use freetype for font display

README.md

@@ -191,9 +191,13 @@ onto a tag nobody is viewing leaves both the order and focus alone.
 **tabbed** — same geometry as monocle, minus a strip at the top where att_wm
 draws one tab per window, the focused one highlighted. Each tab is clickable and
 carries the window's title, elided with an ellipsis when the tab is too narrow.
-Titles are drawn in a 5x8 bitmap font built into the binary (`src/font.zig`) —
-a font stack for one strip of pixels would be a poor trade — scaled by whole
-pixels to suit `tabbar_height`, or by `tab_font_scale` if you would rather say.
+Titles are drawn with FreeType in whatever font the fontconfig pattern
+`tab_font` matches (`"sans:size=11"` by default, so `fc-match 'sans:size=11'`
+shows what you will get), antialiased and subpixel positioned, shrunk to fit
+when `tabbar_height` leaves no room for the size asked for. Codepoints the
+matched font has no glyph for send att_wm back to fontconfig for one that does,
+so a CJK or emoji title is not a row of boxes; there is no shaping, so scripts
+that need it come out as unjoined letters.
 The same window list is published over IPC, so a bar can draw its own tab strip
 alongside (the bundled quickshell config does). Set `tabbar_height = 0` to drop
 the built-in strip entirely and let the bar own it.
@@ -492,7 +496,8 @@ river's identifier is shared between them.
 | `src/config.zig` | Compile-time configuration |
 | `src/ipc.zig` | Socket server and JSON encoding |
 | `src/shm.zig` | memfd buffers for the tab bar, and drawing into them |
-| `src/font.zig` | The built-in 5x8 bitmap font — no Wayland, unit tested |
+| `src/Face.zig` | The tab bar's font: fontconfig matching, FreeType rasterising |
+| `src/font.zig` | Measuring and eliding titles — no font needed, unit tested |
 | `src/sys.zig` | Thin Linux syscall wrappers |
 
 The single most important invariant: **river only permits window management