DevTools: fix stick to bottom in console viewport

third_party/WebKit/Source/devtools/front_end/console/ConsoleView.js

 /*
  * Copyright (C) 2007, 2008 Apple Inc.  All rights reserved.
  * Copyright (C) 2009 Joseph Pecoraro
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
@@ skipping 136 matching lines @@
 
     this._updateFilterStatus();
     WebInspector.moduleSetting("consoleTimestampsEnabled").addChangeListener(this._consoleTimestampsSettingChanged, this);
 
     this._registerWithMessageSink();
     WebInspector.targetManager.observeTargets(this);
 
     this._initConsoleMessages();
 
     WebInspector.context.addFlavorChangeListener(WebInspector.ExecutionContext, this._executionContextChanged, this);
+
+    this._messagesElement.addEventListener("mousedown", this._updateStickToBottomOnMouseDown.bind(this), false);
+    this._messagesElement.addEventListener("mousewheel", this._updateStickToBottomOnMouseWheel.bind(this), false);
+    this._messagesElement.addEventListener("mouseup", this._updateStickToBottomOnMouseUp.bind(this), false);
+    this._messagesElement.addEventListener("mouseleave", this._updateStickToBottomOnMouseUp.bind(this), false);
+    this._messagesElement.addEventListener("keydown", this._updateStickToBottomOnKeyDown.bind(this), true);
 }
 
 WebInspector.ConsoleView.persistedHistorySize = 300;
 
 WebInspector.ConsoleView.prototype = {
     /**
      * @return {!WebInspector.SearchableView}
      */
     searchableView: function()
     {
@@ skipping 179 matching lines @@
         if (this._promptElement === WebInspector.currentFocusElement())
             return;
         // Set caret position before setting focus in order to avoid scrolling
         // by focus().
         this._prompt.moveCaretToEndOfPrompt();
         WebInspector.setCurrentFocusElement(this._promptElement);
     },
 
     restoreScrollPositions: function()
     {
-        if (this._viewport.scrolledToBottom())
+        if (this._viewport.stickToBottom())
             this._immediatelyScrollToBottom();
         else
             WebInspector.Widget.prototype.restoreScrollPositions.call(this);
     },
 
     onResize: function()
     {
         this._scheduleViewportRefresh();
         this._hidePromptSuggestBox();
-        if (this._viewport.scrolledToBottom())
+        if (this._viewport.stickToBottom())
             this._immediatelyScrollToBottom();
         for (var i = 0; i < this._visibleViewMessages.length; ++i)
             this._visibleViewMessages[i].onResize();
     },
 
     _hidePromptSuggestBox: function()
     {
         this._prompt.hideSuggestBox();
         this._prompt.clearAutoComplete(true);
     },
 
     _scheduleViewportRefresh: function()
     {
         /**
          * @this {WebInspector.ConsoleView}
          * @return {!Promise.<undefined>}
          */
         function invalidateViewport()
         {
+            if (this._muteViewportUpdates)
+                return Promise.resolve();
             if (this._needsFullUpdate) {
                 this._updateMessageList();
                 delete this._needsFullUpdate;
             } else {
                 this._viewport.invalidate();
             }
             return Promise.resolve();
         }
+        if (this._muteViewportUpdates)
+            return;
         this._viewportThrottler.schedule(invalidateViewport.bind(this));
     },
 
     _immediatelyScrollToBottom: function()
     {
         // This will scroll viewport and trigger its refresh.
+        this._viewport.setStickToBottom(true);
         this._promptElement.scrollIntoView(true);
     },
 
     _updateFilterStatus: function()
     {
         this._filterStatusTextElement.textContent = WebInspector.UIString(this._hiddenByFilterCount === 1 ? "%d message is hidden by filters." : "%d messages are hidden by filters.", this._hiddenByFilterCount);
         this._filterStatusMessageElement.style.display = this._hiddenByFilterCount ? "" : "none";
     },
 
