MaxPane can crash SublimeText

[deathaxe]

Summary

I often use MaxPane package to temporarily maximize a view in a multi group layout. Stupid but sometimes I forget a view is maximized and try to push a file to a second pane. This is the time Sublime Text reminds me about the maximized pane by crashing. It suddenly exists.

The issue was reported in 2014 at jisaacks/MaxPane#10

Expected behavior

Sublime Text may display a error message if something prevents it from creating a new pane and abort the new_pane command, but it should not crash.

Actual behavior

Sublime Text crashes and exits.

Steps to reproduce

1. Create a 2 column layout
2. Open a file in each group
3. Focus the left view
4. Run max_pane command to maximize the first group
5. open a second file in the maximized pane
6. Press ctrl+k, ctrl+up to move the file to second group (by new_pane)
7. Crash!

or

1. Create a 2 column layout
2. Open a file in each group
3. Focus the left view
4. Run max_pane command to maximize the first group
5. Press Shift+Alt+2 to create a new 2 column layout
6. Crash!

Environment

• Operating system and version:
  • Windows 10 x64
• Monitor:
  • Resolution 1900x1200
  • dpi_scale used in ST 1.0
• Sublime Text:
  • Build 3139
  • 64 bit

[keith-hall]

are you able to provide an example that doesn't require MaxPane to be installed, just to make it clearer what is happening/where it is crashing?

i.e. a specific combination of window.set_layout followed by new_pane? I guess changing that line to window.run_command('set_layout', l) makes no difference?

[deathaxe]

I have a layout with two groups which window.get_layout() returns
{'cols': [0.0, 0.5, 1.0], 'rows': [0.0, 1.0], 'cells': [[0, 0, 1, 1], [1, 0, 2, 1]]} for.

By calling MaxPane while left pane is active, the layout is changed to:
{'cols': [0.0, 1.0, 1.0], 'rows': [0.0, 1.0], 'cells': [[0, 0, 1, 1], [1, 0, 2, 1]]}

I guess this means it just sets the maximized column/row to maximum relative width/height.

The maximized left group contains 3 views/documents.

Pressing Ctrl+K, Ctrlk+Up immediately crashes Sublime Text.

Running window.run_command("new_pane") from console works the first time - view is moved, but the second call crashes Sublime Text.

Doing the same thing with right group maximized causes both keybinding and running "new_pane" from console to crash the very first time.

I guess the width/height of 0.0 of the "hidden" views causes some layout calculation to fail maybe with division by 0?

[wbond]

This is almost certainly caused by the same thing as #961

[evandrocoan]

are you able to provide an example that doesn't require MaxPane to be installed

@keith-hall, I managed to create a minimal example by exhaustively testing MaxPane code.

1. Close a Sublime Text Vanilla Install
2. Create the plugin:

   import sublime
   import sublime_plugin
   
   class MaxPaneEvents(sublime_plugin.EventListener):
       def on_activated(self, view):
           w = view.window()
           w.set_layout({'rows': [0.0, 1.0], 'cols': [0.0, 0.5, 1.0], 'cells': [[0, 0, 1, 1], [1, 0, 2, 1]]})

3. Create the keybind:

   {
       "keys": ["alt+shift+7"],
       "command": "set_layout",
       "args":
       {"cells": [[0, 0, 1, 1], [1, 0, 2, 1], [2, 0, 3, 1]], "cols": [0.0, 1.0, 1.0, 1.0], "rows": [0.0, 1.0]},
   },

4. Open Sublime Text
5. Press Alt+Shit+7
6. Sublime Text Crashes

It instantaneously creates a dump file with the following: ae9e693d-13ca-484a-ae72-9b150d059cfd.zip

Dump Summary
------------
Dump File:  ae9e693d-13ca-484a-ae72-9b150d059cfd.dmp : F:\SublimeText\Vanilla\ae9e693d-13ca-484a-ae72-9b150d059cfd.dmp
Last Write Time:    04-Aug-19 22:47:35
Process Name:   sublime_text.exe : F:\SublimeText\Vanilla\sublime_text.exe
Process Architecture:   x64
Exception Code: 0xC0000005
Exception Information:  The thread tried to read from or write to a virtual address for which it does not have the appropriate access.
Heap Information:   Not Present

System Information
------------------
OS Version: 10.0.15063
CLR Version(s):

Modules
-------
Module Name Module Path Module Version
----------- ----------- --------------
sublime_text.exe    F:\SublimeText\Vanilla\sublime_text.exe 1.0.0.1
ntdll.dll   C:\Windows\System32\ntdll.dll   10.0.15063.1155
kernel32.dll    C:\Windows\System32\kernel32.dll    10.0.15063.1058
...

