[GTK3] Implemented HiDPI support (needs GTK 3.10)

src/Gtk/Avalonia.Gtk3/FramebufferManager.cs

@@ -26,7 +26,7 @@ namespace Avalonia.Gtk3
                 throw new InvalidOperationException("Window is not in drawing state");
             var width = (int) _window.ClientSize.Width;
             var height = (int) _window.ClientSize.Height;
-            return new ImageSurfaceFramebuffer(_window.CurrentCairoContext, width, height);
+            return new ImageSurfaceFramebuffer(_window.CurrentCairoContext, _window.GtkWidget, width, height);
         }
     }
 }

src/Gtk/Avalonia.Gtk3/ImageSurfaceFramebuffer.cs

@@ -13,12 +13,19 @@ namespace Avalonia.Gtk3
     class ImageSurfaceFramebuffer : ILockedFramebuffer
     {
         private IntPtr _context;
+        private readonly GtkWidget _widget;
         private CairoSurface _surface;
+        private int _factor;
 
-        public ImageSurfaceFramebuffer(IntPtr context, int width, int height)
+        public ImageSurfaceFramebuffer(IntPtr context, GtkWidget widget, int width, int height)
         {
             _context = context;
+            _widget = widget;
+            _factor = (int)(Native.GtkWidgetGetScaleFactor?.Invoke(_widget) ?? 1u);
+            width *= _factor;
+            height *= _factor;
             _surface = Native.CairoImageSurfaceCreate(1, width, height);
+            
             Width = width;
             Height = height;
             Address = Native.CairoImageSurfaceGetData(_surface);
@@ -31,6 +38,7 @@ namespace Avalonia.Gtk3
             if(_context == IntPtr.Zero || _surface == null)
                 return;
             Native.CairoSurfaceMarkDirty(_surface);
+            Native.CairoScale(_context, 1d / _factor, 1d / _factor);
             Native.CairoSetSourceSurface(_context, _surface, 0, 0);
             Native.CairoPaint(_context);
             _context = IntPtr.Zero;
@@ -43,8 +51,15 @@ namespace Avalonia.Gtk3
         public int Height { get; }
         public int RowBytes { get; }
 
-        //TODO: Proper DPI detect
-        public Size Dpi => new Size(96, 96);
+        
+        public Size Dpi
+        {
+            get
+            {
+                
+                return new Size(96, 96) * _factor;
+            }
+        }
 
         public PixelFormat Format => PixelFormat.Bgra8888;
     }

src/Gtk/Avalonia.Gtk3/Interop/DynLoader.cs

@@ -13,7 +13,7 @@ namespace Avalonia.Gtk3.Interop
     internal interface IDynLoader
     {
         IntPtr LoadLibrary(string dll);
-        IntPtr GetProcAddress(IntPtr dll, string proc);
+        IntPtr GetProcAddress(IntPtr dll, string proc, bool optional);
 
     }
 
@@ -91,10 +91,10 @@ namespace Avalonia.Gtk3.Interop
             return handle;
         }
 
-        public IntPtr GetProcAddress(IntPtr dll, string proc)
+        public IntPtr GetProcAddress(IntPtr dll, string proc, bool optional)
         {
             var ptr = DlSym(dll, proc);
-            if (ptr == IntPtr.Zero)
+            if (ptr == IntPtr.Zero && !optional)
                 throw new NativeException(DlErrorString());
             return ptr;
         }
@@ -118,10 +118,10 @@ namespace Avalonia.Gtk3.Interop
             throw new NativeException("Error loading " + dll + " error " + err);
         }
 
-        IntPtr IDynLoader.GetProcAddress(IntPtr dll, string proc)
+        IntPtr IDynLoader.GetProcAddress(IntPtr dll, string proc, bool optional)
         {
             var ptr = GetProcAddress(dll, proc);
-            if (ptr == IntPtr.Zero)
+            if (ptr == IntPtr.Zero && !optional)
                 throw new NativeException("Error " + Marshal.GetLastWin32Error());
             return ptr;
         }

src/Gtk/Avalonia.Gtk3/Interop/Native.cs

@@ -50,6 +50,10 @@ namespace Avalonia.Gtk3.Interop
 
             [UnmanagedFunctionPointer(CallingConvention.Cdecl), GtkImport(GtkDll.Gtk)]
             public delegate IntPtr gtk_widget_get_window(GtkWidget gtkWidget);
+
+            [UnmanagedFunctionPointer(CallingConvention.Cdecl), GtkImport(GtkDll.Gtk, optional: true)]
+            public delegate uint gtk_widget_get_scale_factor(GtkWidget gtkWidget);
+
             [UnmanagedFunctionPointer(CallingConvention.Cdecl), GtkImport(GtkDll.Gtk)]
             public delegate IntPtr gtk_widget_get_screen(GtkWidget gtkWidget);
             [UnmanagedFunctionPointer(CallingConvention.Cdecl), GtkImport(GtkDll.Gtk)]
@@ -130,6 +134,9 @@ namespace Avalonia.Gtk3.Interop
             [UnmanagedFunctionPointer(CallingConvention.Cdecl), GtkImport(GtkDll.Cairo)]
             public delegate void cairo_set_source_surface(IntPtr cr, CairoSurface surface, double x, double y);
 
