Factor out duplicated code for bitmap scaling in wxArtProvider.

Move duplicated code responsible for rescaling bitmaps in wxArtProvider to the
shared wxArtPrvider::RescaleBitmap() method.

Additionally, make this new method work even in wxUSE_IMAGE==0 case.

See #17071.

See https://github.com/wxWidgets/wxWidgets/pull/64.

include/wx/artprov.h

@@ -188,6 +188,9 @@ public:
     // the topmost provider if platform_dependent = false
     static wxSize GetSizeHint(const wxArtClient& client, bool platform_dependent = false);
 
+    // Rescale bitmap (used internally if requested size is other than the available).
+    static void RescaleBitmap(wxBitmap& bmp, const wxSize& sizeNeeded);
+
 protected:
     friend class wxArtProviderModule;
 #if wxUSE_ARTPROVIDER_STD

src/common/artprov.cpp

@@ -212,6 +212,29 @@ wxArtProvider::~wxArtProvider()
 // wxArtProvider: retrieving bitmaps/icons
 // ----------------------------------------------------------------------------
 
+void wxArtProvider::RescaleBitmap(wxBitmap& bmp, const wxSize& sizeNeeded)
+{
+    wxCHECK_RET( sizeNeeded.IsFullySpecified(), wxS("New size must be given") );
+
+#if wxUSE_IMAGE
+    wxImage img = bmp.ConvertToImage();
+    img.Rescale(sizeNeeded.x, sizeNeeded.y);
+    bmp = wxBitmap(img);
+#else // !wxUSE_IMAGE
+    // Fallback method of scaling the bitmap
+    wxBitmap newBmp(sizeNeeded);
+    newBmp.UseAlpha(bmp.HasAlpha());
+    {
+        wxMemoryDC dc(newBmp);
+        double scX = (double)sizeNeeded.GetWidth() / bmp.GetWidth();
+        double scY = (double)sizeNeeded.GetHeight() / bmp.GetHeight();
+        dc.SetUserScale(scX, scY);
+        dc.DrawBitmap(bmp, 0, 0);
+    }
+    bmp = newBmp;
+#endif // wxUSE_IMAGE/!wxUSE_IMAGE
+}
+
 /*static*/ wxBitmap wxArtProvider::GetBitmap(const wxArtID& id,
                                              const wxArtClient& client,
                                              const wxSize& size)
@@ -256,17 +279,13 @@ wxArtProvider::~wxArtProvider()
         }
 
         // if we didn't get the correct size, resize the bitmap
-#if wxUSE_IMAGE && (!defined(__WXMSW__) || wxUSE_WXDIB)
         if ( bmp.IsOk() && sizeNeeded != wxDefaultSize )
         {
             if ( bmp.GetSize() != sizeNeeded )
             {
-                wxImage img = bmp.ConvertToImage();
+                RescaleBitmap(bmp, sizeNeeded);
-                img.Rescale(sizeNeeded.x, sizeNeeded.y);
-                bmp = wxBitmap(img);
             }
         }
-#endif // wxUSE_IMAGE
 
         sm_cache->PutBitmap(hashId, bmp);
     }

src/generic/datavgen.cpp

@@ -570,7 +570,7 @@ public:
     void Resort();
 
 private:
-    wxDataViewMainWindow *m_window;
+    wxDataViewMainWindow * const m_window;
     wxDataViewTreeNode  *m_parent;
 
     // Corresponding model item.

src/msw/artmsw.cpp

@@ -150,7 +150,6 @@ static wxBitmap CreateFromStdIcon(const char *iconName,
     wxBitmap bmp;
     bmp.CopyFromIcon(icon);
 
-#if wxUSE_IMAGE
     // The standard native message box icons are in message box size (32x32).
     // If they are requested in any size other than the default or message
     // box size, they must be rescaled first.
@@ -159,12 +158,9 @@ static wxBitmap CreateFromStdIcon(const char *iconName,
         const wxSize size = wxArtProvider::GetNativeSizeHint(client);
         if ( size != wxDefaultSize )
         {
-            wxImage img = bmp.ConvertToImage();
+            wxArtProvider::RescaleBitmap(bmp, size);
-            img.Rescale(size.x, size.y);
-            bmp = wxBitmap(img);
         }
     }
-#endif // wxUSE_IMAGE
 
     return bmp;
 }