Decouple caching from `Paragraph` API

7 files changed, 129 insertions, 96 deletions

diff --git a/core/src/renderer/null.rs b/core/src/renderer/null.rs
index e8709dbc..560b5b43 100644
--- a/core/src/renderer/null.rs
+++ b/core/src/renderer/null.rs
@@ -79,7 +79,7 @@ impl text::Paragraph for () {
 
     fn resize(&mut self, _new_bounds: Size) {}
 
-    fn compare(&self, _text: Text<&str>) -> text::Difference {
+    fn compare(&self, _text: Text<()>) -> text::Difference {
         text::Difference::None
     }
 
diff --git a/core/src/text.rs b/core/src/text.rs
index b30feae0..e437a635 100644
--- a/core/src/text.rs
+++ b/core/src/text.rs
@@ -1,8 +1,7 @@
 //! Draw and interact with text.
-mod paragraph;
-
 pub mod editor;
 pub mod highlighter;
+pub mod paragraph;
 
 pub use editor::Editor;
 pub use highlighter::Highlighter;
diff --git a/core/src/text/paragraph.rs b/core/src/text/paragraph.rs
index 8ff04015..66cadb5c 100644
--- a/core/src/text/paragraph.rs
+++ b/core/src/text/paragraph.rs
@@ -1,3 +1,4 @@
+//! Draw paragraphs.
 use crate::alignment;
 use crate::text::{Difference, Hit, Text};
 use crate::{Point, Size};
@@ -15,7 +16,7 @@ pub trait Paragraph: Sized + Default {
 
     /// Compares the [`Paragraph`] with some desired [`Text`] and returns the
     /// [`Difference`].
-    fn compare(&self, text: Text<&str, Self::Font>) -> Difference;
+    fn compare(&self, text: Text<(), Self::Font>) -> Difference;
 
     /// Returns the horizontal alignment of the [`Paragraph`].
     fn horizontal_alignment(&self) -> alignment::Horizontal;
@@ -34,26 +35,87 @@ pub trait Paragraph: Sized + Default {
     /// Returns the distance to the given grapheme index in the [`Paragraph`].
     fn grapheme_position(&self, line: usize, index: usize) -> Option<Point>;
 
-    /// Updates the [`Paragraph`] to match the given [`Text`], if needed.
-    fn update(&mut self, text: Text<&str, Self::Font>) {
-        match self.compare(text) {
+    /// Returns the minimum width that can fit the contents of the [`Paragraph`].
+    fn min_width(&self) -> f32 {
+        self.min_bounds().width
+    }
+
+    /// Returns the minimum height that can fit the contents of the [`Paragraph`].
+    fn min_height(&self) -> f32 {
+        self.min_bounds().height
+    }
+}
+
+/// A [`Paragraph`] of plain text.
+#[derive(Debug, Clone, Default)]
+pub struct Plain<P: Paragraph> {
+    raw: P,
+    content: String,
+}
+
+impl<P: Paragraph> Plain<P> {
+    /// Creates a new [`Plain`] paragraph.
+    pub fn new(text: Text<&str, P::Font>) -> Self {
+        let content = text.content.to_owned();
+
+        Self {
+            raw: P::with_text(text),
+            content,
+        }
+    }
+
+    /// Updates the plain [`Paragraph`] to match the given [`Text`], if needed.
+    pub fn update(&mut self, text: Text<&str, P::Font>) {
+        if self.content != text.content {
+            text.content.clone_into(&mut self.content);
+            self.raw = P::with_text(text);
+            return;
+        }
+
+        match self.raw.compare(Text {
+            content: (),
+            bounds: text.bounds,
+            size: text.size,
+            line_height: text.line_height,
+            font: text.font,
+            horizontal_alignment: text.horizontal_alignment,
+            vertical_alignment: text.vertical_alignment,
+            shaping: text.shaping,
+        }) {
             Difference::None => {}
             Difference::Bounds => {
-                self.resize(text.bounds);
+                self.raw.resize(text.bounds);
             }
             Difference::Shape => {
-                *self = Self::with_text(text);
+                self.raw = P::with_text(text);
             }
         }
     }
 
-    /// Returns the minimum width that can fit the contents of the [`Paragraph`].
-    fn min_width(&self) -> f32 {
-        self.min_bounds().width
+    /// Returns the horizontal alignment of the [`Paragraph`].
+    pub fn horizontal_alignment(&self) -> alignment::Horizontal {
+        self.raw.horizontal_alignment()
     }
 
