Draft `reactive-rendering` feature for `button`

6 files changed, 156 insertions, 86 deletions

diff --git a/Cargo.toml b/Cargo.toml
index 2db66da2..bf85ada2 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -22,20 +22,20 @@ all-features = true
 maintenance = { status = "actively-developed" }
 
 [features]
-default = ["wgpu", "tiny-skia", "fira-sans", "auto-detect-theme"]
-# Enable the `wgpu` GPU-accelerated renderer backend
+default = ["wgpu", "tiny-skia", "fira-sans", "auto-detect-theme", "reactive-rendering"]
+# Enables the `wgpu` GPU-accelerated renderer backend
 wgpu = ["iced_renderer/wgpu", "iced_widget/wgpu"]
-# Enable the `tiny-skia` software renderer backend
+# Enables the `tiny-skia` software renderer backend
 tiny-skia = ["iced_renderer/tiny-skia"]
-# Enables the `Image` widget
+# Enables the `image` widget
 image = ["image-without-codecs", "image/default"]
-# Enables the `Image` widget, without any built-in codecs of the `image` crate
+# Enables the `image` widget, without any built-in codecs of the `image` crate
 image-without-codecs = ["iced_widget/image", "dep:image"]
-# Enables the `Svg` widget
+# Enables the `svg` widget
 svg = ["iced_widget/svg"]
-# Enables the `Canvas` widget
+# Enables the `canvas` widget
 canvas = ["iced_widget/canvas"]
-# Enables the `QRCode` widget
+# Enables the `qr_code` widget
 qr_code = ["iced_widget/qr_code"]
 # Enables the `markdown` widget
 markdown = ["iced_widget/markdown"]
@@ -55,18 +55,18 @@ system = ["iced_winit/system"]
 web-colors = ["iced_renderer/web-colors"]
 # Enables the WebGL backend, replacing WebGPU
 webgl = ["iced_renderer/webgl"]
-# Enables the syntax `highlighter` module
+# Enables syntax highligthing
 highlighter = ["iced_highlighter", "iced_widget/highlighter"]
-# Enables experimental multi-window support.
-multi-window = ["iced_winit/multi-window"]
 # Enables the advanced module
 advanced = ["iced_core/advanced", "iced_widget/advanced"]
-# Enables embedding Fira Sans as the default font on Wasm builds
+# Embeds Fira Sans as the default font on Wasm builds
 fira-sans = ["iced_renderer/fira-sans"]
-# Enables auto-detecting light/dark mode for the built-in theme
+# Auto-detects light/dark mode for the built-in theme
 auto-detect-theme = ["iced_core/auto-detect-theme"]
 # Enables strict assertions for debugging purposes at the expense of performance
 strict-assertions = ["iced_renderer/strict-assertions"]
+# Redraws only when widgets react to some runtime event
+reactive-rendering = ["iced_winit/reactive-rendering"]
 
 [dependencies]
 iced_core.workspace = true
diff --git a/examples/multi_window/Cargo.toml b/examples/multi_window/Cargo.toml
index 2e222dfb..3f89417f 100644
--- a/examples/multi_window/Cargo.toml
+++ b/examples/multi_window/Cargo.toml
@@ -6,4 +6,4 @@ edition = "2021"
 publish = false
 
 [dependencies]
-iced = { path = "../..", features = ["debug", "multi-window"] }
+iced = { path = "../..", features = ["debug"] }
diff --git a/widget/src/button.rs b/widget/src/button.rs
index a3394a01..5850cea0 100644
--- a/widget/src/button.rs
+++ b/widget/src/button.rs
@@ -26,6 +26,7 @@ use crate::core::theme::palette;
 use crate::core::touch;
 use crate::core::widget::tree::{self, Tree};
 use crate::core::widget::Operation;
+use crate::core::window;
 use crate::core::{
     Background, Clipboard, Color, Element, Layout, Length, Padding, Rectangle,
     Shadow, Shell, Size, Theme, Vector, Widget,
@@ -81,6 +82,7 @@ where
     padding: Padding,
     clip: bool,
     class: Theme::Class<'a>,
+    status: Option<Status>,
 }
 
 enum OnPress<'a, Message> {
@@ -117,6 +119,7 @@ where
             padding: DEFAULT_PADDING,
             clip: false,
             class: Theme::default(),
+            status: None,
         }
     }
 
@@ -294,49 +297,85 @@ where
             return event::Status::Captured;
         }
 
