[PATCH] user32: Create a mask from alpha channel when loading a 32 bpp icon. (v3)

[Dmitry Timoshkov]

This patch fixes applications that draws 32 bpp icons manually.

v3: create 8-bit intermediate mask from alpha instead of 32-bit.

Signed-off-by: Dmitry Timoshkov <dmitry at baikal.ru>
---
 dlls/user32/cursoricon.c | 35 +++++++++++++++++++++++++++++++++++
 1 file changed, 35 insertions(+)

diff --git a/dlls/user32/cursoricon.c b/dlls/user32/cursoricon.c
index 0adb73bf56..5d63a42373 100644
--- a/dlls/user32/cursoricon.c
+++ b/dlls/user32/cursoricon.c
@@ -1296,6 +1296,41 @@ static HICON create_icon_from_bmi( const BITMAPINFO *bmi, DWORD maxsize, HMODULE
                        0, 0, bmi_width, bmi_height,
                        mask_bits, bmi_copy, DIB_RGB_COLORS, SRCCOPY );
     }
+    else
+    {
+        if (bmi_has_alpha( bmi, color_bits ))
+        {
+            DWORD alpha_mask_bits_size = bmi_width * bmi_height;
+            unsigned char *alpha_mask_bits = HeapAlloc( GetProcessHeap(), 0, alpha_mask_bits_size );
+
+            if (alpha_mask_bits)
+            {
+                const unsigned char *src = color_bits;
+                unsigned char *dst = alpha_mask_bits;
+
+                while (alpha_mask_bits_size--)
+                {
+                    *dst++ = src[3] == 0xff ? 0 : 1;
+                    src += 4;
+                }
+
+                /* DIB palette and color count are already initialized correctly
+                 * for the monochrome case, so just correct the bit depth.
+                 */
+                if (bmi_copy->bmiHeader.biSize != sizeof(BITMAPCOREHEADER))
+                    bmi_copy->bmiHeader.biBitCount = 8;
+                else
+                    ((BITMAPCOREINFO *)bmi_copy)->bmciHeader.bcBitCount = 8;
+
+                SelectObject( hdc, mask );
+                StretchDIBits( hdc, 0, 0, width, height,
+                               0, 0, bmi_width, bmi_height,
+                               alpha_mask_bits, bmi_copy, DIB_RGB_COLORS, SRCCOPY );
+
+                HeapFree( GetProcessHeap(), 0, alpha_mask_bits );
+            }
+        }
+    }
     ret = TRUE;
 
 done:
-- 
2.17.1