-    /// Returns the minimum height that can fit the contents of the [`Paragraph`].
-    fn min_height(&self) -> f32 {
-        self.min_bounds().height
+    /// Returns the vertical alignment of the [`Paragraph`].
+    pub fn vertical_alignment(&self) -> alignment::Vertical {
+        self.raw.vertical_alignment()
+    }
+
+    /// Returns the minimum boundaries that can fit the contents of the
+    /// [`Paragraph`].
+    pub fn min_bounds(&self) -> Size {
+        self.raw.min_bounds()
+    }
+
+    /// Returns the minimum width that can fit the contents of the
+    /// [`Paragraph`].
+    pub fn min_width(&self) -> f32 {
+        self.raw.min_width()
+    }
+
+    /// Returns the cached [`Paragraph`].
+    pub fn raw(&self) -> &P {
+        &self.raw
     }
 }
diff --git a/core/src/widget/text.rs b/core/src/widget/text.rs
index 91c9893d..2aeb0765 100644
--- a/core/src/widget/text.rs
+++ b/core/src/widget/text.rs
@@ -3,7 +3,8 @@ use crate::alignment;
 use crate::layout;
 use crate::mouse;
 use crate::renderer;
-use crate::text::{self, Paragraph};
+use crate::text;
+use crate::text::paragraph::{self, Paragraph};
 use crate::widget::tree::{self, Tree};
 use crate::{
     Color, Element, Layout, Length, Pixels, Point, Rectangle, Size, Theme,
@@ -155,7 +156,7 @@ where
 
 /// The internal state of a [`Text`] widget.
 #[derive(Debug, Default)]
-pub struct State<P: Paragraph>(P);
+pub struct State<P: Paragraph>(paragraph::Plain<P>);
 
 impl<'a, Message, Theme, Renderer> Widget<Message, Theme, Renderer>
     for Text<'a, Theme, Renderer>
@@ -168,7 +169,9 @@ where
     }
 
     fn state(&self) -> tree::State {
-        tree::State::new(State(Renderer::Paragraph::default()))
+        tree::State::new(State::<Renderer::Paragraph>(
+            paragraph::Plain::default(),
+        ))
     }
 
     fn size(&self) -> Size<Length> {
@@ -294,7 +297,7 @@ pub fn draw<Renderer>(
     };
 
     renderer.fill_paragraph(
-        paragraph,
+        paragraph.raw(),
         Point::new(x, y),
         appearance.color.unwrap_or(style.text_color),
         *viewport,
diff --git a/graphics/src/text/paragraph.rs b/graphics/src/text/paragraph.rs
index a5fefe8f..ea59c0af 100644
--- a/graphics/src/text/paragraph.rs
+++ b/graphics/src/text/paragraph.rs
@@ -1,8 +1,8 @@
 //! Draw paragraphs.
 use crate::core;
 use crate::core::alignment;
-use crate::core::text::{Hit, LineHeight, Shaping, Text};
-use crate::core::{Font, Pixels, Point, Size};
+use crate::core::text::{Hit, Shaping, Text};
+use crate::core::{Font, Point, Size};
 use crate::text;
 
 use std::fmt;
@@ -10,11 +10,11 @@ use std::sync::{self, Arc};
 
 /// A bunch of text.
 #[derive(Clone, PartialEq)]
-pub struct Paragraph(Option<Arc<Internal>>);
+pub struct Paragraph(Arc<Internal>);
 
+#[derive(Clone)]
 struct Internal {
     buffer: cosmic_text::Buffer,
-    content: String, // TODO: Reuse from `buffer` (?)
     font: Font,
     shaping: Shaping,
     horizontal_alignment: alignment::Horizontal,
@@ -52,9 +52,7 @@ impl Paragraph {
     }
 
     fn internal(&self) -> &Arc<Internal> {
-        self.0
-            .as_ref()
-            .expect("paragraph should always be initialized")
+        &self.0
     }
 }
 
@@ -90,9 +88,8 @@ impl core::text::Paragraph for Paragraph {
 
         let min_bounds = text::measure(&buffer);
 
