Backlog: optional Space-key gesture for faster LIME input-method switching

[limeimetw]

Request

A Google Play reviewer asked whether LIME can add a faster Space-key swipe gesture for switching input methods.

Original public review text:

希望可以新增空白鍵快速滑動切換輸入法

Current behavior

Current LIME 6 documentation says Space has these roles:

• Tap Space inserts a space or confirms candidates depending on composition state.
• Long-press Space opens the LIME internal input-method menu.
• Horizontal Space-key sliding moves the text caret.

docs/SLIDING_SPACE.md records that the old Android Space-key horizontal IM-switch path was removed when Space sliding was reassigned to caret movement. docs/manuals/faq.md also explains that LIME 3 used Space horizontal swipes for internal IM switching, while LIME 6 uses that gesture for caret movement and uses long-press Space for internal IM switching.

Desired behavior to evaluate

Evaluate whether LIME should offer an optional quick gesture or preference that lets users switch LIME internal input methods from the Space key more quickly than the current long-press menu, without breaking existing Space-key caret movement.

Product questions

• Should Space-key swipe remain dedicated to caret movement, or should switching be optional/configurable?
• If configurable, should the option affect Android only or both Android and iOS?
• Should the request mean LIME internal input-method switching only, or also system keyboard switching?
• How should gesture conflicts be resolved among Space tap, long-press, caret slide, and any proposed IM-switch gesture?

Acceptance considerations

• Existing Space-key caret movement must continue to work unless the user explicitly changes a setting.
• Existing long-press Space internal-IM menu must remain available.
• The setting, if added, must be documented in the user manual and FAQ because it changes the LIME 3 → LIME 6 Space gesture migration guidance.