Draw the selected bitmap correctly in wxMSW buttons.

Clear the previously drawn bitmap before drawing the new one.

Closes #12550.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@75664 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

docs/changes.txt

@@ -27,3 +27,4 @@ wxMSW:
 
 - Improve wxMimeTypesManager open command detection (Eric Jensen).
 - Make wxFILTER_INCLUDE_LIST in wxTextValidator actually usable.
+- Fix handling of selected images in wxBitmapButton (Artur Wieczorek).

src/msw/anybutton.cpp

@@ -1175,7 +1175,13 @@ bool wxAnyButton::MSWOnDraw(WXDRAWITEMSTRUCT *wxdis)
             }
         }
     }
-
+    else
+    {
+        // clear the background (and erase any previous bitmap)
+        COLORREF colBg = wxColourToRGB(GetBackgroundColour());
+        AutoHBRUSH hbrushBackground(colBg);
+        FillRect(hdc, &rectBtn, hbrushBackground);
+    }
 
     // draw the image, if any
     if ( m_imageData )