migrations/egui
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impl<F> Widget for F where F: FnOnce(&mut Ui) -> Response

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This enables functions that return `impl Widget`, so that you can
create a widget by just returning a lambda from a function.

For instance: `ui.add(toggle(bool))` (instead of `toggle(ui, bool)`)
This commit is contained in:
Emil Ernerfeldt
2021-02-20 11:58:08 +01:00
parent 6fe70e685b
commit 040553da78
4 changed files with 62 additions and 48 deletions
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28
egui_demo_lib/src/apps/demo/toggle_switch.rs
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@@ -9,7 +9,12 @@
/// | |.......|
/// \_______\_____/
/// ```
pub fn toggle(ui: &mut egui::Ui, on: &mut bool) -> egui::Response {
///
/// ## Example:
/// ``` ignore
/// toggle_ui(ui, &mut my_bool);
/// ```
pub fn toggle_ui(ui: &mut egui::Ui, on: &mut bool) -> egui::Response {
// Widget code can be broken up in four steps:
// 1. Decide a size for the widget
// 2. Allocate space for it
@@ -58,7 +63,7 @@ pub fn toggle(ui: &mut egui::Ui, on: &mut bool) -> egui::Response {
/// Here is the same code again, but a bit more compact:
#[allow(dead_code)]
fn toggle_compact(ui: &mut egui::Ui, on: &mut bool) -> egui::Response {
fn toggle_ui_compact(ui: &mut egui::Ui, on: &mut bool) -> egui::Response {
let desired_size = ui.spacing().interact_size.y * egui::vec2(2.0, 1.0);
let (rect, response) = ui.allocate_exact_size(desired_size, egui::Sense::click());
*on ^= response.clicked(); // toggle if clicked
@@ -77,14 +82,13 @@ fn toggle_compact(ui: &mut egui::Ui, on: &mut bool) -> egui::Response {
response
}
pub fn demo(ui: &mut egui::Ui, on: &mut bool) {
ui.horizontal_wrapped_for_text(egui::TextStyle::Button, |ui| {
toggle(ui, on).on_hover_text("Click to toggle");
ui.add(crate::__egui_github_link_file!());
})
.response
.on_hover_text(
"It's easy to create your own widgets!\n\
This toggle switch is just one function and 15 lines of code.",
);
// A wrapper that allows the more idiomatic usage pattern: `ui.add(toggle(&mut my_bool))`
/// iOS-style toggle switch.
///
/// ## Example:
/// ``` ignore
/// ui.add(toggle(&mut my_bool));
/// ```
pub fn toggle(on: &mut bool) -> impl egui::Widget + '_ {
move |ui: &mut egui::Ui| toggle_ui(ui, on)
}