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Bug 239304 - Splitpanel hangs sometimes..
Summary: Splitpanel hangs sometimes..
Alias: None
Product: platform
Classification: Unclassified
Component: Window System (show other bugs)
Version: 8.0
Hardware: PC All
: P3 normal with 3 votes (vote)
Assignee: Stanislav Aubrecht
Depends on:
Reported: 2013-12-10 10:41 UTC by o_watkins
Modified: 2014-11-11 12:18 UTC (History)
3 users (show)

See Also:
Issue Type: DEFECT
Exception Reporter:

split drag hangs sometimes (173.16 KB, image/png)
2013-12-10 10:41 UTC, o_watkins
Splitpane border is not draggable even when mouse hovers over it (58.22 KB, image/png)
2014-02-11 18:48 UTC, ebakke

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Description o_watkins 2013-12-10 10:41:15 UTC
Created attachment 143005 [details]
split drag hangs sometimes

When I try and drag a splitpanel(border) between two open windows in a multi window mode, it sometimes gets caught or hangs. I have to release my mouse and try again. After a while this gets really annoying.
Comment 1 ebakke 2014-02-11 18:44:50 UTC
I have observed this bug both on Windows and MacOS, but it seems to be much more frequent on MacOS. It makes split panes very hard to use.

In addition to split panes getting "stuck" in the middle of a drag operation like o_watkins describes, I have even observed them getting stuck even before the drag operation starts; it is simply not possible to drag them at all (and the drag cursor never appears). The workaround is to resize the window or another part of the layout to try to get it "unstuck".

I have also observed that the possible area in which the mouse pointer must be located in order to start a split pane drag changes width, from a maximum of 3 pixels (which is already too narrow to be easy to use) and down to 2 pixels (possibly less--I'm observing 2 pixels right now in my open NetBeans window). Even when the mouse pointer is hovering directly over the splitpane border, it is frequently not draggable (see the attached screenshot).

Product Version: NetBeans IDE 7.4 (Build 201310111528)
Updates: NetBeans IDE is updated to version NetBeans 7.4 Patch 2
Java: 1.8.0-ea; Java HotSpot(TM) 64-Bit Server VM 25.0-b59
Runtime: Java(TM) SE Runtime Environment 1.8.0-ea-b117
System: Mac OS X version 10.9.1 running on x86_64; UTF-8; en_US (nb)
User directory: /Users/ebakke/Library/Application Support/NetBeans/7.4
Cache directory: /Users/ebakke/Library/Caches/NetBeans/7.4
Comment 2 ebakke 2014-02-11 18:48:43 UTC
Created attachment 145054 [details]
Splitpane border is not draggable even when mouse hovers over it

Screenshot shows mouse pointer hovering directly over the border of the splitpane; yet, the mouse pointer does not turn into a drag cursor, and it is not possible to drag the border. If the cursor is moved exactly 2 or 3 pixels further up (but not more or less), the cursor turns into a drag cursor, and a drag will succeed (well, not always--I have observed it get stuck even when starting a drag once the cursor is a drag cursor).
Comment 3 rtuck99 2014-04-18 10:36:57 UTC
I see this bug all the time in NetBeans. It is super annoying, especially when my colleagues are watching who all use Eclipse or IntelliJ!

I have seen it in NetBeans 7.4 and 8.0.
It reproduces on Windows (7) and Linux (Ubuntu 13.10).

To reproduce:

Open a Java project, split the editor pane in two side-by-side (it also happens with one editor pane about 50% of the time), so that it shows two .java files open.

Click in one of the editor panes, then try to drag the divider (it doesn't seem to matter which one).

The divider will usually either not drag at all, or will drag a few pixels and then get stuck.

Attempting to drag it a second time will then work.
Comment 4 twolf2919 2014-09-30 15:00:17 UTC
Same issue as others have described.  Like many, I have an editor panel that takes up 3/4 of the screen with a horizontal split pane separating it from the output/cvs/.... panels/tabs below.  Sometimes/oftentimes I need to adjust the splitter to give me more room for a specific operation.  But, more often than not, when I hover over the split panel *NOTHING* happens - i.e. the cursor does not change to indicate dragging is possible.  Sometimes, when I don't pay enough attention, I try dragging anyway - usually with some unpleasant results (e.g. NB thinks I want to drag one of the tabs in the bottom panel).

This problem has been around forever - well, for at least a year or two.  Others have commented that the problem occurs on Windows an Linux too - and, that makes sense, as I *think* it started happening when I had to switch from Apple's JDK to Sun's/Oracle's!

Please find a way to fix this - it's frustrating as heck.  My workaround has been to bring up Apple's "Spaces/Mission Control" and then just go back to NB.  That somehow causes the split panel to reset.
Comment 5 ebakke 2014-09-30 22:13:38 UTC
This bug makes split pane adjustments very cumbersome, and could potentially make new users believe that it's not possible (since one must typically try multiple times, and since the mouse cursor frequently does not indicate draggable behavior either). Would it be OK to change the bug priority to P3, as per ("Prevents users from using the software efficiently, could be an annoyance, or could result in a bad impression of Netbeans' usability")?
Comment 6 ebakke 2014-10-09 20:47:14 UTC
I just discovered that this bug also occurs when the "Size Group" feature is used to resize a split pane in the NetBeans window system. To test this feature, right-click a tab, select Size Group, then use the arrow keys to resize the pane. Like when using the mouse to resize the pane, the Size Group action often becomes non-responsive on the first attempt (either immediately or after being moved the first step), requiring multiple attempts before the pane will change size.

I suspect this is the same bug. It might be easier to debug via the Size Group feature, since no mouse events are involved.
Comment 7 Stanislav Aubrecht 2014-10-10 11:59:27 UTC
core-main 876b6d8fc143
Comment 8 Quality Engineering 2014-10-11 11:30:16 UTC
Integrated into 'main-silver', will be available in build *201410110714* on (upload may still be in progress)

User: S. Aubrecht <>
Log: #239304 - don't use stale split divider for dragging/resizing
Comment 9 ebakke 2014-10-13 16:09:25 UTC
Thanks for the patch--I just downloaded and ran IDE build 201410130001. Now I can't reproduce the bug using the "Size Group" feature, but the bug is still present when dragging split panes with the mouse. I can reproduce it consistently by opening a file in the editor and opening the Properties window. When the pane between the editor and the Properties window is dragged, it always hangs the first time, and then works on subsequent attempts. Closing and reopening the Properties window re-triggers the bug.
Comment 10 Stanislav Aubrecht 2014-10-24 13:00:52 UTC
core-main 19ca536e2128

Hopefully the fix will work as it's difficult to reproduce with mouse actions.
Comment 11 Quality Engineering 2014-10-29 11:41:22 UTC
Integrated into 'main-silver', will be available in build *201410290913* on (upload may still be in progress)

User: S. Aubrecht <>
Log: #239304 - don't use stale split divider for mouse resizing
Comment 12 ebakke 2014-11-03 17:09:01 UTC
I just tried IDE build 201411030002, and I can no longer reproduce the splitpanel bug with the mouse. I'll let you know if I encounter it again after the next release. Thanks for the fix!
Comment 13 Stanislav Aubrecht 2014-11-10 14:53:12 UTC
Transplanted to release801 branch as 5082a553612e
Comment 14 Quality Engineering 2014-11-10 23:19:44 UTC
Integrated into 'releases/release801', will be available in build *201411102027* or newer. Wait for official and publicly available build.

User: S. Aubrecht <>
Log: #239304 - don't use stale split divider for mouse resizing