Merge pull request #2662 from iced-rs/reactive-rendering

Reactive Rendering

7 files changed, 126 insertions, 57 deletions

diff --git a/core/src/element.rs b/core/src/element.rs
index 6ebb8a15..03e56b43 100644
--- a/core/src/element.rs
+++ b/core/src/element.rs
@@ -1,4 +1,3 @@
-use crate::event::{self, Event};
 use crate::layout;
 use crate::mouse;
 use crate::overlay;
@@ -6,8 +5,8 @@ use crate::renderer;
 use crate::widget;
 use crate::widget::tree::{self, Tree};
 use crate::{
-    Border, Clipboard, Color, Layout, Length, Rectangle, Shell, Size, Vector,
-    Widget,
+    Border, Clipboard, Color, Event, Layout, Length, Rectangle, Shell, Size,
+    Vector, Widget,
 };
 
 use std::borrow::Borrow;
@@ -309,7 +308,7 @@ where
         self.widget.operate(tree, layout, renderer, operation);
     }
 
-    fn on_event(
+    fn update(
         &mut self,
         tree: &mut Tree,
         event: Event,
@@ -319,11 +318,11 @@ where
         clipboard: &mut dyn Clipboard,
         shell: &mut Shell<'_, B>,
         viewport: &Rectangle,
-    ) -> event::Status {
+    ) {
         let mut local_messages = Vec::new();
         let mut local_shell = Shell::new(&mut local_messages);
 
-        let status = self.widget.on_event(
+        self.widget.update(
             tree,
             event,
             layout,
@@ -335,8 +334,6 @@ where
         );
 
         shell.merge(local_shell, &self.mapper);
-
-        status
     }
 
     fn draw(
@@ -447,7 +444,7 @@ where
             .operate(state, layout, renderer, operation);
     }
 
-    fn on_event(
+    fn update(
         &mut self,
         state: &mut Tree,
         event: Event,
@@ -457,10 +454,10 @@ where
         clipboard: &mut dyn Clipboard,
         shell: &mut Shell<'_, Message>,
         viewport: &Rectangle,
-    ) -> event::Status {
-        self.element.widget.on_event(
+    ) {
+        self.element.widget.update(
             state, event, layout, cursor, renderer, clipboard, shell, viewport,
-        )
+        );
     }
 
     fn draw(
diff --git a/core/src/layout/flex.rs b/core/src/layout/flex.rs
index ac80d393..2cff5bfd 100644
--- a/core/src/layout/flex.rs
+++ b/core/src/layout/flex.rs
@@ -79,6 +79,7 @@ where
     let max_cross = axis.cross(limits.max());
 
     let mut fill_main_sum = 0;
+    let mut some_fill_cross = false;
     let (mut cross, cross_compress) = match axis {
         Axis::Vertical if width == Length::Shrink => (0.0, true),
         Axis::Horizontal if height == Length::Shrink => (0.0, true),
@@ -90,6 +91,10 @@ where
     let mut nodes: Vec<Node> = Vec::with_capacity(items.len());
     nodes.resize(items.len(), Node::default());
 
