Support panel auto-scaling for HiDPI displays

	*Fix scaling of panel widgets, buttons, and the menu bar
	*Draw grab handles at the ends of the panel
	*Fix size of _almost_ all included applets
	*Fix panel snapping coordinates
	*Down-scale monitor coordinates to support multi-monitors

 Author:    Victor Kareh <[email protected]>
 Date:      Wed Dec 20 14:03:18 2017 -0500

6 files changed, 55 insertions, 25 deletions

diff --git a/mate-panel/main.c b/mate-panel/main.c
index 06fdc2f4..4289c158 100644
--- a/mate-panel/main.c
+++ b/mate-panel/main.c
@@ -85,9 +85,6 @@ main (int argc, char **argv)
 
 	gtk_init (&argc, &argv);
 
-    /* FIXME: High dpi scaling does not work... */
-    gdk_x11_display_set_window_scale (gdk_display_get_default (), 1);
-
 	error = NULL;
 	if (!g_option_context_parse (context, &argc, &argv, &error)) {
 		g_printerr ("%s\n", error->message);
diff --git a/mate-panel/panel-run-dialog.c b/mate-panel/panel-run-dialog.c
index e00d0c51..a696138e 100644
--- a/mate-panel/panel-run-dialog.c
+++ b/mate-panel/panel-run-dialog.c
@@ -1695,6 +1695,7 @@ panel_run_dialog_setup_entry (PanelRunDialog *dialog,
 	GdkScreen             *screen;
 	int                    width_request;
 	GtkWidget             *entry;
+	gint                   scale;
 
 	dialog->combobox = PANEL_GTK_BUILDER_GET (gui, "comboboxentry");
 
@@ -1707,9 +1708,10 @@ panel_run_dialog_setup_entry (PanelRunDialog *dialog,
 		(GTK_COMBO_BOX (dialog->combobox), 0);
 
 	screen = gtk_window_get_screen (GTK_WINDOW (dialog->run_dialog));
+	scale = gtk_widget_get_scale_factor (GTK_WINDOW (dialog->run_dialog));
 
         /* 1/4 the width of the first monitor should be a good value */
-	width_request = panel_multiscreen_width (screen, 0) / 4;
+	width_request = panel_multiscreen_width (screen, 0) / (4 * scale);
 	g_object_set (G_OBJECT (dialog->combobox),
 		      "width_request", width_request,
 		      NULL);
diff --git a/mate-panel/panel-struts.c b/mate-panel/panel-struts.c
index 644dafb0..d59587e5 100644
--- a/mate-panel/panel-struts.c
+++ b/mate-panel/panel-struts.c
@@ -404,7 +404,8 @@ panel_struts_register_strut (PanelToplevel    *toplevel,
 			     PanelOrientation  orientation,
 			     int               strut_size,
 			     int               strut_start,
-			     int               strut_end)
+			     int               strut_end,
+			     gint              scale)
 {
 	PanelStrut *strut;
 	gboolean    new_strut = FALSE;
@@ -440,24 +441,24 @@ panel_struts_register_strut (PanelToplevel    *toplevel,
 		strut->geometry.x      = strut->strut_start;
 		strut->geometry.y      = monitor_y;
 		strut->geometry.width  = strut->strut_end - strut->strut_start + 1;
-		strut->geometry.height = strut->strut_size;
+		strut->geometry.height = strut->strut_size / scale;
 		break;
 	case PANEL_ORIENTATION_BOTTOM:
 		strut->geometry.x      = strut->strut_start;
 		strut->geometry.y      = monitor_y + monitor_height - strut->strut_size;
 		strut->geometry.width  = strut->strut_end - strut->strut_start + 1;
-		strut->geometry.height = strut->strut_size;
+		strut->geometry.height = strut->strut_size / scale;
 		break;
 	case PANEL_ORIENTATION_LEFT:
 		strut->geometry.x      = monitor_x;
 		strut->geometry.y      = strut->strut_start;
-		strut->geometry.width  = strut->strut_size;
+		strut->geometry.width  = strut->strut_size / scale;
 		strut->geometry.height = strut->strut_end - strut->strut_start + 1;
 		break;
 	case PANEL_ORIENTATION_RIGHT:
 		strut->geometry.x      = monitor_x + monitor_width - strut->strut_size;
 		strut->geometry.y      = strut->strut_start;
-		strut->geometry.width  = strut->strut_size;
+		strut->geometry.width  = strut->strut_size / scale;
 		strut->geometry.height = strut->strut_end - strut->strut_start + 1;
 		break;
 	}
diff --git a/mate-panel/panel-struts.h b/mate-panel/panel-struts.h
index b96b93e6..e7d8185f 100644
--- a/mate-panel/panel-struts.h
+++ b/mate-panel/panel-struts.h
@@ -36,7 +36,8 @@ gboolean panel_struts_register_strut           (PanelToplevel    *toplevel,
 						PanelOrientation  orientation,
 						int               strut_size,
 						int               strut_start,
-						int               strut_end);
+						int               strut_end,
+						gint              scale);
 
