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Make multi-touch demo a bit nicer looking

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This commit is contained in:
Emil Ernerfeldt 2021-10-18 21:00:25 +02:00
parent 96be848e42
commit ebd2c859ac
2 changed files with 66 additions and 45 deletions
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17
egui/src/ui.rs
View file

@ -997,6 +997,8 @@ impl Ui {
self.placer.advance_cursor(amount);
}
/// Show some text.
///
/// Shortcut for `add(Label::new(text))`
///
/// See also [`Label`].
@ -1005,6 +1007,8 @@ impl Ui {
label.into().ui(self)
}
/// Show colored text.
///
/// Shortcut for `add(Label::new(text).text_color(color))`
pub fn colored_label(
&mut self,
@ -1014,11 +1018,15 @@ impl Ui {
label.into().text_color(color).ui(self)
}
/// Show large text.
///
/// Shortcut for `add(Label::new(text).heading())`
pub fn heading(&mut self, label: impl Into<Label>) -> Response {
label.into().heading().ui(self)
}
/// Show monospace (fixed width) text.
///
/// Shortcut for `add(Label::new(text).monospace())`
pub fn monospace(&mut self, label: impl Into<Label>) -> Response {
label.into().monospace().ui(self)
@ -1031,11 +1039,20 @@ impl Ui {
label.into().code().ui(self)
}
/// Show small text.
///
/// Shortcut for `add(Label::new(text).small())`
pub fn small(&mut self, label: impl Into<Label>) -> Response {
label.into().small().ui(self)
}
/// Show text that stand out a bit (e.g. slightly brighter).
///
/// Shortcut for `add(Label::new(text).strong())`
pub fn strong(&mut self, label: impl Into<Label>) -> Response {
label.into().strong().ui(self)
}
/// Shortcut for `add(Hyperlink::new(url))`
///
/// See also [`Hyperlink`].