+    // FIRST PASS
+    // We lay out non-fluid elements in the main axis.
+    // If we need to compress the cross axis, then we skip any of these elements
+    // that are also fluid in the cross axis.
     for (i, (child, tree)) in items.iter().zip(trees.iter_mut()).enumerate() {
         let (fill_main_factor, fill_cross_factor) = {
             let size = child.as_widget().size();
@@ -121,6 +126,41 @@ where
             nodes[i] = layout;
         } else {
             fill_main_sum += fill_main_factor;
+            some_fill_cross = some_fill_cross || fill_cross_factor != 0;
+        }
+    }
+
+    // SECOND PASS (conditional)
+    // If we must compress the cross axis and there are fluid elements in the
+    // cross axis, we lay out any of these elements that are also non-fluid in
+    // the main axis (i.e. the ones we deliberately skipped in the first pass).
+    //
+    // We use the maximum cross length obtained in the first pass as the maximum
+    // cross limit.
+    if cross_compress && some_fill_cross {
+        for (i, (child, tree)) in items.iter().zip(trees.iter_mut()).enumerate()
+        {
+            let (fill_main_factor, fill_cross_factor) = {
+                let size = child.as_widget().size();
+
+                axis.pack(size.width.fill_factor(), size.height.fill_factor())
+            };
+
+            if fill_main_factor == 0 && fill_cross_factor != 0 {
+                let (max_width, max_height) = axis.pack(available, cross);
+
+                let child_limits =
+                    Limits::new(Size::ZERO, Size::new(max_width, max_height));
+
+                let layout =
+                    child.as_widget().layout(tree, renderer, &child_limits);
+                let size = layout.size();
+
+                available -= axis.main(size);
+                cross = cross.max(axis.cross(size));
+
+                nodes[i] = layout;
+            }
         }
     }
 
@@ -135,6 +175,9 @@ where
         },
     };
 
+    // THIRD PASS
+    // We only have the elements that are fluid in the main axis left.
+    // We use the remaining space to evenly allocate space based on fill factors.
     for (i, (child, tree)) in items.iter().zip(trees).enumerate() {
         let (fill_main_factor, fill_cross_factor) = {
             let size = child.as_widget().size();
@@ -142,10 +185,16 @@ where
             axis.pack(size.width.fill_factor(), size.height.fill_factor())
         };
 
-        if fill_main_factor != 0 || (cross_compress && fill_cross_factor != 0) {
+        if fill_main_factor != 0 {
             let max_main =
                 remaining * fill_main_factor as f32 / fill_main_sum as f32;
 
+            let max_main = if max_main.is_nan() {
+                f32::INFINITY
+            } else {
+                max_main
+            };
+
             let min_main = if max_main.is_infinite() {
                 0.0
             } else {
@@ -178,6 +227,8 @@ where
     let pad = axis.pack(padding.left, padding.top);
     let mut main = pad.0;
 
+    // FOURTH PASS
+    // We align all the laid out nodes in the cross axis, if needed.
     for (i, node) in nodes.iter_mut().enumerate() {
         if i > 0 {
             main += spacing;
diff --git a/core/src/overlay.rs b/core/src/overlay.rs
index f09de831..383663af 100644
--- a/core/src/overlay.rs
+++ b/core/src/overlay.rs
@@ -5,13 +5,12 @@ mod group;
 pub use element::Element;
 pub use group::Group;
 
-use crate::event::{self, Event};
 use crate::layout;
 use crate::mouse;
 use crate::renderer;
 use crate::widget;
 use crate::widget::Tree;
-use crate::{Clipboard, Layout, Point, Rectangle, Shell, Size, Vector};
+use crate::{Clipboard, Event, Layout, Point, Rectangle, Shell, Size, Vector};
 
 /// An interactive component that can be displayed on top of other widgets.
 pub trait Overlay<Message, Theme, Renderer>
@@ -57,7 +56,7 @@ where
     ///   * a [`Clipboard`], if available
     ///
     /// By default, it does nothing.
-    fn on_event(
+    fn update(
         &mut self,
         _event: Event,
         _layout: Layout<'_>,
@@ -65,8 +64,7 @@ where
         _renderer: &Renderer,
         _clipboard: &mut dyn Clipboard,
         _shell: &mut Shell<'_, Message>,
-    ) -> event::Status {
-        event::Status::Ignored
+    ) {
     }
 
     /// Returns the current [`mouse::Interaction`] of the [`Overlay`].
diff --git a/core/src/overlay/element.rs b/core/src/overlay/element.rs
index 32e987a3..ed870feb 100644
--- a/core/src/overlay/element.rs
+++ b/core/src/overlay/element.rs
@@ -1,11 +1,10 @@
 pub use crate::Overlay;
 
