App crashes when opening relatively small ".txt" file (~306 KB, ~9.8k lines)

[Chandramauli-Arm64]

⚠️ This issue respects the following points: ⚠️

• This is a bug. Not a question or feature request.
• The topic is not already reported at Issues. (I've searched it).
• Markor is up to date. See Releases for the latest version. Updates are available from F-Droid and GitHub.
• The bug is still present in the latest development version (git master). (Please download and try the test version of Markor, named Marder. Don't worry; Markor and Marder appear as completely separate applications. You can install both side-by-side, and Markor settings are not touched. In case the issue is resolved there, you don't need to create a bug report. The change will be part of the next Markor update.)

Description

Hello,

I am experiencing a consistent crash when trying to open a .txt file in Markor.

Details:

• File size: ~306 KB

• Line count: ~9,858 lines

• File type: .txt (plain text, no special formatting)

Behavior:

The app closes after 3 second while staying blank dark screen when attempting to open the file.

No error message is shown — it simply auto-closes.

Environment:

Occurs on both:

1. Latest stable version of Markor:-

Package: net.gsantner.markor
Version: v2.16.1 (163)
Flavor: Default (release)
Build date: 2026-03-19T08:25Z
ISource: com.Google Play
VCS Hash: f33eb6a8dfb210f27bfe7294430d4d39b795bd0f
VCS Msg: Markor v2.16.1 (code 163)

2. Nightly build (Marder):-

Package: net.gsantner.markor_test
Version: v2.16.1-1040 (260411)
Flavor: Atest (debug)
Build date: 2026-04-11T10:40Z
ISource: com.Google Play
VCS Hash: 81d040a369bc1fae465700ee62337b765903fecf
VCS Msg: Add Markor settings shortcut to Android system settings, by gsantner

Additional notes:

I am aware of existing crash reports related to large files (>1 MB), but this file is significantly smaller.

The issue appears reproducible across both versions, suggesting it may not be version-specific.

The file is plain text and does not contain unusual formatting.

Question:

Is this crash related to the number of lines (~10k), or could there be another limitation or parsing issue involved?

Crash video:-

VID_20260504_154104.mp4

VID_20260504_154553.mp4

Thank you.

Steps to reproduce

1. Write a plain text file around 300 to 400 Kb in size
2. Try to open it in markor
3. See the result.

Information

Android version: 15 (Realme ui 7)
Device: Realm p1 5g (RMX 3870)
App Version: 2.16.1

Source

GitHub Releases

Format / File type

Plaintext

Additional info / Log

The same file opens instantly without any issue in:
- Neovim (Termux)
- ZArchiver text viewer

**This suggests**:
- The file is valid
- The file size (~306 KB, ~9.8k lines) is not problematic
- The issue is likely specific to Markor’s parsing or rendering layer

[harshad1]

Do you have a sample file

[Chandramauli-Arm64]

Do you have a sample file

Sorry, I can't provide a sample file now because it will take time to create it and the txt file I am using has some sensitive things in it. So, I am unable to provide it here but
You can try with your terminal history if you use it frequently and redirect the output into a history.txt file.

[guanglinn]

It seems that fix #2769 did not have much effect in terms of loading large text files.
This app is still slow to open a file of several hundred KB

[Chandramauli-Arm64]

It seems that fix #2769 did not have much effect in terms of loading large text files. This app is still slow to open a file of several hundred KB

Yes

[Chandramauli-Arm64]

Do you have a sample file

@harshad1 I have created a sample file of 280 Kb with 10,000 lines and you can try to open it.

output.txt

[SamuelMiller]

Some issue with my 700+ page MD file

[Nihmar]

I have a bunch of 5000+ lines md files of around 300kb, and while it doesn't crash, it takes even 20 seconds to catch up and let me scroll on the file

[harshad1]

I have a pixel 7 and at least on my device opening output.txt it is instant

What device do you have? Can you try an alternative text editor to see if it's markor or something else?

[guanglinn]

I think the best approach is to switch to a high performance and stable text editor kernel (that is many excellent editor do), although it may require a lot of effort, but that will solve many problems, we don't need to put a lot of effort to think about how to improve performance and build wheels, such as implementing line numbers, syntax highlighting for various languages, core search functionality, and large text support ... for Android EditText.

[guanglinn]

@gsantner
I think I can help Markor adopt a stable high performance text editor kernel - CodeMirror which is suitable for mobile devices.
If you agree, I will experiment Markor with CodeMirror kernel on my branch first, then apply it to master branch when stable.

[guanglinn]

I have tried. I open a 1.59 MB (33216 lines) text file using the CodeMirror kernel, it takes almost within 1 second, see

Open a 1.59 MB (33216 lines) text file with CodeMirror kernel:

Takes 1 second.

SVID_20260518_100506_1.mp4

Open that file with Markor (EditText):

Takes over 10 seconds.

SVID_20260518_102009_1.mp4

[guanglinn]

Can I use Android EditText to load large files? - Gemini

[harshad1]

I think The problem is view mode

It opens in edit text just fine and even layout is fast enough.

Switching to view mode or default view mode is very slow.

[guanglinn]

I think view mode is no problem, the rendering speed of WebView is even much faster than EditText when displaying large text.

I have a test, it takes only 1 second to open a large text file (1.59 MB, 33216 lines) in a WebView based editor with CodeMirror kernel, while Markor takes over 10 seconds with EditText to open it. #2814 (comment)

That is why EditText is a performance bottleneck for Markor.
Most users have to abandon Markor just because opening or editing a hundreds of KB file is too slow.