fix(input): correct batch overflow handling

[qiin2333]

改了啥呀

• 同步上游修复：LizardByte/Sunshine#5456
• 修正相对鼠标移动、垂直滚轮和水平滚轮合批中的 4 处溢出判断
• 仅在 16 位有符号加法真正溢出时终止合批

为啥要改

__builtin_add_overflow() 在发生溢出时返回 true，原代码却对结果取反了。这个小小的 ! 把逻辑整个颠倒：正常输入无法合批，极端溢出反而可能写入回绕结果。杂鱼 bug 这次乖乖退场啦。

修复后，高频鼠标和滚轮输入可以按设计合并；发生溢出时则保留两个独立事件，避免位移或滚动量回绕。

验证

• git diff --check：通过
• 源码检查：4 处正确溢出判断，0 处残留反向判断
• 独立边界测试：正常相加、SHRT_MAX + 1、SHRT_MIN - 1 均通过
• 完整 GCC 构建未完成：本机 MSYS2 cc1plus.exe 启动即返回 0xC0000139；备用 Clang 检查被工程现有工具链/依赖兼容问题阻断，未出现由本补丁导致的诊断

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

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📥 Commits

Reviewing files that changed from the base of the PR and between c172c62 and 57c1dcf.

📒 Files selected for processing (1)

• src/input.cpp

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src/**/*.{cpp,c,h}

⚙️ CodeRabbit configuration file

src/**/*.{cpp,c,h}: Sunshine 核心 C++ 源码，自托管游戏串流服务器。审查要点：内存安全、 线程安全、RAII 资源管理、安全漏洞。注意预处理宏控制的平台相关代码。

Files:

• src/input.cpp

🔇 Additional comments (1)

src/input.cpp (1)

1423-1426: LGTM!

Also applies to: 1465-1465, 1486-1486

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Summary by CodeRabbit

• Bug 修复
  • 修复输入消息批处理中的溢出判断问题。
  • 改善相对鼠标移动、垂直滚轮和水平滚轮事件的批处理行为，避免在未溢出时提前终止处理。

Walkthrough

修正输入消息批处理中相对鼠标移动、垂直滚轮和水平滚轮的 16-bit 加法溢出判断，使批处理仅在发生溢出时终止。

Changes

输入批处理溢出判断

Layer / File(s)	Summary
修正三类输入批处理的溢出条件 src/input.cpp	相对鼠标移动、垂直滚轮和水平滚轮批处理均改为直接使用 __builtin_add_overflow 的结果，仅在加法溢出时终止批处理。

Estimated code review effort: 2 (Simple) | ~10 minutes

Possibly related PRs

• AlkaidLab/foundation-sunshine#852：同样修改 src/input.cpp 中输入批处理的 __builtin_add_overflow 条件逻辑。

Suggested reviewers: yundi339

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	标题简洁且准确概括了输入批处理溢出判断修复。
Description check	✅ Passed	描述与本次修改一致，说明了修复内容、原因和验证情况。
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch codex/fix-input-batch-overflow

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