Introduce `viewport` to `Widget::draw`

This should eventually allow us to only generate primitives that are
visible.

22 files changed, 84 insertions, 20 deletions

diff --git a/native/src/element.rs b/native/src/element.rs
index 514a135b..10e1b5fb 100644
--- a/native/src/element.rs
+++ b/native/src/element.rs
@@ -1,6 +1,7 @@
+use crate::layout;
+use crate::overlay;
 use crate::{
-    layout, overlay, Clipboard, Color, Event, Hasher, Layout, Length, Point,
-    Widget,
+    Clipboard, Color, Event, Hasher, Layout, Length, Point, Rectangle, Widget,
 };
 
 /// A generic [`Widget`].
@@ -260,9 +261,10 @@ where
         defaults: &Renderer::Defaults,
         layout: Layout<'_>,
         cursor_position: Point,
+        viewport: &Rectangle,
     ) -> Renderer::Output {
         self.widget
-            .draw(renderer, defaults, layout, cursor_position)
+            .draw(renderer, defaults, layout, cursor_position, viewport)
     }
 
     /// Computes the _layout_ hash of the [`Element`].
@@ -356,9 +358,10 @@ where
         defaults: &Renderer::Defaults,
         layout: Layout<'_>,
         cursor_position: Point,
+        viewport: &Rectangle,
     ) -> Renderer::Output {
         self.widget
-            .draw(renderer, defaults, layout, cursor_position)
+            .draw(renderer, defaults, layout, cursor_position, viewport)
     }
 
     fn hash_layout(&self, state: &mut Hasher) {
@@ -437,12 +440,14 @@ where
         defaults: &Renderer::Defaults,
         layout: Layout<'_>,
         cursor_position: Point,
+        viewport: &Rectangle,
     ) -> Renderer::Output {
         renderer.explain(
             defaults,
             self.element.widget.as_ref(),
             layout,
             cursor_position,
+            viewport,
             self.color,
         )
     }
diff --git a/native/src/layout/debugger.rs b/native/src/layout/debugger.rs
index e4b21609..4c6dd793 100644
--- a/native/src/layout/debugger.rs
+++ b/native/src/layout/debugger.rs
@@ -1,4 +1,4 @@
-use crate::{Color, Layout, Point, Renderer, Widget};
+use crate::{Color, Layout, Point, Rectangle, Renderer, Widget};
 
 /// A renderer able to graphically explain a [`Layout`].
 ///
@@ -21,6 +21,7 @@ pub trait Debugger: Renderer {
         widget: &dyn Widget<Message, Self>,
         layout: Layout<'_>,
         cursor_position: Point,
+        viewport: &Rectangle,
         color: Color,
     ) -> Self::Output;
 }
diff --git a/native/src/overlay/menu.rs b/native/src/overlay/menu.rs
index c2df468e..29e4e63d 100644
--- a/native/src/overlay/menu.rs
+++ b/native/src/overlay/menu.rs
@@ -253,9 +253,13 @@ where
         layout: Layout<'_>,
         cursor_position: Point,
     ) -> Renderer::Output {
-        let primitives =
-            self.container
-                .draw(renderer, defaults, layout, cursor_position);
+        let primitives = self.container.draw(
+            renderer,
+            defaults,
+            layout,
+            cursor_position,
+            &layout.bounds(),
+        );
 
         renderer.decorate(
             layout.bounds(),
@@ -368,6 +372,7 @@ where
         _defaults: &Renderer::Defaults,
         layout: Layout<'_>,
         cursor_position: Point,
+        _viewport: &Rectangle,
     ) -> Renderer::Output {
         self::Renderer::draw(
             renderer,
diff --git a/native/src/renderer/null.rs b/native/src/renderer/null.rs
index b06b0e28..a3c3cf33 100644
--- a/native/src/renderer/null.rs
+++ b/native/src/renderer/null.rs
@@ -35,6 +35,7 @@ impl column::Renderer for Null {
         _content: &[Element<'_, Message, Self>],
         _layout: Layout<'_>,
         _cursor_position: Point,
+        _viewport: &Rectangle,
     ) {
     }
 }
@@ -46,6 +47,7 @@ impl row::Renderer for Null {
         _content: &[Element<'_, Message, Self>],
         _layout: Layout<'_>,
         _cursor_position: Point,
+        _viewport: &Rectangle,
     ) {
     }
 }
@@ -237,6 +239,7 @@ impl container::Renderer for Null {
         _defaults: &Self::Defaults,
         _bounds: Rectangle,
         _cursor_position: Point,
+        _viewport: &Rectangle,
         _style: &Self::Style,
         _content: &Element<'_, Message, Self>,
         _content_layout: Layout<'_>,
diff --git a/native/src/user_interface.rs b/native/src/user_interface.rs
index 00a290f1..59d91f42 100644
--- a/native/src/user_interface.rs
+++ b/native/src/user_interface.rs
@@ -1,4 +1,6 @@
-use crate::{layout, overlay, Clipboard, Element, Event, Layout, Point, Size};
+use crate::layout;
+use crate::overlay;
+use crate::{Clipboard, Element, Event, Layout, Point, Rectangle, Size};
 
