Desktop: Trackpad pinch to zoom (#3271)

* prototype pinch gesture

* pinch to zoom

* fix

Author: timon-schelling

desktop/src/cef/consts.rs

@@ -8,5 +8,7 @@ pub(crate) const SCROLL_LINE_WIDTH: usize = 40;
 pub(crate) const SCROLL_SPEED_X: f32 = 3.0;
 pub(crate) const SCROLL_SPEED_Y: f32 = 3.0;
 
+pub(crate) const PINCH_ZOOM_SPEED: f64 = 300.0;
+
 pub(crate) const MULTICLICK_TIMEOUT: Duration = Duration::from_millis(500);
 pub(crate) const MULTICLICK_ALLOWED_TRAVEL: usize = 4;

desktop/src/cef/input.rs

@@ -7,7 +7,7 @@ use winit::event::{ButtonSource, ElementState, MouseButton, MouseScrollDelta, Wi
 mod keymap;
 use keymap::{ToNativeKeycode, ToVKBits};
 
-use super::consts::{MULTICLICK_ALLOWED_TRAVEL, MULTICLICK_TIMEOUT, SCROLL_LINE_HEIGHT, SCROLL_LINE_WIDTH, SCROLL_SPEED_X, SCROLL_SPEED_Y};
+use super::consts::{MULTICLICK_ALLOWED_TRAVEL, MULTICLICK_TIMEOUT, PINCH_ZOOM_SPEED, SCROLL_LINE_HEIGHT, SCROLL_LINE_WIDTH, SCROLL_SPEED_X, SCROLL_SPEED_Y};
 
 pub(crate) fn handle_window_event(browser: &Browser, input_state: &mut InputState, event: &WindowEvent) {
 	match event {
@@ -129,6 +129,20 @@ pub(crate) fn handle_window_event(browser: &Browser, input_state: &mut InputStat
 				}
 			}
 		}
+		WindowEvent::PinchGesture { delta, .. } => {
+			if !delta.is_normal() {
+				return;
+			}
+			let Some(host) = browser.host() else { return };
+
+			let mut mouse_event: MouseEvent = input_state.into();
+			mouse_event.modifiers |= cef_event_flags_t::EVENTFLAG_CONTROL_DOWN as u32;
+			mouse_event.modifiers |= cef_event_flags_t::EVENTFLAG_PRECISION_SCROLLING_DELTA as u32;
+
+			let delta = (delta * PINCH_ZOOM_SPEED).round() as i32;
+
+			host.send_mouse_wheel_event(Some(&mouse_event), 0, delta);
+		}
 		_ => {}
 	}
 }