fix(hdr): re-anchor SDR white before HDR encoding

[qiin2333]

改了啥呀

• 把客户端/主机 SDR 白点比值抽成统一的线性 scRGB 预编码变换，PQ 与 HLG 共用同一条路径
• 从当前物理输出读取 Windows SDR reference white；VDD 有 producer metadata 时优先使用，并与光标常量缓冲状态解耦
• 用对数亮度区间平滑回落增益，保证 0.5–2.5 倍范围内映射严格单调，不再出现亮度反转
• 让全帧、未缩放和缩放分析都复用编码前变换，使 HDR10+、HDR Vivid 与 Dolby Vision 元数据描述实际编码像素
• 允许加密 PQ/HLG 会话在运行中更新客户端白点，不重建显示器或编码器

为啥要改

PQ 是绝对亮度编码，主机 scRGB 桌面的 SDR band 却锚定在主机自己的 Windows SDR 白点。客户端白点没参与换算时，普通桌面内容会被送进错误的绝对亮度，怎么调 PQ 参数都只是在错误基准上继续调，结果就是那种白茫茫的杂鱼画面啦。

这次在进入 PQ/HLG OETF 前完成重锚，同时让动态元数据分析看到同一份变换后的像素。旧客户端没有上报白点时保持原行为；SDR 会话和其他客户端路径不受影响。

配套 Moonlight 客户端修复：qiin2333/moonlight-qt#203

验证

• cmake --preset dev-win -DBUILD_TESTS=ON -DBUILD_WEB_UI=OFF -DFETCH_GUI=OFF -DSUNSHINE_ENABLE_TRAY=OFF -DCMAKE_BUILD_TYPE=Release
• ninja -C build -j 6 sunshine tests/test_sunshine.exe
• 93 个 HDR10+/HDR Vivid/Dolby Vision/动态白点相关测试通过
• 24 个 PQ、HLG 与 HDR analysis shader 变体通过 FXC 编译
• 白点增益 0.5–2.5 数值扫描无亮度反转
• git diff --check origin/master...HEAD

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Reviewing files that changed from the base of the PR and between 4eb2095 and f00653c.

⛔ Files ignored due to path filters (6)

• src_assets/windows/assets/shaders/directx/hdr_luminance_analysis_cs.hlsl is excluded by !**/*.hlsl
• src_assets/windows/assets/shaders/directx/include/convert_hybrid_log_gamma_base.hlsl is excluded by !**/*.hlsl
• src_assets/windows/assets/shaders/directx/include/convert_perceptual_quantizer_base.hlsl is excluded by !**/*.hlsl
• src_assets/windows/assets/shaders/directx/include/convert_yuv420_nv12p010_cs_base.hlsl is excluded by !**/*.hlsl
• src_assets/windows/assets/shaders/directx/include/convert_yuv420_nv12p010_cs_scaled_base.hlsl is excluded by !**/*.hlsl
• src_assets/windows/assets/shaders/directx/include/hdr_pre_encode_transform.hlsl is excluded by !**/*.hlsl

📒 Files selected for processing (5)

• src/platform/common.h
• src/platform/windows/display.h
• src/platform/windows/display_base.cpp
• src/platform/windows/display_vram.cpp
• src/stream.cpp

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• GitHub Check: Windows

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📓 Path-based instructions (2)

平台抽象层代码（Windows/Linux/macOS）。确保各平台实现一致， 注意 Windows API 调用的错误处理和资源释放。

⚙️ CodeRabbit configuration file

Files:

• src/platform/common.h
• src/platform/windows/display_base.cpp
• src/platform/windows/display.h
• src/platform/windows/display_vram.cpp

Sunshine 核心 C++ 源码，自托管游戏串流服务器。审查要点：内存安全、 线程安全、RAII 资源管理、安全漏洞。注意预处理宏控制的平台相关代码。

⚙️ CodeRabbit configuration file

Files:

• src/platform/common.h
• src/platform/windows/display_base.cpp
• src/stream.cpp
• src/platform/windows/display.h
• src/platform/windows/display_vram.cpp

🔇 Additional comments (2)

src/stream.cpp (1)

2079-2079: LGTM!

