Implement repaint_after for eframe web (#1760)

* Implement repaint_after for eframe web

Follow-up to #1694

* cargo fmt

* Simplify demo UI for "repaint_after"

eframe/src/web/backend.rs

@@ -2,7 +2,9 @@ use super::{glow_wrapping::WrappedGlowPainter, *};
 
 use crate::epi;
 
+use egui::mutex::{Mutex, MutexGuard};
 use egui::TexturesDelta;
+
 pub use egui::{pos2, Color32};
 
 // ----------------------------------------------------------------------------
@@ -34,21 +36,34 @@ impl WebInput {
 
 use std::sync::atomic::Ordering::SeqCst;
 
-pub struct NeedRepaint(std::sync::atomic::AtomicBool);
+/// Stores when to do the next repaint.
+pub struct NeedRepaint(Mutex<f64>);
 
 impl Default for NeedRepaint {
     fn default() -> Self {
-        Self(true.into())
+        Self(Mutex::new(f64::NEG_INFINITY)) // start with a repaint
     }
 }
 
 impl NeedRepaint {
-    pub fn fetch_and_clear(&self) -> bool {
-        self.0.swap(false, SeqCst)
+    /// Returns the time (in [`now_sec`] scale) when
+    /// we should next repaint.
+    pub fn when_to_repaint(&self) -> f64 {
+        *self.0.lock()
     }
 
-    pub fn set_true(&self) {
-        self.0.store(true, SeqCst);
+    /// Unschedule repainting.
+    pub fn clear(&self) {
+        *self.0.lock() = f64::INFINITY;
+    }
+
+    pub fn repaint_after(&self, num_seconds: f64) {
+        let mut repaint_time = self.0.lock();
+        *repaint_time = repaint_time.min(now_sec() + num_seconds);
+    }
+
+    pub fn repaint_asap(&self) {
+        *self.0.lock() = f64::NEG_INFINITY;
     }
 }
 
@@ -194,7 +209,7 @@ impl AppRunner {
         {
             let needs_repaint = needs_repaint.clone();
             egui_ctx.set_request_repaint_callback(move || {
-                needs_repaint.0.store(true, SeqCst);
+                needs_repaint.repaint_asap();
             });
         }
 
@@ -420,7 +435,6 @@ fn start_runner(app_runner: AppRunner) -> Result<AppRunnerRef, JsValue> {
     super::events::install_canvas_events(&runner_container)?;
     super::events::install_document_events(&runner_container)?;
     text_agent::install_text_agent(&runner_container)?;
-    super::events::repaint_every_ms(&runner_container, 1000)?; // just in case. TODO(emilk): make it a parameter
 
     super::events::paint_and_schedule(&runner_container.runner, runner_container.panicked.clone())?;
 

eframe/src/web/events.rs

@@ -7,14 +7,14 @@ pub fn paint_and_schedule(
 ) -> Result<(), JsValue> {
     fn paint_if_needed(runner_ref: &AppRunnerRef) -> Result<(), JsValue> {
         let mut runner_lock = runner_ref.lock();
-        if runner_lock.needs_repaint.fetch_and_clear() {
+        if runner_lock.needs_repaint.when_to_repaint() <= now_sec() {
+            runner_lock.needs_repaint.clear();
             runner_lock.clear_color_buffer();
             let (repaint_after, clipped_primitives) = runner_lock.logic()?;
             runner_lock.paint(&clipped_primitives)?;
-            if repaint_after.is_zero() {
-                runner_lock.needs_repaint.set_true();
-            }
-            // TODO: schedule a repaint after `repaint_after` when it is not zero
+            runner_lock
+                .needs_repaint
+                .repaint_after(repaint_after.as_secs_f64());
             runner_lock.auto_save();
         }
 
@@ -75,7 +75,7 @@ pub fn install_document_events(runner_container: &AppRunnerContainer) -> Result<
             {
                 runner_lock.input.raw.events.push(egui::Event::Text(key));
             }
-            runner_lock.needs_repaint.set_true();
+            runner_lock.needs_repaint.repaint_asap();
 
             let egui_wants_keyboard = runner_lock.egui_ctx().wants_keyboard_input();
 
@@ -123,7 +123,7 @@ pub fn install_document_events(runner_container: &AppRunnerContainer) -> Result<
                     modifiers,
                 });
             }
-            runner_lock.needs_repaint.set_true();
+            runner_lock.needs_repaint.repaint_asap();
         },
     )?;
 
