Use the surface output event to keep track of the suggested scale value

The event will be sent when the surface becomes visible on an output. With this change the GdkMirWindowImpl keeps track of the scale value and sends a configure event on change.

Signed-off-by: Andreas Pokorny <andreas.pokorny@canonical.com>

gdk/mir/gdkmir-private.h

@@ -89,6 +89,8 @@ void _gdk_mir_window_impl_set_surface_state (GdkMirWindowImpl *impl, MirSurfaceS
 
 void _gdk_mir_window_impl_set_surface_type (GdkMirWindowImpl *impl, MirSurfaceType type);
 
+void _gdk_mir_window_set_surface_output (GdkWindow *window, gdouble scale);
+
 void _gdk_mir_window_impl_set_cursor_state (GdkMirWindowImpl *impl, gdouble x, gdouble y, gboolean cursor_inside, guint button_state);
 
 void _gdk_mir_window_impl_get_cursor_state (GdkMirWindowImpl *impl, gdouble *x, gdouble *y, gboolean *cursor_inside, guint *button_state);

gdk/mir/gdkmireventsource.c

@@ -544,6 +544,13 @@ handle_close_event (GdkWindow *window)
   gdk_window_destroy_notify (window);
 }
 
+static void
+handle_surface_output_event (GdkWindow                  *window,
+                             const MirSurfaceOutputEvent *event)
+{
+  _gdk_mir_window_set_surface_output (window, mir_surface_output_event_get_scale (event));
+}
+
 typedef struct
 {
   GdkWindow *window;
@@ -598,6 +605,9 @@ gdk_mir_event_source_queue_event (GdkDisplay     *display,
     case mir_event_type_close_surface:
       handle_close_event (window);
       break;
+    case mir_event_type_surface_output:
+      handle_surface_output_event (window, mir_event_get_surface_output_event (event));
+      break;
     default:
       g_warning ("Ignoring unknown Mir event %d", mir_event_get_type (event));
       // FIXME?

gdk/mir/gdkmirwindowimpl.c

@@ -16,6 +16,7 @@
  */
 
 #include <inttypes.h>
+#include <math.h>
 
 #include "config.h"
 
@@ -65,6 +66,7 @@ struct _GdkMirWindowImpl
 
   /* Surface being rendered to (only exists when window visible) */
   MirSurface *surface;
+  MirBufferStream *buffer_stream;
 
   /* Cairo context for current frame */
   cairo_surface_t *cairo_surface;
@@ -80,6 +82,8 @@ struct _GdkMirWindowImpl
 
   /* TRUE if cursor is inside this window */
   gboolean cursor_inside;
+
+  gint output_scale;
 };
 
 struct _GdkMirWindowImplClass
@@ -91,6 +95,14 @@ G_DEFINE_TYPE (GdkMirWindowImpl, gdk_mir_window_impl, GDK_TYPE_WINDOW_IMPL)
 
 static cairo_surface_t *gdk_mir_window_impl_ref_cairo_surface (GdkWindow *window);
 
+static void
+drop_cairo_surface (GdkWindow *window)
+{
+  GdkMirWindowImpl *impl = GDK_MIR_WINDOW_IMPL (window->impl);
+
+  g_clear_pointer (&impl->cairo_surface, cairo_surface_destroy);
+}
+
 GdkWindowImpl *
 _gdk_mir_window_impl_new (void)
 {
@@ -144,6 +156,7 @@ gdk_mir_window_impl_init (GdkMirWindowImpl *impl)
 {
   impl->type_hint = GDK_WINDOW_TYPE_HINT_NORMAL;
   impl->surface_state = mir_surface_state_unknown;
+  impl->output_scale = 1;
 }
 
 static void
@@ -356,6 +369,7 @@ ensure_surface_full (GdkWindow *window,
                                       impl->has_rect ? &impl->rect : NULL,
                                       impl->has_rect ? impl->edge : mir_edge_attachment_any,
                                       buffer_usage);
+  impl->buffer_stream = mir_surface_get_buffer_stream (impl->surface);
 
   /* FIXME: can't make an initial resize event */
   // MirEvent *resize_event;
@@ -448,6 +462,7 @@ gdk_mir_window_impl_ref_cairo_surface (GdkWindow *window)
   if (window->gl_paint_context)
     {
       cairo_surface = cairo_image_surface_create (pixel_format, window->width, window->height);
+      cairo_surface_set_device_scale (cairo_surface, (double) impl->output_scale, (double) impl->output_scale);
     }
   else if (impl->visible)
     {
@@ -496,6 +511,7 @@ gdk_mir_window_impl_ref_cairo_surface (GdkWindow *window)
                                                            region.width,
                                                            region.height,
                                                            region.stride);
+      cairo_surface_set_device_scale (cairo_surface, (double) impl->output_scale, (double) impl->output_scale);
     }
   else
     cairo_surface = cairo_image_surface_create (pixel_format, 0, 0);
@@ -1344,8 +1360,8 @@ static gint
 gdk_mir_window_impl_get_scale_factor (GdkWindow *window)
 {
   //g_printerr ("gdk_mir_window_impl_get_scale_factor window=%p\n", window);
-  /* Don't support monitor scaling */
+  GdkMirWindowImpl *impl = GDK_MIR_WINDOW_IMPL (window->impl);
-  return 1;
+  return impl->output_scale;
 }
 
 static void
@@ -1603,6 +1619,30 @@ gdk_mir_window_get_mir_surface (GdkWindow *window)
   return impl->surface;
 }
 
+void
+_gdk_mir_window_set_surface_output (GdkWindow *window, gdouble scale)
+{
+  // g_printerr ("_gdk_mir_window_impl_set_surface_output impl=%p\n", impl);
+  GdkMirWindowImpl *impl = GDK_MIR_WINDOW_IMPL (window->impl);
+  GdkRectangle area = {0, 0, window->width, window->height};
+  cairo_region_t *region;
+  gint new_scale = (gint) round (scale);
+
+  if (impl->output_scale != new_scale)
+    {
+      impl->output_scale = new_scale;
+
+      drop_cairo_surface (window);
+
+      if (impl->buffer_stream)
+        mir_buffer_stream_set_scale (impl->buffer_stream, (float) new_scale);
+
+      region = cairo_region_create_rectangle (&area);
+      _gdk_window_invalidate_for_expose (window, region);
+      cairo_region_destroy (region);
+    }
+}
+
 static void
 gdk_mir_window_impl_class_init (GdkMirWindowImplClass *klass)
 {