Environment

• Operating system and version:
  • Windows 10 build 15063 x64
  • Resolution 1920x1080
  • dpi_scale 1.0
  • Sublime Text:
  • Build 3207
  • 64 bit

@deathaxe, while searching for the cause of the crashed, I figured out you can fix the MaxPane package by changing these lines:

        w.set_layout(l)

            w.set_layout(PaneManager.popLayout(w))

        w.set_layout(l)

# -->
        sublime.set_timeout( lambda: w.set_layout(l), 100 )

            layout = PaneManager.popLayout(w)
            sublime.set_timeout( lambda: w.set_layout( layout ), 100 )

        sublime.set_timeout( lambda: w.set_layout(l), 100 )

@wbond, the crash itself happens because MaxPane is trying to change the layout by the on_activated() event, which is triggered right after we set our layout with Alt+Shift+Keys.

When the layout is maximized, i.e., with the state:

1. {'cells': [[0, 0, 1, 1], [1, 0, 2, 1]], 'rows': [0.0, 1.0], 'cols': [0.0, 1.0, 1.0]}

And we call the Alt+Shift+3 key, then Sublime Text correctly sets the layout, but the on_activated() event from MaxPane is triggered immediately trying to change the layout back to the Unmaximized State of the pane.

Adding the delay fixes the crash problem because now Sublime Text is not trying to change the layout twice in row and inside the on_activated() event, as there is a delay added to MaxPane layout change commands.

I tried adding a delay of 0 instead of 100 milliseconds, but when I tested, if I try to randomly keep maximizing panes and changing layouts highly often/fast, Sublime Text still crashing some random times, not easily reproducible.

[deathaxe]

Great investigation. Can reproduce the crash with your example. Very helpfull.

But can't find the lines to change in max_pane.py in the current upstream master though.

But nevertheless your minimal example stops crashing if we use on_activated_async. This enables ST to set the maximized layout first before it is reverted by the asynchronously queued event listener.

class MaxPaneEvents(sublime_plugin.EventListener):
    def on_activated_async(self, view):
        w = view.window()
        w.set_layout({'rows': [0.0, 1.0], 'cols': [0.0, 0.5, 1.0], 'cells': [[0, 0, 1, 1], [1, 0, 2, 1]]})

If we don't like the flickering caused by the asynchronous event listener and in order to keep compatibility with ST2, the following fix works as well

class MaxPaneEvents(sublime_plugin.EventListener):
    def on_activated(self, view):
        def worker():
            w = view.window()
            w.set_layout({'rows': [0.0, 1.0], 'cols': [0.0, 0.5, 1.0], 'cells': [[0, 0, 1, 1], [1, 0, 2, 1]]})
        sublime.set_timeout(worker)

Package Control and other plugins which used to work for ST2 use set_timeout very often to queue functions and sync with the core.

[deathaxe]

Updated MaxPane for various reasons recently, including ...

• the delayed execution of commands by the EventListener (thanks to @evandrocoan)
• add a workaround for issue Changing the panels layout changes the panel focus to the leftest panel if actual pane only has the transient view #2919 (thanks to @evandrocoan)
• replaced unneccessary run_command() calls by just calling plugin internal functions
• store layouts in the window.settings() to be able to restore them even after ST3 was closed
• various cleanups

Not sure whether it helps fixing occational crashes, but hope it makes things better.

[evandrocoan]

I did the same things as you, except I kept using run_command(), dropped support for Sublime Text 2 and I also edited my fork of the Origami package and integrated their "zoom" functionality/feature with the maximize pane feature. Now you can mix between them without any lost of layouts, i.e., create new panes, destroy panes, ...

1. evandroforks/Origami@9d5556b
2. evandrocoan/MaxPane@1136b91

[deathaxe]

Haven't seen crashs using MaxPane anymore.

Can't repreoduce this issue using the minimal examples in ST4 anymore.