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.