Add DPI scaling to KIPLATFORM

GTK needs to check current scaling but wx doesn't provide this
functionality in 3.0, so we can bypass by going straight to the source.

common/gal/dpi_scaling.cpp

@@ -28,6 +28,7 @@
 #include <env_vars.h>
 #include <pgm_base.h>
 #include <settings/common_settings.h>
+#include <kiplatform/ui.h>
 
 #include <wx/log.h>
 
@@ -117,7 +118,7 @@ double DPI_SCALING::GetScaleFactor() const
         // Use the native WX reporting.
         // On Linux, this will not work until WX 3.2 and GTK >= 3.10
         // Otherwise it returns 1.0
-        val = m_window->GetContentScaleFactor();
+        val = KIPLATFORM::UI::GetSystemScaleFactor( m_window );
         wxLogTrace( traceHiDpi, "Scale factor (WX): %f", *val );
     }
 

libs/kiplatform/gtk/ui.cpp

@@ -91,3 +91,16 @@ void KIPLATFORM::UI::EllipsizeChoiceBox( wxChoice* aChoice )
     // Only the list of cells must be freed, the renderer isn't ours to free
     g_list_free( cells );
 }
+
+
+double KIPLATFORM::UI::GetSystemScaleFactor( const wxWindow* aWindow )
+{
+    double val = 1.0;
+
+    GtkWidget* widget = static_cast<GtkWidget*>( aWindow->GetHandle() );
+
+    if( widget && gtk_check_version( 3, 10, 0 ) == NULL )
+        val = gtk_widget_get_scale_factor( widget );
+
+    return val;
+}

libs/kiplatform/include/kiplatform/ui.h

@@ -85,6 +85,14 @@ namespace KIPLATFORM
          * @param aChoice is the choice box to ellipsize
          */
         void EllipsizeChoiceBox( wxChoice* aChoice );
+
+        /**
+         * Tries to determine the system scaling factor currently in use for the window.  Under wx3.0, GTK
+         * fails to properly detect the scale factor.
+         * @param aWindow pointer to the window to check
+         * @return System scale factor in use, defaulting to the wxWidgets method
+         */
+        double GetSystemScaleFactor( const wxWindow* aWindow );
     }
 }
 

libs/kiplatform/msw/ui.cpp

@@ -95,3 +95,9 @@ void KIPLATFORM::UI::EllipsizeChoiceBox( wxChoice* aChoice )
 {
     // Not implemented
 }
+
+
+double KIPLATFORM::UI::GetSystemScaleFactor( const wxWindow* aWindow )
+{
+    return aWindow->GetContentScaleFactor();
+}

libs/kiplatform/osx/ui.mm

@@ -25,6 +25,7 @@
 #include <wx/nonownedwnd.h>
 #include <wx/toplevel.h>
 #include <wx/button.h>
+#include <wx/window.h>
 
 
 bool KIPLATFORM::UI::IsDarkTheme()
@@ -91,3 +92,9 @@ void KIPLATFORM::UI::EllipsizeChoiceBox( wxChoice* aChoice )
 {
     // Not implemented
 }
+
+
+double KIPLATFORM::UI::GetSystemScaleFactor( const wxWindow* aWindow )
+{
+    return aWindow->GetContentScaleFactor();
+}