EvView: render correctly on hi-dpi displays

Make EvPixbufCache generate surfaces with extra resolution based on
gtk_widget_get_scale_factor(). Handle cairo surfaces with a device
scale in ev_view_draw(). Trigger an update of the pixbuf cache when
the scale factor changes.

https://bugzilla.gnome.org/show_bug.cgi?id=723431

origin commit:
https://git.gnome.org/browse/evince/commit/?id=a612f8

libview/ev-pixbuf-cache.c

@@ -296,9 +296,9 @@ copy_job_to_job_info (EvJobRender   *job_render,
 
 		job_info->selection_points = job_render->selection_points;
 		job_info->selection = cairo_surface_reference (job_render->selection);
-		job_info->selection_scale = job_render->scale;
 		if (job_info->selection)
 			set_device_scale_on_surface (job_info->selection, job_info->device_scale);
+		job_info->selection_scale = job_render->scale * job_info->device_scale;
 		g_assert (job_info->selection_points.x1 >= 0);
 
 		job_info->selection_region_points = job_render->selection_points;
@@ -1093,7 +1093,7 @@ ev_pixbuf_cache_get_selection_surface (EvPixbufCache   *pixbuf_cache,
 		if (job_info->selection)
 			set_device_scale_on_surface (job_info->selection, job_info->device_scale);
 		job_info->selection_points = job_info->target_points;
-		job_info->selection_scale = scale;
+		job_info->selection_scale = scale * job_info->device_scale;
 		g_object_unref (rc);
 		ev_document_doc_mutex_unlock ();
 	}

libview/ev-view.c

@@ -5690,10 +5690,14 @@ draw_surface (cairo_t 	      *cr,
 	      gint             target_width,
 	      gint             target_height)
 {
-	gint width, height;
+	gdouble width, height;
+	gdouble device_scale_x = 1, device_scale_y = 1;
 
-	width = cairo_image_surface_get_width (surface);
-	height = cairo_image_surface_get_height (surface);
+#ifdef HAVE_HIDPI_SUPPORT
+	cairo_surface_get_device_scale (surface, &device_scale_x, &device_scale_y);
+#endif
+	width = cairo_image_surface_get_width (surface) / device_scale_x;
+	height = cairo_image_surface_get_height (surface) / device_scale_y;
 
 	cairo_save (cr);
 	cairo_translate (cr, x, y);
@@ -5712,8 +5716,8 @@ draw_surface (cairo_t 	      *cr,
 	}
 
 	cairo_surface_set_device_offset (surface,
-					 offset_x,
-					 offset_y);
+					 offset_x * device_scale_x,
+					 offset_y * device_scale_y);
 	cairo_set_source_surface (cr, surface, 0, 0);
 	cairo_paint (cr);
 	cairo_restore (cr);
@@ -5848,9 +5852,18 @@ draw_one_page (EvView       *view,
 		if (region) {
 			double scale_x, scale_y;
 			GdkRGBA color;
+			double device_scale_x = 1, device_scale_y = 1;
 
 			scale_x = (gdouble)width / cairo_image_surface_get_width (page_surface);
 			scale_y = (gdouble)height / cairo_image_surface_get_height (page_surface);
+
+#ifdef HAVE_HIDPI_SUPPORT
+			cairo_surface_get_device_scale (page_surface, &device_scale_x, &device_scale_y);
+#endif
+
+			scale_x *= device_scale_x;
+			scale_y *= device_scale_y;
+
 			_ev_view_get_selection_colors (view, &color, NULL);
 			draw_selection_region (cr, region, &color, real_page_area.x, real_page_area.y,
 					       scale_x, scale_y);