     /**
@@ skipping 586 matching lines @@
         this._currentMatchRangeIndex = index;
         this._searchableView.updateCurrentMatchIndex(index);
         matchRange = this._regexMatchRanges[index];
         var message = this._visibleViewMessages[matchRange.messageIndex];
         var highlightNode = message.searchHighlightNode(matchRange.matchIndex);
         highlightNode.classList.add(WebInspector.highlightedCurrentSearchResultClassName);
         this._viewport.scrollItemIntoView(matchRange.messageIndex);
         highlightNode.scrollIntoViewIfNeeded();
     },
 
+    _updateStickToBottomOnMouseDown: function()
+    {
+        this._muteViewportUpdates = true;
+        this._viewport.setStickToBottom(false);
+        this._wasScrolledToBottom = this._messagesElement.isScrolledToBottom();
+    },
+
+    _updateStickToBottomOnMouseUp: function()
+    {
+        if (!this._muteViewportUpdates)
+            return;
+
+        this._muteViewportUpdates = false;
+        if (this._wasScrolledToBottom) {
+            // Clicking the scrollbar may trigger events in the order:
+            // mousedown > mouseup > scroll. Delay querying isScrolledToBottom
+            // to give time for smooth scroll events to arrive. The value for
+            // the longest timeout duration is retrieved from crbug.com/575409.
+            setTimeout(updateViewportState.bind(this), 200);
+        } else {
+            // In another case, when users drag the scroll thumb to the bottom,
+            // the viewport should stick. Checking whether the mouse is released
+            // at the bottom of the viewport is not verifiable after an async
+            // timeout, so we do it immediately.
+            updateViewportState.call(this);
+        }
+        delete this._wasScrolledToBottom;
+
+        /**
+         * @this {!WebInspector.ConsoleView}
+         */
+        function updateViewportState()
+        {
+            this._viewport.setStickToBottom(this._messagesElement.isScrolledToBottom());
+            this._scheduleViewportRefresh();
+            this._updateViewportStickinessForTest();
+        }
+    },
+
+    _updateViewportStickinessForTest: function()
+    {
+        // This method is sniffed in tests.
+    },
+
+    _updateStickToBottomOnMouseWheel: function()
+    {
+        this._updateStickToBottomOnMouseDown();
+        this._updateStickToBottomOnMouseUp();
+    },
+
+    _updateStickToBottomOnKeyDown: function(event)

[dgozman, 2016/08/03 21:19:01]

Can we instead listen to prompt text changed or something?

[luoe, 2016/08/04 23:13:01]

Yeah, that would be better.

+    {
+        if (event.key === "Escape")

[dgozman, 2016/08/03 21:19:01]

This still looks really hacky. What happens if I do Ctrl+Shift+F? Or any other
shortcut we have?

[luoe, 2016/08/04 23:13:01]

You're right, I hadn't thought of that.  Modified to fire a stick to bottom on
input events (includes paste).

+            return;
+
+        if (event.key === "PageUp" || event.key === "PageDown")

[dgozman, 2016/08/03 21:19:00]

Ctrl+Home/End? Opt+Something on mac? There could be more.

[luoe, 2016/08/04 23:13:01]

On Mac, Fn-Arrow keys map to PageUp/Down/Home/End.  When pressing Fn-ArrowUp,
keydown handler still fires just one PageUp event with key == "PageUp", even
though two keys are pressed.  So this should be handled correctly.

Although I didn't take into account regular Home/End keys.  Will do.

+            this._updateStickToBottomOnMouseWheel();
+        else
+            this._viewport.setStickToBottom(true);
+    },
+
     __proto__: WebInspector.VBox.prototype
 }
 
 /**
  * @constructor
  * @extends {WebInspector.Object}
  * @param {!WebInspector.ConsoleView} view
  */
 WebInspector.ConsoleViewFilter = function(view)
 {
@@ skipping 322 matching lines @@
             return true;
         }
         return false;
     }
 }
 
 /**
 * @typedef {{messageIndex: number, matchIndex: number}}
 */
 WebInspector.ConsoleView.RegexMatchRange;