-        match event {
-            Event::Mouse(mouse::Event::ButtonPressed(mouse::Button::Left))
-            | Event::Touch(touch::Event::FingerPressed { .. }) => {
-                if self.on_press.is_some() {
-                    let bounds = layout.bounds();
+        let mut update = || {
+            match event {
+                Event::Mouse(mouse::Event::ButtonPressed(
+                    mouse::Button::Left,
+                ))
+                | Event::Touch(touch::Event::FingerPressed { .. }) => {
+                    if self.on_press.is_some() {
+                        let bounds = layout.bounds();
 
-                    if cursor.is_over(bounds) {
-                        let state = tree.state.downcast_mut::<State>();
+                        if cursor.is_over(bounds) {
+                            let state = tree.state.downcast_mut::<State>();
 
-                        state.is_pressed = true;
+                            state.is_pressed = true;
 
-                        return event::Status::Captured;
+                            return event::Status::Captured;
+                        }
                     }
                 }
-            }
-            Event::Mouse(mouse::Event::ButtonReleased(mouse::Button::Left))
-            | Event::Touch(touch::Event::FingerLifted { .. }) => {
-                if let Some(on_press) = self.on_press.as_ref().map(OnPress::get)
-                {
-                    let state = tree.state.downcast_mut::<State>();
+                Event::Mouse(mouse::Event::ButtonReleased(
+                    mouse::Button::Left,
+                ))
+                | Event::Touch(touch::Event::FingerLifted { .. }) => {
+                    if let Some(on_press) =
+                        self.on_press.as_ref().map(OnPress::get)
+                    {
+                        let state = tree.state.downcast_mut::<State>();
 
-                    if state.is_pressed {
-                        state.is_pressed = false;
+                        if state.is_pressed {
+                            state.is_pressed = false;
 
-                        let bounds = layout.bounds();
+                            let bounds = layout.bounds();
 
-                        if cursor.is_over(bounds) {
-                            shell.publish(on_press);
-                        }
+                            if cursor.is_over(bounds) {
+                                shell.publish(on_press);
+                            }
 
-                        return event::Status::Captured;
+                            return event::Status::Captured;
+                        }
                     }
                 }
+                Event::Touch(touch::Event::FingerLost { .. }) => {
+                    let state = tree.state.downcast_mut::<State>();
+
+                    state.is_pressed = false;
+                }
+                _ => {}
+            }
+
+            event::Status::Ignored
+        };
+
+        let update_status = update();
+
+        let current_status = if self.on_press.is_none() {
+            Status::Disabled
+        } else if cursor.is_over(layout.bounds()) {
+            let state = tree.state.downcast_ref::<State>();
+
+            if state.is_pressed {
+                Status::Pressed
+            } else {
+                Status::Hovered
             }
-            Event::Touch(touch::Event::FingerLost { .. }) => {
-                let state = tree.state.downcast_mut::<State>();
+        } else {
+            Status::Active
+        };
 
-                state.is_pressed = false;
+        if let Event::Window(window::Event::RedrawRequested(_now)) = event {
+            self.status = Some(current_status);
+        } else {
+            match self.status {
+                Some(status) if status != current_status => {
+                    shell.request_redraw(window::RedrawRequest::NextFrame);
+                }
+                _ => {}
             }
-            _ => {}
         }
 
-        event::Status::Ignored
+        update_status
     }
 
     fn draw(
@@ -351,23 +390,8 @@ where
     ) {
         let bounds = layout.bounds();
         let content_layout = layout.children().next().unwrap();
-        let is_mouse_over = cursor.is_over(bounds);
-
-        let status = if self.on_press.is_none() {
-            Status::Disabled
-        } else if is_mouse_over {
-            let state = tree.state.downcast_ref::<State>();
-
-            if state.is_pressed {
-                Status::Pressed
-            } else {
-                Status::Hovered
-            }
-        } else {
-            Status::Active
-        };
-
-        let style = theme.style(&self.class, status);
+        let style =
+            theme.style(&self.class, self.status.unwrap_or(Status::Disabled));
 
         if style.background.is_some()
             || style.border.width > 0.0
diff --git a/winit/Cargo.toml b/winit/Cargo.toml
index bd6feb00..b8f5a723 100644
--- a/winit/Cargo.toml
+++ b/winit/Cargo.toml
@@ -22,7 +22,7 @@ x11 = ["winit/x11"]
 wayland = ["winit/wayland"]
 wayland-dlopen = ["winit/wayland-dlopen"]
 wayland-csd-adwaita = ["winit/wayland-csd-adwaita"]
-multi-window = ["iced_runtime/multi-window"]
+reactive-rendering = []
 
 [dependencies]
 iced_futures.workspace = true
diff --git a/winit/src/program.rs b/winit/src/program.rs
index 8d1eec3a..2ac7ad0d 100644
--- a/winit/src/program.rs
+++ b/winit/src/program.rs
@@ -691,6 +691,7 @@ async fn run_instance<P, C>(
     let mut ui_caches = FxHashMap::default();
     let mut user_interfaces = ManuallyDrop::new(FxHashMap::default());
     let mut clipboard = Clipboard::unconnected();
+    let mut redraw_queue = Vec::new();
 
     debug.startup_finished();
 
