Implement error callback system for simplified error handling

[Copilot]

This PR transforms the error callback system from per-provider to global configuration, making error handling more convenient and accessible throughout the CCAP implementation as requested in feedback.

Key Changes

Error Callback System

• C++ Interface: ccap::setErrorCallback() and ccap::getErrorCallback() replace per-provider callbacks
• C Interface: ccap_set_error_callback() for global error handling
• Thread-safe: Global callback storage with mutex protection
• Exception-safe: User callback exceptions are caught to prevent library crashes

Simplified Usage

Before (Per-Provider):

ccap::Provider provider;
provider.setErrorCallback([](ccap::ErrorCode errorCode, const std::string& description) {
    std::cerr << "Error: " << description << std::endl;
});

After (Global):

// Set once globally
ccap::setErrorCallback([](ccap::ErrorCode errorCode, const std::string& description) {
    std::cerr << "Error: " << description << std::endl;
});

ccap::Provider provider; // No per-provider setup needed

Comprehensive Error Codes

Detailed error codes cover all common scenarios:

• NoDeviceFound - No camera device found during discovery
• InvalidDevice - Invalid device name or index specified
• DeviceOpenFailed - Camera device open failed
• DeviceStartFailed - Camera start failed
• UnsupportedResolution - Requested resolution not supported
• UnsupportedPixelFormat - Requested pixel format not supported
• FrameCaptureTimeout - Frame capture timeout
• FrameCaptureFailed - Frame capture failed
• And more covering various error scenarios

Benefits

Convenience

• One-time Setup: Configure error handling globally instead of per provider instance
• Implementation Access: CCAP internal code can easily access and invoke error callbacks
• Consistent Handling: All camera operations use the same error reporting mechanism

Updated Examples

All desktop examples now demonstrate the global callback approach:

• C++ examples use ccap::setErrorCallback()
• C examples use ccap_set_error_callback()
• Consistent error handling patterns across all examples

Implementation Details

Error Reporting Integration

• Added error reporting calls throughout Linux (V4L2) and Windows (DirectShow) implementations
• Global callbacks are triggered for device discovery failures, open failures, start failures, etc.
• Maintains backward compatibility for existing error handling through return values

Thread Safety

• Global callback storage protected by std::mutex
• Thread-local storage ensures thread safety for C interface string returns
• Exception handling prevents user callback errors from crashing the library

Documentation Updates

• Updated README.md with global callback examples for both C++ and C interfaces
• Enhanced C_Interface.md documentation with detailed error handling section
• All documentation now reflects the simplified global approach

Testing

• ✅ All existing functionality preserved and working
• ✅ Global error callbacks working correctly for both C++ and C interfaces
• ✅ Error code to string conversion working
• ✅ Thread safety validated
• ✅ Exception safety in callbacks validated
• ✅ Cross-platform compatibility maintained
• ✅ All examples updated and building successfully

This enhancement significantly simplifies error handling setup while providing the same detailed error information, making the library more convenient to use and integrate.

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[wysaid]

The current implementation differs from my expectations. I want the error callback to be configured globally, not per provider. With a globally configured callback, the CCAP implementation can access and invoke it more conveniently, not limited to provider members. Additionally, some examples in the examples directory currently omit this error callback; please add it to all of them.
@copilot

[Copilot]

The current implementation differs from my expectations. I want the error callback to be configured globally, not per provider. With a globally configured callback, the CCAP implementation can access ...

I've implemented the global error callback system as requested. The changes include:

Global Error Callback Functions:

• C++: ccap::setGlobalErrorCallback() and ccap::getGlobalErrorCallback()
• C: ccap_set_global_error_callback()

All Examples Updated:

• Removed per-provider error callbacks from all 8 desktop examples
• Added global error callback setup to each example
• All examples now use the global approach consistently

Thread-Safe Implementation:

• Global callback storage with mutex protection
• Error reporting throughout the CCAP implementation now uses the global callback
• Maintains backward compatibility while providing the convenience you requested

The global callback is now accessible from all CCAP implementation code without being limited to specific provider instances. Commit: 425c680

[wysaid]

Go on; remove the "global" keyword from your naming, do not use "setGlobalErrorCallback"; use "setErrorCallback" instead. The C interface does the same. @copilot

[Copilot]

Go on; remove the "global" keyword from your naming, do not use "setGlobalErrorCallback"; use "setErrorCallback" instead. The C interface does the same. @copilot

I've removed the "global" keyword from all error callback function names as requested:

C++ Interface:

• setGlobalErrorCallback() → setErrorCallback()
• getGlobalErrorCallback() → getErrorCallback()

C Interface:

• ccap_set_global_error_callback() → ccap_set_error_callback()

Updated all header files, implementations, examples, and documentation. The functionality remains exactly the same - only the naming has been simplified. Build verification successful.

Commit: d2300cf

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