Hacktoberfest 2026：維護者為十月標記出來的 issue，仍然開放、適合新手。 瀏覽 Hacktoberfest issue

Accelerated backspace measures the wrong code point and can split an emoji

未關閉 適合新手
  • 哪裡不對？
#423 1 則留言 0 個 reaction 已指派 0 人 在 GitHub 檢視

維護者通常 1 天內回覆

還沒有人認領這個 Issue。

評估

難度
2/5
預估耗時
1-3 小時
新手友好度
65/100
Issue 類型
缺陷
描述清晰度
描述清楚
活躍度
冷清
技術堆疊
android, java
領域
mobile

研究方向

閱讀 app/src/main/java/helium314/keyboard/latin/inputlogic/InputLogic.java 第2019–2026行附近的程式碼，從加速退格邏輯及其如何讀取游標前的碼點開始檢查。分別檢查一般字元後接表情符號，以及表情符號後接一般字元時的刪除長度；完成的標準是第二次刪除使用重新讀取的碼點，且不會拆開表情符號或多刪一個一般字元。

由索引模型根據 Issue 內容生成。

描述

Summary

In InputLogic.handleBackspaceEvent, the accelerated (held-backspace) second deletion measures its length from the first code point instead of the one it is actually about to delete. When the second character back is a multi-code-point emoji, this deletes the wrong number of chars and can split the emoji, leaving an orphaned surrogate or a stray variation selector / ZWJ.

Present at tag v4.1.2 (f0ff166ae).

Location

app/src/main/java/helium314/keyboard/latin/inputlogic/InputLogic.java, around lines 2019–2026:

final int codePointBeforeCursorToDeleteAgain = mConnection.getCodePointBeforeCursor();
if (codePointBeforeCursorToDeleteAgain != Constants.NOT_A_CODE) {
    final int lengthToDeleteAgain = codePointBeforeCursor > 0xFE00          // <-- first code point
            || StringUtils.mightBeEmoji(codePointBeforeCursor)              // <-- first code point
                    ? mConnection.getCharCountToDeleteBeforeCursor()
                    : 1;
    mConnection.deleteTextBeforeCursor(lengthToDeleteAgain);
    totalDeletedLength += lengthToDeleteAgain;
}

The guard correctly re-reads the cursor into codePointBeforeCursorToDeleteAgain, but the ternary that decides the delete length still tests codePointBeforeCursor — the value from before the first deletion.

Consequences

Both directions are wrong:

  • First char plain, second an emoji → the branch evaluates false, so lengthToDeleteAgain is 1. A single char is removed from a multi-char emoji, splitting it.
  • First char an emoji, second plain → the branch evaluates true, so getCharCountToDeleteBeforeCursor() is used against a plain character and may remove more than intended.

Only reachable once mDeleteCount > Constants.DELETE_ACCELERATE_AT, i.e. while holding backspace, which is probably why it has gone unnoticed.

Suggested fix

Use the re-read value in the condition, so it describes the character actually being deleted:

final int lengthToDeleteAgain = codePointBeforeCursorToDeleteAgain > 0xFE00
        || StringUtils.mightBeEmoji(codePointBeforeCursorToDeleteAgain)
                ? mConnection.getCharCountToDeleteBeforeCursor()
                : 1;

Notes

Found while merging v4.1.2 into a downstream fork. This almost certainly predates LeanType — the surrounding accelerated-delete code comes from the HeliBoard/AOSP lineage — so it may be worth forwarding to Helium314/HeliBoard as well.

I have no reproduction on a physical device; this is from reading the code, so please sanity-check the emoji-splitting claim against real input before acting on it.

主要語言
Kotlin
星號
1k
分支
59
平均合併
13 小時 21 分鐘
30 天內合併 PR
48

環境準備

從這裡開始

  1. 先讀完整個 Issue，再讀專案的貢獻指南。
  2. 在 Issue 下留言說明你要接手 —— 這能避免兩個人做同樣的事。
  3. Fork 儲存庫，在一個分支上完成修改。
  4. 送出 Pull Request，並在描述裡引用這個 Issue 編號。

LeanBitLab/LeanType 的其他 Issue

查看 LeanBitLab/LeanType 的全部 Issue

相似的 Issue

更多 Kotlin Issue

把新 issue 寄到你的電子郵件信箱

精選適合新手參與的 GitHub issue 摘要。