Bring wxMSW wxBitmap::SetBitmapXXX(wxBitmap()) in line with wxGTK.

Remove or reset the corresponding bitmap if the provided one is invalid
instead of asserting, this is what wxGTK does and this behaviour seems to be
more useful.

Also document this behaviour as it's now implemented in both wxMSW and wxGTK.

Closes #13569.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/branches/WX_3_0_BRANCH@76404 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

docs/changes.txt

@@ -646,6 +646,7 @@ wxMSW:
 - Fix loading of top to bottom BMP files in wxBitmap (Artur Wieczorek).
 - Fix resource leak in wxStaticBitmap with RGBA icons (Artur Wieczorek).
 - Fix toolbar repainting after deleting a tool from it (Artur Wieczorek).
+- Allow resetting bitmaps used in wxButton (Artur Wieczorek).
 - Fix handling of deleting directories in wxFileSystemWatcher (Eric Raijmakers).
 - Disable the use of new style wxDirDialog under Vista to work around a bug in
   its implementation under this system (jtrauntvein).

interface/wx/anybutton.h

@@ -102,9 +102,8 @@ public:
         states.
 
         @param bitmap
-            The bitmap to display in the button. Under wxGTK the bitmap can be
-            invalid to remove the currently displayed bitmap, however this is
-            not supported in wxMSW currently.
+            The bitmap to display in the button. If the bitmap is invalid, any
+            currently shown bitmaps are removed from the button.
         @param dir
             The position of the bitmap inside the button. By default it is
             positioned to the left of the text, near to the left button border.
@@ -119,6 +118,9 @@ public:
     /**
         Sets the bitmap to be shown when the mouse is over the button.
 
+        If @a bitmap is invalid, the normal bitmap will be used in the current
+        state.
+
         @see GetBitmapCurrent()
 
         @since 2.9.1 (available as wxBitmapButton::SetBitmapHover() in previous
@@ -129,6 +131,12 @@ public:
     /**
         Sets the bitmap for the disabled button appearance.
 
+        If @a bitmap is invalid, the disabled bitmap is set to the
+        automatically generated greyed out version of the normal bitmap, i.e.
+        the same bitmap as is used by default if this method is not called at
+        all. Use SetBitmap() with an invalid bitmap to remove the bitmap
+        completely (for all states).
+
         @see GetBitmapDisabled(), SetBitmapLabel(),
              SetBitmapPressed(), SetBitmapFocus()
 
@@ -140,6 +148,9 @@ public:
         Sets the bitmap for the button appearance when it has the keyboard
         focus.
 
+        If @a bitmap is invalid, the normal bitmap will be used in the focused
+        state.
+
         @see GetBitmapFocus(), SetBitmapLabel(),
              SetBitmapPressed(), SetBitmapDisabled()
 

src/msw/anybutton.cpp

@@ -671,6 +671,31 @@ wxBitmap wxAnyButton::DoGetBitmap(State which) const
 
 void wxAnyButton::DoSetBitmap(const wxBitmap& bitmap, State which)
 {
+    if ( !bitmap.IsOk() )
+    {
+        if ( m_imageData  )
+        {
+            // Normal image is special: setting it enables images for the
+            // button and resetting it to nothing disables all of them.
+            if ( which == State_Normal )
+            {
+                delete m_imageData;
+                m_imageData = NULL;
+            }
+            else
+            {
+                // Replace the removed bitmap with the normal one.
+                wxBitmap bmpNormal = m_imageData->GetBitmap(State_Normal);
+                m_imageData->SetBitmap(which == State_Disabled
+                                            ? bmpNormal.ConvertToDisabled()
+                                            : bmpNormal,
+                                       which);
+            }
+        }
+
+        return;
+    }
+
 #if wxUSE_UXTHEME
     wxXPButtonImageData *oldData = NULL;
 #endif // wxUSE_UXTHEME
@@ -757,8 +782,7 @@ void wxAnyButton::DoSetBitmapMargins(wxCoord x, wxCoord y)
 
 void wxAnyButton::DoSetBitmapPosition(wxDirection dir)
 {
-    wxCHECK_RET( m_imageData, "SetBitmap() must be called first" );
-
+    if ( m_imageData )
         m_imageData->SetBitmapPosition(dir);
     InvalidateBestSize();
 }