-use crate::event::{self, Event};
 use crate::layout;
 use crate::mouse;
 use crate::renderer;
 use crate::widget;
-use crate::{Clipboard, Layout, Point, Rectangle, Shell, Size};
+use crate::{Clipboard, Event, Layout, Point, Rectangle, Shell, Size};
 
 /// A generic [`Overlay`].
 #[allow(missing_debug_implementations)]
@@ -50,7 +49,7 @@ where
     }
 
     /// Processes a runtime [`Event`].
-    pub fn on_event(
+    pub fn update(
         &mut self,
         event: Event,
         layout: Layout<'_>,
@@ -58,9 +57,9 @@ where
         renderer: &Renderer,
         clipboard: &mut dyn Clipboard,
         shell: &mut Shell<'_, Message>,
-    ) -> event::Status {
+    ) {
         self.overlay
-            .on_event(event, layout, cursor, renderer, clipboard, shell)
+            .update(event, layout, cursor, renderer, clipboard, shell);
     }
 
     /// Returns the current [`mouse::Interaction`] of the [`Element`].
@@ -149,7 +148,7 @@ where
         self.content.operate(layout, renderer, operation);
     }
 
-    fn on_event(
+    fn update(
         &mut self,
         event: Event,
         layout: Layout<'_>,
@@ -157,11 +156,11 @@ where
         renderer: &Renderer,
         clipboard: &mut dyn Clipboard,
         shell: &mut Shell<'_, B>,
-    ) -> event::Status {
+    ) {
         let mut local_messages = Vec::new();
         let mut local_shell = Shell::new(&mut local_messages);
 
-        let event_status = self.content.on_event(
+        self.content.update(
             event,
             layout,
             cursor,
@@ -171,8 +170,6 @@ where
         );
 
         shell.merge(local_shell, self.mapper);
-
-        event_status
     }
 
     fn mouse_interaction(
diff --git a/core/src/overlay/group.rs b/core/src/overlay/group.rs
index 6541d311..2b374252 100644
--- a/core/src/overlay/group.rs
+++ b/core/src/overlay/group.rs
@@ -1,4 +1,3 @@
-use crate::event;
 use crate::layout;
 use crate::mouse;
 use crate::overlay;
@@ -73,7 +72,7 @@ where
         )
     }
 
-    fn on_event(
+    fn update(
         &mut self,
         event: Event,
         layout: Layout<'_>,
@@ -81,21 +80,17 @@ where
         renderer: &Renderer,
         clipboard: &mut dyn Clipboard,
         shell: &mut Shell<'_, Message>,
-    ) -> event::Status {
-        self.children
-            .iter_mut()
-            .zip(layout.children())
-            .map(|(child, layout)| {
-                child.on_event(
-                    event.clone(),
-                    layout,
-                    cursor,
-                    renderer,
-                    clipboard,
-                    shell,
-                )
-            })
-            .fold(event::Status::Ignored, event::Status::merge)
+    ) {
+        for (child, layout) in self.children.iter_mut().zip(layout.children()) {
+            child.update(
+                event.clone(),
+                layout,
+                cursor,
+                renderer,
+                clipboard,
+                shell,
+            );
+        }
     }
 
     fn draw(
diff --git a/core/src/shell.rs b/core/src/shell.rs
index 2952ceff..12ebbaa8 100644
--- a/core/src/shell.rs
+++ b/core/src/shell.rs
@@ -1,3 +1,5 @@
+use crate::event;
+use crate::time::Instant;
 use crate::window;
 
 /// A connection to the state of a shell.
@@ -9,6 +11,7 @@ use crate::window;
 #[derive(Debug)]
 pub struct Shell<'a, Message> {
     messages: &'a mut Vec<Message>,
+    event_status: event::Status,
     redraw_request: Option<window::RedrawRequest>,
     is_layout_invalid: bool,
     are_widgets_invalid: bool,
@@ -19,6 +22,7 @@ impl<'a, Message> Shell<'a, Message> {
     pub fn new(messages: &'a mut Vec<Message>) -> Self {
         Self {
             messages,
+            event_status: event::Status::Ignored,
             redraw_request: None,
             is_layout_invalid: false,
             are_widgets_invalid: false,
@@ -35,14 +39,37 @@ impl<'a, Message> Shell<'a, Message> {
         self.messages.push(message);
     }
 