Also applies to: 2089-2090

src/platform/windows/display_vram.cpp (1)

738-738: 🩺 Stability & Availability

无需为 clientSdrWhiteNits 增加并发同步。

动态参数处理和 session->convert(*img) 都在同一视频线程中顺序执行。当前调用路径不会并发读写 hdr_pre_encode.clientSdrWhiteNits。

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Summary by CodeRabbit

• 新功能

  • 改进 Windows HDR 显示处理，支持更准确地识别和应用显示器 SDR 白电平。
  • HDR 预处理现统一支持 HDR10（PQ）与 HLG，提升不同 HDR 内容的显示一致性。
  • 捕获链路可优先使用来源设备提供的 SDR 白电平信息。

• 问题修复

  • 加密 HDR 会话现可正确应用 HDR 转换参数，不再局限于 HLG 模式。
  • 更新相关说明，使 HDR 转换与显示行为描述更加准确。

Walkthrough

本次变更新增 Windows SDR 白电平查询和缓存。捕获白点优先使用生产者元数据。HDR 预编码流程现在同时支持 PQ 和 HLG。客户端 SDR 白点更新适用于所有加密 HDR 动态范围。

Changes

HDR 白电平处理

Layer / File(s)	Summary
显示器 SDR 白电平查询与捕获白点 src/platform/windows/display.h, src/platform/windows/display_base.cpp, src/platform/windows/display_vram.cpp	display_base_t 记录选定输出并查询缓存的 DisplayConfig SDR 白电平。display_vram_t 优先使用生产者白电平，其次使用显示器查询值，最后回退到 300 尼特。光标生产者白电平会单独保存。
PQ/HLG 预编码与分析派发 src/platform/windows/display_vram.cpp, src/platform/common.h	HlgDisplayParams 和相关函数统一为 HDR 预编码结构与流程。预编码现在支持 PQ 和 HLG。HDR 分析使用统一输入源，并绑定预编码常量缓冲。相关注释改为 HDR 术语。
HDR 会话白点更新 src/stream.cpp	CLIENT_SDR_WHITE_NITS 更新仅在 SDR 动态范围时拒绝。所有加密 HDR 动态范围均可更新该参数。

Estimated code review effort: 4 (Complex) | ~45 minutes

Merge Risk: ⚪ Minimal · up to f0065

The PR re-anchors HDR encoding to the client SDR white point while keeping updates authenticated and isolated to the active session. No actionable merge-blocking risk remains after normal checks and review.

Sequence Diagram(s)

sequenceDiagram
  participant 加密HDR会话
  participant stream.cpp
  participant display_vram_t
  participant display_base_t
  participant QueryDisplayConfig
  加密HDR会话->>stream.cpp: 更新 CLIENT_SDR_WHITE_NITS
  stream.cpp->>display_vram_t: 设置客户端 SDR 白点
  display_vram_t->>display_vram_t: 读取生产者 SDR 白点
  display_vram_t->>display_base_t: 查询显示器 SDR 白点
  display_base_t->>QueryDisplayConfig: 查询活动显示路径
  QueryDisplayConfig-->>display_base_t: 返回 SDR 白电平
  display_base_t-->>display_vram_t: 返回缓存值
  display_vram_t->>display_vram_t: 更新 HDR 预编码参数

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Suggested reviewers: yundi339

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 20.83% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 24 functions across 5 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Title check	✅ Passed	标题准确概括了主要变更：在 HDR 编码前重新锚定 SDR 白点。标题简洁、明确，并与 PQ、HLG 共用的预编码变换及 Windows SDR 白点查询逻辑相关。
Description check	✅ Passed	描述与变更内容直接相关。它说明了 SDR 白点重锚定、PQ 与 HLG 共享变换、Windows 输出查询、VDD 元数据优先级、动态更新范围及验证结果。

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