Text input fails in Chromium --app windows; GTK_IM_MODULE=xim restores input #407

Description

I encountered a possible GTK/IME-related input issue with Chromium-based web applications launched using Chromium's --app mode, and I wanted to check whether WebApp Manager is affected by the same behavior.

The issue appears to occur specifically when the website is launched with the --app flag. A normal browser window does not exhibit the problem.

In the affected --app window:

• Text fields may show a blinking caret that freezes or behaves incorrectly after focus.
• Keyboard input fails to register in the field.
• Search boxes and other text inputs are affected.

During debugging, I found that setting the XIM input module before launching the application completely restores normal text input and caret behavior:

export GTK_IM_MODULE=xim

This makes me suspect an interaction between Chromium's --app mode, GTK input-method handling, and Linux IME frameworks.

Steps to Reproduce

1. Launch a Chromium-based web application using the --app flag.
2. Open a page containing a text input field or search box.
3. Click inside the field.
4. Observe the caret.
5. Attempt to type.

I tested this with multiple unrelated websites, including Discord, Twitch, YouTube, Hulu, and Crunchyroll.

For comparison, launching the same sites in a normal browser window does not reproduce the issue.

Expected Behavior

Text fields should accept keyboard input normally, with the caret blinking and behaving as expected.

Actual Behavior

When launched using --app, the caret may freeze or behave incorrectly, and keyboard input fails to register.

Workaround

Launching the Chromium-based application with:

GTK_IM_MODULE=xim

Restores normal keyboard input and caret behavior.

Additional Information

I encountered this while developing a separate application that launches websites as standalone Chromium app windows. I have not yet confirmed whether WebApp Manager reproduces the issue, but WebApp Manager uses a similar app-style approach, so I wanted to check whether this behavior is already known or tracked.

If WebApp Manager does not reproduce the issue or does not use the affected configuration, feel free to close the report.