fix(linux): add a lock to PipeWire DMA-BUFs to avoid unexpected buffer overwrite and flicker - #5498

Description

• Added a lock to the pipewire capture buffer, to avoid Kwin overwriting the content of this buffer when we are reading it, causing the video stream to flicker intermittently.
• The lock is correctly released after we made a copy of its content or on error.
• Only implemented for CUDA/NVENC, since this is the only device I have.

Screenshot

Issues Fixed or Closed

• Might be a workaround for Desktop (apps) keeps flickering through game stream #3235

Roadmap Issues

Type of Change

• feat: New feature (non-breaking change which adds functionality)
• fix: Bug fix (non-breaking change which fixes an issue)
• docs: Documentation only changes
• style: Changes that do not affect the meaning of the code (white-space, formatting, missing semicolons, etc.)
• refactor: Code change that neither fixes a bug nor adds a feature
• perf: Code change that improves performance
• test: Adding missing tests or correcting existing tests
• build: Changes that affect the build system or external dependencies
• ci: Changes to CI configuration files and scripts
• chore: Other changes that don't modify src or test files
• revert: Reverts a previous commit
• BREAKING CHANGE: Introduces a breaking change (can be combined with any type above)

Checklist

• Code follows the style guidelines of this project
• Code has been self-reviewed
• Code has been commented, particularly in hard-to-understand areas
• Code docstring/documentation-blocks for new or existing methods/components have been added or updated
• Unit tests have been added or updated for any new or modified functionality

AI Usage

See our AI usage policy.

• None: No AI tools were used in creating this PR
• Light: AI provided minor assistance (formatting, simple suggestions)
• Moderate: AI helped with code generation or debugging specific parts
• Heavy: AI generated most or all of the code changes