refactor: Change firehose from a drifting overlay to a fixed bottom strip and message display from a top-pinned section to a centered overlay.

engine/scroll.py

@@ -1,5 +1,5 @@
 """
-Scroll engine — the main frame loop with headline rendering and message display.
+Render engine — ticker content, scroll motion, message panel, and firehose overlay.
 Depends on: config, terminal, render, effects, ntfy, mic.
 """
 
@@ -16,7 +16,7 @@ from engine.effects import noise, glitch_bar, fade_line, vis_trunc, next_headlin
 
 
 def stream(items, ntfy_poller, mic_monitor):
-    """Main rendering loop. Scrolls headlines, shows ntfy messages, applies effects."""
+    """Main render loop with four layers: message, ticker, scroll motion, firehose."""
     random.shuffle(items)
     pool = list(items)
     seen = set()
@@ -28,16 +28,21 @@ def stream(items, ntfy_poller, mic_monitor):
 
     w, h = tw(), th()
     fh = config.FIREHOSE_H if config.FIREHOSE else 0
-    sh = h - fh                    # scroll zone height
+    ticker_view_h = h - fh         # reserve fixed firehose strip at bottom
     GAP = 3            # blank rows between headlines
-    scroll_interval = config.SCROLL_DUR / (sh + 15) * 2
+    scroll_step_interval = config.SCROLL_DUR / (ticker_view_h + 15) * 2
 
-    # active blocks: (content_rows, color, canvas_y, meta_idx)
+    # Taxonomy:
+    # - message: centered ntfy overlay panel
+    # - ticker: large headline text content
+    # - scroll: upward camera motion applied to ticker content
+    # - firehose: fixed carriage-return style strip pinned at bottom
+    # Active ticker blocks: (content_rows, color, canvas_y, meta_idx)
     active = []
-    cam = 0            # viewport top in virtual canvas coords
-    next_y = sh        # canvas-y where next block starts (off-screen bottom)
+    scroll_cam = 0     # viewport top in virtual canvas coords
+    ticker_next_y = ticker_view_h  # canvas-y where next block starts (off-screen bottom)
     noise_cache = {}
-    scroll_accum = 0.0
+    scroll_motion_accum = 0.0
 
     def _noise_at(cy):
         if cy not in noise_cache:
@@ -53,16 +58,17 @@ def stream(items, ntfy_poller, mic_monitor):
         t0 = time.monotonic()
         w, h = tw(), th()
         fh = config.FIREHOSE_H if config.FIREHOSE else 0
-        sh = h - fh
+        ticker_view_h = h - fh
 
         # ── Check for ntfy message ────────────────────────
-        msg_h = 0  # rows consumed by message zone at top
+        msg_h = 0
+        msg_overlay = []
         msg = ntfy_poller.get_active_message()
 
         buf = []
         if msg is not None:
             m_title, m_body, m_ts = msg
-            # ── Message zone: pinned to top, scroll continues below ──
+            # ── Message overlay: centered in the viewport ──
             display_text = m_body or m_title or "(empty)"
             display_text = re.sub(r"\s+", " ", display_text.upper())
             cache_key = (display_text, w)
@@ -76,10 +82,12 @@ def stream(items, ntfy_poller, mic_monitor):
             elapsed_s = int(time.monotonic() - m_ts)
             remaining = max(0, config.MESSAGE_DISPLAY_SECS - elapsed_s)
             ts_str = datetime.now().strftime("%H:%M:%S")
+            panel_h = len(msg_rows) + 2  # meta + border
+            panel_top = max(0, (h - panel_h) // 2)
             row_idx = 0
             for mr in msg_rows:
                 ln = vis_trunc(mr, w)
-                buf.append(f"\033[{row_idx+1};1H  {ln}{RST}\033[K")
+                msg_overlay.append(f"\033[{panel_top + row_idx + 1};1H  {ln}{RST}\033[K")
                 row_idx += 1
             # Meta line: title (if distinct) + source + countdown
             meta_parts = []
@@ -87,49 +95,46 @@ def stream(items, ntfy_poller, mic_monitor):
                 meta_parts.append(m_title)
             meta_parts.append(f"ntfy \u00b7 {ts_str} \u00b7 {remaining}s")
             meta = "  " + " \u00b7 ".join(meta_parts) if len(meta_parts) > 1 else "  " + meta_parts[0]
-            buf.append(f"\033[{row_idx+1};1H{MSG_META}{meta}{RST}\033[K")
+            msg_overlay.append(f"\033[{panel_top + row_idx + 1};1H{MSG_META}{meta}{RST}\033[K")
             row_idx += 1
-            # Border — constant boundary between message and scroll
+            # Border — constant boundary under message panel
             bar = "\u2500" * (w - 4)
-            buf.append(f"\033[{row_idx+1};1H  {MSG_BORDER}{bar}{RST}\033[K")
-            row_idx += 1
-            msg_h = row_idx
+            msg_overlay.append(f"\033[{panel_top + row_idx + 1};1H  {MSG_BORDER}{bar}{RST}\033[K")
 
