[wf9a5m75]

Why

Tiles drew a labelled marker as one baked bitmap per text and position. The street-tree sample labels trees by species and side, so every relabel built a bitmap per combination on the main thread, and the map stalled while panning.

What

Labels are drawn into tiles as text

• Atlas: tiles put only the body (dot or pin) in the atlas and draw the text after all bodies, on both the GPU and the CPU paths.
• Shared bodies: icons that differ only in their label share one body bitmap.
• Lazy baking: ColorDefaultIcon and ImageIcon compute their layout up front. The full bitmap is baked only when the icon is used as a native marker.
• Pixel alignment: text starts on a whole pixel, so a label that crosses a seam lines up on both tiles.
• Declutter: a labelled marker wins its declutter cell.
• Hit testing: taps use the label-inclusive layout size without baking.
• One layout: DefaultIconLayout has a general form that takes the body's rectangle. The pin and ImageIcon both use it. develop's "center a side label on the pin" fix is preserved as the pin's side centre.

ImageIcon labels

ImageIcon now has the same label options as ColorDefaultIcon: label, labelTextColor, labelTextSize, labelTypeFace, labelStrokeColor, labelPosition. They are appended with defaults, so existing calls are unchanged.

Vertical labels: labelWritingMode

• Values follow CSS writing-mode: horizontal-tb (default) and vertical-rl / vertical-lr.
• Vertical text uses CoreText's vertical glyph forms: katakana stand upright, ー becomes a vertical bar, and small kana sit in their vertical position.
• Use case: markers packed along a horizontal street can be named, because a vertical label is one character wide.
• Measuring and drawing for both the baked and the tile paths go through one typesetter (LabelTypesetter).

Labels no longer cut at a tile seam right after relabelling

• Cause: a tile searched its surroundings by the largest overhang any tile had seen so far. Right after a relabel, a tile with no markers of its own could search with a value that had not grown yet, return empty, and leave the label reaching in from its neighbour cut at the seam.
• Fix: labelled icons record their overhang when they are created, and tiles search by that value.
• Rejected alternative: scanning all markers per tile version. Reading @Published state for 144k markers cost 0.7–1.4 s per pass, even in a Release build.

API

Additions only, all with defaults (see api/MapConductorCore.api.swift):

• ColorDefaultIcon.labelWritingMode, defaultLabelWritingMode, and the matching init / copy parameters.
• ImageIcon's label properties and labelWritingMode, plus the matching init / copy parameters.

Checked

On an iPad, with the street-tree sample (144k markers):

• Labels: labels appear through the tile path and swap without a freeze.
• Vertical labels: labels on horizontal streets render vertically.
• Seams: with the tile grid shown, labels are no longer cut at a seam at zoom 17.5.

Not yet:

• Native markers: the native-marker path (under minMarkerCount) with horizontal and vertical labels has not been checked on a device.
• ImageDefaultIcon: it still bakes as before.
• Unit tests: none added; the package's tests cannot run on the device or simulator here.

The same design is to follow on Android and JS.