 use std::hash::Hasher;
 
@@ -327,6 +329,8 @@ where
         renderer: &mut Renderer,
         cursor_position: Point,
     ) -> Renderer::Output {
+        let viewport = Rectangle::with_size(self.bounds);
+
         let overlay = if let Some(mut overlay) =
             self.root.overlay(Layout::new(&self.base.layout))
         {
@@ -365,6 +369,7 @@ where
                 &Renderer::Defaults::default(),
                 Layout::new(&self.base.layout),
                 base_cursor,
+                &viewport,
             );
 
             renderer.overlay(
@@ -378,6 +383,7 @@ where
                 &Renderer::Defaults::default(),
                 Layout::new(&self.base.layout),
                 cursor_position,
+                &viewport,
             )
         }
     }
diff --git a/native/src/widget.rs b/native/src/widget.rs
index a10281df..8687ce6f 100644
--- a/native/src/widget.rs
+++ b/native/src/widget.rs
@@ -73,7 +73,9 @@ pub use text::Text;
 #[doc(no_inline)]
 pub use text_input::TextInput;
 
-use crate::{layout, overlay, Clipboard, Event, Hasher, Layout, Length, Point};
+use crate::{
+    layout, overlay, Clipboard, Event, Hasher, Layout, Length, Point, Rectangle,
+};
 
 /// A component that displays information and allows interaction.
 ///
@@ -137,6 +139,7 @@ where
         defaults: &Renderer::Defaults,
         layout: Layout<'_>,
         cursor_position: Point,
+        viewport: &Rectangle,
     ) -> Renderer::Output;
 
     /// Computes the _layout_ hash of the [`Widget`].
diff --git a/native/src/widget/button.rs b/native/src/widget/button.rs
index fd74563a..995ba7bc 100644
--- a/native/src/widget/button.rs
+++ b/native/src/widget/button.rs
@@ -217,6 +217,7 @@ where
         defaults: &Renderer::Defaults,
         layout: Layout<'_>,
         cursor_position: Point,
+        _viewport: &Rectangle,
     ) -> Renderer::Output {
         renderer.draw(
             defaults,
diff --git a/native/src/widget/checkbox.rs b/native/src/widget/checkbox.rs
index 99178aae..e389427e 100644
--- a/native/src/widget/checkbox.rs
+++ b/native/src/widget/checkbox.rs
@@ -180,6 +180,7 @@ where
         defaults: &Renderer::Defaults,
         layout: Layout<'_>,
         cursor_position: Point,
+        _viewport: &Rectangle,
     ) -> Renderer::Output {
         let bounds = layout.bounds();
         let mut children = layout.children();
diff --git a/native/src/widget/column.rs b/native/src/widget/column.rs
index a5ac2101..e874ad42 100644
--- a/native/src/widget/column.rs
+++ b/native/src/widget/column.rs
@@ -1,9 +1,11 @@
 //! Distribute content vertically.
 use std::hash::Hash;
 
+use crate::layout;
+use crate::overlay;
 use crate::{
-    layout, overlay, Align, Clipboard, Element, Event, Hasher, Layout, Length,
-    Point, Widget,
+    Align, Clipboard, Element, Event, Hasher, Layout, Length, Point, Rectangle,
+    Widget,
 };
 
 use std::u32;
@@ -181,8 +183,15 @@ where
         defaults: &Renderer::Defaults,
         layout: Layout<'_>,
         cursor_position: Point,
+        viewport: &Rectangle,
     ) -> Renderer::Output {
-        renderer.draw(defaults, &self.children, layout, cursor_position)
+        renderer.draw(
+            defaults,
+            &self.children,
+            layout,
+            cursor_position,
+            viewport,
+        )
     }
 
     fn hash_layout(&self, state: &mut Hasher) {
@@ -237,6 +246,7 @@ pub trait Renderer: crate::Renderer + Sized {
         content: &[Element<'_, Message, Self>],
         layout: Layout<'_>,
         cursor_position: Point,
+        viewport: &Rectangle,
     ) -> Self::Output;
 }
 
