renderer: use direct FreeType with explicit font files

README.md

@@ -99,12 +99,25 @@ tab-separated data consumable by the runtime dictionary reader.
 
 ## Run and install
 
-Start the daemon with the installed map and font directories:
+Install one or more scalable outline fonts, then pass their files in fallback
+order after the map directory.  The daemon accepts at most four font files and
+does not search the system font database.  For example, the Docker-tested Arch
+packages and paths are:
 
 ```sh
-./strans map font &
+doas pacman -S ttf-dejavu ttf-jigmo
+./strans map \
+    /usr/share/fonts/TTF/DejaVuSans.ttf \
+    /usr/share/fonts/TTF/Jigmo.ttf \
+    /usr/share/fonts/TTF/Jigmo2.ttf &
 ```
 
+These fonts are test fixtures, not runtime requirements.  Any suitable
+scalable outline files may be supplied; their argument order is the glyph
+fallback order.  A collection file uses its first face.  If any named file is
+absent or invalid, the popup disables itself cleanly while input processing
+continues.  `run.sh` and `bench.sh` accept the same font-file arguments.
+
 The IPC socket is placed at `$XDG_RUNTIME_DIR/strans.sock` when
 `XDG_RUNTIME_DIR` is an absolute path.  Otherwise strans uses the per-user
 fallback `/tmp/strans.<uid>`.  A second daemon will not replace a live
@@ -153,7 +166,7 @@ and disconnect affect the engine only when they come from its active owner;
 stale events cannot clear a newer owner's preedit.
 
 The popup is an optional X window, including when the active frontend is
-Wayland.  It uses deterministic font fallback and fixed-width rune cells;
+Wayland.  It uses the explicit font-file order and fixed-width rune cells;
 U+FE0E and U+FE0F variation selectors use zero cells.  It does not perform
 OpenType shaping, color-emoji rendering, or general grapheme clustering, and
 there is no native Wayland popup renderer.  Multi-rune emoji are committed