@@ -137,7 +137,7 @@ pub fn install_document_events(runner_container: &AppRunnerContainer) -> Result<
                     let text = text.replace("\r\n", "\n");
                     if !text.is_empty() {
                         runner_lock.input.raw.events.push(egui::Event::Paste(text));
-                        runner_lock.needs_repaint.set_true();
+                        runner_lock.needs_repaint.repaint_asap();
                     }
                     event.stop_propagation();
                     event.prevent_default();
@@ -152,7 +152,7 @@ pub fn install_document_events(runner_container: &AppRunnerContainer) -> Result<
         "cut",
         |_: web_sys::ClipboardEvent, mut runner_lock| {
             runner_lock.input.raw.events.push(egui::Event::Cut);
-            runner_lock.needs_repaint.set_true();
+            runner_lock.needs_repaint.repaint_asap();
         },
     )?;
 
@@ -162,7 +162,7 @@ pub fn install_document_events(runner_container: &AppRunnerContainer) -> Result<
         "copy",
         |_: web_sys::ClipboardEvent, mut runner_lock| {
             runner_lock.input.raw.events.push(egui::Event::Copy);
-            runner_lock.needs_repaint.set_true();
+            runner_lock.needs_repaint.repaint_asap();
         },
     )?;
 
@@ -171,7 +171,7 @@ pub fn install_document_events(runner_container: &AppRunnerContainer) -> Result<
             &window,
             event_name,
             |_: web_sys::Event, runner_lock| {
-                runner_lock.needs_repaint.set_true();
+                runner_lock.needs_repaint.repaint_asap();
             },
         )?;
     }
@@ -190,38 +190,6 @@ pub fn install_document_events(runner_container: &AppRunnerContainer) -> Result<
     Ok(())
 }
 
-/// Repaint at least every `ms` milliseconds.
-pub fn repaint_every_ms(
-    runner_container: &AppRunnerContainer,
-    milliseconds: i32,
-) -> Result<(), JsValue> {
-    assert!(milliseconds >= 0);
-
-    use wasm_bindgen::JsCast;
-
-    let window = web_sys::window().unwrap();
-
-    let closure = Closure::wrap(Box::new({
-        let runner = runner_container.runner.clone();
-        let panicked = runner_container.panicked.clone();
-
-        move || {
-            // Do not lock the runner if the code has panicked
-            if !panicked.load(Ordering::SeqCst) {
-                runner.lock().needs_repaint.set_true();
-            }
-        }
-    }) as Box<dyn FnMut()>);
-
-    window.set_interval_with_callback_and_timeout_and_arguments_0(
-        closure.as_ref().unchecked_ref(),
-        milliseconds,
-    )?;
-
-    closure.forget();
-    Ok(())
-}
-
 pub fn install_canvas_events(runner_container: &AppRunnerContainer) -> Result<(), JsValue> {
     use wasm_bindgen::JsCast;
     let canvas = canvas_element(runner_container.runner.lock().canvas_id()).unwrap();
@@ -254,7 +222,7 @@ pub fn install_canvas_events(runner_container: &AppRunnerContainer) -> Result<()
                         pressed: true,
                         modifiers,
                     });
-                runner_lock.needs_repaint.set_true();
+                runner_lock.needs_repaint.repaint_asap();
             }
             event.stop_propagation();
             // Note: prevent_default breaks VSCode tab focusing, hence why we don't call it here.
@@ -271,7 +239,7 @@ pub fn install_canvas_events(runner_container: &AppRunnerContainer) -> Result<()
                 .raw
                 .events
                 .push(egui::Event::PointerMoved(pos));
-            runner_lock.needs_repaint.set_true();
+            runner_lock.needs_repaint.repaint_asap();
             event.stop_propagation();
             event.prevent_default();
         },
@@ -294,7 +262,7 @@ pub fn install_canvas_events(runner_container: &AppRunnerContainer) -> Result<()
                         pressed: false,
                         modifiers,
                     });
-                runner_lock.needs_repaint.set_true();
+                runner_lock.needs_repaint.repaint_asap();
 
