qmk/qmk_firmware

[Bug] send_unicode_string() is inefficient for ASCII characters

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#25,382 opened on Jun 18, 2025

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bughelp wanted

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Description

Describe the Bug

send_unicode_string("a")

sends many keystrokes for the unicode code point of the letter a. Eg <ctrl><shift>u61<space> when it could just send a single keystroke.

This is especially noticeable when the keyboard is connected to Linux and all the extra keystrokes are briefly displayed before being replaced by the unicode character.

It makes sending macros with this function slower when the keyboard is connected to any operating system.

I believe that this could be changed directly in send_unicode_string(). If it would somehow be incompatible in some circumstances, a second function called send_mixed_string() could be introduced that would be documented to send single keystrokes for ASCII characters.

This has been implemented as a community module, but it would be desirable to have this efficiency in qmk core. See send_mixed_string.c

Keyboard Used

No response

Link to product page (if applicable)

No response

Operating System

No response

qmk doctor Output

Is AutoHotKey / Karabiner installed

  • AutoHotKey (Windows)
  • Karabiner (macOS)

Other keyboard-related software installed

No response

Additional Context

No response

Contributor guide

Research direction
Examine `send unicode string()` in the source code to understand how it sends Unicode characters. Then implement a check for ASCII characters to send them as single keystrokes instead of multi keystroke sequences. Refer to the community module `send mixed string.c` for inspiration.
Tech stack
c
Domain
embedded iot
Issue type
Bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
2
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
CGit
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
75