SDL3 Input Migration Notes

Summary

The SDL3 input migration is complete for event correctness and runtime stability, including:

• Window-scoped text input control via SDL_StartTextInput(window) / SDL_StopTextInput(window).
• Pixel-size viewport updates for HiDPI via SDL_GetWindowSizeInPixels() and SDL_EVENT_WINDOW_PIXEL_SIZE_CHANGED.
• Float mouse position/relative motion propagation.
• Wheel direction normalization when SDL_MOUSEWHEEL_FLIPPED is set.
• Consistent gamepad timestamp units (milliseconds) for InputState updates.
• SDL_EVENT_TEXT_EDITING plumbing through engine events.

IME Caveat (Current Behavior)

SDL_EVENT_TEXT_EDITING is now emitted as app.engine.events.text-editing and routed through state/input dispatch, but input widgets currently treat it as handled without rendering composition text.

This means:

• Final committed IME characters continue to work through SDL_EVENT_TEXT_INPUT.
• In-progress IME composition (pre-edit text/caret underline/candidate feedback) is not rendered in the input widget yet.

Why This Is Acceptable For Now

• It avoids dropped or unknown events in SDL3.
• It keeps input state machines stable while preserving strict SDL3 semantics.
• It does not regress non-IME keyboard/text workflows.

Follow-up For Full IME UX

Implement composition rendering in input widgets by consuming text-editing payload fields:

• text (composition string)
• start (cursor offset inside composition)
• length (selection length)

Suggested approach:

1. Store transient composition state on the input model/widget.
2. Render composition overlay separately from committed text.
3. Clear composition state on commit (text-input) and blur/disconnect.
4. Add dedicated tests for composition start/update/commit/cancel flows.

See also

• Input