DevTools: "Jump between editing locations" experiment

Source/devtools/front_end/SimpleHistoryManager.js

+/*
+ * Copyright (C) 2014 Google Inc. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+/**
+ * @interface
+ */
+WebInspector.HistoryEntry = function() { }
+
+WebInspector.HistoryEntry.prototype = {
+    /**
+     * @return {boolean}
+     */
+    valid: function() { },
+
+    reveal: function() { }
+};
+
+/**
+ * @constructor
+ * @param {number} historyDepth
+ */
+WebInspector.SimpleHistoryManager = function(historyDepth)
+{
+    this._entries = [];
+    this._activeEntryIndex = -1;
+    this._coalescingReadonly = 0;
+    this._historyDepth = historyDepth;
+}
+
+WebInspector.SimpleHistoryManager.prototype = {
+    readOnlyLock: function()
+    {
+        ++this._coalescingReadonly;
+    },
+
+    releaseReadOnlyLock: function()
+    {
+        --this._coalescingReadonly;
+    },
+
+    /**
+     * @return {boolean}
+     */
+    readOnly: function()
+    {
+        return !!this._coalescingReadonly;
+    },
+
+    /**
+     * @param {!function(!WebInspector.HistoryEntry):boolean} filterOutCallback
+     */
+    filterOut: function(filterOutCallback)
+    {
+        if (this.readOnly())
+            return;
+        var filteredEntries = [];
+        var removedBeforeActiveEntry = 0;
+        for (var i = 0; i < this._entries.length; ++i) {
+            if (!filterOutCallback(this._entries[i])) {
+                filteredEntries.push(this._entries[i]);
+            } else if (i <= this._activeEntryIndex)
+                ++removedBeforeActiveEntry;
+        }
+        this._entries = filteredEntries;
+        this._activeEntryIndex = Math.max(0, this._activeEntryIndex - removedBeforeActiveEntry);
+    },
+
+    /**
+     * @return {boolean}
+     */
+    empty: function()
+    {
+        return !this._entries.length;
+    },
+
+    /**
+     * @return {?WebInspector.HistoryEntry}
+     */
+    active: function()
+    {
+        return this.empty() ? null : this._entries[this._activeEntryIndex];
+    },
+
+    /**
+     * @param {!WebInspector.HistoryEntry} entry
+     */
+    push: function(entry)
+    {
+        if (this.readOnly())
+            return;
+        if (!this.empty())
+            this._entries.splice(this._activeEntryIndex + 1);
+        this._entries.push(entry);
+        if (this._entries.length > this._historyDepth)
+            this._entries.shift();
+        this._activeEntryIndex = this._entries.length - 1;
+    },
+
+    /**
+     * @return {boolean}
+     */
+    rollback: function()
+    {
+        if (this.empty())
+            return false;
+
+        var revealIndex = this._activeEntryIndex - 1;
+        while (revealIndex >= 0 && !this._entries[revealIndex].valid())
+            --revealIndex;
+        if (revealIndex < 0)
+            return false;
+
+        this.readOnlyLock();
+        this._entries[revealIndex].reveal();
+        this.releaseReadOnlyLock();
+
+        this._activeEntryIndex = revealIndex;
+        return true;
+    },
+
+    /**
+     * @return {boolean}
+     */
+    rollover: function()
+    {
+        var revealIndex = this._activeEntryIndex + 1;
+
+        while (revealIndex < this._entries.length && !this._entries[revealIndex].valid())
+            ++revealIndex;
+        if (revealIndex >= this._entries.length)
+            return false;
+
+        this.readOnlyLock();
+        this._entries[revealIndex].reveal();
+        this.releaseReadOnlyLock();
+
+        this._activeEntryIndex = revealIndex;
+        return true;
+    },
+};