user32: Don't try to alpha blend icons when drawing to a monochrome device.

dlls/user32/cursoricon.c

@@ -2054,12 +2054,22 @@ BOOL WINAPI DrawIconEx( HDC hdc, INT x0, INT y0, HICON hIcon,
 
     if (ptr->alpha && (flags & DI_IMAGE))
     {
-        BLENDFUNCTION pixelblend = { AC_SRC_OVER, 0, 255, AC_SRC_ALPHA };
+        BOOL is_mono = FALSE;
 
+        if (GetObjectType( hdc_dest ) == OBJ_MEMDC)
+        {
+            BITMAP bm;
+            HBITMAP bmp = GetCurrentObject( hdc_dest, OBJ_BITMAP );
+            is_mono = GetObjectW( bmp, sizeof(bm), &bm ) && bm.bmBitsPixel == 1;
+        }
+        if (!is_mono)
+        {
+            BLENDFUNCTION pixelblend = { AC_SRC_OVER, 0, 255, AC_SRC_ALPHA };
             SelectObject( hMemDC, ptr->alpha );
             if (GdiAlphaBlend( hdc_dest, x, y, cxWidth, cyWidth, hMemDC,
                                0, 0, ptr->width, ptr->height, pixelblend )) goto done;
         }
+    }
 
     if (flags & DI_MASK)
     {