Draft `Editor` API and `TextEditor` widget

6 files changed, 209 insertions, 83 deletions

diff --git a/core/src/layout/limits.rs b/core/src/layout/limits.rs
index 5d3c1556..39a3d98b 100644
--- a/core/src/layout/limits.rs
+++ b/core/src/layout/limits.rs
@@ -2,7 +2,7 @@
 use crate::{Length, Padding, Size};
 
 /// A set of size constraints for layouting.
-#[derive(Debug, Clone, Copy)]
+#[derive(Debug, Clone, Copy, PartialEq)]
 pub struct Limits {
     min: Size,
     max: Size,
diff --git a/core/src/lib.rs b/core/src/lib.rs
index 1bfba7bd..13a9f06b 100644
--- a/core/src/lib.rs
+++ b/core/src/lib.rs
@@ -12,7 +12,7 @@
 #![forbid(unsafe_code, rust_2018_idioms)]
 #![deny(
     missing_debug_implementations,
-    missing_docs,
+    // missing_docs,
     unused_results,
     clippy::extra_unused_lifetimes,
     clippy::from_over_into,
diff --git a/core/src/renderer/null.rs b/core/src/renderer/null.rs
index 0ffd3649..adf75969 100644
--- a/core/src/renderer/null.rs
+++ b/core/src/renderer/null.rs
@@ -43,6 +43,7 @@ impl Renderer for Null {
 impl text::Renderer for Null {
     type Font = Font;
     type Paragraph = ();
+    type Editor = ();
 
     const ICON_FONT: Font = Font::DEFAULT;
     const CHECKMARK_ICON: char = '0';
@@ -66,6 +67,14 @@ impl text::Renderer for Null {
     ) {
     }
 
+    fn fill_editor(
+        &mut self,
+        _editor: &Self::Editor,
+        _position: Point,
+        _color: Color,
+    ) {
+    }
+
     fn fill_text(
         &mut self,
         _paragraph: Text<'_, Self::Font>,
@@ -106,3 +115,32 @@ impl text::Paragraph for () {
         None
     }
 }
+
+impl text::Editor for () {
+    type Font = Font;
+
+    fn with_text(_text: &str) -> Self {}
+
+    fn cursor(&self) -> text::editor::Cursor {
+        text::editor::Cursor::Caret(Point::ORIGIN)
+    }
+
+    fn perform(&mut self, _action: text::editor::Action) {}
+
+    fn bounds(&self) -> Size {
+        Size::ZERO
+    }
+
+    fn min_bounds(&self) -> Size {
+        Size::ZERO
+    }
+
+    fn update(
+        &mut self,
+        _new_bounds: Size,
+        _new_font: Self::Font,
+        _new_size: Pixels,
+        _new_line_height: text::LineHeight,
+    ) {
+    }
+}
diff --git a/core/src/text.rs b/core/src/text.rs
index ff85696e..5aacbcc5 100644
--- a/core/src/text.rs
+++ b/core/src/text.rs
@@ -1,4 +1,11 @@
 //! Draw and interact with text.
+mod paragraph;
+
+pub mod editor;
+
+pub use editor::Editor;
+pub use paragraph::Paragraph;
+
 use crate::alignment;
 use crate::{Color, Pixels, Point, Size};
 
@@ -126,6 +133,31 @@ impl Hit {
     }
 }
 
+/// The difference detected in some text.
+///
+/// You will obtain a [`Difference`] when you [`compare`] a [`Paragraph`] with some
+/// [`Text`].
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum Difference {
+    /// No difference.
+    ///
+    /// The text can be reused as it is!
+    None,
+
+    /// A bounds difference.
+    ///
+    /// This normally means a relayout is necessary, but the shape of the text can
+    /// be reused.
+    Bounds,
+
+    /// A shape difference.
+    ///
+    /// The contents, alignment, sizes, fonts, or any other essential attributes
+    /// of the shape of the text have changed. A complete reshape and relayout of
+    /// the text is necessary.
+    Shape,
+}
+
 /// A renderer capable of measuring and drawing [`Text`].
 pub trait Renderer: crate::Renderer {
     /// The font type used.
@@ -134,6 +166,9 @@ pub trait Renderer: crate::Renderer {
     /// The [`Paragraph`] of this [`Renderer`].
     type Paragraph: Paragraph<Font = Self::Font> + 'static;
 
+    /// The [`Editor`] of this [`Renderer`].
+    type Editor: Editor<Font = Self::Font> + 'static;
+
     /// The icon font of the backend.
     const ICON_FONT: Self::Font;
 
@@ -165,6 +200,13 @@ pub trait Renderer: crate::Renderer {
         color: Color,
     );
 
