1 files changed, 24 insertions, 6 deletions

diff --git a/src/gui/font.c b/src/gui/font.c
index 5989dd4e..5ea595f9 100644
--- a/src/gui/font.c
+++ b/src/gui/font.c
@@ -3,6 +3,7 @@
 // fallback, and the light target for shape-preserving grayscale text.
 #include "font.h"
 #include <freetype-zig.h>
+#include <freetype/ftbitmap.h>
 
 #include <stdlib.h>
 #include <string.h>
@@ -126,7 +127,7 @@ void ui_font_cell_metrics(UIFont *f, float px, int32_t *cell_w, int32_t *cell_h,
   *ascent = asc > 0 ? asc : 1;
 }
 
-static int raster(UIFont *f, float px, int32_t cp, uint8_t *out,
+static int raster(UIFont *f, float px, int32_t cp, int bold, uint8_t *out,
                   int32_t stride, int32_t cell_w, int32_t cell_h,
                   int32_t ascent, int centered) {
   if (!f || !out || stride < cell_w || cell_w <= 0 || cell_h <= 0)
@@ -140,6 +141,22 @@ static int raster(UIFont *f, float px, int32_t cp, uint8_t *out,
       FT_Get_Char_Index(f->face, (FT_ULong)(uint32_t)cp);
   if (FT_Load_Glyph(f->face, glyph_index, load_flags()) != 0)
     return 0;
+  if (bold) {
+    // Synthetic bold thickens the hinted outline before it is rendered, so
+    // the wider stems are rasterized as one shape and keep hinted edges; the
+    // advance is untouched, as the cell grid requires. Strength is Ghostty's
+    // heuristic: 1/32 of the line height in 26.6, rounded up (one pixel at a
+    // 32 px line). A bitmap strike has no outline: widen it by one whole pixel,
+    // the classic overstrike, which keeps its pixels sharp.
+    FT_GlyphSlot slot = f->face->glyph;
+    if (slot->format == FT_GLYPH_FORMAT_OUTLINE) {
+      const FT_Pos height = f->face->size->metrics.height;
+      FT_Outline_Embolden(&slot->outline, (height + 31) / 32);
+    } else if (slot->format == FT_GLYPH_FORMAT_BITMAP &&
+               FT_GlyphSlot_Own_Bitmap(slot) == 0) {
+      FT_Bitmap_Embolden(f->library, &slot->bitmap, 64, 0);
+    }
+  }
   if (FT_Render_Glyph(f->face->glyph, FT_RENDER_MODE_NORMAL) != 0)
     return 0;
 
@@ -187,13 +204,14 @@ static int raster(UIFont *f, float px, int32_t cp, uint8_t *out,
   return 1;
 }
 
-int ui_font_raster(UIFont *f, float px, int32_t cp, uint8_t *out,
+int ui_font_raster(UIFont *f, float px, int32_t cp, int bold, uint8_t *out,
                    int32_t stride, int32_t cell_w, int32_t cell_h,
                    int32_t ascent) {
-  return raster(f, px, cp, out, stride, cell_w, cell_h, ascent, 0);
+  return raster(f, px, cp, bold, out, stride, cell_w, cell_h, ascent, 0);
 }
 
-int ui_font_raster_centered(UIFont *f, float px, int32_t cp, uint8_t *out,
-                            int32_t stride, int32_t width, int32_t height) {
-  return raster(f, px, cp, out, stride, width, height, 0, 1);
+int ui_font_raster_centered(UIFont *f, float px, int32_t cp, int bold,
+                            uint8_t *out, int32_t stride, int32_t width,
+                            int32_t height) {
+  return raster(f, px, cp, bold, out, stride, width, height, 0, 1);
 }