Fix wide characters being cut off

Fixes #791.

9 files changed, 112 insertions, 57 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 77c7dcbb..526f611b 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,10 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 
 ## 0.7.0-dev
 
+### Fixed
+
+- Wide characters sometimes being cut off
+
 ## 0.6.0
 
 ### Packaging
diff --git a/Cargo.lock b/Cargo.lock
index 74820442..1eddd108 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -26,6 +26,7 @@ name = "alacritty"
 version = "0.7.0-dev"
 dependencies = [
  "alacritty_terminal",
+ "bitflags",
  "clap",
  "copypasta",
  "crossfont",
diff --git a/alacritty/Cargo.toml b/alacritty/Cargo.toml
index f8049fed..081ea4dc 100644
--- a/alacritty/Cargo.toml
+++ b/alacritty/Cargo.toml
@@ -29,6 +29,7 @@ urlocator = "0.1.3"
 copypasta = { version = "0.7.0", default-features = false }
 libc = "0.2"
 unicode-width = "0.1"
+bitflags = "1"
 
 [build-dependencies]
 gl_generator = "0.14.0"
diff --git a/alacritty/res/text.f.glsl b/alacritty/res/text.f.glsl
index c0c1bd1b..d5e26881 100644
--- a/alacritty/res/text.f.glsl
+++ b/alacritty/res/text.f.glsl
@@ -9,31 +9,31 @@ layout(location = 0, index = 1) out vec4 alphaMask;
 
 uniform sampler2D mask;
 
-void main()
-{
+#define COLORED 2
+
+void main() {
     if (backgroundPass != 0) {
-        if (bg.a == 0.0)
+        if (bg.a == 0.0) {
             discard;
+        }
 
         alphaMask = vec4(1.0);
         color = vec4(bg.rgb, 1.0);
-    } else {
-        if (fg.a != 0.0) {
-            // Color glyphs, like emojis.
-            vec4 glyphColor = texture(mask, TexCoords);
-            alphaMask = vec4(glyphColor.a);
+    } else if ((int(fg.a) & COLORED) != 0) {
+        // Color glyphs, like emojis.
+        vec4 glyphColor = texture(mask, TexCoords);
+        alphaMask = vec4(glyphColor.a);
 
-            // Revert alpha premultiplication.
-            if (glyphColor.a != 0) {
-                glyphColor.rgb = vec3(glyphColor.rgb / glyphColor.a);
-            }
-
-            color = vec4(glyphColor.rgb, 1.0);
-        } else {
-            // Regular text glyphs.
-            vec3 textColor = texture(mask, TexCoords).rgb;
-            alphaMask = vec4(textColor, textColor.r);
-            color = vec4(fg.rgb, 1.0);
+        // Revert alpha premultiplication.
+        if (glyphColor.a != 0) {
+            glyphColor.rgb = vec3(glyphColor.rgb / glyphColor.a);
         }
+
+        color = vec4(glyphColor.rgb, 1.0);
+    } else {
+        // Regular text glyphs.
+        vec3 textColor = texture(mask, TexCoords).rgb;
+        alphaMask = vec4(textColor, textColor.r);
+        color = vec4(fg.rgb, 1.0);
     }
 }
diff --git a/alacritty/res/text.v.glsl b/alacritty/res/text.v.glsl
index 0f5fd3f9..31e6f934 100644
--- a/alacritty/res/text.v.glsl
+++ b/alacritty/res/text.v.glsl
@@ -1,18 +1,20 @@
 #version 330 core
 // Cell properties.
-layout (location = 0) in vec2 gridCoords;
+layout(location = 0) in vec2 gridCoords;
 
 // Glyph properties.
-layout (location = 1) in vec4 glyph;
+layout(location = 1) in vec4 glyph;
 
 // uv mapping.
-layout (location = 2) in vec4 uv;
+layout(location = 2) in vec4 uv;
 
-// Text foreground rgb packed together with multicolor flag.
-layout (location = 3) in vec4 textColor;
+// Text foreground rgb packed together with cell flags. textColor.a
+// are the bitflags; consult RenderingGlyphFlags in renderer/mod.rs
+// for the possible values.
+layout(location = 3) in vec4 textColor;
 
 // Background color.
-layout (location = 4) in vec4 backgroundColor;
+layout(location = 4) in vec4 backgroundColor;
 
 out vec2 TexCoords;
 flat out vec4 fg;
@@ -24,9 +26,9 @@ uniform vec4 projection;
 
 uniform int backgroundPass;
 
+#define WIDE_CHAR 1
 
-void main()
-{
+void main() {
     vec2 projectionOffset = projection.xy;
     vec2 projectionScale = projection.zw;
 
@@ -39,8 +41,14 @@ void main()
     vec2 cellPosition = cellDim * gridCoords;
 
     if (backgroundPass != 0) {
-        vec2 finalPosition = cellPosition + cellDim * position;
-        gl_Position = vec4(projectionOffset + projectionScale * finalPosition, 0.0, 1.0);
+        vec2 backgroundDim = cellDim;
+        if ((int(textColor.a) & WIDE_CHAR) != 0) {
+            // Update wide char x dimension so it'll cover the following spacer.
+            backgroundDim.x *= 2;
+        }
+        vec2 finalPosition = cellPosition + backgroundDim * position;
+        gl_Position =
+            vec4(projectionOffset + projectionScale * finalPosition, 0.0, 1.0);
 
