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/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
package org.mozilla.tv.firefox.webrender
import androidx.lifecycle.Lifecycle
import androidx.lifecycle.LifecycleObserver
import androidx.lifecycle.OnLifecycleEvent
import android.content.Context
import android.os.Bundle
import android.util.AttributeSet
import android.view.View
import android.view.ViewGroup
import android.webkit.WebView
import mozilla.components.browser.engine.system.SystemEngineView
import org.mozilla.tv.firefox.ext.canGoBackTwice
import org.mozilla.tv.firefox.ext.restoreState
import org.mozilla.tv.firefox.ext.saveState
import org.mozilla.tv.firefox.ext.webRenderComponents
import org.mozilla.tv.firefox.session.SessionRepo
/**
* Caches a [SystemEngineView], which internally maintains a [WebView].
*
* This allows us to maintain [WebView] state when the view would otherwise
* be destroyed
*/
class EngineViewCache(private val sessionRepo: SessionRepo) : LifecycleObserver {
companion object {
// According to Android docs, WebView.saveState and WebView.restoreState do "not restore
// display data"[1] (the exact meaning of this is not specified). Some discussion about
// them online implies that they do not behave as expected[2][3], and that previous
// versions had broken implementations[4]. However, we ship to a limited number of devices,
// and after thorough testing on each these methods have been found to restore state
// relatively well.
//
// If we encounter strange state bugs in the WebView, this code should be considered
// suspect. But until then, it solves some very important problems[5][6].
//
private var state: Bundle? = null
}
private var cachedView: SystemEngineView? = null
private var shouldPersist = true
fun getEngineView(
context: Context,
attrs: AttributeSet,
initialize: SystemEngineView.() -> Unit
): SystemEngineView {
fun View?.removeFromParentIfAble() {
// If the WebView has already been added to the view hierarchy, we
// need to remove it from its parent before attempting to add it
// again. Otherwise an IllegalStateException will be thrown
(this?.parent as? ViewGroup)?.removeView(cachedView)
}
fun createAndCacheEngineView(): SystemEngineView {
// This will need to be updated for GeckoView.
val engineView = context.webRenderComponents.engine.createView(context, attrs) as SystemEngineView
return engineView.apply {
state?.let { this.restoreState(it) }
initialize()
}.also {
cachedView = it
}
}
cachedView?.removeFromParentIfAble()
sessionRepo.canGoBackTwice = { cachedView?.canGoBackTwice() }
return cachedView ?: createAndCacheEngineView()
}
@OnLifecycleEvent(Lifecycle.Event.ON_CREATE)
private fun onCreate() {
shouldPersist = true
}
@OnLifecycleEvent(Lifecycle.Event.ON_DESTROY)
private fun onDestroy() {
state = when (shouldPersist) {
true -> cachedView?.saveState()
false -> null
}
clear()
}
private fun clear() {
sessionRepo.canGoBackTwice = null
cachedView?.onStop()
cachedView?.onDestroy()
cachedView = null
}
fun doNotPersist() {
shouldPersist = false
}
}