+            [UnmanagedFunctionPointer(CallingConvention.Cdecl), GtkImport(GtkDll.Cairo)]
+            public delegate void cairo_scale(IntPtr context, double sx, double sy);
+
             [UnmanagedFunctionPointer(CallingConvention.Cdecl), GtkImport(GtkDll.Cairo)]
             public delegate void cairo_paint(IntPtr context);
 
@@ -275,6 +282,7 @@ namespace Avalonia.Gtk3.Interop
         public static D.gtk_widget_hide GtkWidgetHide;
         public static D.gdk_get_native_handle GetNativeGdkWindowHandle;
         public static D.gtk_widget_get_window GtkWidgetGetWindow;
+        public static D.gtk_widget_get_scale_factor GtkWidgetGetScaleFactor;
         public static D.gtk_widget_get_screen GtkWidgetGetScreen;
         public static D.gtk_widget_realize GtkWidgetRealize;
         public static D.gtk_window_get_size GtkWindowGetSize;
@@ -343,6 +351,7 @@ namespace Avalonia.Gtk3.Interop
         public static D.cairo_surface_flush CairoSurfaceFlush;
         public static D.cairo_surface_destroy CairoSurfaceDestroy;
         public static D.cairo_set_source_surface CairoSetSourceSurface;
+        public static D.cairo_scale CairoScale;
         public static D.cairo_paint CairoPaint;
     }
 

src/Gtk/Avalonia.Gtk3/Interop/Resolver.cs

@@ -128,9 +128,11 @@ namespace Avalonia.Gtk3.Interop
                 if(import == null)
                     continue;
                 IntPtr lib = dlls[import.Dll];
-                
-                var funcPtr = loader.GetProcAddress(lib, import.Name ?? fieldInfo.FieldType.Name);
-                fieldInfo.SetValue(null, Marshal.GetDelegateForFunctionPointer(funcPtr, fieldInfo.FieldType));
+
+                var funcPtr =  loader.GetProcAddress(lib, import.Name ?? fieldInfo.FieldType.Name, import.Optional);
+
+                if (funcPtr != IntPtr.Zero)
+                    fieldInfo.SetValue(null, Marshal.GetDelegateForFunctionPointer(funcPtr, fieldInfo.FieldType));
             }
 
             var nativeHandleNames = new[] { "gdk_win32_window_get_handle", "gdk_x11_window_get_xid", "gdk_quartz_window_get_nswindow" };
@@ -139,7 +141,7 @@ namespace Avalonia.Gtk3.Interop
                 try
                 {
                     Native.GetNativeGdkWindowHandle = (Native.D.gdk_get_native_handle)Marshal
-                        .GetDelegateForFunctionPointer(loader.GetProcAddress(dlls[GtkDll.Gdk], name), typeof(Native.D.gdk_get_native_handle));
+                        .GetDelegateForFunctionPointer(loader.GetProcAddress(dlls[GtkDll.Gdk], name, false), typeof(Native.D.gdk_get_native_handle));
                     break;
                 }
                 catch { }

src/Gtk/Avalonia.Gtk3/TopLevelImpl.cs

@@ -21,6 +21,7 @@ namespace Avalonia.Gtk3
         protected readonly List<IDisposable> Disposables = new List<IDisposable>();
         private Size _lastSize;
         private Point _lastPosition;
+        private double _lastScaling;
         private uint _lastKbdEvent;
         private uint _lastSmoothScrollEvent;
 
@@ -63,7 +64,12 @@ namespace Avalonia.Gtk3
                 PositionChanged?.Invoke(pos);
                 _lastPosition = pos;
             }
-
+            var scaling = Scaling;
+            if (_lastScaling != scaling)
+            {
+                ScalingChanged?.Invoke(scaling);
+                _lastScaling = scaling;
+            }
             return false;
         }
 
@@ -228,7 +234,8 @@ namespace Avalonia.Gtk3
         }
 
 
-        public double Scaling => 1; //TODO: Implement scaling
+        public double Scaling => (double) 1 / (Native.GtkWidgetGetScaleFactor?.Invoke(GtkWidget) ?? 1);
+
         public IPlatformHandle Handle => this;
 
         string IPlatformHandle.HandleDescriptor => "HWND";