Sign in to follow this  

noob GDI troubles

This topic is 4390 days old which is more than the 365 day threshold we allow for new replies. Please post a new topic.

If you intended to correct an error in the post then please contact us.

Recommended Posts

My program makes colored snow. It's just a learning tool. Anyway, when I move my program off screen, and then move it back into view.....the entire client window gets erased and the background brush is restored. I lose all the snow I made. How can I prevent that? Ideally, I want to save the client area and then restore it. I think I need to work with WM_PAINT, but I'm at a loss.
#define WIN32_LEAN_AND_MEAN   //restricts to API
#include <windows.h>		  //master Windows header
#include <stdio.h> 
#include <stdlib.h> 

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

const int xw = (640 + (GetSystemMetrics(SM_CXFIXEDFRAME)*2))+1,
		  yw = (480 + GetSystemMetrics(SM_CYCAPTION)+ (GetSystemMetrics(SM_CYFIXEDFRAME)*2)+ GetSystemMetrics(SM_CYMENU))+1;

int WINAPI WinMain (HINSTANCE hInstance, HINSTANCE hPrevInstance,
                    PSTR szCmdLine, int iCmdShow)
{
	 static TCHAR szAppName[] = TEXT ("PK");
     HWND         hwnd;
     MSG          msg;
	 WNDCLASSEX  wndclass;

	 wndclass.cbSize = sizeof(WNDCLASSEX);
	 wndclass.style = CS_OWNDC | CS_HREDRAW | CS_VREDRAW;
	 wndclass.lpfnWndProc = WndProc;
	 wndclass.cbClsExtra = 0;
	 wndclass.cbWndExtra = 0;
	 wndclass.hInstance = hInstance;
	 wndclass.hIcon = LoadIcon(NULL, IDI_APPLICATION);
	 wndclass.hCursor = LoadCursor(NULL, IDC_ARROW);
	 wndclass.hbrBackground = (HBRUSH) GetStockObject(WHITE_BRUSH);
	 wndclass.lpszMenuName = NULL;
	 wndclass.lpszClassName = szAppName;
	 wndclass.hIconSm = LoadIcon(NULL, IDI_APPLICATION);


     if (!RegisterClassEx (&wndclass))
     {
		return 0 ;
     }
     
     hwnd = CreateWindowEx(
	 NULL,
	 szAppName,
	 TEXT ("Photo Knight"),
	 WS_SYSMENU | WS_MINIMIZEBOX,
	 CW_USEDEFAULT,
	 CW_USEDEFAULT,
	 xw,
	 yw,
	 NULL,
	 NULL,
	 hInstance,
	 NULL);
     
     ShowWindow (hwnd, iCmdShow);
     UpdateWindow (hwnd);


 while(true)
 {
	 if(PeekMessage(&msg,NULL,0,0,PM_REMOVE))
	 {
		 if(msg.message == WM_QUIT)
		 {
			 break;
		 }
		 else
		 {
		 TranslateMessage(&msg);
		 DispatchMessage(&msg);
		 }
	 }
	 else
	 {
		 HDC hdc = GetDC(hwnd);
		 SetPixel(hdc,rand()%xw,rand()%yw,RGB(rand()%256,100,100));
		 ReleaseDC(hwnd,hdc);
	 }
	 }
 }

LRESULT CALLBACK WndProc (HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
    switch (message) 
    {
        case WM_CREATE:
			{
			return 0;
			}
			break;
        case WM_DESTROY:
			{
            PostQuitMessage(0); 
            return 0; 
			}
			break;
		case WM_PAINT:
			{
			PAINTSTRUCT ps;
			BeginPaint(hwnd, &ps);
			EndPaint(hwnd, &ps);
			return 0;
			}
		   break;
			
		default:
			{
			}
			break;
	}
    return DefWindowProc(hwnd, message, wParam, lParam); 
} 

Share this post


Link to post
Share on other sites

This topic is 4390 days old which is more than the 365 day threshold we allow for new replies. Please post a new topic.

If you intended to correct an error in the post then please contact us.

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

Sign in to follow this