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Implement trackpad pinch-to-zoom for plots in egui_web (#333)

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This adds a new `zoom_delta` to input.
This is hooked up to ctrl-scroll on egui_web and egui_glium.

Browsers convert trackpad pinch gestures to ctrl-scroll,
so this means you can not pinch-to-zoom plots (on trackpad).

In the future we can support multitouch pinch-to-zoom via the same
`InputState::zoom_factor()` function
This commit is contained in:
Emil Ernerfeldt
2021-04-25 17:04:34 +02:00
committed by GitHub
parent 7f0689e566
commit c2744a1437
8 changed files with 72 additions and 29 deletions
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13
egui_web/src/lib.rs
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@@ -963,13 +963,20 @@ fn install_canvas_events(runner_ref: &AppRunnerRef) -> Result<(), JsValue> {
canvas_size_in_points(runner_ref.0.lock().canvas_id()).y
}
web_sys::WheelEvent::DOM_DELTA_LINE => {
24.0 // TODO: tweak this
8.0 // magic value!
}
_ => 1.0,
};
runner_lock.input.raw.scroll_delta.x -= scroll_multiplier * event.delta_x() as f32;
runner_lock.input.raw.scroll_delta.y -= scroll_multiplier * event.delta_y() as f32;
let delta = -scroll_multiplier
* egui::Vec2::new(event.delta_x() as f32, event.delta_y() as f32);
if event.ctrl_key() {
runner_lock.input.raw.zoom_delta *= (delta.y / 200.0).exp();
} else {
runner_lock.input.raw.scroll_delta += delta;
}
runner_lock.needs_repaint.set_true();
event.stop_propagation();
event.prevent_default();