-        # Effective scroll zone: below message, above firehose
-        scroll_h = sh - msg_h
+        # Ticker draws above the fixed firehose strip; message is a centered overlay.
+        ticker_h = ticker_view_h - msg_h
 
-        # ── Scroll: headline rendering (always runs) ──────
-        # Advance scroll on schedule
-        scroll_accum += config.FRAME_DT
-        while scroll_accum >= scroll_interval:
-            scroll_accum -= scroll_interval
-            cam += 1
+        # ── Ticker content + scroll motion (always runs) ──
+        scroll_motion_accum += config.FRAME_DT
+        while scroll_motion_accum >= scroll_step_interval:
+            scroll_motion_accum -= scroll_step_interval
+            scroll_cam += 1
 
             # Enqueue new headlines when room at the bottom
-            while next_y < cam + sh + 10 and queued < config.HEADLINE_LIMIT:
+            while ticker_next_y < scroll_cam + ticker_view_h + 10 and queued < config.HEADLINE_LIMIT:
                 t, src, ts = next_headline(pool, items, seen)
-                content, hc, midx = make_block(t, src, ts, w)
-                active.append((content, hc, next_y, midx))
-                next_y += len(content) + GAP
+                ticker_content, hc, midx = make_block(t, src, ts, w)
+                active.append((ticker_content, hc, ticker_next_y, midx))
+                ticker_next_y += len(ticker_content) + GAP
                 queued += 1
 
             # Prune off-screen blocks and stale noise
             active = [(c, hc, by, mi) for c, hc, by, mi in active
-                      if by + len(c) > cam]
+                      if by + len(c) > scroll_cam]
             for k in list(noise_cache):
-                if k < cam:
+                if k < scroll_cam:
                     del noise_cache[k]
 
-        # Draw scroll zone (below message zone, above firehose)
-        top_zone = max(1, int(scroll_h * 0.25))
-        bot_zone = max(1, int(scroll_h * 0.10))
+        # Draw ticker zone (above fixed firehose strip)
+        top_zone = max(1, int(ticker_h * 0.25))
+        bot_zone = max(1, int(ticker_h * 0.10))
         grad_offset = (time.monotonic() * config.GRAD_SPEED) % 1.0
-        scroll_buf_start = len(buf)  # track where scroll rows start in buf
-        for r in range(scroll_h):
-            scr_row = msg_h + r + 1  # 1-indexed ANSI screen row
-            cy = cam + r
+        ticker_buf_start = len(buf)  # track where ticker rows start in buf
+        for r in range(ticker_h):
+            scr_row = r + 1  # 1-indexed ANSI screen row
+            cy = scroll_cam + r
             top_f = min(1.0, r / top_zone) if top_zone > 0 else 1.0
-            bot_f = min(1.0, (scroll_h - 1 - r) / bot_zone) if bot_zone > 0 else 1.0
+            bot_f = min(1.0, (ticker_h - 1 - r) / bot_zone) if bot_zone > 0 else 1.0
             row_fade = min(top_f, bot_f)
             drawn = False
             for content, hc, by, midx in active:
@@ -160,22 +165,24 @@ def stream(items, ntfy_poller, mic_monitor):
                 else:
                     buf.append(f"\033[{scr_row};1H\033[K")
 
-        # Draw firehose zone
-        if config.FIREHOSE and fh > 0:
-            for fr in range(fh):
-                fline = firehose_line(items, w)
-                buf.append(f"\033[{sh + fr + 1};1H{fline}\033[K")
-
-        # Glitch — base rate + mic-reactive spikes (scroll zone only)
+        # Glitch — base rate + mic-reactive spikes (ticker zone only)
         mic_excess = mic_monitor.excess
         glitch_prob = 0.32 + min(0.9, mic_excess * 0.16)
         n_hits = 4 + int(mic_excess / 2)
-        scroll_buf_len = len(buf) - scroll_buf_start
-        if random.random() < glitch_prob and scroll_buf_len > 0:
-            for _ in range(min(n_hits, scroll_buf_len)):
-                gi = random.randint(0, scroll_buf_len - 1)
-                scr_row = msg_h + gi + 1
-                buf[scroll_buf_start + gi] = f"\033[{scr_row};1H{glitch_bar(w)}"
+        ticker_buf_len = len(buf) - ticker_buf_start
+        if random.random() < glitch_prob and ticker_buf_len > 0:
+            for _ in range(min(n_hits, ticker_buf_len)):
+                gi = random.randint(0, ticker_buf_len - 1)
+                scr_row = gi + 1
+                buf[ticker_buf_start + gi] = f"\033[{scr_row};1H{glitch_bar(w)}"
+
+        if config.FIREHOSE and fh > 0:
+            for fr in range(fh):
+                scr_row = h - fh + fr + 1
+                fline = firehose_line(items, w)
+                buf.append(f"\033[{scr_row};1H{fline}\033[K")
+        if msg_overlay:
+            buf.extend(msg_overlay)
 
         sys.stdout.buffer.write("".join(buf).encode())
         sys.stdout.flush()