Fix key pressed event (#2334)

* Fix key press event

* Add example with key presses

* Changelog line for key_press fix

* PR review improvements

* Add PR link in changelog

Co-authored-by: Emil Ernerfeldt <[email protected]>

CHANGELOG.md

@@ -8,6 +8,7 @@ NOTE: [`epaint`](crates/epaint/CHANGELOG.md), [`eframe`](crates/eframe/CHANGELOG
 * MSRV (Minimum Supported Rust Version) is now `1.65.0` ([#2314](https://github.com/emilk/egui/pull/2314)).
 * ⚠️ BREAKING: egui now expects integrations to do all color blending in gamma space ([#2071](https://github.com/emilk/egui/pull/2071)).
 * ⚠️ BREAKING: if you have overlapping interactive widgets, only the top widget (last added) will be interactive ([#2244](https://github.com/emilk/egui/pull/2244)).
+* Keyboard press events are only present at the frame when the key was pressed, consistent with how key releases work ([#2334](https://github.com/emilk/egui/pull/2334)).
 
 ### Added ⭐
 * Added helper functions for animating panels that collapse/expand ([#2190](https://github.com/emilk/egui/pull/2190)).

crates/egui/src/input_state.rs

@@ -138,7 +138,11 @@ impl Default for InputState {
 
 impl InputState {
     #[must_use]
-    pub fn begin_frame(mut self, new: RawInput, requested_repaint_last_frame: bool) -> InputState {
+    pub fn begin_frame(
+        mut self,
+        mut new: RawInput,
+        requested_repaint_last_frame: bool,
+    ) -> InputState {
         let time = new.time.unwrap_or(self.time + new.predicted_dt as f64);
         let unstable_dt = (time - self.time) as f32;
 
@@ -160,24 +164,26 @@ impl InputState {
         let mut keys_down = self.keys_down;
         let mut scroll_delta = Vec2::ZERO;
         let mut zoom_factor_delta = 1.0;
-        for event in &new.events {
-            match event {
-                Event::Key { key, pressed, .. } => {
-                    if *pressed {
-                        keys_down.insert(*key);
-                    } else {
-                        keys_down.remove(key);
-                    }
-                }
-                Event::Scroll(delta) => {
-                    scroll_delta += *delta;
-                }
-                Event::Zoom(factor) => {
-                    zoom_factor_delta *= *factor;
+        new.events.retain(|event| match event {
+            Event::Key { key, pressed, .. } => {
+                if *pressed {
+                    // We only retain presses that are novel (i.e. the first Press event, not those generated by key-repeat)
+                    keys_down.insert(*key)
+                } else {
+                    keys_down.remove(key);
+                    true
                 }
-                _ => {}
             }
-        }
+            Event::Scroll(delta) => {
+                scroll_delta += *delta;
+                true
+            }
+            Event::Zoom(factor) => {
+                zoom_factor_delta *= *factor;
+                true
+            }
+            _ => true,
+        });
         InputState {
             pointer,
             touch_states: self.touch_states,
@@ -285,7 +291,7 @@ impl InputState {
         self.num_presses(desired_key) > 0
     }
 
-    /// How many times were the given key pressed this frame?
+    /// How many times was the given key pressed this frame?
     pub fn num_presses(&self, desired_key: Key) -> usize {
         self.events
             .iter()

examples/keyboard_events/Cargo.toml

@@ -0,0 +1,13 @@
+[package]
+name = "keyboard_events"
+version = "0.1.0"
+authors = ["Jose Palazon <[email protected]>"]
+license = "MIT OR Apache-2.0"
+edition = "2021"
+rust-version = "1.65"
+publish = false
+
+
+[dependencies]
+eframe = { path = "../../crates/eframe" }
+tracing-subscriber = "0.3"

examples/keyboard_events/README.md

@@ -0,0 +1,3 @@
+```sh
+cargo run -p hello_world
+```

examples/keyboard_events/src/main.rs

@@ -0,0 +1,48 @@
+#![cfg_attr(not(debug_assertions), windows_subsystem = "windows")] // hide console window on Windows in release
+
+use eframe::egui;
+use egui::*;
+fn main() {
+    // Log to stdout (if you run with `RUST_LOG=debug`).
+    tracing_subscriber::fmt::init();
+
+    let options = eframe::NativeOptions::default();
+    eframe::run_native(
+        "Keyboard events",
+        options,
+        Box::new(|_cc| Box::new(Content::default())),
+    );
+}
+
+#[derive(Default)]
+struct Content {
+    text: String,
+}
+
+impl eframe::App for Content {
+    fn update(&mut self, ctx: &egui::Context, _frame: &mut eframe::Frame) {
+        egui::CentralPanel::default().show(ctx, |ui| {
+            ui.heading("Press/Hold/Release example. Press A to test.");
+            if ui.button("Clear").clicked() {
+                self.text.clear();
+            }
+            ScrollArea::vertical()
+                .auto_shrink([false; 2])
+                .stick_to_bottom(true)
+                .show(ui, |ui| {
+                    ui.label(&self.text);
+                });
+
+            if ctx.input().key_pressed(Key::A) {
+                self.text.push_str("\nPressed");
+            }
+            if ctx.input().key_down(Key::A) {
+                self.text.push_str("\nHeld");
+                ui.ctx().request_repaint(); // make sure we note the holding.
+            }
+            if ctx.input().key_released(Key::A) {
+                self.text.push_str("\nReleased");
+            }
+        });
+    }
+}