DevTools: fix stick to bottom in console viewport

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

Index: third_party/WebKit/Source/devtools/front_end/console/ConsoleView.js
diff --git a/third_party/WebKit/Source/devtools/front_end/console/ConsoleView.js b/third_party/WebKit/Source/devtools/front_end/console/ConsoleView.js
index f41672c9b35a9187a1f414a30b8484b5c94d47c0..0bfa0cbf4f4aa2e55b6ecab2b9eb2e13e20f828f 100644
--- a/third_party/WebKit/Source/devtools/front_end/console/ConsoleView.js
+++ b/third_party/WebKit/Source/devtools/front_end/console/ConsoleView.js
@@ -154,6 +154,12 @@ WebInspector.ConsoleView = function()
     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;
@@ -353,7 +359,7 @@ WebInspector.ConsoleView.prototype = {
 
     restoreScrollPositions: function()
     {
-        if (this._viewport.scrolledToBottom())
+        if (this._viewport.stickToBottom())
             this._immediatelyScrollToBottom();
         else
             WebInspector.Widget.prototype.restoreScrollPositions.call(this);
@@ -363,7 +369,7 @@ WebInspector.ConsoleView.prototype = {
     {
         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();
@@ -383,6 +389,8 @@ WebInspector.ConsoleView.prototype = {
          */
         function invalidateViewport()
         {
+            if (this._muteViewportUpdates)
+                return Promise.resolve();
             if (this._needsFullUpdate) {
                 this._updateMessageList();
                 delete this._needsFullUpdate;
@@ -391,12 +399,15 @@ WebInspector.ConsoleView.prototype = {
             }
             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);
     },
 
@@ -1003,6 +1014,67 @@ WebInspector.ConsoleView.prototype = {
         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
 }