-        Self(Some(Arc::new(Internal {
+        Self(Arc::new(Internal {
             buffer,
-            content: text.content.to_owned(),
             font: text.font,
             horizontal_alignment: text.horizontal_alignment,
             vertical_alignment: text.vertical_alignment,
@@ -100,59 +97,31 @@ impl core::text::Paragraph for Paragraph {
             bounds: text.bounds,
             min_bounds,
             version: font_system.version(),
-        })))
+        }))
     }
 
     fn resize(&mut self, new_bounds: Size) {
-        let paragraph = self
-            .0
-            .take()
-            .expect("paragraph should always be initialized");
-
-        match Arc::try_unwrap(paragraph) {
-            Ok(mut internal) => {
-                let mut font_system =
-                    text::font_system().write().expect("Write font system");
-
-                internal.buffer.set_size(
-                    font_system.raw(),
-                    Some(new_bounds.width),
-                    Some(new_bounds.height),
-                );
-
-                internal.bounds = new_bounds;
-                internal.min_bounds = text::measure(&internal.buffer);
-
-                self.0 = Some(Arc::new(internal));
-            }
-            Err(internal) => {
-                let metrics = internal.buffer.metrics();
-
-                // If there is a strong reference somewhere, we recompute the
-                // buffer from scratch
-                *self = Self::with_text(Text {
-                    content: &internal.content,
-                    bounds: internal.bounds,
-                    size: Pixels(metrics.font_size),
-                    line_height: LineHeight::Absolute(Pixels(
-                        metrics.line_height,
-                    )),
-                    font: internal.font,
-                    horizontal_alignment: internal.horizontal_alignment,
-                    vertical_alignment: internal.vertical_alignment,
-                    shaping: internal.shaping,
-                });
-            }
-        }
+        let paragraph = Arc::make_mut(&mut self.0);
+
+        let mut font_system =
+            text::font_system().write().expect("Write font system");
+
+        paragraph.buffer.set_size(
+            font_system.raw(),
+            Some(new_bounds.width),
+            Some(new_bounds.height),
+        );
+
+        paragraph.bounds = new_bounds;
+        paragraph.min_bounds = text::measure(&paragraph.buffer);
     }
 
-    fn compare(&self, text: Text<&str>) -> core::text::Difference {
+    fn compare(&self, text: Text<()>) -> core::text::Difference {
         let font_system = text::font_system().read().expect("Read font system");
         let paragraph = self.internal();
         let metrics = paragraph.buffer.metrics();
 
         if paragraph.version != font_system.version
-            || paragraph.content != text.content
             || metrics.font_size != text.size.0
             || metrics.line_height != text.line_height.to_absolute(text.size).0
             || paragraph.font != text.font
@@ -231,7 +200,7 @@ impl core::text::Paragraph for Paragraph {
 
 impl Default for Paragraph {
     fn default() -> Self {
-        Self(Some(Arc::new(Internal::default())))
+        Self(Arc::new(Internal::default()))
     }
 }
 
@@ -240,7 +209,6 @@ impl fmt::Debug for Paragraph {
         let paragraph = self.internal();
 
         f.debug_struct("Paragraph")
-            .field("content", &paragraph.content)
             .field("font", &paragraph.font)
             .field("shaping", &paragraph.shaping)
             .field("horizontal_alignment", &paragraph.horizontal_alignment)
@@ -253,8 +221,7 @@ impl fmt::Debug for Paragraph {
 
 impl PartialEq for Internal {
     fn eq(&self, other: &Self) -> bool {
-        self.content == other.content
-            && self.font == other.font
+        self.font == other.font
             && self.shaping == other.shaping
             && self.horizontal_alignment == other.horizontal_alignment
             && self.vertical_alignment == other.vertical_alignment
@@ -271,7 +238,6 @@ impl Default for Internal {
                 font_size: 1.0,
                 line_height: 1.0,
             }),
-            content: String::new(),
             font: Font::default(),
             shaping: Shaping::default(),
             horizontal_alignment: alignment::Horizontal::Left,
@@ -298,7 +264,7 @@ pub struct Weak {
 impl Weak {
     /// Tries to update the reference into a [`Paragraph`].
     pub fn upgrade(&self) -> Option<Paragraph> {
-        self.raw.upgrade().map(Some).map(Paragraph)
+        self.raw.upgrade().map(Paragraph)
     }
 }
 
diff --git a/widget/src/pick_list.rs b/widget/src/pick_list.rs
index 97de5b48..f7f7b65b 100644
--- a/widget/src/pick_list.rs
+++ b/widget/src/pick_list.rs
@@ -6,7 +6,8 @@ use crate::core::layout;
 use crate::core::mouse;
 use crate::core::overlay;
 use crate::core::renderer;
-use crate::core::text::{self, Paragraph as _, Text};
+use crate::core::text::paragraph;
+use crate::core::text::{self, Text};
 use crate::core::touch;
 use crate::core::widget::tree::{self, Tree};
 use crate::core::{
@@ -622,8 +623,8 @@ struct State<P: text::Paragraph> {
     keyboard_modifiers: keyboard::Modifiers,
     is_open: bool,
     hovered_option: Option<usize>,
-    options: Vec<P>,
-    placeholder: P,
+    options: Vec<paragraph::Plain<P>>,
+    placeholder: paragraph::Plain<P>,
 }
 
