Set scale factor correctly for icons loaded from resources

::LoadIcon() selects the icon of scaled size in the DPI-aware programs,
which is nice, but only works right if we actually set the scale factor
for the icon correctly.

include/wx/msw/icon.h

@@ -71,7 +71,7 @@ public:
 #endif // WXWIN_COMPATIBILITY_3_0
 
     WXHICON GetHICON() const { return (WXHICON)GetHandle(); }
-    bool InitFromHICON(WXHICON icon, int width, int height);
+    bool InitFromHICON(WXHICON icon, int width, int height, double scale = 1.0);
 
     // create from bitmap (which should have a mask unless it's monochrome):
     // there shouldn't be any implicit bitmap -> icon conversion (i.e. no

src/msw/gdiimage.cpp

@@ -586,7 +586,26 @@ bool wxICOResourceHandler::LoadIcon(wxIcon *icon,
         }
     }
 
-    return icon->CreateFromHICON((WXHICON)hicon);
+    if ( !hicon )
+        return false;
+
+    wxSize size;
+    double scale = 1.0;
+    if ( hasSize )
+    {
+        size.x = desiredWidth;
+        size.y = desiredHeight;
+    }
+    else // We loaded an icon of default size.
+    {
+        // LoadIcon() returns icons of scaled size, so we must use the correct
+        // scaling factor of them.
+        size = wxGetHiconSize(hicon);
+        if ( const wxWindow* win = wxApp::GetMainTopWindow() )
+            scale = win->GetDPIScaleFactor();
+    }
+
+    return icon->InitFromHICON((WXHICON)hicon, size.x, size.y, scale);
 }
 
 #if wxUSE_PNG_RESOURCE_HANDLER

src/msw/icon.cpp

@@ -154,7 +154,7 @@ bool wxIcon::CreateFromHICON(WXHICON icon)
     return InitFromHICON(icon, size.GetWidth(), size.GetHeight());
 }
 
-bool wxIcon::InitFromHICON(WXHICON icon, int width, int height)
+bool wxIcon::InitFromHICON(WXHICON icon, int width, int height, double scale)
 {
 #if wxDEBUG_LEVEL >= 2
     if ( icon != NULL )
@@ -170,6 +170,7 @@ bool wxIcon::InitFromHICON(WXHICON icon, int width, int height)
     GetGDIImageData()->m_handle = (WXHANDLE)icon;
     GetGDIImageData()->m_width = width;
     GetGDIImageData()->m_height = height;
+    GetGDIImageData()->m_scaleFactor = scale;
 
     return IsOk();
 }