Bohdan Triapitsyn
1d1c215230
Merge main and reshape the follow opt-out to the gestures the timeline was missing: a middle-button press starts the platform autoscroll pan (the only scroll gesture on wheel-less mice and tablets with a pointer), Shift+Space scrolls up from the keyboard, and an upward wheel over a nested scroller that still has room above stays with that scroller instead of releasing the chat. The grace re-pin timer and scroll-direction tracking are dropped: returning to within the end band already re-arms follow, and the mode machine is built without timers on purpose. Pause/Break never move the viewport and are not gestures. Closes #1640
42 lines
2.2 KiB
TypeScript
42 lines
2.2 KiB
TypeScript
// Gesture classification for the chat timeline's follow opt-out.
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//
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// The timeline releases live follow on REAL upward gestures only. Wheel and
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// touch carry their direction; this module answers the same question for the
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// inputs that do not: which keys mean "scroll up", when a middle-button press
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// starts a pan, and when an upward wheel belongs to a nested scroller (a tool
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// output box) that can still consume it. Pure functions, no DOM ownership,
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// so the rules are testable without a renderer.
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// A nested scroller inside the timeline marks itself with this attribute
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// (see ToolPart). Wheel-up over it scrolls the box, not the conversation, for
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// as long as the box has room above.
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const NESTED_SCROLLABLE_SELECTOR = '[data-scrollable]';
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export const isFollowReleaseKey = (
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event: Pick<KeyboardEvent, 'altKey' | 'ctrlKey' | 'key' | 'metaKey' | 'shiftKey'>,
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): boolean => {
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// Modified keys are shortcuts, not navigation.
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if (event.altKey || event.ctrlKey || event.metaKey) return false;
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if (event.key === ' ') return event.shiftKey;
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return event.key === 'ArrowUp' || event.key === 'PageUp' || event.key === 'Home';
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};
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const nestedScrollable = (root: HTMLElement, target: EventTarget | null): HTMLElement | null => {
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if (!(target instanceof Element)) return null;
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const nested = target.closest(NESTED_SCROLLABLE_SELECTOR);
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return nested instanceof HTMLElement && nested !== root ? nested : null;
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};
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// An upward wheel over a nested scroller that still has content above stays
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// with that scroller; the timeline must not treat it as leaving the end.
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export const nestedScrollableConsumesWheelUp = (root: HTMLElement, target: EventTarget | null): boolean => {
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const nested = nestedScrollable(root, target);
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return nested !== null && nested.scrollTop > 0;
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};
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// Middle-button press starts the platform's autoscroll pan (Windows/Linux
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// Chromium); the pan then scrolls without wheel events, so the press itself is
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// the gesture. Inside a nested scroller the pan belongs to that scroller.
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export const isMiddleButtonPan = (root: HTMLElement, event: Pick<MouseEvent, 'button' | 'target'>): boolean =>
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event.button === 1 && nestedScrollable(root, event.target) === null;
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