Add proper underline and strikeout support

This makes use of the new rectangle rendering methods used to display
the colored visual bell to add proper underline and strikeout support to
Alacritty.

2 files changed, 200 insertions, 67 deletions

diff --git a/src/renderer/lines.rs b/src/renderer/lines.rs
new file mode 100644
index 00000000..556dcb0d
--- /dev/null
+++ b/src/renderer/lines.rs
@@ -0,0 +1,143 @@
+// Copyright 2016 Joe Wilm, The Alacritty Project Contributors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+use std::collections::HashMap;
+
+use crate::term::{ SizeInfo, RenderableCell};
+use crate::term::cell::Flags;
+use crate::renderer::Rect;
+use font::Metrics;
+use crate::Rgb;
+
+/// Lines for underline and strikeout.
+pub struct Lines<'a> {
+    inner: Vec<(Rect<f32>, Rgb)>,
+    last_starts: HashMap<Flags, Option<RenderableCell>>,
+    last_cell: Option<RenderableCell>,
+    metrics: &'a Metrics,
+    size: &'a SizeInfo,
+}
+
+impl<'a> Lines<'a> {
+    pub fn new(metrics: &'a Metrics, size: &'a SizeInfo) -> Self {
+        let mut last_starts = HashMap::new();
+        last_starts.insert(Flags::UNDERLINE, None);
+        last_starts.insert(Flags::STRIKEOUT, None);
+
+        Self {
+            inner: Vec::new(),
+            last_cell: None,
+            last_starts,
+            metrics,
+            size,
+        }
+    }
+
+    /// Convert the stored lines to rectangles for the renderer.
+    pub fn rects(mut self) -> Vec<(Rect<f32>, Rgb)> {
+        // If there's still a line pending, draw it until the last cell
+        for (flag, start_cell) in self.last_starts.iter_mut() {
+            if let Some(start) = start_cell {
+                self.inner.push(
+                    create_rect(
+                        &start,
+                        &self.last_cell.unwrap(),
+                        *flag,
+                        &self.metrics,
+                        &self.size,
+                    )
+                );
+            }
+        }
+
+        self.inner
+    }
+
+    /// Update the stored lines with the next cell info.
+    pub fn update_lines(&mut self, cell: &RenderableCell) {
+        for (flag, start_cell) in self.last_starts.iter_mut() {
+            let flag = *flag;
+            *start_cell = match *start_cell {
+                // Check for end if line is present
+                Some(ref mut start) => {
+                    // No change in line
+                    if cell.line == start.line && cell.flags.contains(flag) && cell.fg == start.fg {
+                        continue;
+                    }
+
+                    self.inner.push(
+                        create_rect(
+                            &start,
+                            &self.last_cell.unwrap(),
+                            flag,
+                            &self.metrics,
+                            &self.size,
+                        )
+                    );
+
+                    // Start a new line if the flag is present
+                    if cell.flags.contains(flag) {
+                        Some(*cell)
+                    } else {
+                        None
+                    }
+                }
+                // Check for new start of line
+                None => if cell.flags.contains(flag) {
+                    Some(*cell)
+                } else {
+                    None
+                },
+            };
+        }
+
+        self.last_cell = Some(*cell);
+    }
+}
+
+/// Create a rectangle between two cells.
+fn create_rect(
+    start: &RenderableCell,
+    end: &RenderableCell,
+    flag: Flags,
+    metrics: &Metrics,
+    size: &SizeInfo,
+) -> (Rect<f32>, Rgb) {
+    let start_x = start.column.0 as f32 * size.cell_width;
+    let end_x = (end.column.0 + 1) as f32 * size.cell_width;
+    let width = end_x - start_x;
+
+    let (position, height) = match flag {
+        Flags::UNDERLINE => (metrics.underline_position, metrics.underline_thickness),
+        Flags::STRIKEOUT => (metrics.strikeout_position, metrics.strikeout_thickness),
+        _ => unimplemented!("Invalid flag for cell line drawing specified"),
+    };
+
+    let cell_bottom = (start.line.0 as f32 + 1.) * size.cell_height;
+    let baseline = cell_bottom + metrics.descent;
+
+    let mut y = baseline - position - height / 2.;
+    let max_y = cell_bottom - height;
+    if y > max_y {
+        y = max_y;
+    }
+
+    let rect = Rect::new(
+        start_x + size.padding_x,
+        y + size.padding_y,
+        width,
+        height,
+    );
+
+    (rect, start.fg)
+}
diff --git a/src/renderer/mod.rs b/src/renderer/mod.rs
index c05301cc..42a17486 100644
--- a/src/renderer/mod.rs
+++ b/src/renderer/mod.rs
@@ -23,16 +23,19 @@ use std::time::Duration;
 
 use cgmath;
 use fnv::FnvHasher;
+use glutin::dpi::PhysicalSize;
 use font::{self, FontDesc, FontKey, GlyphKey, Rasterize, RasterizedGlyph, Rasterizer};
+use notify::{watcher, DebouncedEvent, RecursiveMode, Watcher};
+
 use crate::gl::types::*;
 use crate::gl;
 use crate::index::{Column, Line, RangeInclusive};
-use notify::{watcher, DebouncedEvent, RecursiveMode, Watcher};
 use crate::Rgb;
-
 use crate::config::{self, Config, Delta};
 use crate::term::{self, cell, RenderableCell};
-use glutin::dpi::PhysicalSize;
+use crate::renderer::lines::Lines;
+
+pub mod lines;
 