@@ -758,14 +759,30 @@ async fn run_instance<P, C>(
             }
             Event::EventLoopAwakened(event) => {
                 match event {
-                    event::Event::NewEvents(
-                        event::StartCause::Init
-                        | event::StartCause::ResumeTimeReached { .. },
-                    ) => {
+                    event::Event::NewEvents(event::StartCause::Init) => {
                         for (_id, window) in window_manager.iter_mut() {
                             window.raw.request_redraw();
                         }
                     }
+                    event::Event::NewEvents(
+                        event::StartCause::ResumeTimeReached { .. },
+                    ) => {
+                        let now = Instant::now();
+
+                        while let Some((target, id)) =
+                            redraw_queue.last().copied()
+                        {
+                            if target > now {
+                                break;
+                            }
+
+                            let _ = redraw_queue.pop();
+
+                            if let Some(window) = window_manager.get_mut(id) {
+                                window.raw.request_redraw();
+                            }
+                        }
+                    }
                     event::Event::PlatformSpecific(
                         event::PlatformSpecific::MacOS(
                             event::MacOS::ReceivedUrl(url),
@@ -857,23 +874,19 @@ async fn run_instance<P, C>(
                             status: core::event::Status::Ignored,
                         });
 
-                        let _ = control_sender.start_send(Control::ChangeFlow(
-                            match ui_state {
-                                user_interface::State::Updated {
-                                    redraw_request: Some(redraw_request),
-                                } => match redraw_request {
-                                    window::RedrawRequest::NextFrame => {
-                                        window.raw.request_redraw();
-
-                                        ControlFlow::Wait
-                                    }
-                                    window::RedrawRequest::At(at) => {
-                                        ControlFlow::WaitUntil(at)
-                                    }
-                                },
-                                _ => ControlFlow::Wait,
-                            },
-                        ));
+                        if let user_interface::State::Updated {
+                            redraw_request: Some(redraw_request),
+                        } = ui_state
+                        {
+                            match redraw_request {
+                                window::RedrawRequest::NextFrame => {
+                                    window.raw.request_redraw();
+                                }
+                                window::RedrawRequest::At(at) => {
+                                    redraw_queue.push((at, id));
+                                }
+                            }
+                        }
 
                         let physical_size = window.state.physical_size();
 
@@ -1065,13 +1078,25 @@ async fn run_instance<P, C>(
                                     &mut messages,
                                 );
 
+                            #[cfg(not(feature = "reactive-rendering"))]
                             window.raw.request_redraw();
 
-                            if !uis_stale {
-                                uis_stale = matches!(
-                                    ui_state,
-                                    user_interface::State::Outdated
-                                );
+                            match ui_state {
+                                #[cfg(feature = "reactive-rendering")]
+                                user_interface::State::Updated {
+                                    redraw_request: Some(redraw_request),
+                                } => match redraw_request {
+                                    window::RedrawRequest::NextFrame => {
+                                        window.raw.request_redraw();
+                                    }
+                                    window::RedrawRequest::At(at) => {
+                                        redraw_queue.push((at, id));
+                                    }
+                                },
+                                user_interface::State::Outdated => {
+                                    uis_stale = true;
+                                }
+                                user_interface::State::Updated { .. } => {}
                             }
 
                             for (event, status) in window_events
@@ -1139,6 +1164,24 @@ async fn run_instance<P, C>(
                                 actions = 0;
                             }
                         }
+
+                        if !redraw_queue.is_empty() {
+                            redraw_queue.sort_by(
+                                |(target_a, _), (target_b, _)| {
+                                    target_a.cmp(target_b).reverse()
+                                },
+                            );
+
+                            let (target, _id) = redraw_queue
+                                .last()
+                                .copied()
+                                .expect("Redraw queue is not empty");
+
+                            let _ =
+                                control_sender.start_send(Control::ChangeFlow(
+                                    ControlFlow::WaitUntil(target),
+                                ));
+                        }
                     }
                     _ => {}
                 }
diff --git a/winit/src/program/state.rs b/winit/src/program/state.rs
index a7fa2788..b8a58960 100644
--- a/winit/src/program/state.rs
+++ b/winit/src/program/state.rs
@@ -190,7 +190,10 @@ where
                         ..
                     },
                 ..
-            } => _debug.toggle(),
+            } => {
+                _debug.toggle();
+                window.request_redraw();
+            }
             _ => {}
         }
     }