Add auto-fitting text zone option

[flocom]

Summary

Adds a per-screenshot Text zone to the Text tab: an optional rectangle that the headline + subheadline are confined to. When enabled, the font size is reduced automatically so the whole text fits inside the zone — entirely, centered, and without breaking any word across lines.

What's new

• UI (Text tab): a Text zone (auto-fit) toggle, X / Y / W / H sliders (% of canvas), and a draggable / resizable dashed overlay on the preview (corner handles). The overlay is a DOM element, so it is never part of the exported PNG/ZIP.
• Auto-shrink: the font scale is computed to fit the zone height (binary search over re-wrapped layout) and shrunk further so the widest single word still fits the zone width on one line (no mid-word break).
• Placement: text wraps at the zone width and is centered both horizontally and vertically inside the rectangle.

Implementation

• app.js
  • textZone {enabled, x, y, width, height} added to text defaults + normalizeTextSettings (backwards compatible; copied to panorama panels).
  • New maxWordWidth() and computeZoneFit() helpers; textVerticalExtent() gains a wrap-width override; drawTextToContext() confines wrap width / centre / vertical anchor when a zone is active.
  • UI module: toggle, sliders, and pointer-based drag/resize of the overlay; synced from syncUIWithState / updateTextUI and on tab switch.
• index.html — zone controls + overlay markup.
• styles.css — styles for the controls and the dashed rectangle/handles.

Verification

• node --check app.js passes.
• Dev server serves all assets (200, no errors).
• Standalone algorithm tests (7/7): shrinks for a small zone, block fits zone height, every word fits zone width, long single word forced to fit, no shrink when text already fits, headline + subheadline both fit.

Note: like the existing overlap auto-fit, the fitting is computed in the browser; the server-side MCP renderer (which already lacks auto-fit) ignores the zone.

🤖 Generated with Claude Code

---

Generated by Claude Code