Account for font.offset and glyph.offset in built-in font

This commit takes into account `font.offset` and `font.glyph_offset`
when generating built-in font.

3 files changed, 42 insertions, 11 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 74887563..5f48967f 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -16,6 +16,8 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 - OSC 4 not handling `?`
 - `?` in OSC strings reporting default colors instead of modified ones
 - OSC 104 not clearing colors when second parameter is empty
+- Builtin font lines not contiguous when `font.offset` is used
+- `font.glyph_offset` is no longer applied on builtin font
 
 ## 0.10.0
 
diff --git a/alacritty/src/renderer/builtin_font.rs b/alacritty/src/renderer/builtin_font.rs
index 17e85799..e905a1ef 100644
--- a/alacritty/src/renderer/builtin_font.rs
+++ b/alacritty/src/renderer/builtin_font.rs
@@ -5,6 +5,8 @@ use std::{cmp, mem};
 
 use crossfont::{BitmapBuffer, Metrics, RasterizedGlyph};
 
+use crate::config::ui_config::Delta;
+
 // Colors which are used for filling shade variants.
 const COLOR_FILL_ALPHA_STEP_1: Pixel = Pixel { _r: 192, _g: 192, _b: 192 };
 const COLOR_FILL_ALPHA_STEP_2: Pixel = Pixel { _r: 128, _g: 128, _b: 128 };
@@ -14,17 +16,29 @@ const COLOR_FILL_ALPHA_STEP_3: Pixel = Pixel { _r: 64, _g: 64, _b: 64 };
 const COLOR_FILL: Pixel = Pixel { _r: 255, _g: 255, _b: 255 };
 
 /// Returns the rasterized glyph if the character is part of the built-in font.
-pub fn builtin_glyph(character: char, metrics: &Metrics) -> Option<RasterizedGlyph> {
-    match character {
+pub fn builtin_glyph(
+    character: char,
+    metrics: &Metrics,
+    offset: &Delta<i8>,
+    glyph_offset: &Delta<i8>,
+) -> Option<RasterizedGlyph> {
+    let mut glyph = match character {
         // Box drawing characters and block elements.
-        '\u{2500}'..='\u{259f}' => Some(box_drawing(character, metrics)),
-        _ => None,
-    }
+        '\u{2500}'..='\u{259f}' => box_drawing(character, metrics, offset),
+        _ => return None,
+    };
+
+    // Since we want to ignore `glyph_offset` for the built-in font, subtract it to compensate its
+    // addition when loading glyphs in the renderer.
+    glyph.left -= glyph_offset.x as i32;
+    glyph.top -= glyph_offset.y as i32;
+
+    Some(glyph)
 }
 
-fn box_drawing(character: char, metrics: &Metrics) -> RasterizedGlyph {
-    let height = metrics.line_height as usize;
-    let width = metrics.average_advance as usize;
+fn box_drawing(character: char, metrics: &Metrics, offset: &Delta<i8>) -> RasterizedGlyph {
+    let height = (metrics.line_height as i32 + offset.y as i32) as usize;
+    let width = (metrics.average_advance as i32 + offset.x as i32) as usize;
     let stroke_size = cmp::max(metrics.underline_thickness as usize, 1);
     let heavy_stroke_size = stroke_size * 3;
     // Certain symbols require larger canvas than the cell itself, since for proper contiguous
@@ -741,13 +755,16 @@ mod test {
             strikeout_thickness: 2.,
         };
 
+        let offset = Default::default();
+        let glyph_offset = Default::default();
+
         // Test coverage of box drawing characters.
         for character in '\u{2500}'..='\u{259f}' {
-            assert!(builtin_glyph(character, &metrics).is_some());
+            assert!(builtin_glyph(character, &metrics, &offset, &glyph_offset).is_some());
         }
 
         for character in ('\u{2450}'..'\u{2500}').chain('\u{25a0}'..'\u{2600}') {
-            assert!(builtin_glyph(character, &metrics).is_none());
+            assert!(builtin_glyph(character, &metrics, &offset, &glyph_offset).is_none());
         }
     }
 }
diff --git a/alacritty/src/renderer/mod.rs b/alacritty/src/renderer/mod.rs
index 50a0e7d7..715d33b5 100644
--- a/alacritty/src/renderer/mod.rs
+++ b/alacritty/src/renderer/mod.rs
@@ -132,6 +132,9 @@ pub struct GlyphCache {
     /// Font size.
     font_size: crossfont::Size,
 
+    /// Font offset.
+    font_offset: Delta<i8>,
+
     /// Glyph offset.
     glyph_offset: Delta<i8>,
 
@@ -168,6 +171,7 @@ impl GlyphCache {
             bold_key: bold,
             italic_key: italic,
             bold_italic_key: bold_italic,
+            font_offset: font.offset,
             glyph_offset: font.glyph_offset,
             metrics,
             builtin_box_drawing: font.builtin_box_drawing,
@@ -274,7 +278,14 @@ impl GlyphCache {
         // for everything else.
         let rasterized = self
             .builtin_box_drawing
-            .then(|| builtin_font::builtin_glyph(glyph_key.character, &self.metrics))
+            .then(|| {
+                builtin_font::builtin_glyph(
+                    glyph_key.character,
+                    &self.metrics,
+                    &self.font_offset,
+                    &self.glyph_offset,
+                )
+            })
             .flatten()
             .map_or_else(|| self.rasterizer.get_glyph(glyph_key), Ok);
 
@@ -342,6 +353,7 @@ impl GlyphCache {
     ) -> Result<(), crossfont::Error> {
         // Update dpi scaling.
         self.rasterizer.update_dpr(dpr as f32);
+        self.font_offset = font.offset;
 
         // Recompute font keys.
         let (regular, bold, italic, bold_italic) =