Add keyboard overlay preset, keyboard submenu, and osk_toggle hotkey. Use overlay caching for osk_toggle.
For now, keyboard menu has only preset path, auto-scale toggle, and opacity.
Related fixes:
- input_keyboard_event: Don't check hotkey binds when device is RETRO_DEVICE_POINTER
- Add input_keymaps_translate_rk_to_ascii() for correct character input to input_keyboard_event
- input_overlay_poll: Delay clearing INPUT_OVERLAY_BLOCKED flag until there is no overlay input (Avoids stray input after osk_toggle)
- Send keyboard events for modifiers before other keys (for correct modifier+key input if hitboxes overlap)
Adds overlay_cache_ptr to keep a disabled overlay in memory when it's expected to be shown again.
Most input_overlay_deinit calls are replaced with input_overlay_unload, which caches the overlay unless initing/deiniting core or disabling overlays.
Loading a cached overlay is done as a swap, intended for osk_toggle.
Related updates:
- Fewer parameters for the overlay loading task. Use current settings when enabling an overlay
- Add input_overlay_check_mouse_cursor() to preserve show/hide mouse behavior
- Don't apply input_overlay_show_mouse_cursor in windowed mode (controlled by mouse grab only)
- Remove some dead code
- Enable core host to refuse connecting new players to limit the number of connected players
- Enable a core to flush outgoing packets and read incoming packets without waiting for the next frame (can be used for lower latency or blocking reads)
Adds a new libretro interface for a core to send and receive custom network packets for implementing a communication based multiplayer system instead of using the default state serialization based multiplayer. Connection management is still done by the frontend while a core gains the ability to easily support tunneling of multi-console data communication traffic.
