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Bug 1331154 - 3. Add a cache to remember the position of the last tab move. r=sebastian

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MozReview-Commit-ID: 5gEpwYuphKm

--HG--
extra : rebase_source : 52da5edee5e8ebdb797cdd3d17787156eba66796
This commit is contained in:
Tom Klein 2017-02-02 15:55:25 -06:00
parent e58cc999fc
commit f892b6de0a
1 changed files with 31 additions and 1 deletions
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32
mobile/android/base/java/org/mozilla/gecko/Tabs.java
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@ -51,6 +51,9 @@ public class Tabs implements BundleEventListener {
// mOrder and mTabs are always of the same cardinality, and contain the same values.
private volatile CopyOnWriteArrayList<Tab> mOrder = new CopyOnWriteArrayList<Tab>();
// A cache that maps a tab ID to an mOrder tab position. All access should be synchronized.
private final TabPositionCache tabPositionCache = new TabPositionCache();
// All writes to mSelectedTab must be synchronized on the Tabs instance.
// In general, it's preferred to always use selectTab()).
private volatile Tab mSelectedTab;
@ -239,6 +242,9 @@ public class Tabs implements BundleEventListener {
if (tabIndex > -1) {
mOrder.add(tabIndex, tab);
if (tabPositionCache.mOrderPosition >= tabIndex) {
tabPositionCache.mTabId = INVALID_TAB_ID;
}
} else {
mOrder.add(tab);
}
@ -271,6 +277,7 @@ public class Tabs implements BundleEventListener {
Tab tab = getTab(id);
mOrder.remove(tab);
mTabs.remove(id);
tabPositionCache.mTabId = INVALID_TAB_ID;
}
}
@ -1076,6 +1083,21 @@ public class Tabs implements BundleEventListener {
return Color.WHITE;
}
/** Holds a tab id and the index in {@code mOrder} of the tab having that id. */
private static class TabPositionCache {
int mTabId;
int mOrderPosition;
TabPositionCache() {
mTabId = INVALID_TAB_ID;
}
void cache(int tabId, int position) {
mTabId = tabId;
mOrderPosition = position;
}
}
/**
* Search for {@code tabId} in {@code mOrder}, starting from position {@code positionHint}.
* Callers must be synchronized.
@ -1116,10 +1138,18 @@ public class Tabs implements BundleEventListener {
// non-private, in the order in which they were added.
synchronized (this) {
final int fromPosition = getOrderPositionForTab(fromTabId, fromPositionHint, true);
final int fromPosition;
if (tabPositionCache.mTabId == fromTabId) {
fromPosition = tabPositionCache.mOrderPosition;
} else {
fromPosition = getOrderPositionForTab(fromTabId, fromPositionHint, true);
}
// Start the toPosition search from the mOrder from position.
final int adjustedToPositionHint = fromPosition + (toPositionHint - fromPositionHint);
final int toPosition = getOrderPositionForTab(toTabId, adjustedToPositionHint, fromPositionHint < toPositionHint);
// Remember where the tab was moved to so that if this move continues we'll be ready.
tabPositionCache.cache(fromTabId, toPosition);
if (fromPosition == -1 || toPosition == -1) {
throw new IllegalStateException("Tabs search failed: (" + fromPositionHint + ", " + toPositionHint + ")" +