Use high quality in wxBitmap::Rescale()

This function is currently used for relatively small icons in
wxArtProvider and wxSearchCtrl, so it shouldn't be a problem to use
wxIMAGE_QUALITY_HIGH from performance point of view and if it ever does
become a problem, the application could easily use wxImage::Rescale()
with a different option directly instead.

interface/wx/bitmap.h

@@ -685,8 +685,13 @@ public:
     /**
         Rescale the given bitmap to the requested size.
 
-        This function uses wxImage::Rescale() to resize the given @a bmp to the
-        requested size. Both the bitmap itself and size must be valid.
+        This function is just a convenient wrapper for wxImage::Rescale() used
+        to resize the given @a bmp to the requested size. If you need more
+        control over resizing, e.g. to specify the quality option different
+        from ::wxIMAGE_QUALITY_HIGH used by default, please use wxImage
+        function directly instead.
+
+        Both the bitmap itself and size must be valid.
 
         @since 3.1.6
      */

src/common/bmpbase.cpp

@@ -71,7 +71,7 @@ void wxBitmapHelpers::Rescale(wxBitmap& bmp, const wxSize& sizeNeeded)
 
 #if wxUSE_IMAGE
     wxImage img = bmp.ConvertToImage();
-    img.Rescale(sizeNeeded.x, sizeNeeded.y);
+    img.Rescale(sizeNeeded.x, sizeNeeded.y, wxIMAGE_QUALITY_HIGH);
     bmp = wxBitmap(img);
 #else // !wxUSE_IMAGE
     // Fallback method of scaling the bitmap