 impl<P: text::Paragraph> State<P> {
@@ -635,7 +636,7 @@ impl<P: text::Paragraph> State<P> {
             is_open: bool::default(),
             hovered_option: Option::default(),
             options: Vec::new(),
-            placeholder: P::default(),
+            placeholder: paragraph::Plain::default(),
         }
     }
 }
diff --git a/widget/src/text_input.rs b/widget/src/text_input.rs
index ba2fbc13..a0fe14a0 100644
--- a/widget/src/text_input.rs
+++ b/widget/src/text_input.rs
@@ -19,7 +19,8 @@ use crate::core::keyboard::key;
 use crate::core::layout;
 use crate::core::mouse::{self, click};
 use crate::core::renderer;
-use crate::core::text::{self, Paragraph as _, Text};
+use crate::core::text::paragraph;
+use crate::core::text::{self, Text};
 use crate::core::time::{Duration, Instant};
 use crate::core::touch;
 use crate::core::widget;
@@ -360,7 +361,7 @@ where
             let icon_layout = children_layout.next().unwrap();
 
             renderer.fill_paragraph(
-                &state.icon,
+                state.icon.raw(),
                 icon_layout.bounds().center(),
                 style.icon,
                 *viewport,
@@ -378,7 +379,7 @@ where
                 cursor::State::Index(position) => {
                     let (text_value_width, offset) =
                         measure_cursor_and_scroll_offset(
-                            &state.value,
+                            state.value.raw(),
                             text_bounds,
                             position,
                         );
@@ -415,14 +416,14 @@ where
 
                     let (left_position, left_offset) =
                         measure_cursor_and_scroll_offset(
-                            &state.value,
+                            state.value.raw(),
                             text_bounds,
                             left,
                         );
 
                     let (right_position, right_offset) =
                         measure_cursor_and_scroll_offset(
-                            &state.value,
+                            state.value.raw(),
                             text_bounds,
                             right,
                         );
@@ -469,9 +470,9 @@ where
 
             renderer.fill_paragraph(
                 if text.is_empty() {
-                    &state.placeholder
+                    state.placeholder.raw()
                 } else {
-                    &state.value
+                    state.value.raw()
                 },
                 Point::new(text_bounds.x, text_bounds.center_y())
                     - Vector::new(offset, 0.0),
@@ -1178,9 +1179,9 @@ pub fn select_all<T>(id: Id) -> Task<T> {
 /// The state of a [`TextInput`].
 #[derive(Debug, Default, Clone)]
 pub struct State<P: text::Paragraph> {
-    value: P,
-    placeholder: P,
-    icon: P,
+    value: paragraph::Plain<P>,
+    placeholder: paragraph::Plain<P>,
+    icon: paragraph::Plain<P>,
     is_focused: Option<Focus>,
     is_dragging: bool,
     is_pasting: Option<Value>,
@@ -1212,9 +1213,9 @@ impl<P: text::Paragraph> State<P> {
     /// Creates a new [`State`], representing a focused [`TextInput`].
     pub fn focused() -> Self {
         Self {
-            value: P::default(),
-            placeholder: P::default(),
-            icon: P::default(),
+            value: paragraph::Plain::default(),
+            placeholder: paragraph::Plain::default(),
+            icon: paragraph::Plain::default(),
             is_focused: None,
             is_dragging: false,
             is_pasting: None,
@@ -1319,7 +1320,7 @@ fn offset<P: text::Paragraph>(
         };
 
         let (_, offset) = measure_cursor_and_scroll_offset(
-            &state.value,
+            state.value.raw(),
             text_bounds,
             focus_position,
         );
@@ -1357,6 +1358,7 @@ fn find_cursor_position<P: text::Paragraph>(
 
     let char_offset = state
         .value
+        .raw()
         .hit_test(Point::new(x + offset, text_bounds.height / 2.0))
         .map(text::Hit::cursor)?;
 
@@ -1386,7 +1388,7 @@ fn replace_paragraph<Renderer>(
     let mut children_layout = layout.children();
     let text_bounds = children_layout.next().unwrap().bounds();
 
-    state.value = Renderer::Paragraph::with_text(Text {
+    state.value = paragraph::Plain::new(Text {
         font,
         line_height,
         content: &value.to_string(),