Implement new winit 0.30 gestures

This has only been tested on Wayland against
rust-windowing/winit#3656 and allows much nicer
interactions when using a touchpad.

The values have been chosen based on what felt pleasant to use on my
Thinkpad x280, I haven’t given it much thought otherwise, and I expect
other touchpads would feel different.

src/controls.rs

@@ -221,6 +221,12 @@ impl OrbitControls {
         self.pan_offset.y -= distance
     }
 
+    pub fn pan_both(&mut self, delta: PhysicalPosition<f32>) {
+        self.pan_offset.x += delta.x;
+        self.pan_offset.y += delta.y;
+        self.update();
+    }
+
     // Processes input received from a mouse scroll-wheel event. Only requires input on the vertical wheel-axis
     pub fn process_mouse_scroll(&mut self, mut yoffset: f32) {
         yoffset *= ZOOM_SENSITIVITY;

src/viewer.rs

@@ -400,6 +400,21 @@ impl winit::application::ApplicationHandler<()> for GltfViewer {
                 self.orbit_controls.process_mouse_scroll(lines * 3.0);
                 self.window.as_ref().unwrap().request_redraw();
             }
+            WindowEvent::PanGesture { delta, .. } => {
+                let mut delta = delta;
+                delta.x /= 1024.;
+                delta.y /= 1024.;
+                self.orbit_controls.pan_both(delta);
+                self.window.as_ref().unwrap().request_redraw();
+            }
+            WindowEvent::PinchGesture { delta, .. } => {
+                self.orbit_controls.process_mouse_scroll(1024. * delta as f32);
+                self.window.as_ref().unwrap().request_redraw();
+            }
+            WindowEvent::RotationGesture { delta, .. } => {
+                self.orbit_controls.rotate_object(-delta * std::f32::consts::PI / 180.);
+                self.window.as_ref().unwrap().request_redraw();
+            }
             WindowEvent::KeyboardInput { event, .. } => {
                 let pressed = match event.state {
                     Pressed => true,