Paint BMP from another function

**Sober** · 04-26-2007

Hello my prob is as follows:

I need to paint an object to the window from anoher void function...and need to access the function at any given moment to paint only then and not when the window is loaded.SO I did create my function as follows:

Code:

void DrawBall(HWND hwnd)
{

           
           BITMAP bm;
            PAINTSTRUCT ps;
            RECT rcClient;
            HBITMAP hbmOld;
            HDC hdcMem;
    int  y_axis=10;
    int x_axis=40;       
             
             HDC hdc = BeginPaint(hwnd, &ps);

            hdcMem = CreateCompatibleDC(hdc);  
     
     
   for(i=1;i<=4;i++)
            {                
             hdcMem = CreateCompatibleDC(hdc);
             hbmOld = SelectObject(hdcMem, g_hbmimg[i]);
			 GetObject(g_hbmimg[i], sizeof(bm), &bm);
			 
              if (i==3)
              {
			    y_axis=380;
			    x_axis=-40;
               }
             
             BitBlt(hdc, x_axis*(i), y_axis,bm.bmWidth,bm.bmHeight, hdcMem, 0, 0, SRCAND);
             
             SelectObject(hdcMem, hbmOld);
			 DeleteDC(hdcMem);
            }
            EndPaint(hwnd, &ps);
}

and accessed it from my the case WM_PAINT: to try to paint it on load first..but the BMP wont be painted

btw I passed the hwnd so as to be able to paint on the window..
DrawBall(hwnd);

am I wrong ? or am I totally wrong?

Using DEV C++ and WIN XP

**pronecracker** · 04-26-2007

maybe something's wrong with the global bitmaps?

You waste some GDI resource by creating hdcMem twice, thereby losing the handle to the first dc created. This cannot be the main problem however.

**Sober** · 04-26-2007

The thing is, I just start Windows programming..two weeks ago. So am not quite well familiar with the functions am learning in fact by myself.So I came to wonder If I can update a BITMAP drawn or draw it once a control has been click for example..So I created the function void and placed the painting code there but it wont paint..unless the code is in the WM_PAINT case... any clue?

btw plz ignore my lame approach to masking using SRCAND....I didnt paste the complete code with masking...

**Sober** · 04-26-2007

aie..Yes ..its only now that I spotted that I created hdcMem twice ..but still....I'll try tomorrow, may be some sleep will help..

**novacain** · 04-26-2007

BeginPaint() can only be called in response to a WM_PAINT message.

To get your app to generate a WM_PAINT msg you use

Code:

//look up the params

InvalidateRect() //set the window and rectangle to repaint
UpdateWindow() //bypass the normal procedure (OS msg que) and send directly to app callback ie faster

In your code the rectangle to redraw will be empty and the HDC invalid

try

Code:

RECT      Rect;
SetRectEmpty(&Rect);
//before the BeginPaint
GetUpdateRect(hWnd,&Rect,FALSE);
if(IsRectEmpty(&Rect))
   return;//nothing to draw or send paint to get something to draw

**Queatrix** · 04-26-2007

Originally Posted by Sober

aie..Yes ..its only now that I spotted that I created hdcMem twice ..but still....I'll try tomorrow, may be some sleep will help..

Yeah, maybe you should "Sober" up some.

**Sober** · 05-01-2007

Hahahaha LOL yeah I did sober up the day after I posted the thread....and indeed I managed to solve the problem..anyway thx

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