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function checkSnapEventSupport(event_type) {
if (event_type == "snapchanged") {
assert_true(window.onsnapchanged !== undefined, "snapchanged not supported");
} else if (event_type == "snapchanging") {
assert_true(window.onsnapchanging !== undefined, "snapchanging not supported");
} else {
assert_unreached(`Unknown snap event type selected: ${event_type}`);
}
}
function assertSnapEvent(evt, expected_ids) {
assert_equals(evt.bubbles, false, "snap events don't bubble");
assert_false(evt.cancelable, "snap events are not cancelable.");
assert_equals(evt.snapTargetBlock, expected_ids.block,
"snap event supplied expected target in block axis");
assert_equals(evt.snapTargetInline, expected_ids.inline,
"snap event supplied expected target in inline axis");
}
async function snap_test_setup(test, scroller, event_type) {
checkSnapEventSupport(event_type);
await waitForScrollReset(test, scroller);
await waitForCompositorCommit();
test.add_cleanup(async () => {
await waitForScrollReset(test, scroller);
});
}
async function test_snap_event(test, test_data, event_type) {
await snap_test_setup(test, test_data.scroller, event_type);
let listener = test_data.scroller ==
document.scrollingElement ? document : test_data.scroller;
const event_promise = waitForSnapEvent(listener, event_type);
await test_data.scrolling_function();
let evt = await event_promise;
assertSnapEvent(evt, test_data.expected_snap_targets);
assert_approx_equals(test_data.scroller.scrollTop,
test_data.expected_scroll_offsets.y, 1,
"vertical scroll offset mismatch.");
assert_approx_equals(test_data.scroller.scrollLeft,
test_data.expected_scroll_offsets.x, 1,
"horizontal scroll offset mismatch.");
}
async function test_snapchanged(test, test_data) {
await test_snap_event(test, test_data, "snapchanged");
}
function waitForEventUntil(event_target, event_type, wait_until) {
return new Promise(resolve => {
let result = null;
const listener = (evt) => {
result = evt;
};
event_target.addEventListener(event_type, listener);
wait_until.then(() => {
event_target.removeEventListener(event_type, listener);
resolve(result);
});
});
}
function waitForEventsUntil(event_target, event_type, wait_until) {
return new Promise(resolve => {
let result = [];
const listener = (evt) => {
result.push(evt);
};
event_target.addEventListener(event_type, listener);
wait_until.then(() => {
event_target.removeEventListener(event_type, listener);
resolve(result);
});
});
}
function waitForOnSnapchanging(event_target) {
return new Promise(resolve => {
let result = null;
const listener = (evt) => {
result = evt;
};
event_target.onsnapchanging = listener;
waitForScrollendEventNoTimeout(event_target).then(() => {
event_target.onsnapchanging = null;
resolve(result);
});
});
}
// Proxy a wait for a snap event. We want to avoid having a test
// timeout in the event of an expected snap event not firing in a particular
// test case as that would cause the entire file to fail.
// Snap events should fire before scrollend, so if a scroll should happen, wait
// for a scrollend event. Otherwise, just do a rAF-based wait.
function waitForSnapEvent(event_target, event_type, scroll_happens = true) {
return scroll_happens ? waitForEventUntil(event_target, event_type,
waitForScrollendEventNoTimeout(event_target))
: waitForEventUntil(event_target, event_type,
waitForAnimationFrames(2));
}
function waitForSnapChangedEvent(event_target, scroll_happens = true) {
return waitForSnapEvent(event_target, "snapchanged", scroll_happens);
}
function getScrollbarToScrollerRatio(scroller) {
// Ideally we'd subtract the length of the scrollbar thumb from
// the dividend but there isn't currently a way to get the
// scrollbar thumb length.
return scroller.clientHeight /
(scroller.scrollHeight - scroller.clientHeight);
}
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