Extend wxBannerWindow background bitmap if necessary.

Ensure that the entire banner window uses the same background colour as the
bitmap, even when the bitmap is too small for the window size. This allows to
avoid using huge bitmaps if extending the bitmap with solid colour looks good
enough.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@69859 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/generic/bannerwindow.cpp

@@ -79,6 +79,8 @@ void wxBannerWindow::SetBitmap(const wxBitmap& bmp)
 {
     m_bitmap = bmp;
 
+    m_colBitmapBg = wxColour();
+
     InvalidateBestSize();
 
     Refresh();
@@ -202,24 +204,43 @@ void wxBannerWindow::OnPaint(wxPaintEvent& WXUNUSED(event))
     }
 }
 
-void wxBannerWindow::DrawBitmapBackground(wxDC& dc)
+wxColour wxBannerWindow::GetBitmapBg()
 {
+    if ( m_colBitmapBg.IsOk() )
+        return m_colBitmapBg;
+
+    // Determine the colour to use to extend the bitmap. It's the colour of the
+    // bitmap pixels at the edge closest to the area where it can be extended.
+    wxImage image(m_bitmap.ConvertToImage());
+
+    // The point we get the colour from. The choice is arbitrary and in general
+    // the bitmap should have the same colour on the entire edge of this point
+    // for extending it to look good.
+    wxPoint p;
+
+    wxSize size = image.GetSize();
+    size.x--;
+    size.y--;
+
     switch ( m_direction )
     {
         case wxTOP:
         case wxBOTTOM:
-        case wxRIGHT:
-            // Draw the bitmap normally, its rightmost or bottom part could be
-            // truncated, as it's meant to be.
-            dc.DrawBitmap(m_bitmap, 0, 0);
+            // The bitmap will be extended to the right.
+            p.x = size.x;
+            p.y = 0;
             break;
 
         case wxLEFT:
-            // The top most part of the bitmap may be truncated but its bottom
-            // must be always visible so intentionally draw it possibly partly
-            // outside of the window.
-            dc.DrawBitmap(m_bitmap,
-                          0, GetClientSize().y - m_bitmap.GetHeight());
+            // The bitmap will be extended from the top.
+            p.x = 0;
+            p.y = 0;
+            break;
+
+        case wxRIGHT:
+            // The bitmap will be extended to the bottom.
+            p.x = 0;
+            p.y = size.y;
             break;
 
         // This case is there only to prevent g++ warnings about not handling
@@ -227,6 +248,67 @@ void wxBannerWindow::DrawBitmapBackground(wxDC& dc)
         case wxALL:
             wxFAIL_MSG( wxS("Unreachable") );
     }
+
+    m_colBitmapBg.Set(image.GetRed(p.x, p.y),
+                      image.GetGreen(p.x, p.y),
+                      image.GetBlue(p.x, p.y));
+
+    return m_colBitmapBg;
+}
+
+void wxBannerWindow::DrawBitmapBackground(wxDC& dc)
+{
+    // We may need to fill the part of the background not covered by the bitmap
+    // with the solid colour extending the bitmap, this rectangle will hold the
+    // area to be filled (which could be empty if the bitmap is big enough).
+    wxRect rectSolid;
+
+    const wxSize size = GetClientSize();
+
+    switch ( m_direction )
+    {
+        case wxTOP:
+        case wxBOTTOM:
+            // Draw the bitmap at the origin, its rightmost could be truncated,
+            // as it's meant to be.
+            dc.DrawBitmap(m_bitmap, 0, 0);
+
+            rectSolid.x = m_bitmap.GetWidth();
+            rectSolid.width = size.x - rectSolid.x;
+            rectSolid.height = size.y;
+            break;
+
+        case wxLEFT:
+            // The top most part of the bitmap may be truncated but its bottom
+            // must be always visible so intentionally draw it possibly partly
+            // outside of the window.
+            rectSolid.width = size.x;
+            rectSolid.height = size.y - m_bitmap.GetHeight();
+            dc.DrawBitmap(m_bitmap, 0, rectSolid.height);
+            break;
+
+        case wxRIGHT:
+            // Draw the bitmap at the origin, possibly truncating its
+            // bottommost part.
+            dc.DrawBitmap(m_bitmap, 0, 0);
+
+            rectSolid.y = m_bitmap.GetHeight();
+            rectSolid.height = size.y - rectSolid.y;
+            rectSolid.width = size.x;
+            break;
+
+        // This case is there only to prevent g++ warnings about not handling
+        // some enum elements in the switch, it can't really happen.
+        case wxALL:
+            wxFAIL_MSG( wxS("Unreachable") );
+    }
+
+    if ( rectSolid.width > 0 && rectSolid.height > 0 )
+    {
+        dc.SetPen(*wxTRANSPARENT_PEN);
+        dc.SetBrush(GetBitmapBg());
+        dc.DrawRectangle(rectSolid);
+    }
 }
 
 void