fix: improve VLC engine detection and null safety

[kt286]

• Add null pointer safety guards for m_qvplayer in all VLC player methods
• Replace inline VLC library detection with DynamicLibraries singleton
• Set playback engine type to VLC when dynamic libraries load successfully

fix: 优化VLC引擎检测和空值安全

• 在所有VLC播放器方法中为m_qvplayer添加空指针安全保护
• 使用DynamicLibraries单例替换内联VLC库检测
• 当动态库加载成功时设置播放引擎类型为VLC

Summary by Sourcery

Improve VLC playback initialization and resilience when the VLC player or libraries are unavailable.

Bug Fixes:

• Prevent VLC player operations from dereferencing an unavailable player instance by adding null-safe fallback behavior.

Enhancements:

• Centralize VLC availability detection through the DynamicLibraries singleton and set the playback engine to VLC after successful library initialization.

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[deepin-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: kt286

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[sourcery-ai]

Reviewer's Guide

This PR centralizes VLC engine detection through the DynamicLibraries singleton and makes the VLC player more robust by adding null-pointer guards around m_qvplayer usage, while ensuring the playback engine type is correctly set to VLC on successful dynamic library initialization.

Sequence diagram for playback engine initialization via DynamicLibraries

sequenceDiagram
    participant DmGlobal
    participant DynamicLibraries

    DmGlobal->>DmGlobal: initPlaybackEngineType()
    DmGlobal->>DynamicLibraries: instance()
    activate DynamicLibraries
    DynamicLibraries->>DynamicLibraries: DynamicLibraries()
    alt [dynamic libraries load failed]
        DynamicLibraries->>DmGlobal: setPlaybackEngineType(0)
    else [dynamic libraries load succeed]
        DynamicLibraries->>DmGlobal: setPlaybackEngineType(1)
    end
    deactivate DynamicLibraries
    DmGlobal->>DmGlobal: engineType used in logging

Loading

File-Level Changes

Change	Details	Files
Use DynamicLibraries singleton to drive playback engine detection instead of inline library checks.	Include core/dynamiclibraries.h in the global module. Replace OS-specific libExist-based VLC/FFmpeg detection logic in initPlaybackEngineType() with a call to DynamicLibraries::instance(), relying on that singleton to set engineType. Adjust logging in initPlaybackEngineType() to report the final engineType value rather than branch-specific messages.	src/libdmusic/global.cpp
Harden VlcPlayer against null m_qvplayer and improve initialization flow for CDA and playback operations.	After init() calls in VlcPlayer methods, add early-return guards when m_qvplayer is null to avoid dereferencing it. Ensure play(), time(), length(), and equalizer-related methods safely handle cases where the underlying VLC player is unavailable, returning default values where needed. In startCdaThread(), verify m_qvplayer after init() before wiring the CDA thread to the media player core.	src/libdmusic/player/vlcplayer.cpp
Set playback engine type to VLC when dynamic libraries initialize successfully.	In DynamicLibraries constructor, set DmGlobal::engineType to 1 (VLC) when dynamic libraries load without errors, instead of only logging success.	src/libdmusic/core/dynamiclibraries.cpp

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[deepin-bot]

TAG Bot

New tag: 7.0.63
DISTRIBUTION: unstable
Suggest: synchronizing this PR through rebase #762

[deepin-bot]

TAG Bot

New tag: 7.0.64
DISTRIBUTION: unstable
Suggest: synchronizing this PR through rebase #765

[deepin-bot]

TAG Bot

New tag: 7.0.65
DISTRIBUTION: unstable
Suggest: synchronizing this PR through rebase #768

[deepin-bot]

TAG Bot

New tag: 7.0.66
DISTRIBUTION: unstable
Suggest: synchronizing this PR through rebase #779