118 lines
3.8 KiB
C++
118 lines
3.8 KiB
C++
/*
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* Copyright (c) Meta Platforms, Inc. and affiliates.
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*
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* This source code is licensed under the MIT license found in the
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* LICENSE file in the root directory of this source tree.
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*/
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#include "ViewEventEmitter.h"
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namespace facebook::react {
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#pragma mark - Accessibility
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void ViewEventEmitter::onAccessibilityAction(std::string const &name) const {
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dispatchEvent("accessibilityAction", [name](jsi::Runtime &runtime) {
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auto payload = jsi::Object(runtime);
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payload.setProperty(runtime, "actionName", name);
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return payload;
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});
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}
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void ViewEventEmitter::onAccessibilityTap() const {
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dispatchEvent("accessibilityTap");
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}
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void ViewEventEmitter::onAccessibilityMagicTap() const {
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dispatchEvent("magicTap");
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}
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void ViewEventEmitter::onAccessibilityEscape() const {
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dispatchEvent("accessibilityEscape");
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}
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#pragma mark - Layout
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void ViewEventEmitter::onLayout(const LayoutMetrics &layoutMetrics) const {
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// A copy of a shared pointer (`layoutEventState_`) establishes shared
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// ownership that will be captured by lambda.
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auto layoutEventState = layoutEventState_;
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// Dispatched `frame` values to JavaScript thread are throttled here.
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// Basic ideas:
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// - Scheduling a lambda with some value that already was dispatched, does
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// nothing.
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// - If some lambda is already in flight, we don't schedule another;
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// - When a lambda is being executed on the JavaScript thread, the *most
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// recent* `frame` value is used (not the value that was current at the
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// moment of scheduling the lambda).
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//
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// This implies the following caveats:
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// - Some events can be skipped;
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// - When values change rapidly, even events with different values
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// can be skipped (only the very last will be delivered).
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// - Ordering is preserved.
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{
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std::lock_guard<std::mutex> guard(layoutEventState->mutex);
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// If a *particular* `frame` was already dispatched to the JavaScript side,
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// no other work is required.
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if (layoutEventState->frame == layoutMetrics.frame &&
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layoutEventState->wasDispatched) {
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return;
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}
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// If the *particular* `frame` was not already dispatched *or*
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// some *other* `frame` was dispatched before,
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// we need to schedule the dispatching.
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layoutEventState->wasDispatched = false;
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layoutEventState->frame = layoutMetrics.frame;
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// Something is already in flight, dispatching another event is not
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// required.
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if (layoutEventState->isDispatching) {
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return;
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}
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layoutEventState->isDispatching = true;
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}
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dispatchEvent(
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"layout",
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[layoutEventState](jsi::Runtime &runtime) {
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auto frame = Rect{};
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{
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std::lock_guard<std::mutex> guard(layoutEventState->mutex);
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layoutEventState->isDispatching = false;
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// If some *particular* `frame` was already dispatched before,
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// and since then there were no other new values of the `frame`
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// observed, do nothing.
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if (layoutEventState->wasDispatched) {
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return jsi::Value::null();
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}
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frame = layoutEventState->frame;
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// If some *particular* `frame` was *not* already dispatched before,
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// it's time to dispatch it and mark as dispatched.
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layoutEventState->wasDispatched = true;
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}
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auto layout = jsi::Object(runtime);
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layout.setProperty(runtime, "x", frame.origin.x);
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layout.setProperty(runtime, "y", frame.origin.y);
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layout.setProperty(runtime, "width", frame.size.width);
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layout.setProperty(runtime, "height", frame.size.height);
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auto payload = jsi::Object(runtime);
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payload.setProperty(runtime, "layout", std::move(layout));
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return jsi::Value(std::move(payload));
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},
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EventPriority::AsynchronousUnbatched);
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}
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} // namespace facebook::react
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