                 text_agent::update_text_agent(runner_lock);
             }
@@ -308,7 +276,7 @@ pub fn install_canvas_events(runner_container: &AppRunnerContainer) -> Result<()
         "mouseleave",
         |event: web_sys::MouseEvent, mut runner_lock| {
             runner_lock.input.raw.events.push(egui::Event::PointerGone);
-            runner_lock.needs_repaint.set_true();
+            runner_lock.needs_repaint.repaint_asap();
             event.stop_propagation();
             event.prevent_default();
         },
@@ -336,7 +304,7 @@ pub fn install_canvas_events(runner_container: &AppRunnerContainer) -> Result<()
                 });
 
             push_touches(&mut *runner_lock, egui::TouchPhase::Start, &event);
-            runner_lock.needs_repaint.set_true();
+            runner_lock.needs_repaint.repaint_asap();
             event.stop_propagation();
             event.prevent_default();
         },
@@ -358,7 +326,7 @@ pub fn install_canvas_events(runner_container: &AppRunnerContainer) -> Result<()
                 .push(egui::Event::PointerMoved(pos));
 
             push_touches(&mut *runner_lock, egui::TouchPhase::Move, &event);
-            runner_lock.needs_repaint.set_true();
+            runner_lock.needs_repaint.repaint_asap();
             event.stop_propagation();
             event.prevent_default();
         },
@@ -385,7 +353,7 @@ pub fn install_canvas_events(runner_container: &AppRunnerContainer) -> Result<()
                 runner_lock.input.raw.events.push(egui::Event::PointerGone);
 
                 push_touches(&mut *runner_lock, egui::TouchPhase::End, &event);
-                runner_lock.needs_repaint.set_true();
+                runner_lock.needs_repaint.repaint_asap();
                 event.stop_propagation();
                 event.prevent_default();
             }
@@ -444,7 +412,7 @@ pub fn install_canvas_events(runner_container: &AppRunnerContainer) -> Result<()
                     .push(egui::Event::Scroll(delta));
             }
 
-            runner_lock.needs_repaint.set_true();
+            runner_lock.needs_repaint.repaint_asap();
             event.stop_propagation();
             event.prevent_default();
         },
@@ -464,7 +432,7 @@ pub fn install_canvas_events(runner_container: &AppRunnerContainer) -> Result<()
                         });
                     }
                 }
-                runner_lock.needs_repaint.set_true();
+                runner_lock.needs_repaint.repaint_asap();
                 event.stop_propagation();
                 event.prevent_default();
             }
@@ -476,7 +444,7 @@ pub fn install_canvas_events(runner_container: &AppRunnerContainer) -> Result<()
         "dragleave",
         |event: web_sys::DragEvent, mut runner_lock| {
             runner_lock.input.raw.hovered_files.clear();
-            runner_lock.needs_repaint.set_true();
+            runner_lock.needs_repaint.repaint_asap();
             event.stop_propagation();
             event.prevent_default();
         },
@@ -488,7 +456,7 @@ pub fn install_canvas_events(runner_container: &AppRunnerContainer) -> Result<()
         move |event: web_sys::DragEvent, mut runner_lock| {
             if let Some(data_transfer) = event.data_transfer() {
                 runner_lock.input.raw.hovered_files.clear();
-                runner_lock.needs_repaint.set_true();
+                runner_lock.needs_repaint.repaint_asap();
                 // Unlock the runner so it can be locked after a future await point
                 drop(runner_lock);
 
@@ -524,7 +492,7 @@ pub fn install_canvas_events(runner_container: &AppRunnerContainer) -> Result<()
                                                 ..Default::default()
                                             },
                                         );
-                                        runner_lock.needs_repaint.set_true();
+                                        runner_lock.needs_repaint.repaint_asap();
                                     }
                                     Err(err) => {
                                         tracing::error!("Failed to read file: {:?}", err);

eframe/src/web/mod.rs

@@ -20,7 +20,6 @@ use std::sync::{
     Arc,
 };
 
-use egui::mutex::{Mutex, MutexGuard};
 use wasm_bindgen::prelude::*;
 use web_sys::EventTarget;
 
@@ -30,7 +29,9 @@ use crate::Theme;
 
