feat: Implement an interactive font face picker at startup, allowing selection of specific font faces from a font file.

engine/app.py

@@ -3,11 +3,14 @@ Application orchestrator — boot sequence, signal handling, main loop wiring.
 """
 
 import sys
+import os
 import time
 import signal
 import atexit
+import termios
+import tty
 
-from engine import config
+from engine import config, render
 from engine.terminal import (
     RST, G_HI, G_MID, G_DIM, W_DIM, W_GHOST, CLR, CURSOR_OFF, CURSOR_ON, tw,
     slow_print, boot_ln,
@@ -26,6 +29,166 @@ TITLE = [
     "  ╚═╝     ╚═╝╚═╝  ╚═╝╚═╝╚═╝  ╚═══╝╚══════╝╚═╝╚═╝  ╚═══╝╚══════╝",
 ]
 
+def _read_picker_key():
+    ch = sys.stdin.read(1)
+    if ch == "\x03":
+        return "interrupt"
+    if ch in ("\r", "\n"):
+        return "enter"
+    if ch == "\x1b":
+        c1 = sys.stdin.read(1)
+        if c1 != "[":
+            return None
+        c2 = sys.stdin.read(1)
+        if c2 == "A":
+            return "up"
+        if c2 == "B":
+            return "down"
+        return None
+    if ch in ("k", "K"):
+        return "up"
+    if ch in ("j", "J"):
+        return "down"
+    if ch in ("q", "Q"):
+        return "enter"
+    return None
+
+def _normalize_preview_rows(rows):
+    """Trim shared left padding and trailing spaces for stable on-screen previews."""
+    non_empty = [r for r in rows if r.strip()]
+    if not non_empty:
+        return [""]
+    left_pad = min(len(r) - len(r.lstrip(" ")) for r in non_empty)
+    out = []
+    for row in rows:
+        if left_pad < len(row):
+            out.append(row[left_pad:].rstrip())
+        else:
+            out.append(row.rstrip())
+    return out
+
+
+def _draw_font_picker(faces, selected):
+    w = tw()
+    h = 24
+    try:
+        h = os.get_terminal_size().lines
+    except Exception:
+        pass
+
+    max_preview_w = max(24, w - 8)
+    header_h = 6
+    footer_h = 3
+    preview_h = max(4, min(config.RENDER_H + 2, max(4, h // 2)))
+    visible = max(1, h - header_h - preview_h - footer_h)
+    top = max(0, selected - (visible // 2))
+    bottom = min(len(faces), top + visible)
+    top = max(0, bottom - visible)
+
+    print(CLR, end="")
+    print(CURSOR_OFF, end="")
+    print()
+    print(f"  {G_HI}FONT PICKER{RST}")
+    print(f"  {W_GHOST}{'─' * (w - 4)}{RST}")
+    print(f"  {W_DIM}{config.FONT_PATH[:max_preview_w]}{RST}")
+    print(f"  {W_GHOST}↑/↓ move · Enter select · q accept current{RST}")
+    print()
+
+    for pos in range(top, bottom):
+        face = faces[pos]
+        active = pos == selected
+        pointer = "▶" if active else " "
+        color = G_HI if active else W_DIM
+        print(f"  {color}{pointer} [{face['index']}] {face['name']}{RST}")
+
+    if top > 0:
+        print(f"  {W_GHOST}… {top} above{RST}")
+    if bottom < len(faces):
+        print(f"  {W_GHOST}… {len(faces) - bottom} below{RST}")
+
+    print()
+    print(f"  {W_GHOST}{'─' * (w - 4)}{RST}")
+    print(f"  {W_DIM}Preview: {faces[selected]['name']}{RST}")
+    preview_rows = faces[selected]["preview_rows"][:preview_h]
+    for row in preview_rows:
+        shown = row[:max_preview_w]
+        print(f"    {shown}")
+
+def pick_font_face():
+    """Interactive startup picker for selecting a face from a font file."""
+    if not config.FONT_PICKER:
+        return
+
+    print(CLR, end="")
+    print(CURSOR_OFF, end="")
+    print()
+    print(f"  {G_HI}FONT PICKER{RST}")
+    print(f"  {W_GHOST}{'─' * (tw() - 4)}{RST}")
+    print(f"  {W_DIM}{config.FONT_PATH}{RST}")
+    print()
+
+    try:
+        faces = render.list_font_faces(config.FONT_PATH, max_faces=64)
+    except Exception as exc:
+        print(f"  {G_DIM}> unable to load font file: {exc}{RST}")
+        print(f"  {W_GHOST}> startup aborted (font selection is required){RST}")
+        time.sleep(1.4)
+        sys.exit(1)
+
+    face_ids = [face["index"] for face in faces]
+    default = config.FONT_INDEX if config.FONT_INDEX in face_ids else faces[0]["index"]
+
+    prepared = []
+    for face in faces:
+        idx = face["index"]
+        name = face["name"]
+        try:
+            fnt = render.load_font_face(config.FONT_PATH, idx)
+            rows = _normalize_preview_rows(render.render_line(name, fnt))
+        except Exception:
+            rows = ["(preview unavailable)"]
+        prepared.append({"index": idx, "name": name, "preview_rows": rows})
+
+    selected = next((i for i, f in enumerate(prepared) if f["index"] == default), 0)
+    if not sys.stdin.isatty():
+        selected_index = prepared[selected]["index"]
+        config.set_font_selection(font_index=selected_index)
+        render.clear_font_cache()
+        print(f"  {G_DIM}> using face {selected_index}{RST}")
+        time.sleep(0.8)
+        print(CLR, end="")
+        print(CURSOR_OFF, end="")
+        print()
+        return
+
+    fd = sys.stdin.fileno()
+    old_settings = termios.tcgetattr(fd)
+    try:
+        tty.setcbreak(fd)
+        while True:
+            _draw_font_picker(prepared, selected)
+            key = _read_picker_key()
+            if key == "up":
+                selected = max(0, selected - 1)
+            elif key == "down":
+                selected = min(len(prepared) - 1, selected + 1)
+            elif key == "enter":
+                break
+            elif key == "interrupt":
+                raise KeyboardInterrupt
+    finally:
+        termios.tcsetattr(fd, termios.TCSADRAIN, old_settings)
+
+    selected = prepared[selected]["index"]
+
+    config.set_font_selection(font_index=selected)
+    render.clear_font_cache()
+    print(f"  {G_DIM}> using face {selected}{RST}")
+    time.sleep(0.8)
+    print(CLR, end="")
+    print(CURSOR_OFF, end="")
+    print()
+
 
 def main():
     atexit.register(lambda: print(CURSOR_ON, end="", flush=True))
@@ -40,6 +203,8 @@ def main():
     w = tw()
     print(CLR, end="")
     print(CURSOR_OFF, end="")
+    pick_font_face()
+    w = tw()
     print()
     time.sleep(0.4)