-    /// Requests a new frame to be drawn.
-    pub fn request_redraw(&mut self, request: window::RedrawRequest) {
+    /// Marks the current event as captured. Prevents "event bubbling".
+    ///
+    /// A widget should capture an event when no ancestor should
+    /// handle it.
+    pub fn capture_event(&mut self) {
+        self.event_status = event::Status::Captured;
+    }
+
+    /// Returns the current [`event::Status`] of the [`Shell`].
+    pub fn event_status(&self) -> event::Status {
+        self.event_status
+    }
+
+    /// Returns whether the current event has been captured.
+    pub fn is_event_captured(&self) -> bool {
+        self.event_status == event::Status::Captured
+    }
+
+    /// Requests a new frame to be drawn as soon as possible.
+    pub fn request_redraw(&mut self) {
+        self.redraw_request = Some(window::RedrawRequest::NextFrame);
+    }
+
+    /// Requests a new frame to be drawn at the given [`Instant`].
+    pub fn request_redraw_at(&mut self, at: Instant) {
         match self.redraw_request {
             None => {
-                self.redraw_request = Some(request);
+                self.redraw_request = Some(window::RedrawRequest::At(at));
             }
-            Some(current) if request < current => {
-                self.redraw_request = Some(request);
+            Some(window::RedrawRequest::At(current)) if at < current => {
+                self.redraw_request = Some(window::RedrawRequest::At(at));
             }
             _ => {}
         }
@@ -95,8 +122,12 @@ impl<'a, Message> Shell<'a, Message> {
     pub fn merge<B>(&mut self, other: Shell<'_, B>, f: impl Fn(B) -> Message) {
         self.messages.extend(other.messages.drain(..).map(f));
 
-        if let Some(at) = other.redraw_request {
-            self.request_redraw(at);
+        if let Some(new) = other.redraw_request {
+            self.redraw_request = Some(
+                self.redraw_request
+                    .map(|current| if current < new { current } else { new })
+                    .unwrap_or(new),
+            );
         }
 
         self.is_layout_invalid =
@@ -104,5 +135,7 @@ impl<'a, Message> Shell<'a, Message> {
 
         self.are_widgets_invalid =
             self.are_widgets_invalid || other.are_widgets_invalid;
+
+        self.event_status = self.event_status.merge(other.event_status);
     }
 }
diff --git a/core/src/widget.rs b/core/src/widget.rs
index 9cfff83d..2a40f823 100644
--- a/core/src/widget.rs
+++ b/core/src/widget.rs
@@ -10,12 +10,11 @@ pub use operation::Operation;
 pub use text::Text;
 pub use tree::Tree;
 
-use crate::event::{self, Event};
 use crate::layout::{self, Layout};
 use crate::mouse;
 use crate::overlay;
 use crate::renderer;
-use crate::{Clipboard, Length, Rectangle, Shell, Size, Vector};
+use crate::{Clipboard, Event, Length, Rectangle, Shell, Size, Vector};
 
 /// A component that displays information and allows interaction.
 ///
@@ -112,7 +111,7 @@ where
     /// Processes a runtime [`Event`].
     ///
     /// By default, it does nothing.
-    fn on_event(
+    fn update(
         &mut self,
         _state: &mut Tree,
         _event: Event,
@@ -122,8 +121,7 @@ where
         _clipboard: &mut dyn Clipboard,
         _shell: &mut Shell<'_, Message>,
         _viewport: &Rectangle,
-    ) -> event::Status {
-        event::Status::Ignored
+    ) {
     }
 
     /// Returns the current [`mouse::Interaction`] of the [`Widget`].