diff --git a/native/src/widget/container.rs b/native/src/widget/container.rs
index b8316e62..5b04d699 100644
--- a/native/src/widget/container.rs
+++ b/native/src/widget/container.rs
@@ -191,11 +191,13 @@ where
         defaults: &Renderer::Defaults,
         layout: Layout<'_>,
         cursor_position: Point,
+        viewport: &Rectangle,
     ) -> Renderer::Output {
         renderer.draw(
             defaults,
             layout.bounds(),
             cursor_position,
+            viewport,
             &self.style,
             &self.content,
             layout.children().next().unwrap(),
@@ -242,6 +244,7 @@ pub trait Renderer: crate::Renderer {
         defaults: &Self::Defaults,
         bounds: Rectangle,
         cursor_position: Point,
+        viewport: &Rectangle,
         style: &Self::Style,
         content: &Element<'_, Message, Self>,
         content_layout: Layout<'_>,
diff --git a/native/src/widget/image.rs b/native/src/widget/image.rs
index 132f249d..9586da0f 100644
--- a/native/src/widget/image.rs
+++ b/native/src/widget/image.rs
@@ -1,5 +1,6 @@
 //! Display images in your user interface.
-use crate::{layout, Element, Hasher, Layout, Length, Point, Size, Widget};
+use crate::layout;
+use crate::{Element, Hasher, Layout, Length, Point, Rectangle, Size, Widget};
 
 use std::{
     hash::{Hash, Hasher as _},
@@ -97,6 +98,7 @@ where
         _defaults: &Renderer::Defaults,
         layout: Layout<'_>,
         _cursor_position: Point,
+        _viewport: &Rectangle,
     ) -> Renderer::Output {
         renderer.draw(self.handle.clone(), layout)
     }
diff --git a/native/src/widget/pane_grid.rs b/native/src/widget/pane_grid.rs
index 5180fd3b..276bfae3 100644
--- a/native/src/widget/pane_grid.rs
+++ b/native/src/widget/pane_grid.rs
@@ -588,6 +588,7 @@ where
         defaults: &Renderer::Defaults,
         layout: Layout<'_>,
         cursor_position: Point,
+        _viewport: &Rectangle,
     ) -> Renderer::Output {
         let picked_split = self
             .state
diff --git a/native/src/widget/pick_list.rs b/native/src/widget/pick_list.rs
index 0e42a3e4..e086e367 100644
--- a/native/src/widget/pick_list.rs
+++ b/native/src/widget/pick_list.rs
@@ -256,6 +256,7 @@ where
         _defaults: &Renderer::Defaults,
         layout: Layout<'_>,
         cursor_position: Point,
+        _viewport: &Rectangle,
     ) -> Renderer::Output {
         self::Renderer::draw(
             renderer,
diff --git a/native/src/widget/progress_bar.rs b/native/src/widget/progress_bar.rs
index 5ab76d47..4f8a7e1b 100644
--- a/native/src/widget/progress_bar.rs
+++ b/native/src/widget/progress_bar.rs
@@ -104,6 +104,7 @@ where
         _defaults: &Renderer::Defaults,
         layout: Layout<'_>,
         _cursor_position: Point,
+        _viewport: &Rectangle,
     ) -> Renderer::Output {
         renderer.draw(
             layout.bounds(),
diff --git a/native/src/widget/radio.rs b/native/src/widget/radio.rs
index a7cabd49..06d3f846 100644
--- a/native/src/widget/radio.rs
+++ b/native/src/widget/radio.rs
@@ -183,6 +183,7 @@ where
         defaults: &Renderer::Defaults,
         layout: Layout<'_>,
         cursor_position: Point,
+        _viewport: &Rectangle,
     ) -> Renderer::Output {
         let bounds = layout.bounds();
         let mut children = layout.children();
diff --git a/native/src/widget/row.rs b/native/src/widget/row.rs
index b37a5cfc..bc8a3df1 100644
--- a/native/src/widget/row.rs
+++ b/native/src/widget/row.rs
@@ -1,11 +1,12 @@
 //! Distribute content horizontally.
-use std::hash::Hash;
-
+use crate::layout;
+use crate::overlay;
 use crate::{
-    layout, overlay, Align, Clipboard, Element, Event, Hasher, Layout, Length,
-    Point, Widget,
+    Align, Clipboard, Element, Event, Hasher, Layout, Length, Point, Rectangle,
+    Widget,
 };
 
