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47 lines
2.2 KiB
47 lines
2.2 KiB
import {dom, EventCB} from 'grainjs';
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const DOUBLE_TAP_INTERVAL_MS = 500;
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/**
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* Helper to handle 'dblclick' events on either browser or mobile.
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*
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* This is equivalent to a 'dblclick' handler when touch events are not supported. When they are,
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* the callback will be called on second touch within a short time of a first one. (In that case,
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* preventDefault() prevents a 'dblclick' event from being emulated.)
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*
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* Background: though mobile browsers we care about already generate 'click' and 'dblclick' events
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* in response to touch events, it doesn't seem to be treated as a direct user interaction. E.g.
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* double-click to edit a cell should focus the editor and open the mobile keyboard, but a
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* JS-issued focus() call only works when triggered by a direct user interaction, and synthesized
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* dblclick doesn't seem to do that.
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*
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* Helpful links on emulated (synthesized) events:
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* - https://developer.mozilla.org/en-US/docs/Web/API/Touch_events/Supporting_both_TouchEvent_and_MouseEvent
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* - https://github.com/w3c/pointerevents/issues/171
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*/
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export function onDblClickMatchElem(elem: EventTarget, selector: string, callback: EventCB): void {
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// According to https://developer.mozilla.org/en-US/docs/Web/CSS/touch-action, this "removes the
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// need for browsers to delay the generation of click events when the user taps the screen".
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// Without it, the delay (e.g. on mobile Chrome) prevents cursor from moving on double-tap.
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dom.styleElem(elem as HTMLElement, 'touch-action', 'manipulation');
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dom.onMatchElem(elem, selector, 'dblclick', (ev, _elem) => {
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callback(ev, _elem);
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});
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let lastTapTime = 0;
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let lastTapElem: EventTarget|null = null;
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dom.onMatchElem(elem, selector, 'touchend', (ev, _elem) => {
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const currentTime = Date.now();
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const tapLength = currentTime - lastTapTime;
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const sameElem = (_elem === lastTapElem);
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lastTapTime = currentTime;
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lastTapElem = _elem;
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// Only consider a gesture a double-tap if it's on the same cell. Otherwise, two-finger
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// gestures, such as zooming, may trigger this too.
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if (sameElem && tapLength < DOUBLE_TAP_INTERVAL_MS && tapLength > 0) {
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ev.preventDefault();
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callback(ev, _elem);
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}
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});
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}
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