tdf#92765: Show the real icon instead of a black square with gtk vclplug.

This partially brings back the behavior before
10a3db37.

Change-Id: I5b372ab56105c05dda6ecb9aa1eed1c6a0c72ea8
Reviewed-on: https://gerrit.libreoffice.org/17420Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Eike Rathke <erack@redhat.com>
Tested-by: Eike Rathke <erack@redhat.com>

vcl/unx/gtk/window/gtksalframe.cxx

@@ -1659,15 +1659,20 @@ bitmapToPixbuf( SalBitmap *pSalBitmap, SalBitmap *pSalAlpha )
         for( nX = 0; nX < pBitmap->mnWidth; nX++ )
         {
             BitmapColor aColor;
-            if (pBitmap->mnBitCount == 24)
+            if (pBitmap->mnFormat == BMP_FORMAT_24BIT_TC_BGR)
             {
-                pBitmap->maColorMask.GetColorFor24Bit(aColor, pData);
-                pData+=3;
+                aColor = BitmapColor(pData[2], pData[1], pData[0]);
+                pData += 3;
+            }
+            else if (pBitmap->mnFormat == BMP_FORMAT_24BIT_TC_RGB)
+            {
+                aColor = BitmapColor(pData[0], pData[1], pData[2]);
+                pData += 3;
             }
             else
             {
                 pBitmap->maColorMask.GetColorFor32Bit(aColor, pData);
-                pData+=4;
+                pData += 4;
             }
             *pDestData++ = aColor.GetRed();
             *pDestData++ = aColor.GetGreen();