Viewport frame-rate readout (Preferences ▸ Graphics) (#1580)

Thanks @sthifen.

crates/ui-egui/src/prefs.rs

@@ -283,6 +283,8 @@ pub struct Prefs {
     pub supersampling: f32,
     /// Supersample only while the view holds still (full speed while orbiting).
     pub supersampling_adaptive: bool,
+    /// Show the frame rate in the view's corner (the view then redraws every frame).
+    pub show_frame_rate: bool,
     /// Show world X/Y/Z component dimensions beside the total distance in Measure.
     pub measure_axis_distances: bool,
     /// Decimals shown for lengths and angles.
@@ -400,6 +402,7 @@ impl Default for Prefs {
             display_quality: "normal".into(),
             supersampling: 1.0,
             supersampling_adaptive: true,
+            show_frame_rate: false,
             measure_axis_distances: true,
             length_decimals: 2,
             angle_decimals: 1,
@@ -624,6 +627,7 @@ fn defaults(app: &mut SolveApp, page: usize) {
             p.display_quality = d.display_quality;
             p.supersampling = d.supersampling;
             p.supersampling_adaptive = d.supersampling_adaptive;
+            p.show_frame_rate = d.show_frame_rate;
             p.measure_axis_distances = d.measure_axis_distances;
             p.color_vision = d.color_vision;
             app.ui.visual_style = 0;
@@ -1310,6 +1314,13 @@ fn page(app: &mut SolveApp, ui: &mut egui::Ui, t: &Tokens) {
             colour_vision_sample(ui, t);
             ui.end_row();
             note(ui, app.tr("ui.colour_vision_note"));
+            // Last, so the colour vision section above keeps its place on the page.
+            ui.label("");
+            ui.end_row();
+            ui.label(app.tr("ui.frame_rate"));
+            ui.checkbox(&mut app.preferences.show_frame_rate, "");
+            ui.end_row();
+            note(ui, app.tr("settings.frame_rate_note"));
         }
         5 => {
             ui.label(crate::i18n::tr_label("Project face edges into new sketches"));