Fix erroneous ButtonDown mouse event reporting.

[EricWF]

After v0.38.0, I was seeing Input fields lose focus whenever the mouse left the input field area (but without having clicked anywhere). This behavior started after the release v0.38.0 release when Mouse ButtonDown began to trigger loss of focus (This change seemed intentional). However, I wasn't pressing the mouse button down.

The erronious ButtonDown events were actually MouseMove events with no keys held down. According to the docs for xterm escape sequences, when SGR (1006) mode is enabled, the encoded button value isn't always incremented by 32 for move movements events. [1]

I believe the correct fix to this issue is to detect mouse movement events with no button down by checking if the "pressed button" is 0. Which appears to indicate that no mouse button is pressed (in this specific case). Whereas, the button value will be set to 1 when left click is pressed for example.

I'm not sure if this change is fully correct for terminals which don't support SGR mode.

[1] https://invisible-island.net/xterm/ctlseqs/ctlseqs.html#h3-Extended-coordinates

Please review the following checklist.

• Docstrings on all new or modified functions / classes
• Updated documentation
• Updated CHANGELOG.md (where appropriate)

[davep]

I'm not seeing the effect you mention in my usual environment (macOS, kitty); so we can recreate and then test out this PR, what environment are you seeing this in?

[EricWF]

Oh, good question. After some testing this appears to only reproduce inside Intellij's builtin terminal implementation.
It does not seem to reproduce with gnome's terminal implementation.
I'm not sure exactly what to provide, so let me know if you would like something in particular. Here are some relevant environment variables:

JEDITERM_SOURCE_ARGS=
FIG_JETBRAINS_SHELL_INTEGRATION=1
TERM=xterm-256color
LANG=en_US.UTF-8
XMODIFIERS=@im=ibus
XDG_SESSION_TYPE=x11
TERMINAL_EMULATOR=JetBrains-JediTerm
XDG_VTNR=2
VTE_VERSION=7400
SHELL=/usr/bin/fish
COLORTERM=truecolor
PLATFORM_TYPE=Linux

I could dig more into whether the bug is in Intellij's terminal. But the behavior seems potentially inline with the very hard to understand documentation about terminal modes.

Testing with my fix applied causes mouse events in TextArea an Input to match across both terminal implementations, and brings the behavior with the Intellij terminal into line with Gnome terminals existing behavior.

[EricWF]

Ah, sorry I just saw your commit. Here's some of the information you need...

You can find a video of the bug & fix here

Here's the code I used to generate the video:

from textual.app import App, ComposeResult
from textual.widgets import Input, TextArea


class InputApp(App):
    def compose(self) -> ComposeResult:
        yield TextArea("I'm not touching the mouse buttons.")


if __name__ == "__main__":
    app = InputApp()
    app.run()

Textual Diagnostics

Versions

Name	Value
Textual	0.41.0
Rich	13.6.0

Python

Name	Value
Version	3.11.6
Implementation	CPython
Compiler	GCC 13.2.0
Executable	/home/eric/.pyenvs/idea/bin/python3

Operating System

Name	Value
System	Linux
Release	6.5.0-2-amd64
Version	#1 SMP PREEMPT_DYNAMIC Debian 6.5.6-1 (2023-10-07)

Terminal

Name	Value
Terminal Application	PyCharm
TERM	xterm-256color
COLORTERM	truecolor
FORCE_COLOR	Not set
NO_COLOR	Not set

Rich Console options

Name	Value
size	width=112, height=22
legacy_windows	False
min_width	1
max_width	112
is_terminal	False
encoding	utf-8
max_height	22
justify	None
overflow	None
no_wrap	False
highlight	None
markup	None
height	None

Additionally, the output captured from _xterm_parser.py can be found below.
mousecodes.log

[EricWF]

@davep Let me know if I can provide more.

[davep]

I suspect everything necessary is here; just needs one of us to find the time to recreate the problem and review (personally I'm on holiday at the moment).

Might take a wee while (lots of holiday all around heading into this time of year, plus lots going on around Textual), but we'll get to it.

[EricWF]

@davep Sounds good. Enjoy your time away.

I would love to land this before the next release. Because I use textual everywhere, having to patch it is :-(

PS. I fixed the link for the video.

[EricWF]

Hey friends, Happy Holidays!

I see there have been a couple of releases since this PR has been created. Unfortunately none of them contain a fix for the issues described here.

How can I help this land?

[willmcgugan]

We have a backlog. But I will be looking at this soon...

[EricWF]

@willmcgugan Please let me know if I can help move things along.

[willmcgugan]

Would you mind creating an issue for this. Or linking to it if it already exists.