 // Shader paths for live reload
 static TEXT_SHADER_F_PATH: &'static str = concat!(env!("CARGO_MANIFEST_DIR"), "/res/text.f.glsl");
@@ -699,6 +702,7 @@ impl QuadRenderer {
         config: &Config,
         props: &term::SizeInfo,
         visual_bell_intensity: f64,
+        cell_line_rects: Lines,
     ) {
         // Swap to rectangle rendering program
         unsafe {
@@ -725,6 +729,11 @@ impl QuadRenderer {
         let rect = Rect::new(0., 0., props.width, props.height);
         self.render_rect(&rect, color, visual_bell_intensity as f32, props);
 
+        // Draw underlines and strikeouts
+        for cell_line_rect in cell_line_rects.rects() {
+            self.render_rect(&cell_line_rect.0, cell_line_rect.1, 255., props);
+        }
+
         // Deactivate rectangle program again
         unsafe {
             // Reset blending strategy
@@ -902,7 +911,8 @@ impl QuadRenderer {
     }
 }
 
-struct Rect<T> {
+#[derive(Debug, Copy, Clone)]
+pub struct Rect<T> {
     x: T,
     y: T,
     width: T,
@@ -910,7 +920,7 @@ struct Rect<T> {
 }
 
 impl<T> Rect<T> {
-    fn new(x: T, y: T, width: T, height: T) -> Self {
+    pub fn new(x: T, y: T, width: T, height: T) -> Self {
         Rect { x, y, width, height }
     }
 }
@@ -998,7 +1008,9 @@ impl<'a> RenderApi<'a> {
             })
             .collect::<Vec<_>>();
 
-        self.render_cells(cells.iter(), glyph_cache);
+        for cell in cells {
+            self.render_cell(cell, glyph_cache);
+        }
     }
 
     #[inline]
@@ -1016,74 +1028,52 @@ impl<'a> RenderApi<'a> {
         }
     }
 
-    pub fn render_cells<'b, I>(
-        &mut self,
-        cells: I,
-        glyph_cache: &mut GlyphCache
-    )
-        where I: Iterator<Item=&'b RenderableCell>
-    {
-        for cell in cells {
-            // Get font key for cell
-            // FIXME this is super inefficient.
-            let font_key = if cell.flags.contains(cell::Flags::BOLD) {
-                glyph_cache.bold_key
-            } else if cell.flags.contains(cell::Flags::ITALIC) {
-                glyph_cache.italic_key
-            } else {
-                glyph_cache.font_key
-            };
-
-            // Don't render text of HIDDEN cells
-            let mut chars = if cell.flags.contains(cell::Flags::HIDDEN) {
-                [' '; cell::MAX_ZEROWIDTH_CHARS + 1]
-            } else {
-                cell.chars
-            };
+    pub fn render_cell(&mut self, cell: RenderableCell, glyph_cache: &mut GlyphCache) {
+        // Get font key for cell
+        // FIXME this is super inefficient.
+        let font_key = if cell.flags.contains(cell::Flags::BOLD) {
+            glyph_cache.bold_key
+        } else if cell.flags.contains(cell::Flags::ITALIC) {
+            glyph_cache.italic_key
+        } else {
+            glyph_cache.font_key
+        };
 
-            // Render tabs as spaces in case the font doesn't support it
-            if chars[0] == '\t' {
-                chars[0] = ' ';
-            }
+        // Don't render text of HIDDEN cells
+        let mut chars = if cell.flags.contains(cell::Flags::HIDDEN) {
+            [' '; cell::MAX_ZEROWIDTH_CHARS + 1]
+        } else {
+            cell.chars
+        };
 
-            let mut glyph_key = GlyphKey {
-                font_key,
-                size: glyph_cache.font_size,
-                c: chars[0],
-            };
+        // Render tabs as spaces in case the font doesn't support it
+        if chars[0] == '\t' {
+            chars[0] = ' ';
+        }
 
-            // Add cell to batch
-            let glyph = glyph_cache.get(glyph_key, self);
-            self.add_render_item(&cell, glyph);
+        let mut glyph_key = GlyphKey {
+            font_key,
+            size: glyph_cache.font_size,
+            c: chars[0],
+        };
 
-            // Render zero-width characters
-            for c in (&chars[1..]).iter().filter(|c| **c != ' ') {
-                glyph_key.c = *c;
-                let mut glyph = *glyph_cache.get(glyph_key, self);
+        // Add cell to batch
+        let glyph = glyph_cache.get(glyph_key, self);
+        self.add_render_item(&cell, glyph);
 
-                // The metrics of zero-width characters are based on rendering
-                // the character after the current cell, with the anchor at the
-                // right side of the preceding character. Since we render the
-                // zero-width characters inside the preceding character, the
-                // anchor has been moved to the right by one cell.
-                glyph.left += glyph_cache.metrics.average_advance as f32;
+        // Render zero-width characters
+        for c in (&chars[1..]).iter().filter(|c| **c != ' ') {
+            glyph_key.c = *c;
+            let mut glyph = *glyph_cache.get(glyph_key, self);
 
-                self.add_render_item(&cell, &glyph);
-            }
+            // The metrics of zero-width characters are based on rendering
+            // the character after the current cell, with the anchor at the
+            // right side of the preceding character. Since we render the
+            // zero-width characters inside the preceding character, the
+            // anchor has been moved to the right by one cell.
+            glyph.left += glyph_cache.metrics.average_advance as f32;
 
-            // FIXME This is a super hacky way to do underlined text. During
-            //       a time crunch to release 0.1, this seemed like a really
-            //       easy, clean hack.
-            if cell.flags.contains(cell::Flags::UNDERLINE) {
-                let glyph_key = GlyphKey {
-                    font_key,
-                    size: glyph_cache.font_size,
-                    c: '_',
-                };
-
-                let underscore = glyph_cache.get(glyph_key, self);
-                self.add_render_item(&cell, underscore);
-            }
+            self.add_render_item(&cell, &glyph);
         }
     }
 }