fix(capi): permitted-values probe call returned 0 before querying - #58
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dasher_get_parameter_string_values(ctx, key, nullptr, 0) - the documented count-only probe - returned 0 without ever asking the engine, because the early-out for a null buffer preceded the query. Every caller following the two-call pattern got an empty list: frontends rendered blank alphabet/palette pickers (seen live on Dasher-GTK, where the footer alphabet dropdown was empty despite the engine carrying 475 alphabets). The probe now populates ctx->stringValues and returns the full count, so callers can size a buffer and call again. Verified: 475 alphabet names enumerate and the engine current alphabet is present in the list. Regression test extends string_values: probe count matches the fetch count and the current alphabet is among the permitted values. Signed-off-by: will wade <willwade@gmail.com>
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This was referenced Aug 25, 2026
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…abel metrics (#42) Fixes #41. Ports the [Dasher-Windows #36](dasher-project/Dasher-Windows#36) choppiness diagnosis to every Apple target. ## 1. macOS frame pacing — the Windows bug, verbatim `MacDasherCanvas` drove `draw(_:)` with a free-running `Timer(1/60)` — decoupled from the compositor, beat-frequency judder, skipped/doubled frames, worst at slow zoom. Now **`CVDisplayLink`** locked to vsync (retained self in the callback context, hops to main; stopped + released on leaving the window). iOS/visionOS already used `CADisplayLink` and are untouched. ## 2. Clamped engine timeline — all four targets The engine consumes raw deltas as zoom amount; every canvas passed unclamped wall-clock `Date()`. A pause (settings sheet over canvas, backgrounded app where `CADisplayLink` stops) injected a **multi-second delta = giant zoom jump** on resume. Bridges now convert timestamps via `timelineMs(forWallMs:)`: deltas capped at 50 ms, backwards clocks hold position, own monotonic accumulation (`resetTimeline()` for recreation). Mirrors Windows' `EngineTimelineTests` contract. ## 3. Real label metrics — all four targets `dasher_set_text_size_callback` was never wired here, so the engine measured labels with its code-point × fontSize/2 estimate — the exact cause of Windows' **squashed/jumbled deep-zoom labels**. Each bridge now measures with the same font opcode-5 draws with (`fontName` is now a bridge property shared by both paths), **returning 0 on success** per the dasher.h contract (the inversion Windows suffered). Frontend cache keyed text+font+size, bounded at 4096, invalidated on `SP_DASHER_FONT` change (`dasher_text_metrics_changed`). ## 4. DasherCore v0.2.5 + probe-then-fetch The old 64-slot `getStringValues` buffer silently truncated longer lists — `SP_DASHER_FONT` runs to hundreds. Now probes the count first (needs v0.2.5's [DasherCore #58](dasher-project/DasherCore#58) fix) and fetches into an exact-size buffer. ## Builds All four schemes compile clean: DasherMac (macOS), DasherApp (iOS device), DasherKeyboard, DasherVision. (iOS *Simulator* x86_64 slice fails on a pre-existing `speechmarkdown_rust` artifact gap — unrelated to this PR, present before it.) ## Not done here Windows pinned their invariants in tests (#37); worth a follow-up once we have a test target strategy for the bridges. Signed-off-by: will wade <willwade@gmail.com>
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Found the hard way: Dasher-GTK's footer alphabet dropdown was blank despite the engine carrying 475 alphabets.
Root cause
dasher_get_parameter_string_values(ctx, key, nullptr, 0)— the documented count-only probe — had its early-out before the engine query:Every caller using the two-call pattern (probe for count, then fetch — exactly what Dasher-GTK's bridge does) got an empty list for every permitted-values parameter: alphabets, palettes, input filters.
Fix
The probe now populates
ctx->stringValuesand returns the full count; callers size a buffer and call again as documented. Verified with a standalone harness against the engine: 475 alphabet names enumerate, and the engine's current alphabet is present in the list (index 105).Test
string_valuesin test_capi_extended now asserts: probe count > 0, probe count == fetch count, and the current alphabet is among the permitted values. Full suite 39/39 green.Same family as the GTK blank-picker symptoms (its dropdown refresh landed app-side, but the list API itself was the blocker).
DCO signed.