[frame_stats] Add a VSync toggle key; show the current VSync state in stats UI

examples/with_winit/README.md

@@ -20,4 +20,5 @@ $ cargo run -p with_winit --release -- [SVG FILES]
 - Space resets the position and zoom of the image.
 - S toggles the frame statistics layer
 - C resets the min/max frame time tracked by statistics
+- V toggles VSync on/off (default: on)
 - Escape exits the program.

examples/with_winit/src/lib.rs

@@ -100,6 +100,7 @@ fn run(
     let mut images = ImageCache::new();
     let mut stats = stats::Stats::new();
     let mut stats_shown = true;
+    let mut vsync_on = true;
     let start = Instant::now();
 
     let mut touch_state = multi_touch::TouchState::new();
@@ -151,6 +152,17 @@ fn run(
                             Some(VirtualKeyCode::C) => {
                                 stats.clear_min_and_max();
                             }
+                            Some(VirtualKeyCode::V) => {
+                                vsync_on = !vsync_on;
+                                render_cx.set_present_mode(
+                                    &mut render_state.surface,
+                                    if vsync_on {
+                                        wgpu::PresentMode::Fifo
+                                    } else {
+                                        wgpu::PresentMode::Immediate
+                                    },
+                                );
+                            }
                             Some(VirtualKeyCode::Escape) => {
                                 *control_flow = ControlFlow::Exit;
                             }
@@ -314,6 +326,7 @@ fn run(
                     width as f64,
                     height as f64,
                     stats.samples(),
+                    vsync_on,
                 );
             }
             let surface_texture = render_state

examples/with_winit/src/stats.rs

@@ -40,17 +40,17 @@ impl Snapshot {
         viewport_width: f64,
         viewport_height: f64,
         samples: T,
+        vsync: bool,
     ) where
         T: Iterator<Item = &'a u64>,
     {
         let width = (viewport_width * 0.4).max(200.).min(600.);
-        let height = width * 0.6;
+        let height = width * 0.7;
         let x_offset = viewport_width - width;
         let y_offset = viewport_height - height;
         let offset = Affine::translate((x_offset, y_offset));
-        let text_height = height * 0.1;
-        let left_margin = width * 0.01;
-        let text_size = (text_height * 0.9) as f32;
+
+        // Draw the background
         sb.fill(
             Fill::NonZero,
             offset,
@@ -58,38 +58,29 @@ impl Snapshot {
             None,
             &Rect::new(0., 0., width, height),
         );
-        text.add(
-            sb,
-            None,
-            text_size,
-            Some(&Brush::Solid(Color::WHITE)),
-            offset * Affine::translate((left_margin, text_height)),
-            &format!("Frame Time: {:.2} ms", self.frame_time_ms),
-        );
-        text.add(
-            sb,
-            None,
-            text_size,
-            Some(&Brush::Solid(Color::WHITE)),
-            offset * Affine::translate((left_margin, 2. * text_height)),
-            &format!("Frame Time (min): {:.2} ms", self.frame_time_min_ms),
-        );
-        text.add(
-            sb,
-            None,
-            text_size,
-            Some(&Brush::Solid(Color::WHITE)),
-            offset * Affine::translate((left_margin, 3. * text_height)),
-            &format!("Frame Time (max): {:.2} ms", self.frame_time_max_ms),
-        );
-        text.add(
-            sb,
-            None,
-            text_size,
-            Some(&Brush::Solid(Color::WHITE)),
-            offset * Affine::translate((left_margin, 4. * text_height)),
-            &format!("Resolution: {viewport_width}x{viewport_height}"),
-        );
+
+        let labels = [
+            format!("Frame Time: {:.2} ms", self.frame_time_ms),
+            format!("Frame Time (min): {:.2} ms", self.frame_time_min_ms),
+            format!("Frame Time (max): {:.2} ms", self.frame_time_max_ms),
+            format!("VSync: {}", if vsync { "on" } else { "off" }),
+            format!("Resolution: {viewport_width}x{viewport_height}"),
+        ];
+
+        // height / 2 is dedicated to the text labels and the rest is filled by the bar graph.
+        let text_height = height * 0.5 / (1 + labels.len()) as f64;
+        let left_margin = width * 0.01;
+        let text_size = (text_height * 0.9) as f32;
+        for (i, label) in labels.iter().enumerate() {
+            text.add(
+                sb,
+                None,
+                text_size,
+                Some(&Brush::Solid(Color::WHITE)),
+                offset * Affine::translate((left_margin, (i + 1) as f64 * text_height)),
+                &label,
+            );
+        }
         text.add(
             sb,
             None,
@@ -112,7 +103,7 @@ impl Snapshot {
             LineTo((bar_width, graph_max_height).into()),
         ];
         for (i, sample) in samples.enumerate() {
-            let t = offset * Affine::translate(((i as f64) * bar_extent, graph_max_height));
+            let t = offset * Affine::translate((i as f64 * bar_extent, graph_max_height));
             // The height of each sample is based on its ratio to the maximum observed frame time.
             // Currently this maximum scale is sticky and a high temporary spike will permanently
             // shrink the draw size of the overall average sample, so scale the size non-linearly to
@@ -121,7 +112,7 @@ impl Snapshot {
             let s = Affine::scale_non_uniform(1., -h.sqrt());
             sb.fill(
                 Fill::NonZero,
-                t * Affine::translate((left_margin, 5. * text_height)) * s,
+                t * Affine::translate((left_margin, (1 + labels.len()) as f64 * text_height)) * s,
                 Color::rgb8(0, 240, 0),
                 None,
                 &bar,

src/util.rs

@@ -92,6 +92,13 @@ impl RenderContext {
             .configure(&self.devices[surface.dev_id].device, &surface.config);
     }
 
+    pub fn set_present_mode(&self, surface: &mut RenderSurface, present_mode: wgpu::PresentMode) {
+        surface.config.present_mode = present_mode;
+        surface
+            .surface
+            .configure(&self.devices[surface.dev_id].device, &surface.config);
+    }
+
     /// Finds or creates a compatible device handle id.
     pub async fn device(&mut self, compatible_surface: Option<&Surface>) -> Option<usize> {
         let compatible = match compatible_surface {