uxtheme: Use TransparentBlt() for bitmaps with all alpha values being 0xff.

Wine-Bug: https://bugs.winehq.org/show_bug.cgi?id=51553Signed-off-by: Zhiyi Zhang <zzhang@codeweavers.com> Signed-off-by: Alexandre Julliard <julliard@winehq.org>

uxtheme: Use TransparentBlt() for bitmaps with all alpha values being 0xff.
96b7a8a3 · Zhiyi Zhang · Alexandre Julliard · ea430bf2 · 96b7a8a3
Commit 96b7a8a3 authored Aug 25, 2021 by Zhiyi Zhang Committed by Alexandre Julliard Aug 25, 2021
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Showing with 9 additions and 2 deletions

msstyles.c dlls/uxtheme/msstyles.c +9 -2

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--- a/dlls/uxtheme/msstyles.c
+++ b/dlls/uxtheme/msstyles.c
@@ -1072,11 +1072,18 @@ static BOOL prepare_alpha (HBITMAP bmp, BOOL* hasAlpha)
    if (!bmp || GetObjectW( bmp, sizeof(dib), &dib ) != sizeof(dib))
        return FALSE;

-    if(dib.dsBm.bmBitsPixel != 32)
+    if (dib.dsBm.bmBitsPixel != 32 || dib.dsBmih.biCompression != BI_RGB)
        /* nothing to do */
        return TRUE;

-    *hasAlpha = TRUE;
+    /* If all alpha values are 0xff, don't use alpha blending */
+    for (n = 0, p = dib.dsBm.bmBits; n < dib.dsBmih.biWidth * dib.dsBmih.biHeight; n++, p += 4)
+        if ((*hasAlpha = (p[3] != 0xff)))
+            break;
+
+    if (!*hasAlpha)
+        return TRUE;
+
    p = dib.dsBm.bmBits;
    n = dib.dsBmih.biHeight * dib.dsBmih.biWidth;
    /* AlphaBlend() wants premultiplied alpha, so do that now */