 void     panel_struts_unregister_strut         (PanelToplevel    *toplevel);
 
diff --git a/mate-panel/panel-toplevel.c b/mate-panel/panel-toplevel.c
index 7aa61e42..42b09d35 100644
--- a/mate-panel/panel-toplevel.c
+++ b/mate-panel/panel-toplevel.c
@@ -83,6 +83,7 @@ struct _PanelToplevelPrivate {
 	gboolean                expand;
 	PanelOrientation        orientation;
 	int                     size;
+	gint                    scale;
 
 	/* relative to the monitor origin */
 	int                     x;
@@ -284,8 +285,15 @@ static GdkScreen* panel_toplevel_get_screen_geometry(PanelToplevel* toplevel, in
 
 	screen = gtk_window_get_screen(GTK_WINDOW(toplevel));
 
-	*width  = WidthOfScreen (gdk_x11_screen_get_xscreen (screen));
-	*height = HeightOfScreen (gdk_x11_screen_get_xscreen (screen));
+	/* To scale the panels up for HiDPI displays, we can either multiply a lot of
+	 * toplevel geometry attributes by the scale factor, then correct for all
+	 * sorts of awful misalignments and pretend it's all good. Or we can just
+	 * make this thing think that the screen is scaled down, and because GTK+
+	 * already scaled everything up without the panel knowing about it, the whole
+	 * thing somehow works well... sigh.
+	 * @see panel_toplevel_get_monitor_geometry() */
+	*width  = WidthOfScreen (gdk_x11_screen_get_xscreen (screen)) / toplevel->priv->scale;
+	*height = HeightOfScreen (gdk_x11_screen_get_xscreen (screen)) / toplevel->priv->scale;
 
 	return screen;
 }
@@ -299,17 +307,24 @@ static GdkScreen* panel_toplevel_get_monitor_geometry(PanelToplevel* toplevel, i
 
 	screen = gtk_window_get_screen(GTK_WINDOW(toplevel));
 
-	if (x) *x = panel_multiscreen_x(screen, toplevel->priv->monitor);
-	if (y) *y = panel_multiscreen_y(screen, toplevel->priv->monitor);
+	if (x) *x = panel_multiscreen_x(screen, toplevel->priv->monitor) / toplevel->priv->scale;
+	if (y) *y = panel_multiscreen_y(screen, toplevel->priv->monitor) / toplevel->priv->scale;
 
+	/* To scale the panels up for HiDPI displays, we can either multiply a lot of
+	 * toplevel geometry attributes by the scale factor, then correct for all
+	 * sorts of awful misalignments and pretend it's all good. Or we can just
+	 * make this thing think that the screen is scaled down, and because GTK+
+	 * already scaled everything up without the panel knowing about it, the whole
+	 * thing somehow works well... sigh.
+	 * @see panel_toplevel_get_screen_geometry() */
 	if (width)
 	{
-		*width  = panel_multiscreen_width(screen, toplevel->priv->monitor);
+		*width  = panel_multiscreen_width(screen, toplevel->priv->monitor) / toplevel->priv->scale;
 	}
 
 	if (height)
 	{
-		*height = panel_multiscreen_height(screen, toplevel->priv->monitor);
+		*height = panel_multiscreen_height(screen, toplevel->priv->monitor) / toplevel->priv->scale;
 	}
 
 	return screen;
@@ -1504,6 +1519,10 @@ static gboolean panel_toplevel_update_struts(PanelToplevel* toplevel, gboolean e
 		}
 	}
 
+	/* Adjust strut size based on scale factor */
+	if (strut > 0)
+		strut += toplevel->priv->size * (toplevel->priv->scale - 1);
+
 	if (orientation != toplevel->priv->orientation) {
 		toplevel->priv->orientation = orientation;
 		g_object_notify (G_OBJECT (toplevel), "orientation");
@@ -1519,7 +1538,8 @@ static gboolean panel_toplevel_update_struts(PanelToplevel* toplevel, gboolean e
 								orientation,
 								strut,
 								strut_start,
-								strut_end);
+								strut_end,
+								toplevel->priv->scale);
 	else
 		panel_struts_unregister_strut (toplevel);
 
@@ -2336,7 +2356,8 @@ panel_toplevel_update_size_from_hints (PanelToplevel  *toplevel,
 	int total_size;
 	int full_hints;
 
