skins2: fix buttons and checkbox artefacts with animated images

If down or over images are missing, they default to the up image. Yet, in case
of animated images, the animation gets played leading to undesirable artefacts.

This patch adds a comparison operator for animated images and do not restart the
animation if they are alike.

modules/gui/skins2/controls/ctrl_button.cpp

@@ -140,6 +140,9 @@ void CtrlButton::setImage( AnimBitmap *pImg )
     if( pImg == m_pImg )
         return;
 
+    if( pImg && m_pImg && *pImg == *m_pImg )
+        return;
+
     AnimBitmap *pOldImg = m_pImg;
     m_pImg = pImg;
 

modules/gui/skins2/controls/ctrl_checkbox.cpp

@@ -167,6 +167,9 @@ void CtrlCheckbox::setImage( AnimBitmap *pImg )
     if( pImg == m_pImgCurrent )
         return;
 
+    if( pImg && m_pImgCurrent && *pImg == *m_pImgCurrent )
+        return;
+
     AnimBitmap *pOldImg = m_pImgCurrent;
     m_pImgCurrent = pImg;
 

modules/gui/skins2/src/anim_bitmap.cpp

@@ -121,3 +121,10 @@ void AnimBitmap::CmdNextFrame::execute()
     m_pParent->notify();
 }
 
+bool AnimBitmap::operator ==( const AnimBitmap& rOther ) const
+{
+    return &m_rBitmap == &rOther.m_rBitmap
+        && m_nbFrames == rOther.m_nbFrames
+        && m_frameRate == rOther.m_frameRate
+        && m_nbLoops == rOther.m_nbLoops;
+}

modules/gui/skins2/src/anim_bitmap.hpp

@@ -58,6 +58,9 @@ public:
     virtual int getWidth() const;
     virtual int getHeight() const;
 
+    /// compare two animated image
+    bool operator==( const AnimBitmap& other ) const;
+
 private:
     /// Bitmap stored
     const GenericBitmap &m_rBitmap;