setHiddenLayers() called load(result, {keepView:true}), so every layer
on/off re-parsed and re-tessellated the whole drawing — arc sampling,
hatch triangulation, complex linetypes and the Slug text batch all rebuilt
from scratch. On an 18 MB DWG a single eye-icon click took 5 s+.
Build every layer once, then switch geometry on and off:
- Merged LineSegments buffers get an index buffer plus a per-segment layer
id (_registerIndexed). A toggle rewrites the index and setDrawRange;
positions, colors and lineDistances are untouched, so draw order, dash
phase and the selection-highlight offsets in meta.colStart stay valid.
- Per-entity meshes (hatch fills, SOLID quads, arrowheads, OLE images,
sprites) are tagged by layer via _addObj and toggled with .visible.
- Slug text builds one merged mesh per CAD layer instead of one per
draw order, so text hides with a visible flag. The shader source is
identical across batches, so three still shares one WebGLProgram.
- Hidden geometry stays in the pick buffers, so _onClick now skips it via
the _metaHidden mask.
- Fit keeps framing only what is drawn: per-layer Box3 + fit samples are
recorded at build and unioned over the visible layers.
- getLayerInfo() caches the O(entities) name/color/count pass per load;
only the visible flag is recomputed.
Layer panel: one delegated click listener instead of re-binding a handler
per row, and a toggle patches the affected row's opacity/icon in place
rather than regenerating the whole list's innerHTML.
Trade-off: hidden layers are now built and kept in memory, so loading a
file with layers already off costs what a full load costs.
Rebuilds dist2.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
SlugTextBatch.add() scaled em-unit glyph outlines by the raw DWG
`height` value, but glyph ink only reaches capHeightEm (~0.74 em) of
the em box. Rendered cap height ended up ~26% short of spec (e.g. a
3.6-height TABLE cell text rendered at ~2.68), while the canvas-sprite
fallback already corrected for this via measured ascent. Divide by
capHeightEm so both paths agree.
Rebuilds dist2 (was stale since before the Entity selection/Property
Inspector/Layer panel work landed).