94
egui_demo_lib/src/apps/demo/multi_touch.rs
View file

@ -4,21 +4,19 @@ use egui::{
};
pub struct MultiTouch {
previous_arrow_start_offset: Vec2,
rotation: f32,
smoothed_velocity: Vec2,
translation: Vec2,
zoom: f32,
last_touch_time: f64,
}
impl Default for MultiTouch {
fn default() -> Self {
Self {
previous_arrow_start_offset: Vec2::ZERO,
rotation: 0.,
smoothed_velocity: Vec2::ZERO,
translation: Vec2::ZERO,
zoom: 1.,
last_touch_time: 0.0,
}
}
}
@ -45,12 +43,19 @@ impl super::View for MultiTouch {
ui.vertical_centered(|ui| {
ui.add(crate::__egui_github_link_file!());
});
ui.colored_label(
Color32::RED,
"This only works on devices which send native touch events (mostly mobiles).",
ui.strong(
"This demo only works on devices with multitouch support (e.g. mobiles and tablets).",
);
ui.separator();
ui.label("Try touch gestures Pinch/Stretch, Rotation, and Pressure with 2+ fingers.");
let num_touches = ui
.input()
.multi_touch()
.map(|mt| mt.num_touches)
.unwrap_or(0);
ui.label(format!("Current touches: {}", num_touches));
Frame::dark_canvas(ui.style()).show(ui, |ui| {
// Note that we use `Sense::drag()` although we do not use any pointer events. With
// the current implementation, the fact that a touch event of two or more fingers is
@ -64,18 +69,18 @@ impl super::View for MultiTouch {
// set up the drawing canvas with normalized coordinates:
let (response, painter) =
ui.allocate_painter(ui.available_size_before_wrap(), Sense::drag());
// normalize painter coordinates to ±1 units in each direction with [0,0] in the center:
let painter_proportions = response.rect.square_proportions();
let to_screen = RectTransform::from_to(
Rect::from_min_size(Pos2::ZERO - painter_proportions, 2. * painter_proportions),
response.rect,
);
let dt = ui.input().unstable_dt;
// check for touch input (or the lack thereof) and update zoom and scale factors, plus
// color and width:
let mut stroke_width = 1.;
let mut color = Color32::GRAY;
let color = Color32::GRAY;
if let Some(multi_touch) = ui.input().multi_touch() {
// This adjusts the current zoom factor and rotation angle according to the dynamic
// change (for the current frame) of the touch gesture:
@ -84,34 +89,15 @@ impl super::View for MultiTouch {
// the translation we get from `multi_touch` needs to be scaled down to the
// normalized coordinates we use as the basis for painting:
self.translation += to_screen.inverse().scale() * multi_touch.translation_delta;
// touch pressure shall make the arrow thicker (not all touch devices support this):
// touch pressure will make the arrow thicker (not all touch devices support this):
stroke_width += 10. * multi_touch.force;
// the drawing color depends on the number of touches:
color = match multi_touch.num_touches {
2 => Color32::GREEN,
3 => Color32::BLUE,
4 => Color32::YELLOW,
_ => Color32::RED,
};
self.last_touch_time = ui.input().time;
} else {
// This has nothing to do with the touch gesture. It just smoothly brings the
// painted arrow back into its original position, for a nice visual effect:
const ZOOM_ROTATE_HALF_LIFE: f32 = 1.; // time[sec] after which half the amount of zoom/rotation will be reverted
let half_life_factor = (-(2_f32.ln()) / ZOOM_ROTATE_HALF_LIFE * dt).exp();
self.zoom = 1. + ((self.zoom - 1.) * half_life_factor);
self.rotation *= half_life_factor;
self.translation *= half_life_factor;
self.slowly_reset(ui);
}
let zoom_and_rotate = self.zoom * Rot2::from_angle(self.rotation);
let arrow_start_offset = self.translation + zoom_and_rotate * vec2(-0.5, 0.5);
let current_velocity = (arrow_start_offset - self.previous_arrow_start_offset) / dt;
self.previous_arrow_start_offset = arrow_start_offset;
// aggregate the average velocity of the arrow's start position from latest samples:
const NUM_SMOOTHING_SAMPLES: f32 = 10.;
self.smoothed_velocity = ((NUM_SMOOTHING_SAMPLES - 1.) * self.smoothed_velocity
+ current_velocity)
/ NUM_SMOOTHING_SAMPLES;
// Paints an arrow pointing from bottom-left (-0.5, 0.5) to top-right (0.5, -0.5), but
// scaled, rotated, and translated according to the current touch gesture:
@ -122,19 +108,37 @@ impl super::View for MultiTouch {
to_screen.scale() * arrow_direction,
Stroke::new(stroke_width, color),
);
// Paints a circle at the origin of the arrow. The size and opacity of the circle
// depend on the current velocity, and the circle is translated in the opposite
// direction of the movement, so it follows the origin's movement. Constant factors
// have been determined by trial and error.
let speed = self.smoothed_velocity.length();
painter.circle_filled(
to_screen * (arrow_start - 0.2 * self.smoothed_velocity),
2. + to_screen.scale().length() * 0.1 * speed,
Color32::RED.linear_multiply(1. / (1. + (5. * speed).powi(2))),
);
// we want continuous UI updates, so the circle can smoothly follow the arrow's origin:
ui.ctx().request_repaint();
});
}
}
impl MultiTouch {
fn slowly_reset(&mut self, ui: &egui::Ui) {
// This has nothing to do with the touch gesture. It just smoothly brings the
// painted arrow back into its original position, for a nice visual effect:
let time_since_last_touch = (ui.input().time - self.last_touch_time) as f32;
let delay = 0.5;
if time_since_last_touch < delay {
ui.ctx().request_repaint();
} else {
// seconds after which half the amount of zoom/rotation will be reverted:
let half_life =
egui::remap_clamp(time_since_last_touch, delay..=1.0, 1.0..=0.0).powf(4.0);
if half_life <= 1e-3 {
self.zoom = 1.0;
self.rotation = 0.0;
self.translation = Vec2::ZERO;
} else {
let dt = ui.input().unstable_dt;
let half_life_factor = (-(2_f32.ln()) / half_life * dt).exp();
self.zoom = 1. + ((self.zoom - 1.) * half_life_factor);
self.rotation *= half_life_factor;
self.translation *= half_life_factor;
ui.ctx().request_repaint();
}
}
}
}