Ellipsize (#467)

* feat: add Ellipsize enum

* chore: API changes needed for ellipsize

Decided not to change "layout()" function for now to avoid breaking the
interface. For now.

* chore: shape ellipsis

* feat: Ellipsize::Start

Since it can only have 1 line, it's easier to implement.

* DROPME: temporarily change rich-text for testing

* test(ellipsize): Testing Ellipsize::Start

Long text in small buffer should produce ellipsis glyphs

* fix: do not need font_system anymore

We moved ellipsis shaping elsewhere so no need to pass font_system to
layout function (which also was recreating a new one in the tests every
time making them take forever).

* feat: Ellipsize::End

* improv(ellipsize): use a single ellipsis shape

* improv: Ellipsie::End && Wrap::None

There is no need to layout the whole line if it's not going to fit.

* fix: mixed bidi text when Ellipsize::End && Wrap::None

* chore: clean up and simplify when line.RTL==span.RTL

* fix(ellipsize): last word is not (word_count -1) if iter().rev()

* refactor(layout): extract the layout algorithm to make it more readable

* improv(ellipsize): Ellipsize::Start && Wrap::None

we iterate in reverse and only layout what's going to be visible

* Revert: delete the previous approach of post processing ellipsis

* doc: explain the interaction between Ellipsize and Wrap

* chore: lower the scope

* feat: Ellipsize the last line of a paragraph

For now only the number of lines is supported

* fix: clear ellipsized field on visual lines

This was causing ellipsis to show on random lines

* chore: remove old tests

will add better tests soon

* chore: clean up changes from previous attempt

* fix: consider the ellipsis width when doing alignment

* feat(ellipsize): add `Height` limit to `Ellipsize`

* fix: ellipsize the start of the last line correctly

* fix: ellipsize at the start of mixed bidi lines

* feat: Ellipsize::Middle

* fix: consider ellipsize::middle when calculating alignment correction

* refactor: improve readability

* refactor: deduplicate "fit_glyphs"

* refactor: combine backward and forward layout into one (wip)

* fix: Backward works in the unified layout_spans

* chore: clean up

* fix: Ellipsize::Middle

* fix: handle large words in bidi boundaries

* chore: clean up and some refactoring

* fix: ellipsis is now the same level as the surrounding text

* fix: try to fit more when ellipsizing::middle

* improv: ellipsis now have the same level as the neighbors

This makes ellipsized RTL text inside a LTR line more readable.

before:

Hello سلام...خوبی؟
Hello خولی؟...سلام

* fix: some extra words were being rendered in Ellipsize::Middle

This was causing the last word (if it's not the same level as the rest)
to be rendered outside the buffer.

* test: a few test cases for ellipsize

* fix: assign the correct byte range to ellipsis

this should fix the panic when selecting or clicking on or near the
ellipsis in the editor.

src/buffer.rs

@@ -11,8 +11,8 @@ use unicode_segmentation::UnicodeSegmentation;
 
 use crate::{
     Affinity, Align, Attrs, AttrsList, BidiParagraphs, BorrowedWithFontSystem, BufferLine, Color,
-    Cursor, FontSystem, Hinting, LayoutCursor, LayoutGlyph, LayoutLine, LineEnding, LineIter,
-    Motion, Renderer, Scroll, ShapeLine, Shaping, Wrap,
+    Cursor, Ellipsize, FontSystem, Hinting, LayoutCursor, LayoutGlyph, LayoutLine, LineEnding,
+    LineIter, Motion, Renderer, Scroll, ShapeLine, Shaping, Wrap,
 };
 
 /// A line of visible text for rendering
@@ -214,6 +214,7 @@ pub struct Buffer {
     /// True if a redraw is requires. Set to false after processing
     redraw: bool,
     wrap: Wrap,
+    ellipsize: Ellipsize,
     monospace_width: Option<f32>,
     tab_width: u16,
     hinting: Hinting,
@@ -229,6 +230,7 @@ impl Clone for Buffer {
             scroll: self.scroll,
             redraw: self.redraw,
             wrap: self.wrap,
+            ellipsize: self.ellipsize,
             monospace_width: self.monospace_width,
             tab_width: self.tab_width,
             hinting: self.hinting,
@@ -258,6 +260,7 @@ impl Buffer {
             scroll: Scroll::default(),
             redraw: false,
             wrap: Wrap::WordOrGlyph,
+            ellipsize: Ellipsize::None,
             monospace_width: None,
             tab_width: 8,
             hinting: Hinting::default(),
@@ -298,6 +301,7 @@ impl Buffer {
                     self.metrics.font_size,
                     self.width_opt,
                     self.wrap,
+                    self.ellipsize,
                     self.monospace_width,
                     self.tab_width,
                     self.hinting,
@@ -542,6 +546,7 @@ impl Buffer {
             self.metrics.font_size,
             self.width_opt,
             self.wrap,
+            self.ellipsize,
             self.monospace_width,
             self.tab_width,
             self.hinting,
@@ -590,6 +595,20 @@ impl Buffer {
         }
     }
 