         TexCoords = vec2(0, 0);
     } else {
@@ -49,7 +57,8 @@ void main()
         glyphOffset.y = cellDim.y - glyphOffset.y;
 
         vec2 finalPosition = cellPosition + glyphSize * position + glyphOffset;
-        gl_Position = vec4(projectionOffset + projectionScale * finalPosition, 0.0, 1.0);
+        gl_Position =
+            vec4(projectionOffset + projectionScale * finalPosition, 0.0, 1.0);
 
         vec2 uvOffset = uv.xy;
         vec2 uvSize = uv.zw;
diff --git a/alacritty/src/renderer/mod.rs b/alacritty/src/renderer/mod.rs
index b347556d..f63f92fd 100644
--- a/alacritty/src/renderer/mod.rs
+++ b/alacritty/src/renderer/mod.rs
@@ -9,6 +9,7 @@ use std::ptr;
 use std::sync::mpsc;
 use std::time::Duration;
 
+use bitflags::bitflags;
 use crossfont::{
     BitmapBuffer, FontDesc, FontKey, GlyphKey, Rasterize, RasterizedGlyph, Rasterizer, Size, Slant,
     Style, Weight,
@@ -123,7 +124,7 @@ pub struct RectShaderProgram {
 #[derive(Copy, Debug, Clone)]
 pub struct Glyph {
     tex_id: GLuint,
-    multicolor: u8,
+    multicolor: bool,
     top: i16,
     left: i16,
     width: i16,
@@ -359,30 +360,46 @@ impl GlyphCache {
     }
 }
 
+// NOTE: These flags must be in sync with their usage in the text.*.glsl shaders.
+bitflags! {
+    #[repr(C)]
+    struct RenderingGlyphFlags: u8 {
+        const WIDE_CHAR = 0b0000_0001;
+        const COLORED   = 0b0000_0010;
+    }
+}
+
 #[derive(Debug)]
 #[repr(C)]
 struct InstanceData {
     // Coords.
     col: u16,
     row: u16,
+
     // Glyph offset.
     left: i16,
     top: i16,
+
     // Glyph size.
     width: i16,
     height: i16,
+
     // UV offset.
     uv_left: f32,
     uv_bot: f32,
+
     // uv scale.
     uv_width: f32,
     uv_height: f32,
+
     // Color.
     r: u8,
     g: u8,
     b: u8,
-    // Flag indicating that a glyph uses multiple colors; like an Emoji.
-    multicolor: u8,
+
+    // Cell flags like multicolor or fullwidth character.
+    cell_flags: RenderingGlyphFlags,
+
     // Background color.
     bg_r: u8,
     bg_g: u8,
@@ -441,6 +458,10 @@ impl Batch {
             self.tex = glyph.tex_id;
         }
 
+        let mut cell_flags = RenderingGlyphFlags::empty();
+        cell_flags.set(RenderingGlyphFlags::COLORED, glyph.multicolor);
+        cell_flags.set(RenderingGlyphFlags::WIDE_CHAR, cell.flags.contains(Flags::WIDE_CHAR));
+
         self.instances.push(InstanceData {
             col: cell.column.0 as u16,
             row: cell.line.0 as u16,
@@ -458,12 +479,12 @@ impl Batch {
             r: cell.fg.r,
             g: cell.fg.g,
             b: cell.fg.b,
+            cell_flags,
 
             bg_r: cell.bg.r,
             bg_g: cell.bg.g,
             bg_b: cell.bg.b,
             bg_a: (cell.bg_alpha * 255.0) as u8,
-            multicolor: glyph.multicolor,
         });
     }
 
@@ -586,10 +607,10 @@ impl QuadRenderer {
             // UV offset.
             add_attr!(4, gl::FLOAT, f32);
 
-            // Color and multicolor flag.
+            // Color and cell flags.
             //
             // These are packed together because of an OpenGL driver issue on macOS, which caused a
-            // `vec3(u8)` text color and a `u8` multicolor flag to increase the rendering time by a
+            // `vec3(u8)` text color and a `u8` cell flags to increase the rendering time by a
             // huge margin.
             add_attr!(4, gl::UNSIGNED_BYTE, u8);
 
@@ -1067,7 +1088,7 @@ fn load_glyph(
         },
         Err(AtlasInsertError::GlyphTooLarge) => Glyph {
             tex_id: atlas[*current_atlas].id,
-            multicolor: 0,
+            multicolor: false,
             top: 0,
             left: 0,
             width: 0,
@@ -1581,7 +1602,7 @@ impl Atlas {
 
