feat: Listen for SIGTERM and exit the application gracefully.

[lichaofan2008]

DDE may kill the deepin-camera circumstances, the logging system would consider it.
监听 SIGTERM 信号，正常退出应用。
由于DDE在某些情况下会kill掉deepin-camera进程，同时埋点会认为deepin-camera出错，所以这里监听信号，正常退出。

v20 BUG 分支合一到v25主线
Task: https://pms.uniontech.com/task-view-383481.html

Summary by Sourcery

Enhancements:

• Add a SIGTERM signal handler in the main entry point to perform a controlled application exit.

[sourcery-ai]

Reviewer's guide (collapsed on small PRs)

Reviewer's Guide

Adds SIGTERM handling in main.cpp so the deepin-camera process can exit cleanly when killed by DDE, avoiding it being logged as a crash, by registering a simple signal handler at application startup.

Sequence diagram for graceful SIGTERM handling in deepin_camera

sequenceDiagram
    actor User
    participant DDE
    participant deepin_camera_main as deepin_camera_main
    participant LoggingSystem

    User->>DDE: Trigger action that ends camera session
    DDE->>deepin_camera_main: SIGTERM
    deepin_camera_main->>deepin_camera_main: handleSignal(sig)
    deepin_camera_main->>LoggingSystem: Record normal application exit
    deepin_camera_main-->>DDE: Process exits with code 0

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Flow diagram for deepin_camera main with SIGTERM registration

flowchart TD
    A["Start main"] --> B["Log 'Starting deepin-camera application...' via qInfo"]
    B --> C["Register SIGTERM handler using signal(SIGTERM, handleSignal)"]
    C --> D["Run deepin-camera main event loop and application logic"]
    D --> E["Normal shutdown path (user closes app or app finishes)"]
    E --> F["Exit with code 0"]

    %% Asynchronous SIGTERM path
    C -->|"Asynchronous SIGTERM received"| G["handleSignal invoked with sig"]
    G --> H["Log 'Received signal: sig' via qWarning"]
    H --> F

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File-Level Changes

Change	Details	Files
Introduce a SIGTERM handler and register it at application startup so the process exits gracefully when killed.	Include the header to enable use of signal handling APIs. Define a handleSignal function that logs the received signal via qWarning and terminates the process with exit(0). Register handleSignal as the handler for SIGTERM at the beginning of main() so that kill’s default signal is handled gracefully.	src/main.cpp

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[sourcery-ai]

Hey there - I've reviewed your changes and found some issues that need to be addressed.

Prompt for AI Agents

Please address the comments from this code review:

## Individual Comments

### Comment 1
<location> `src/main.cpp:125-128` </location>
<code_context>

+// 由于DDE在某些情况下会kill掉deepin-camera进程，同时埋点会认为deepin-camera出错，所以这里监听信号，正常退出
+// 添加信号处理函数
+static void handleSignal(int sig)
+{
+    qWarning() << "Received signal:" << sig;
+    exit(0);
+}
+
</code_context>

<issue_to_address>
**issue (bug_risk):** Avoid calling non–async-signal-safe functions (like qWarning and exit) inside a signal handler.

In a signal handler, only async-signal-safe functions are allowed. `qWarning()` and `exit()` are not safe here and can cause undefined behavior or deadlocks if the signal interrupts code holding locks. Prefer a minimal handler (e.g., set an atomic flag or write to a pipe) and let the main thread handle logging/shutdown, or use `_exit()`/`std::_Exit()` if you must terminate immediately without Qt teardown.
</issue_to_address>

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[deepin-ci-robot]

deepin pr auto review

我来对这个Git diff进行详细审查：

1. 代码逻辑和语法：

• 整体语法规范，没有明显的语法错误
• 代码结构清晰，注释详细
• 函数命名规范，遵循了项目的命名约定

2. 代码质量改进建议：

a) 分辨率限制相关：

// 优点：
- 将分辨率限制的硬编码值统一移到了v4l2_formats.h中
- 添加了is_valid_resolution()函数来统一验证分辨率
- 注释更详细地说明了限制分辨率的原因

// 建议改进：
- 可以考虑将MAX_WIDTH_LIMIT和MAX_HEIGHT_LIMIT定义为结构体或类，便于统一管理
- 建议添加分辨率限制的单元测试

b) 信号处理相关：

// 优点：
- 添加了信号处理机制，提高了程序的健壮性
- 注释说明了添加信号处理的原因

// 建议改进：
- handleSignal函数可以添加更多信号的处理（如SIGINT）
- 可以考虑使用更现代的C++信号处理方式，如std::signal
- 建议在退出前添加资源清理代码

3. 性能方面：

• 没有明显的性能问题
• 分辨率验证逻辑的优化减少了重复代码
• 使用is_valid_resolution()函数提高了代码复用性

4. 安全性方面：

// 优点：
- 添加了对分辨率的有效性检查
- 使用信号处理机制防止异常退出

// 建议改进：
- 在handleSignal中添加日志记录，便于问题追踪
- 可以考虑添加对分辨率上限的动态配置机制

5. 具体建议：

a) 对is_valid_resolution函数的改进：

int is_valid_resolution(int width, int height)
{
    // 添加参数有效性检查
    if (width <= 0 || height <= 0) {
        return 0;
    }
    
    // 检查是否在限制范围内
    if (width > MAX_WIDTH_LIMIT || height > MAX_HEIGHT_LIMIT) {
        return 0;
    }
    
    // 检查对齐要求
    return (width % 16 == 0 && height % 8 == 0);
}

b) 对信号处理的改进：

static void handleSignal(int sig)
{
    qWarning() << "Received signal:" << sig;
    // 添加资源清理代码
    cleanup_resources();
    exit(0);
}

// 注册更多信号
signal(SIGTERM, handleSignal);
signal(SIGINT, handleSignal);  // 处理Ctrl+C

6. 其他建议：

• 考虑添加配置文件支持，使分辨率限制可配置
• 添加更多的错误处理和日志记录
• 考虑添加分辨率切换的平滑过渡机制

总的来说，这些改动提高了代码的可维护性和健壮性，但仍有改进空间。建议在后续版本中逐步完善这些方面。

[deepin-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: lichaofan2008, lzwind

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• debian/deepin/OWNERS

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[lichaofan2008]

/merge