Function tick

src/components/ScrollKeybindingHandler.tsx:657–714

()

      }
    }
    function tick(): void {
      const sel = selection.getState();
      const s = scrollRef.current;
      const dir = dirRef.current;
      // dir === 0 defends against a stale interval (start() may have set one
      // after the immediate tick already called stop() at a scroll boundary).
      // ticks cap defends against a lost release event (mouse released
      // outside terminal window) leaving isDragging stuck true.
      if (!sel?.isDragging || !sel.focus || !s || dir === 0 || ++ticksRef.current > AUTOSCROLL_MAX_TICKS) {
        stop();
        return;
      }
      // scrollBy accumulates into pendingScrollDelta; the screen buffer
      // doesn't update until the next render drains it. If a previous
      // tick's scroll hasn't drained yet, captureScrolledRows would read
      // stale content (same rows as last tick → duplicated in the
      // accumulator AND missing the rows that actually scrolled out).
      // Skip this tick; the 50ms interval will retry after Ink's 16ms
      // render catches up. Also prevents shiftAnchor from desyncing.
      if (s.getPendingDelta() !== 0) return;
      const top = s.getViewportTop();
      const bottom = top + s.getViewportHeight() - 1;
      // Clamp anchor within [top, bottom]. Not [0, bottom]: the ScrollBox
      // padding row at 0 would produce a blank line between scrolledOffAbove
      // and the on-screen content in getSelectedText. The padding-row
      // highlight was a minor visual nicety; text correctness wins.
      if (dir < 0) {
        if (s.getScrollTop() <= 0) {
          stop();
          return;
        }
        // Scrolling up: content moves down in viewport, so anchor row +N.
        // Clamp to actual scroll distance so anchor stays in sync when near
        // the top boundary (renderer clamps scrollTop to 0 on drain).
        const actual = Math.min(AUTOSCROLL_LINES, s.getScrollTop());
        // Capture rows about to scroll out the BOTTOM before scrollBy
        // overwrites them. Only rows inside the selection are captured
        // (captureScrolledRows intersects with selection bounds).
        selection.captureScrolledRows(bottom - actual + 1, bottom, 'below');
        selection.shiftAnchor(actual, 0, bottom);
        s.scrollBy(-AUTOSCROLL_LINES);
      } else {
        const max = Math.max(0, s.getScrollHeight() - s.getViewportHeight());
        if (s.getScrollTop() >= max) {
          stop();
          return;
        }
        // Scrolling down: content moves up in viewport, so anchor row -N.
        // Clamp to actual scroll distance so anchor stays in sync when near
        // the bottom boundary (renderer clamps scrollTop to max on drain).
        const actual_0 = Math.min(AUTOSCROLL_LINES, max - s.getScrollTop());
        // Capture rows about to scroll out the TOP.
        selection.captureScrolledRows(top, top + actual_0 - 1, 'above');
        selection.shiftAnchor(-actual_0, top, bottom);
        s.scrollBy(AUTOSCROLL_LINES);
      }
      onScrollRef.current?.(false, s);
    }