+    fn fill_editor(
+        &mut self,
+        editor: &Self::Editor,
+        position: Point,
+        color: Color,
+    );
+
     /// Draws the given [`Text`] at the given position and with the given
     /// [`Color`].
     fn fill_text(
@@ -174,84 +216,3 @@ pub trait Renderer: crate::Renderer {
         color: Color,
     );
 }
-
-/// A text paragraph.
-pub trait Paragraph: Sized + Default {
-    /// The font of this [`Paragraph`].
-    type Font: Copy + PartialEq;
-
-    /// Creates a new [`Paragraph`] laid out with the given [`Text`].
-    fn with_text(text: Text<'_, Self::Font>) -> Self;
-
-    /// Lays out the [`Paragraph`] with some new boundaries.
-    fn resize(&mut self, new_bounds: Size);
-
-    /// 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;
-
-    /// Returns the vertical alignment of the [`Paragraph`].
-    fn vertical_alignment(&self) -> alignment::Vertical;
-
-    /// Returns the minimum boundaries that can fit the contents of the
-    /// [`Paragraph`].
-    fn min_bounds(&self) -> Size;
-
-    /// Tests whether the provided point is within the boundaries of the
-    /// [`Paragraph`], returning information about the nearest character.
-    fn hit_test(&self, point: Point) -> Option<Hit>;
-
-    /// 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
-    }
-
-    /// Returns the minimum height that can fit the contents of the [`Paragraph`].
-    fn min_height(&self) -> f32 {
-        self.min_bounds().height
-    }
-}
-
-/// The difference detected in some text.
-///
-/// You will obtain a [`Difference`] when you [`compare`] a [`Paragraph`] with some
-/// [`Text`].
-#[derive(Debug, Clone, Copy, PartialEq, Eq)]
-pub enum Difference {
-    /// No difference.
-    ///
-    /// The text can be reused as it is!
-    None,
-
-    /// A bounds difference.
-    ///
-    /// This normally means a relayout is necessary, but the shape of the text can
-    /// be reused.
-    Bounds,
-
-    /// A shape difference.
-    ///
-    /// The contents, alignment, sizes, fonts, or any other essential attributes
-    /// of the shape of the text have changed. A complete reshape and relayout of
-    /// the text is necessary.
-    Shape,
-}
diff --git a/core/src/text/editor.rs b/core/src/text/editor.rs
new file mode 100644
index 00000000..a4fd0ec1
--- /dev/null
+++ b/core/src/text/editor.rs
@@ -0,0 +1,68 @@
+use crate::text::LineHeight;
+use crate::{Pixels, Point, Rectangle, Size};
+
+pub trait Editor: Sized + Default {
+    type Font: Copy + PartialEq + Default;
+
+    /// Creates a new [`Editor`] laid out with the given text.
+    fn with_text(text: &str) -> Self;
+
+    fn cursor(&self) -> Cursor;
+
+    fn perform(&mut self, action: Action);
+
+    /// Returns the current boundaries of the [`Editor`].
+    fn bounds(&self) -> Size;
+
+    /// Returns the minimum boundaries that can fit the contents of the
+    /// [`Editor`].
+    fn min_bounds(&self) -> Size;
+
+    /// Updates the [`Editor`] with some new attributes.
+    fn update(
+        &mut self,
+        new_bounds: Size,
+        new_font: Self::Font,
+        new_size: Pixels,
+        new_line_height: LineHeight,
+    );
+
+    /// Returns the minimum width that can fit the contents of the [`Editor`].
+    fn min_width(&self) -> f32 {
+        self.min_bounds().width
+    }
+
+    /// Returns the minimum height that can fit the contents of the [`Editor`].
+    fn min_height(&self) -> f32 {
+        self.min_bounds().height
+    }
+}
+
+#[derive(Debug, Clone, Copy, PartialEq)]
+pub enum Action {
+    MoveLeft,
+    MoveRight,
+    MoveUp,
+    MoveDown,
+    MoveLeftWord,
+    MoveRightWord,
+    MoveHome,
+    MoveEnd,
+    SelectWord,
+    SelectLine,
+    Insert(char),
+    Backspace,
+    Delete,
+    Click(Point),
+    Drag(Point),
+}
+
+/// The cursor of an [`Editor`].
+#[derive(Debug, Clone)]
+pub enum Cursor {
+    /// Cursor without a selection
+    Caret(Point),
+
+    /// Cursor selecting a range of text
+    Selection(Vec<Rectangle>),
+}
diff --git a/core/src/text/paragraph.rs b/core/src/text/paragraph.rs
new file mode 100644
index 00000000..de1fb74d
--- /dev/null
+++ b/core/src/text/paragraph.rs
@@ -0,0 +1,59 @@
+use crate::alignment;
+use crate::text::{Difference, Hit, Text};
+use crate::{Point, Size};
+
+/// A text paragraph.
+pub trait Paragraph: Sized + Default {
+    /// The font of this [`Paragraph`].
+    type Font: Copy + PartialEq;
+
+    /// Creates a new [`Paragraph`] laid out with the given [`Text`].
+    fn with_text(text: Text<'_, Self::Font>) -> Self;
+
+    /// Lays out the [`Paragraph`] with some new boundaries.
+    fn resize(&mut self, new_bounds: Size);
+
+    /// 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;
+
+    /// Returns the vertical alignment of the [`Paragraph`].
+    fn vertical_alignment(&self) -> alignment::Vertical;
+
+    /// Returns the minimum boundaries that can fit the contents of the
+    /// [`Paragraph`].
+    fn min_bounds(&self) -> Size;
+
+    /// Tests whether the provided point is within the boundaries of the
+    /// [`Paragraph`], returning information about the nearest character.
+    fn hit_test(&self, point: Point) -> Option<Hit>;
+
+    /// 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
+    }
+
+    /// Returns the minimum height that can fit the contents of the [`Paragraph`].
+    fn min_height(&self) -> f32 {
+        self.min_bounds().height
+    }
+}