Make FontSystem global and simplify Paragraph API

core/src/renderer/null.rs

@@ -58,16 +58,6 @@ impl text::Renderer for Null {
 
     fn load_font(&mut self, _font: Cow<'static, [u8]>) {}
 
-    fn create_paragraph(&self, _text: Text<'_, Self::Font>) -> Self::Paragraph {
-    }
-
-    fn resize_paragraph(
-        &self,
-        _paragraph: &mut Self::Paragraph,
-        _new_bounds: Size,
-    ) {
-    }
-
     fn fill_paragraph(
         &mut self,
         _paragraph: &Self::Paragraph,
@@ -88,24 +78,12 @@ impl text::Renderer for Null {
 impl text::Paragraph for () {
     type Font = Font;
 
-    fn content(&self) -> &str {
-        ""
-    }
+    fn with_text(_text: Text<'_, Self::Font>) -> Self {}
 
-    fn text_size(&self) -> Pixels {
-        Pixels(16.0)
-    }
+    fn resize(&mut self, _new_bounds: Size) {}
 
-    fn font(&self) -> Self::Font {
-        Font::default()
-    }
-
-    fn line_height(&self) -> text::LineHeight {
-        text::LineHeight::default()
-    }
-
-    fn shaping(&self) -> text::Shaping {
-        text::Shaping::default()
+    fn compare(&self, _text: Text<'_, Self::Font>) -> text::Difference {
+        text::Difference::None
     }
 
     fn horizontal_alignment(&self) -> alignment::Horizontal {
@@ -120,10 +98,6 @@ impl text::Paragraph for () {
         None
     }
 
-    fn bounds(&self) -> Size {
-        Size::ZERO
-    }
-
     fn min_bounds(&self) -> Size {
         Size::ZERO
     }

core/src/text.rs

@@ -156,33 +156,6 @@ pub trait Renderer: crate::Renderer {
     /// Loads a [`Self::Font`] from its bytes.
     fn load_font(&mut self, font: Cow<'static, [u8]>);
 
-    /// Creates a new [`Paragraph`] laid out with the given [`Text`].
-    fn create_paragraph(&self, text: Text<'_, Self::Font>) -> Self::Paragraph;
-
-    /// Lays out the given [`Paragraph`] with some new boundaries.
-    fn resize_paragraph(
-        &self,
-        paragraph: &mut Self::Paragraph,
-        new_bounds: Size,
-    );
-
-    /// Updates a [`Paragraph`] to match the given [`Text`], if needed.
-    fn update_paragraph(
-        &self,
-        paragraph: &mut Self::Paragraph,
-        text: Text<'_, Self::Font>,
-    ) {
-        match compare(paragraph, text) {
-            Difference::None => {}
-            Difference::Bounds => {
-                self.resize_paragraph(paragraph, text.bounds);
-            }
-            Difference::Shape => {
-                *paragraph = self.create_paragraph(text);
-            }
-        }
-    }
-
     /// Draws the given [`Paragraph`] at the given position and with the given
     /// [`Color`].
     fn fill_paragraph(
@@ -201,25 +174,21 @@ pub trait Renderer: crate::Renderer {
         color: Color,
     );
 }
+
 /// A text paragraph.
-pub trait Paragraph: Default {
+pub trait Paragraph: Sized + Default {
     /// The font of this [`Paragraph`].
-    type Font;
+    type Font: Copy + PartialEq;
 
-    /// Returns the content of the [`Paragraph`].
-    fn content(&self) -> &str;
+    /// Creates a new [`Paragraph`] laid out with the given [`Text`].
+    fn with_text(text: Text<'_, Self::Font>) -> Self;
 
-    /// Returns the text size of the [`Paragraph`].
-    fn text_size(&self) -> Pixels;
+    /// Lays out the [`Paragraph`] with some new boundaries.
+    fn resize(&mut self, new_bounds: Size);
 
-    /// Returns the [`LineHeight`] of the [`Paragraph`].
-    fn line_height(&self) -> LineHeight;
-
-    /// Returns the [`Self::Font`] of the [`Paragraph`].
-    fn font(&self) -> Self::Font;
-
-    /// Returns the [`Shaping`] strategy of the [`Paragraph`].
-    fn shaping(&self) -> Shaping;
+    /// Compares the [`Paragraph`] with some desired [`Text`] and returns the
+    /// [`Difference`].
+    fn compare(&self, text: Text<'_, Self::Font>) -> Difference;
 
     /// Returns the horizontal alignment of the [`Paragraph`].
     fn horizontal_alignment(&self) -> alignment::Horizontal;
@@ -227,9 +196,6 @@ pub trait Paragraph: Default {
     /// Returns the vertical alignment of the [`Paragraph`].
     fn vertical_alignment(&self) -> alignment::Vertical;
 
-    /// Returns the boundaries of the [`Paragraph`].
-    fn bounds(&self) -> Size;
-
     /// Returns the minimum boundaries that can fit the contents of the
     /// [`Paragraph`].
     fn min_bounds(&self) -> Size;
@@ -241,6 +207,19 @@ pub trait Paragraph: 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<'_, Self::Font>) {
+        match self.compare(text) {
+            Difference::None => {}
+            Difference::Bounds => {
+                self.resize(text.bounds);
+            }
+            Difference::Shape => {
+                *self = Self::with_text(text);
+            }
+        }
+    }
+
     /// Returns the minimum width that can fit the contents of the [`Paragraph`].
     fn min_width(&self) -> f32 {
         self.min_bounds().width
@@ -276,26 +255,3 @@ pub enum Difference {
     /// the text is necessary.
     Shape,
 }
-
-/// Compares a [`Paragraph`] with some desired [`Text`] and returns the
-/// [`Difference`].
-pub fn compare<Font: PartialEq>(
-    paragraph: &impl Paragraph<Font = Font>,
-    text: Text<'_, Font>,
-) -> Difference {
-    if paragraph.content() != text.content
-        || paragraph.text_size() != text.size
-        || paragraph.line_height().to_absolute(text.size)
-            != text.line_height.to_absolute(text.size)
-        || paragraph.font() != text.font
-        || paragraph.shaping() != text.shaping
-        || paragraph.horizontal_alignment() != text.horizontal_alignment
-        || paragraph.vertical_alignment() != text.vertical_alignment
-    {
-        Difference::Shape
-    } else if paragraph.bounds() != text.bounds {
-        Difference::Bounds
-    } else {
-        Difference::None
-    }
-}

core/src/widget/text.rs

@@ -212,19 +212,16 @@ where
 
     let State(ref mut paragraph) = state;
 
-    renderer.update_paragraph(
-        paragraph,
-        text::Text {
-            content,
-            bounds,
-            size,
-            line_height,
-            font,
-            shaping,
-            horizontal_alignment,
-            vertical_alignment,
-        },
-    );
+    paragraph.update(text::Text {
+        content,
+        bounds,
+        size,
+        line_height,
+        font,
+        shaping,
+        horizontal_alignment,
+        vertical_alignment,
+    });
 
     let size = limits.resolve(paragraph.min_bounds());