         Glyph {
             tex_id: self.id,
-            multicolor: multicolor as u8,
+            multicolor,
             top: glyph.top as i16,
             left: glyph.left as i16,
             width: width as i16,
diff --git a/alacritty/src/renderer/rects.rs b/alacritty/src/renderer/rects.rs
index fcd8c82e..2a727b4c 100644
--- a/alacritty/src/renderer/rects.rs
+++ b/alacritty/src/renderer/rects.rs
@@ -162,6 +162,12 @@ impl RenderLines {
             return;
         }
 
+        // Include wide char spacer if the current cell is a wide char.
+        let mut end: Point = cell.into();
+        if cell.flags.contains(Flags::WIDE_CHAR) {
+            end.col += 1;
+        }
+
         // Check if there's an active line.
         if let Some(line) = self.inner.get_mut(&flag).and_then(|lines| lines.last_mut()) {
             if cell.fg == line.color
@@ -169,13 +175,13 @@ impl RenderLines {
                 && cell.line == line.end.line
             {
                 // Update the length of the line.
-                line.end = cell.into();
+                line.end = end;
                 return;
             }
         }
 
         // Start new line if there currently is none.
-        let line = RenderLine { start: cell.into(), end: cell.into(), color: cell.fg };
+        let line = RenderLine { start: cell.into(), end, color: cell.fg };
         match self.inner.get_mut(&flag) {
             Some(lines) => lines.push(line),
             None => {
diff --git a/alacritty/src/url.rs b/alacritty/src/url.rs
index 5d35667d..b33b532e 100644
--- a/alacritty/src/url.rs
+++ b/alacritty/src/url.rs
@@ -79,7 +79,12 @@ impl Urls {
         };
 
         let point: Point = cell.into();
-        let end = point;
+        let mut end = point;
+
+        // Include the following wide char spacer.
+        if cell.flags.contains(Flags::WIDE_CHAR) {
+            end.col += 1;
+        }
 
         // Reset URL when empty cells have been skipped.
         if point != Point::default() && Some(point.sub(num_cols, 1)) != self.last_point {
@@ -88,8 +93,8 @@ impl Urls {
 
         self.last_point = Some(end);
 
-        // Extend current state if a wide char spacer is encountered.
-        if cell.flags.intersects(Flags::WIDE_CHAR_SPACER | Flags::LEADING_WIDE_CHAR_SPACER) {
+        // Extend current state if a leading wide char spacer is encountered.
+        if cell.flags.intersects(Flags::LEADING_WIDE_CHAR_SPACER) {
             if let UrlLocation::Url(_, mut end_offset) = self.state {
                 if end_offset != 0 {
                     end_offset += 1;
@@ -252,4 +257,24 @@ mod tests {
         assert_eq!(urls.urls[2].start().col, Column(17));
         assert_eq!(urls.urls[2].end().col, Column(21));
     }
+
+    #[test]
+    fn wide_urls() {
+        let input = text_to_cells("test https://こんにちは (http:여보세요) ing");
+        let num_cols = input.len() + 9;
+
+        let mut urls = Urls::new();
+
+        for cell in input {
+            urls.update(Column(num_cols), &cell);
+        }
+
+        assert_eq!(urls.urls.len(), 2);
+
+        assert_eq!(urls.urls[0].start().col, Column(5));
+        assert_eq!(urls.urls[0].end().col, Column(17));
+
+        assert_eq!(urls.urls[1].start().col, Column(20));
+        assert_eq!(urls.urls[1].end().col, Column(28));
+    }
 }
diff --git a/alacritty_terminal/src/term/mod.rs b/alacritty_terminal/src/term/mod.rs
index cdcfad9d..fa2c5513 100644
--- a/alacritty_terminal/src/term/mod.rs
+++ b/alacritty_terminal/src/term/mod.rs
@@ -165,8 +165,8 @@ impl<'a, C> Iterator for RenderableCellsIter<'a, C> {
                 let cell = self.inner.next()?;
                 let cell = RenderableCell::new(self, cell);
 
-                // Skip empty cells.
-                if !cell.is_empty() {
+                // Skip empty cells and wide char spacers.
+                if !cell.is_empty() && !cell.flags.contains(Flags::WIDE_CHAR_SPACER) {
                     return Some(cell);
                 }
             }
@@ -282,18 +282,6 @@ impl<'a, C> RenderableCellsIter<'a, C> {
                 // Check line-wrapping, leading spacer.
                 || (self.grid[buffer_prev].flags.contains(Flags::LEADING_WIDE_CHAR_SPACER)
                     && selection.contains(prev.col, prev.line))
-        } else if cell.flags.contains(Flags::WIDE_CHAR_SPACER) {
-            // Check if spacer's wide char is selected.
-            let prev = point.sub(num_cols, 1);
-            let buffer_prev = self.grid.visible_to_buffer(prev);
-
-            if self.grid[buffer_prev].flags.contains(Flags::WIDE_CHAR) {
-                // Check previous cell for trailing spacer.
-                self.is_selected(prev)
-            } else {
-                // Check next cell for line-wrapping, leading spacer.
-                self.is_selected(point.add(num_cols, 1))
-            }
         } else {
             false
         }