forked from unom/punktfunk
Bring the SDL presenter (Linux/Deck + Windows) to parity with the Android and
Apple clients: a persisted TouchMode selects how a touchscreen drives the host —
* Trackpad (default): relative cursor with pointer ballistics + the shared
gesture vocabulary (tap = left click, two-finger tap = right click,
two-finger drag = scroll, tap-then-drag = held left drag, three-finger tap =
cycle the stats overlay).
* Direct pointer: the cursor jumps to and follows the finger (absolute).
* Touch passthrough: every finger is a real host touchscreen contact.
Previously the presenter had no finger handling, so SDL synthesized mouse events
from touch and — under the stream's relative-mouse lock — walked the host cursor
into the corner (the reported Deck bug). SDL touch->mouse synthesis is now off;
DIRECT touchscreens route through a new incremental gesture engine (a port of
Android TouchInput.kt / Apple TouchMouse.swift), while INDIRECT trackpads keep
driving the mouse. Fingers map through the aspect-fit letterbox onto the content
rect.
TouchMode lives in the shared trust::Settings (default trackpad, so passthrough
is opt-in like the other clients); the GTK and WinUI settings screens both gained
a "Touch input" picker. Gesture engine, letterbox mapping, and settings
back-compat are unit-tested (28 tests green); clippy -D warnings clean; full
Linux client + session build verified on-host.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>