From e48433392638e92e8e0152debdf794ad8190a967 Mon Sep 17 00:00:00 2001
From: Vadim Zeitlin <vadim@wxwidgets.org>
Date: Sat, 11 Jan 2014 14:24:35 +0000
Subject: [PATCH] wxBitmap with cleared alpha channel doesn't keep its alpha
 flag any more.

Explicitly reset wxBitmap alpha flag after clearing its alpha channel to
ensure that we don't treat it as having alpha after going to all the trouble
of ensuring that it doesn't/

See #14403.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@75588 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
---
 include/wx/msw/bitmap.h | 3 ++-
 src/msw/bitmap.cpp      | 4 ++--
 src/msw/dc.cpp          | 5 +++++
 3 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/include/wx/msw/bitmap.h b/include/wx/msw/bitmap.h
index 4668eaf93f..09f9a85ce3 100644
--- a/include/wx/msw/bitmap.h
+++ b/include/wx/msw/bitmap.h
@@ -168,7 +168,8 @@ public:
     // these functions are internal and shouldn't be used, they risk to
     // disappear in the future
     bool HasAlpha() const;
-    void UseAlpha();
+    void UseAlpha(bool use = true);
+    void ResetAlpha() { UseAlpha(false); }
 
     // support for scaled bitmaps
     virtual double GetScaleFactor() const { return 1.0; }
diff --git a/src/msw/bitmap.cpp b/src/msw/bitmap.cpp
index cf30c16840..a702165509 100644
--- a/src/msw/bitmap.cpp
+++ b/src/msw/bitmap.cpp
@@ -1203,10 +1203,10 @@ wxDC *wxBitmap::GetSelectedInto() const
 #endif
 }
 
-void wxBitmap::UseAlpha()
+void wxBitmap::UseAlpha(bool use)
 {
     if ( GetBitmapData() )
-        GetBitmapData()->m_hasAlpha = true;
+        GetBitmapData()->m_hasAlpha = use;
 }
 
 bool wxBitmap::HasAlpha() const
diff --git a/src/msw/dc.cpp b/src/msw/dc.cpp
index 8df8d87545..891291fd12 100644
--- a/src/msw/dc.cpp
+++ b/src/msw/dc.cpp
@@ -2718,6 +2718,11 @@ static bool AlphaBlt(wxMSWDCImpl* dcDst,
                     }
                 }
 
+                // Using wxAlphaPixelData sets the internal "has alpha" flag
+                // which is usually what we need, but in this particular case
+                // we use it to get rid of alpha, not set it, so reset it back.
+                bmpOld.ResetAlpha();
+
                 dcDst->DoSelect(bmpOld);
             }