Display: Support fractional scaling if enabled

src/Objects/MonitorManager.vala

@@ -23,6 +23,7 @@ public class Display.MonitorManager : GLib.Object {
     public Gee.LinkedList<Display.VirtualMonitor> virtual_monitors { get; construct; }
     public Gee.LinkedList<Display.Monitor> monitors { get; construct; }
 
+    public bool fractional_scale_enabled { get; private set; }
     public bool global_scale_required { get; private set; }
     public bool mirroring_supported { get; private set; }
     public int max_width { get; private set; }
@@ -103,6 +104,13 @@ public class Display.MonitorManager : GLib.Object {
             global_scale_required = false;
         }
 
+        uint layout_mode = 1; // Absence of "layout-mode" means logical (= 1) according to the documentation.
+        var layout_mode_variant = properties.lookup ("layout-mode");
+        if (layout_mode_variant != null) {
+            layout_mode = layout_mode_variant.get_uint32 ();
+        }
+        fractional_scale_enabled = layout_mode == 1;
+
         var max_screen_size_variant = properties.lookup ("max-screen-size");
         if (max_screen_size_variant != null) {
             max_width = max_screen_size_variant.get_child_value (0).get_int32 ();

src/Views/DisplaysView.vala

@@ -67,7 +67,12 @@ public class Display.DisplaysView : Gtk.Box {
 
             var action_bar = new Gtk.ActionBar ();
             action_bar.add_css_class (Granite.STYLE_CLASS_FLAT);
-            action_bar.pack_start (dpi_box);
+
+            unowned Display.MonitorManager monitor_manager = Display.MonitorManager.get_default ();
+            if (monitor_manager.global_scale_required) {
+                action_bar.pack_start (dpi_box);
+            }
+
             action_bar.pack_start (mirror_box);
 
             var schema_source = GLib.SettingsSchemaSource.get_default ();
@@ -99,7 +104,6 @@ public class Display.DisplaysView : Gtk.Box {
                 apply_button.sensitive = changed;
             });
 
-            unowned Display.MonitorManager monitor_manager = Display.MonitorManager.get_default ();
             mirror_box.sensitive = monitor_manager.monitors.size > 1;
             monitor_manager.notify["monitor-number"].connect (() => {
                 mirror_box.sensitive = monitor_manager.monitors.size > 1;

src/Widgets/DisplayWidget.vala

@@ -27,6 +27,23 @@ public struct Display.Resolution {
 }
 
 public class Display.DisplayWidget : Gtk.Box {
+    private static double[] scales;
+    private static string[] string_scales;
+
+    static construct {
+        unowned var monitor_manager = MonitorManager.get_default ();
+
+        if (monitor_manager.fractional_scale_enabled) {
+            scales = { 0.75, 1.00, 1.25, 1.50, 1.75, 2.00 };
+        } else {
+            scales = { 1.00, 2.00 };
+        }
+
+        foreach (var scale in scales) {
+            string_scales += "%d %%".printf ((int) (scale * 100));
+        }
+    }
+
     public signal void set_as_primary ();
     public signal void check_position ();
     public signal void configuration_changed ();
@@ -52,6 +69,8 @@ public class Display.DisplayWidget : Gtk.Box {
     private Gtk.ComboBox refresh_combobox;
     private Gtk.ListStore refresh_list_store;
 
+    private Gtk.DropDown scale_drop_down;
+
     private int real_width = 0;
     private int real_height = 0;
 
@@ -237,6 +256,15 @@ public class Display.DisplayWidget : Gtk.Box {
 
         populate_refresh_rates ();
 
+        scale_drop_down = new Gtk.DropDown.from_strings (string_scales) {
+            margin_start = 12,
+            margin_end = 12
+        };
+
+        var scale_label = new Granite.HeaderLabel (_("Scaling factor")) {
+            mnemonic_widget = scale_drop_down
+        };
+
         var popover_box = new Gtk.Box (VERTICAL, 0) {
             margin_top = 6,
             margin_bottom = 12
@@ -249,6 +277,11 @@ public class Display.DisplayWidget : Gtk.Box {
         popover_box.append (refresh_label);
         popover_box.append (refresh_combobox);
 
+        if (!MonitorManager.get_default ().global_scale_required) {
+            popover_box.append (scale_label);
+            popover_box.append (scale_drop_down);
+        }
+
         var popover = new Gtk.Popover () {
             child = popover_box,
             position = BOTTOM
@@ -275,6 +308,7 @@ public class Display.DisplayWidget : Gtk.Box {
         use_switch.bind_property ("active", resolution_combobox, "sensitive");
         use_switch.bind_property ("active", rotation_combobox, "sensitive");
         use_switch.bind_property ("active", refresh_combobox, "sensitive");
+        use_switch.bind_property ("active", scale_drop_down, "sensitive");
 
         use_switch.notify["active"].connect (() => {
             if (rotation_combobox.active == -1) rotation_combobox.set_active (0);
@@ -398,6 +432,24 @@ public class Display.DisplayWidget : Gtk.Box {
             }
         });
 
+        virtual_monitor.notify["scale"].connect (update_selected_scale);
+        update_selected_scale ();
+        scale_drop_down.notify["selected-item"].connect ((drop_down, param_spec) => {
+            // Prevent breaking autohide by closing popover
+            popover.popdown ();
+
+            var i = ((Gtk.DropDown) drop_down).selected;
+
+            if (i < 0 || i > scales.length) {
+                warning ("Invalid scale selected.");
+                return;
+            }
+
+            virtual_monitor.scale = scales[i];
+
+            configuration_changed ();
+        });
+
         rotation_combobox.set_active ((int) virtual_monitor.transform);
         on_vm_transform_changed ();
 
@@ -408,6 +460,14 @@ public class Display.DisplayWidget : Gtk.Box {
         check_position ();
     }
 
+    private void update_selected_scale () {
+        for (uint i = 0; i < scales.length; i++) {
+            if (scales[i] == virtual_monitor.scale) {
+                scale_drop_down.selected = i;
+            }
+        }
+    }
+
     private void populate_refresh_rates () {
         refresh_list_store.clear ();