Low-Level DigitalPaint: Processing the Window Activation Messages

This tutorial is giving an example on how to process the window activation messages:

Start with the project you created in Low-Level DigitalPaint: Drawing Text.

1. Add the following function before the OnOpen function definition:

   static L_VOID OnActivate 
   ( 
   HWND hWnd, 
   pPAINTHANDLE pPaint, 
   pBITMAPHANDLE pBitmap, 
   HPALETTE hPalette, 
   L_INT nZoom, 
   L_INT nHScroll, 
   L_INT nVScroll 
   ) 
   { 
      PAINTXFORM XForm ; 
      HDC hdcCompatibility ; 
      RECT rcDCRect ; 
      //set the painting toolkit data 
      hdcCompatibility = GetDC ( hWnd ) ; 
      L_PntSetMetrics ( pPaint, hdcCompatibility, pBitmap, hPalette ) ; 
      ReleaseDC ( hWnd, hdcCompatibility ) ; 
      XForm.nZoom    = nZoom ; 
      XForm.nXOffset = nHScroll ; 
      XForm.nYOffset = nVScroll ; 
      L_PntSetTransformation ( pPaint, &XForm ) ; 
      GetClientRect ( hWnd, &rcDCRect ) ; 
      L_PntSetDCExtents ( pPaint, &rcDCRect ) ; 
   } 

2. Add the following line after the "break;" statement of the "case WM_PAINT:" statement:

   case WM_ACTIVATE: 
   if ( WA_INACTIVE != LOWORD ( wParam ) ) 
   { 
      HDC hDC = GetDC(hWnd); 
      HPALETTE hPalette = L_CreatePaintPalette(hDC, &hBitmap); 
      OnActivate ( hWnd, pPaint, &hBitmap, hPalette, nZoomFactor, nHScroll, nVScroll ) ; 
      if(hPalette) 
         DeleteObject(hPalette); 
      ReleaseDC(hWnd, hDC); 
      return 0 ; 
   } 

3. Compile and run the project by selecting Build->Execute tutorial.exe from the menu.