Add element preview (images/videos/audio), video speed/loop props, and preview toggle

[yuto-trd]

Description

Implement element preview functionality with support for images, videos, and audio waveforms. Enhance video rendering and introduce a mechanism for preview invalidation. Add properties for speed and loop configuration in video sources, and provide a toggle to disable previews.

Breaking changes

None.

Fixed issues

None.

[chatgpt-codex-connector]

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[Copilot]

Pull request overview

This PR implements a comprehensive element preview system for the Beutl application, adding visual feedback for video (thumbnails) and audio (waveforms) elements in the timeline. The implementation includes new custom controls for rendering previews,ViewModel integration for managing preview data, serialization support for preview preferences, and operator implementations that provide preview data through a new interface. Additionally, video sources now support speed and loop properties.

Key Changes

• Added IElementPreviewProvider interface with implementations in SourceVideoOperator and SourceSoundOperator to generate thumbnails and waveform data respectively
• Introduced WaveformControl and ThumbnailStripControl custom Avalonia controls to render audio waveforms and video thumbnails in the timeline
• Extended ElementViewModel with preview management logic including cancellation, throttling, and invalidation handling

Reviewed changes

Copilot reviewed 18 out of 19 changed files in this pull request and generated 12 comments.

Show a summary per file

File	Description
src/Beutl/Views/WaveformControl.cs	New control for rendering audio waveform visualization with thread-safe chunk updates
src/Beutl/Views/ThumbnailStripControl.cs	New control for rendering video thumbnail strips with proper bitmap disposal
src/Beutl/Views/ElementView.axaml.cs	Wires up preview controls to ElementViewModel events for thumbnail and waveform updates
src/Beutl/Views/ElementView.axaml	Adds preview controls to the UI and toggle menu item for disabling previews
src/Beutl/ViewModels/TimelineViewModel.cs	Adds persistence of preview-disabled elements state to/from JSON
src/Beutl/ViewModels/ElementViewModel.cs	Core preview management logic with async loading, cancellation, and event handling
src/Beutl.ProjectSystem/SceneComposer.cs	Adds explicit ClearSounds() call to prevent audio accumulation
src/Beutl.ProjectSystem/Operation/IElementPreviewProvider.cs	New interface defining preview generation contract for operators
src/Beutl.Operators/Source/SourceVideoOperator.cs	Implements video thumbnail generation and preview invalidation tracking
src/Beutl.Operators/Source/SourceSoundOperator.cs	Implements audio waveform chunk generation with proper audio composing
src/Beutl.Operators/Source/SourceImageOperator.cs	Minor UTF-8 BOM fix (no functional changes)
src/Beutl.Language/Strings*.resx	Adds localized strings for the "Disable Preview" toggle option
src/Beutl.Language/Strings.Designer.cs	Generated code for new localization strings
src/Beutl.Engine/Properties/AssemblyInfo.cs	Grants InternalsVisibleTo access to Beutl.Operators assembly
src/Beutl.Engine/Graphics/SourceVideo.cs	Adds Speed and IsLoop properties, exposes internal DrawInternal method for thumbnail rendering
src/Beutl.Engine/Engine/EngineObject.cs	Changes reflection cache to use concurrent collections for thread safety
src/Beutl.Engine/Audio/Composing/Composer.cs	Makes AddSound and ClearSounds public, removes automatic clearing
src/Beutl.Engine.SourceGenerators/EngineObjectResourceGenerator.cs	Wraps disposal logic in if (disposing) block and fixes indentation

Files not reviewed (1)

• src/Beutl.Language/Strings.Designer.cs: Language not supported

Comments suppressed due to low confidence (2)

src/Beutl/ViewModels/ElementViewModel.cs:662

• Poor error handling: empty catch block.

        catch (OperationCanceledException)
        {
        }

src/Beutl/ViewModels/ElementViewModel.cs:665

• Poor error handling: empty catch block.

        catch
        {
        }

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[github-actions]

No TODO comments were found.

[github-actions]

Package	Line Rate	Branch Rate	Complexity	Health
Beutl.Operators	3%	0%	140	➖
Beutl.Core	34%	31%	3144	➖
Beutl.Engine	27%	24%	9892	➖
Beutl.Threading	100%	94%	118	✔
Beutl.Utilities	73%	67%	358	➖
Beutl.Configuration	38%	19%	282	➖
Beutl.Extensibility	2%	0%	105	➖
Beutl.ProjectSystem	17%	10%	1867	➖
Beutl.Language	0%	0%	659	➖
Summary	27% (10575 / 39487)	25% (2815 / 11277)	16565	➖

Minimum allowed line rate is 0%