[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 
---
 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:

[Alexandre Julliard]

Dmitry Timoshkov  writes:
> 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 );

Rows need to be 32-bit aligned. I expect it would also cause less code
duplication to directly create a 1-bpp bitmap.

[Dmitry Timoshkov]

Alexandre Julliard  wrote:
> > - 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 );
>
> Rows need to be 32-bit aligned.

Well spotted, thanks.
> I expect it would also cause less code
> duplication to directly create a 1-bpp bitmap.

What kind of code duplication do you have in mind?

[Alexandre Julliard]

Dmitry Timoshkov  writes:
> Alexandre Julliard  wrote:
> > > - 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 );
> >
> > Rows need to be 32-bit aligned.
>
> Well spotted, thanks.
> > I expect it would also cause less code
> > duplication to directly create a 1-bpp bitmap.
>
> What kind of code duplication do you have in mind?

The duplicate setting of biBitCount and the StretchDIBits call. If you
generate a 1-bpp mask you can get rid of all that and simply fall
through to the normal code path.

[Dmitry Timoshkov]

Alexandre Julliard  wrote:
> > > I expect it would also cause less code
> > > duplication to directly create a 1-bpp bitmap.
> >
> > What kind of code duplication do you have in mind?
>
> The duplicate setting of biBitCount and the StretchDIBits call. If you
> generate a 1-bpp mask you can get rid of all that and simply fall
> through to the normal code path.

With the setting of biBitCount and the StretchDIBits call it's still going
to be considerably less code than the 1-bpp mask generarion from the 32-bpp
RGBA bitmap.

[Alexandre Julliard]

Dmitry Timoshkov  writes:
> Alexandre Julliard  wrote:
> > > > I expect it would also cause less code
> > > > duplication to directly create a 1-bpp bitmap.
> > >
> > > What kind of code duplication do you have in mind?
> >
> > The duplicate setting of biBitCount and the StretchDIBits call. If you
> > generate a 1-bpp mask you can get rid of all that and simply fall
> > through to the normal code path.
>
> With the setting of biBitCount and the StretchDIBits call it's still going
> to be considerably less code than the 1-bpp mask generarion from the 32-bpp
> RGBA bitmap.

I don't see why, it should be about the same amount of code as an 8-bpp
mask, with just a couple of extra shifts and masks.