-	total_size = non_panel_widget_size + requisition_size;
+	/* Scale down the size so that the panel only takes what it needs for the applets it has. */
+	total_size = non_panel_widget_size + (requisition_size / toplevel->priv->scale);
 
 	nb_size_hints = toplevel->priv->panel_widget->nb_applets_size_hints;
 	if (nb_size_hints <= 0)
@@ -4317,7 +4338,7 @@ panel_toplevel_class_init (PanelToplevelClass *klass)
 	widget_class->button_press_event   = panel_toplevel_button_press_event;
 	widget_class->button_release_event = panel_toplevel_button_release_event;
 #if GTK_CHECK_VERSION (3, 18, 0)
-	widget_class->configure_event      = panel_toplevel_configure_event;	
+	widget_class->configure_event      = panel_toplevel_configure_event;
 #endif
 	widget_class->key_press_event      = panel_toplevel_key_press_event;
 	widget_class->motion_notify_event  = panel_toplevel_motion_notify_event;
@@ -4752,6 +4773,7 @@ panel_toplevel_init (PanelToplevel *toplevel)
 	toplevel->priv->expand          = TRUE;
 	toplevel->priv->orientation     = PANEL_ORIENTATION_BOTTOM;
 	toplevel->priv->size            = DEFAULT_SIZE;
+	toplevel->priv->scale           = gtk_widget_get_scale_factor (GTK_WIDGET (toplevel));
 	toplevel->priv->x               = 0;
 	toplevel->priv->y               = 0;
 	toplevel->priv->x_right         = -1;
@@ -4826,6 +4848,7 @@ panel_toplevel_init (PanelToplevel *toplevel)
 	toplevel->priv->attach_hidden     = FALSE;
 	toplevel->priv->updated_geometry_initial = FALSE;
 	toplevel->priv->initial_animation_done   = FALSE;
+
 #if GTK_CHECK_VERSION (3, 18, 0)
 	widget = GTK_WIDGET (toplevel);
 	gtk_widget_add_events (widget,
diff --git a/mate-panel/panel-widget.c b/mate-panel/panel-widget.c
index cedcbb21..ce9d88b0 100644
--- a/mate-panel/panel-widget.c
+++ b/mate-panel/panel-widget.c
@@ -1214,6 +1214,7 @@ panel_widget_get_preferred_size(GtkWidget	     *widget,
 	GList *list;
 	GList *ad_with_hints;
 	gboolean dont_fill;
+	gint scale;
 
 	g_return_if_fail(PANEL_IS_WIDGET(widget));
 	g_return_if_fail(minimum_size != NULL);
@@ -1231,6 +1232,7 @@ panel_widget_get_preferred_size(GtkWidget	     *widget,
 	natural_size->height = minimum_size->height;
 
 	ad_with_hints = NULL;
+	scale = gtk_widget_get_scale_factor(widget);
 
 	for (list = panel->applet_list; list!=NULL; list = g_list_next(list)) {
 		AppletData *ad = list->data;
@@ -1254,8 +1256,10 @@ panel_widget_get_preferred_size(GtkWidget	     *widget,
 
 			else if (panel->packed)
 			{
-				minimum_size->width += child_min_size.width;
-				natural_size->width += child_natural_size.width;
+				/* Just because everything is bigger when scaled up doesn't mean
+				 * that the applets need any less room when the panel is packed. */
+				minimum_size->width += child_min_size.width * scale;
+				natural_size->width += child_natural_size.width * scale;
 			}
 		} else {
 			if (minimum_size->width < child_min_size.width &&
@@ -1271,8 +1275,10 @@ panel_widget_get_preferred_size(GtkWidget	     *widget,
 
 			else if (panel->packed)
 			{
-				minimum_size->height += child_min_size.height;
-				natural_size->height += child_natural_size.height;
+				/* Just because everything is bigger when scaled up doesn't mean
+				 * that the applets need any less room when the panel is packed. */
+				minimum_size->height += child_min_size.height * scale;
+				natural_size->height += child_natural_size.height * scale;
 			}
 		}
 	}
@@ -1409,9 +1415,9 @@ panel_widget_size_allocate(GtkWidget *widget, GtkAllocation *allocation)
 	gtk_widget_set_allocation (widget, allocation);
 	if (gtk_widget_get_realized (widget))
 		gdk_window_move_resize (gtk_widget_get_window (widget),
-					allocation->x, 
+					allocation->x,
 					allocation->y,
-					allocation->width, 
+					allocation->width,
 					allocation->height);
 
 	if(panel->orient == GTK_ORIENTATION_HORIZONTAL)