 // ----------------------------------------------------------------------------
 
-/// Current time in seconds (since undefined point in time)
+/// Current time in seconds (since undefined point in time).
+///
+/// Monotonically increasing.
 pub fn now_sec() -> f64 {
     web_sys::window()
         .expect("should have a Window")

eframe/src/web/text_agent.rs

@@ -55,7 +55,7 @@ pub fn install_text_agent(runner_container: &AppRunnerContainer) -> Result<(), J
             if !text.is_empty() && !is_composing.get() {
                 input_clone.set_value("");
                 runner_lock.input.raw.events.push(egui::Event::Text(text));
-                runner_lock.needs_repaint.set_true();
+                runner_lock.needs_repaint.repaint_asap();
             }
         }
     })?;
@@ -75,7 +75,7 @@ pub fn install_text_agent(runner_container: &AppRunnerContainer) -> Result<(), J
                     .raw
                     .events
                     .push(egui::Event::CompositionStart);
-                runner_lock.needs_repaint.set_true();
+                runner_lock.needs_repaint.repaint_asap();
             }
         })?;
 
@@ -85,7 +85,7 @@ pub fn install_text_agent(runner_container: &AppRunnerContainer) -> Result<(), J
             move |event: web_sys::CompositionEvent, mut runner_lock: MutexGuard<'_, AppRunner>| {
                 if let Some(event) = event.data().map(egui::Event::CompositionUpdate) {
                     runner_lock.input.raw.events.push(event);
-                    runner_lock.needs_repaint.set_true();
+                    runner_lock.needs_repaint.repaint_asap();
                 }
             },
         )?;
@@ -99,7 +99,7 @@ pub fn install_text_agent(runner_container: &AppRunnerContainer) -> Result<(), J
 
                 if let Some(event) = event.data().map(egui::Event::CompositionEnd) {
                     runner_lock.input.raw.events.push(event);
-                    runner_lock.needs_repaint.set_true();
+                    runner_lock.needs_repaint.repaint_asap();
                 }
             }
         })?;

egui_demo_app/src/backend_panel.rs

@@ -49,12 +49,11 @@ pub struct BackendPanel {
     pub open: bool,
 
     #[cfg_attr(feature = "serde", serde(skip))]
-    // go back to [`Reactive`] mode each time we start
+    // go back to [`RunMode::Reactive`] mode each time we start
     run_mode: RunMode,
 
     #[cfg_attr(feature = "serde", serde(skip))]
-    // reset to 1 second as default repaint_after idle timeout.
-    repaint_after_timeout: std::time::Duration,
+    repaint_after_seocnds: f32,
 
     /// current slider value for current gui scale
     #[cfg_attr(feature = "serde", serde(skip))]
@@ -71,7 +70,7 @@ impl Default for BackendPanel {
         Self {
             open: false,
             run_mode: Default::default(),
-            repaint_after_timeout: std::time::Duration::from_secs(1),
+            repaint_after_seocnds: 1.0,
             pixels_per_point: None,
             frame_history: Default::default(),
             egui_windows: Default::default(),
@@ -85,13 +84,16 @@ impl BackendPanel {
             .on_new_frame(ctx.input().time, frame.info().cpu_usage);
 
         match self.run_mode {
-            RunMode::Reactive => {
-                ctx.request_repaint_after(self.repaint_after_timeout);
-            }
             RunMode::Continuous => {
                 // Tell the backend to repaint as soon as possible
                 ctx.request_repaint();
             }
+            RunMode::Reactive => {
+                // let the computer rest for a bit
+                ctx.request_repaint_after(std::time::Duration::from_secs_f32(
+                    self.repaint_after_seocnds,
+                ));
+            }
         }
     }
 
@@ -243,16 +245,18 @@ impl BackendPanel {
             ));
         } else {
             ui.label("Only running UI code when there are animations or input.");
-            ui.label("but if there's no input for the repaint_after duration, we force an update");
-            ui.label("repaint_after (in seconds)");
-            let mut seconds = self.repaint_after_timeout.as_secs_f32();
-            if egui::DragValue::new(&mut seconds)
+
+            ui.horizontal(|ui| {
+                ui.spacing_mut().item_spacing.x = 0.0;
+                ui.label("(but at least every ");
+                egui::DragValue::new(&mut self.repaint_after_seocnds)
                     .clamp_range(0.1..=10.0)
+                    .speed(0.1)
+                    .suffix(" s")
                     .ui(ui)
-                .changed()
-            {
-                self.repaint_after_timeout = std::time::Duration::from_secs_f32(seconds);
-            }
+                    .on_hover_text("Repaint this often, even if there is no input.");
+                ui.label(")");
+            });
         }
     }
 }