TRUE;
}

LRESULT CALLBACK WndProc( HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
{
wchar_t buffer[256];
swprintf(buffer,L"message is: %d\n");
OutputDebugStringW(buffer);
switch (uMsg)
{
case WM_SIZE:
{
ReSizeGLScene(LOWORD(lParam),HIWORD(lParam));
return 0;
}
case WM_PAINT:
{
DrawGLScene();
SwapBuffers(hDC);
RECT rect;
GetClientRect(hWnd,&rect);
ValidateRect(hWnd,&rect);
return 0;
}
}
return DefWindowProc(hWnd,uMsg,wParam,lParam);
}

int WINAPI WinMain( HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow)
{
MSG msg;
BOOL done=FALSE;
fullscreen=FALSE;
CreateGLWindow("NeHe's OpenGL Framework",640,480,16,fullscreen);
while(GetMessage(&msg,NULL,0,0))
{
TranslateMessage(&msg);
DispatchMessage(&msg);
}

return 0;
}

I found that when i put the window upon another window which is repainted constantly my window is got repainted also.