+use std::hash::Hash;
 use std::u32;
 
 /// A container that distributes its contents horizontally.
@@ -182,8 +183,15 @@ where
         defaults: &Renderer::Defaults,
         layout: Layout<'_>,
         cursor_position: Point,
+        viewport: &Rectangle,
     ) -> Renderer::Output {
-        renderer.draw(defaults, &self.children, layout, cursor_position)
+        renderer.draw(
+            defaults,
+            &self.children,
+            layout,
+            cursor_position,
+            viewport,
+        )
     }
 
     fn hash_layout(&self, state: &mut Hasher) {
@@ -238,6 +246,7 @@ pub trait Renderer: crate::Renderer + Sized {
         children: &[Element<'_, Message, Self>],
         layout: Layout<'_>,
         cursor_position: Point,
+        viewport: &Rectangle,
     ) -> Self::Output;
 }
 
diff --git a/native/src/widget/scrollable.rs b/native/src/widget/scrollable.rs
index cb181899..60ec2d7d 100644
--- a/native/src/widget/scrollable.rs
+++ b/native/src/widget/scrollable.rs
@@ -303,6 +303,7 @@ where
         defaults: &Renderer::Defaults,
         layout: Layout<'_>,
         cursor_position: Point,
+        _viewport: &Rectangle,
     ) -> Renderer::Output {
         let bounds = layout.bounds();
         let content_layout = layout.children().next().unwrap();
@@ -335,6 +336,10 @@ where
                 defaults,
                 content_layout,
                 cursor_position,
+                &Rectangle {
+                    y: bounds.y + offset as f32,
+                    ..bounds
+                },
             )
         };
 
diff --git a/native/src/widget/slider.rs b/native/src/widget/slider.rs
index 3255dd04..d6e366aa 100644
--- a/native/src/widget/slider.rs
+++ b/native/src/widget/slider.rs
@@ -259,6 +259,7 @@ where
         _defaults: &Renderer::Defaults,
         layout: Layout<'_>,
         cursor_position: Point,
+        _viewport: &Rectangle,
     ) -> Renderer::Output {
         let start = *self.range.start();
         let end = *self.range.end();
diff --git a/native/src/widget/space.rs b/native/src/widget/space.rs
index f1576ffb..032f341d 100644
--- a/native/src/widget/space.rs
+++ b/native/src/widget/space.rs
@@ -71,6 +71,7 @@ where
         _defaults: &Renderer::Defaults,
         layout: Layout<'_>,
         _cursor_position: Point,
+        _viewport: &Rectangle,
     ) -> Renderer::Output {
         renderer.draw(layout.bounds())
     }
diff --git a/native/src/widget/svg.rs b/native/src/widget/svg.rs
index 114d5e41..ede1aff8 100644
--- a/native/src/widget/svg.rs
+++ b/native/src/widget/svg.rs
@@ -1,5 +1,6 @@
 //! Display vector graphics in your application.
-use crate::{layout, Element, Hasher, Layout, Length, Point, Size, Widget};
+use crate::layout;
+use crate::{Element, Hasher, Layout, Length, Point, Rectangle, Size, Widget};
 
 use std::{
     hash::{Hash, Hasher as _},
@@ -103,6 +104,7 @@ where
         _defaults: &Renderer::Defaults,
         layout: Layout<'_>,
         _cursor_position: Point,
+        _viewport: &Rectangle,
     ) -> Renderer::Output {
         renderer.draw(self.handle.clone(), layout)
     }
diff --git a/native/src/widget/text.rs b/native/src/widget/text.rs
index 48a69e34..c2544b8e 100644
--- a/native/src/widget/text.rs
+++ b/native/src/widget/text.rs
@@ -149,6 +149,7 @@ where
         defaults: &Renderer::Defaults,
         layout: Layout<'_>,
         _cursor_position: Point,
+        _viewport: &Rectangle,
     ) -> Renderer::Output {
         renderer.draw(
             defaults,
diff --git a/native/src/widget/text_input.rs b/native/src/widget/text_input.rs
index 32a57ce6..64182f2d 100644
--- a/native/src/widget/text_input.rs
+++ b/native/src/widget/text_input.rs
@@ -497,6 +497,7 @@ where
         _defaults: &Renderer::Defaults,
         layout: Layout<'_>,
         cursor_position: Point,
+        _viewport: &Rectangle,
     ) -> Renderer::Output {
         let bounds = layout.bounds();
         let text_bounds = layout.children().next().unwrap().bounds();