+    /// Get the current [`Ellipsize`]
+    pub const fn ellipsize(&self) -> Ellipsize {
+        self.ellipsize
+    }
+
+    /// Set the current [`Ellipsize`]
+    pub fn set_ellipsize(&mut self, font_system: &mut FontSystem, ellipsize: Ellipsize) {
+        if ellipsize != self.ellipsize {
+            self.ellipsize = ellipsize;
+            self.relayout(font_system);
+            self.shape_until_scroll(font_system, false);
+        }
+    }
+
     /// Get the current `monospace_width`
     pub const fn monospace_width(&self) -> Option<f32> {
         self.monospace_width
@@ -1406,6 +1425,11 @@ impl BorrowedWithFontSystem<'_, Buffer> {
         self.inner.set_wrap(self.font_system, wrap);
     }
 
+    /// Set the current [`Ellipsize`]
+    pub fn set_ellipsize(&mut self, ellipsize: Ellipsize) {
+        self.inner.set_ellipsize(self.font_system, ellipsize);
+    }
+
     /// Set the current buffer dimensions
     pub fn set_size(&mut self, width_opt: Option<f32>, height_opt: Option<f32>) {
         self.inner.set_size(self.font_system, width_opt, height_opt);

src/buffer_line.rs

@@ -1,10 +1,12 @@
+#![allow(clippy::too_many_arguments)]
+
 #[cfg(not(feature = "std"))]
 use alloc::{string::String, vec::Vec};
 use core::mem;
 
 use crate::{
-    Align, Attrs, AttrsList, Cached, FontSystem, Hinting, LayoutLine, LineEnding, ShapeLine,
-    Shaping, Wrap,
+    Align, Attrs, AttrsList, Cached, Ellipsize, FontSystem, Hinting, LayoutLine, LineEnding,
+    ShapeLine, Shaping, Wrap,
 };
 
 /// A line (or paragraph) of text that is shaped and laid out
@@ -242,6 +244,7 @@ impl BufferLine {
         font_size: f32,
         width_opt: Option<f32>,
         wrap: Wrap,
+        ellipsize: Ellipsize,
         match_mono_width: Option<f32>,
         tab_width: u16,
         hinting: Hinting,
@@ -258,6 +261,7 @@ impl BufferLine {
                 font_size,
                 width_opt,
                 wrap,
+                ellipsize,
                 align,
                 &mut layout,
                 match_mono_width,

src/layout.rs

@@ -152,6 +152,29 @@ impl Display for Align {
     }
 }
 
+#[derive(Debug, Clone, Copy, PartialEq, Default)]
+pub enum Ellipsize {
+    /// No Ellipsizing
+    #[default]
+    None,
+    /// Ellipsizes the start of the last visual line that fits within the `EllipsizeHeightLimit`
+    Start(EllipsizeHeightLimit),
+    /// Ellipsizes the middle of the last visual line that fits within the `EllipsizeHeightLimit`.
+    Middle(EllipsizeHeightLimit),
+    /// Ellipsizes the end of the last visual line that fits within the `EllipsizeHeightLimit`.
+    End(EllipsizeHeightLimit),
+}
+
+#[derive(Debug, Clone, Copy, PartialEq)]
+pub enum EllipsizeHeightLimit {
+    /// Number of lines to show before ellipsizing the rest. Only works if `Wrap` is NOT set to
+    /// `Wrap::None`. Otherwise, it will be ignored and the behavior will be the same as `Lines(1)`
+    Lines(usize),
+    /// Ellipsizes the last line that fits within the given height limit. If `Wrap` is set to
+    /// `Wrap::None`, the behavior will be the same as `Lines(1)`
+    Height(f32),
+}
+
 /// Metrics hinting strategy
 #[derive(Debug, Eq, PartialEq, Clone, Copy, Default)]
 pub enum Hinting {