Add :icon: escapes, resolved through Theme::icons, on every Font

[jdolan]

Summary

• A registered icon renders inline in any Text as :name:, on both the bitmap and TrueType paths, with no opt-in, matching color escapes. Unregistered names stay literal, so 12:30:45 is untouched.
• ImageAtlas gains named images (addImageWithName / imageWithName) and a generation counter. Theme::addIcon registers an Image under a name and compiles the icon atlas; Theme::icon looks one up.
• MVC_IconEscapeLength defines the escape syntax once, shared by Text, Font+Bitmap and TextView.
• TrueType path: MVC_LayoutText resolves escapes into the layout string plus spans. An icon occupies a run of non-breaking placeholder characters at least a line height wide, measured with the same engine that lays out and renders the text, and is drawn as a square of the line height centered in that slot. Coda lacks U+00A0, so the placeholder codepoint is chosen per Font and cached on it.
• Bitmap path: an icon token advances by whole cells and draws centered in its slot.
• A Text tracks the atlas generation it was prepared against, so icons registered later, a Theme swap, or window attachment re-resolve it.
• Text::sizeText measures arbitrary text as the Text would render it. TextView uses it for the caret (fixing a pre-existing bitmap-metrics mismatch) and treats a registered :icon: as one cursor unit.
• HUD registers its icons by name and restores the heart on the health readout.

Test plan

• make -j builds clean
• make check passes (7 suites; new cases in ImageAtlas and Text)
• Examples/HUD and Examples/Hello run without error
• Visual: HUD heart centered in its whole-cell slot; :heart: on a Coda line stays glued to its word when narrowed; typing :heart: in an Input renders inline and Backspace removes it as one unit

🤖 Generated with Claude Code

[Copilot]

🟡 Changes recommended

Icon rendering does not currently match the PR’s stated “matching color escapes” behavior and the TrueType wrap-fragment selection can misplace icons under narrow wrap widths.

Once you've addressed the issues Copilot identified, you can request another Copilot review.

Pull request overview

Adds inline :icon: escape support across Text rendering and caret navigation by introducing named icons in ImageAtlas, Theme-level icon registration/lookup, and shared parsing/layout helpers so both TrueType and bitmap font paths can resolve and render icons consistently.

Changes:

• Introduces named images + generation tracking in ImageAtlas, and Theme APIs addIcon / icon for registering and resolving icons.
• Adds MVC_IconEscapeLength and MVC_LayoutText to parse icon escapes and produce layout spans (text + icon placeholders) for TrueType rendering.
• Updates Text/TextView/bitmap font paths and examples/tests to measure, render, and edit icon escapes as single cursor units.

File summaries

File	Description
Tests/ObjectivelyMVC/Text.c	Adds tests for icon escape parsing, TrueType layout span generation, and bitmap cell advance behavior.
Tests/ObjectivelyMVC/ImageAtlas.c	Adds tests for named image registration and atlas generation increments.
Tests/ObjectivelyMVC/Font+Bitmap.c	Updates tests to match new bitmap sizing API signature (icons parameter).
Sources/ObjectivelyMVC/Theme.h	Documents/exports Theme icon registration and lookup APIs; updates icon atlas documentation.
Sources/ObjectivelyMVC/Theme.c	Implements Theme::addIcon and Theme::icon and wires them into the interface.
Sources/ObjectivelyMVC/TextView.c	Uses Text::sizeText for caret measurement and treats :icon: as one cursor unit during editing/navigation.
Sources/ObjectivelyMVC/Text.h	Adds icon escape parsing + layout APIs, span/run structures, Text icon-staleness tracking, and Text::sizeText.
Sources/ObjectivelyMVC/Text.c	Implements icon parsing/layout, icon-aware invalidation, TrueType icon run rendering, and Text::sizeText.
Sources/ObjectivelyMVC/ImageAtlas.h	Adds named image map and generation field; declares addImageWithName / imageWithName.
Sources/ObjectivelyMVC/ImageAtlas.c	Implements named image registration/lookup, generation updates, and lifecycle management.
Sources/ObjectivelyMVC/Font+Bitmap.h	Extends bitmap render/measure APIs to accept an icon atlas for :icon: resolution.
Sources/ObjectivelyMVC/Font+Bitmap.c	Adds icon tokenization/rendering in bitmap font path and propagates atlas into render/measure.
Sources/ObjectivelyMVC/Font.h	Adds per-Font cached icon placeholder and updates bitmap API signatures.
Sources/ObjectivelyMVC/Font.c	Frees cached icon placeholder on Font deallocation.
Examples/HUD.c	Registers HUD icons by name via Theme and demonstrates inline :heart: rendering in labels.

Review details

• Files reviewed: 15/15 changed files
• Comments generated: 5
• Review effort level: Lite

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