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Add a global mutex to serialize PAGDecoder frame rendering across shared EGL contexts. #3565

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Add a global mutex to serialize PAGDecoder frame rendering across shared EGL contexts. #3565

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3 changes: 3 additions & 0 deletions src/rendering/PAGDecoder.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -30,6 +30,8 @@

namespace pag {

static std::mutex renderLocker = {};

@shlzxjp shlzxjp Jul 15, 2026

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建议从根本上解决而非打补丁规避。真正的根因在于渲染引擎（tgfx）层：多个 PAGDecoder 各自 GLDevice::Make(sharedContext) 创建的 EGLContext 共享同一命名空间，缺乏对并发 GL 访问的保护，低端驱动才会错乱。

在 PAGDecoder 层加一把全局锁只是把并发压平为串行来规避问题，存在两个固有缺陷：

  1. 进程内所有 decoder 的首帧渲染被完全串行化，即使分属不相干的 context/业务，多视图首屏耗时线性叠加；
  2. 无法覆盖其他同样使用 GLDevice::Make(currentContext) 的并发 GL 路径（如 StillImage 等），本 PR 也未保护 reader 销毁（reader = nullptr）时的 GL 对象释放——它在锁作用域之外，仍与其他 decoder 的 renderFrame 并发。

根治方向：在 tgfx GLDevice 层对共享命名空间的并发访问做 per-context 锁 + makeCurrent 纪律，从渲染引擎层根除，让所有上层调用方自动受益，而非在每个调用点各自打补丁。


static std::string DefaultCacheKeyGeneratorFunc(PAGDecoder* decoder,
std::shared_ptr<PAGComposition> composition) {
if (!composition->isPAGFile() || pag::ContentVersion::Get(composition) > 0) {
Expand Down Expand Up @@ -196,6 +198,7 @@ bool PAGDecoder::readFrameInternal(int index, std::shared_ptr<BitmapBuffer> bitm
}
auto success = sequenceFile->readFrame(index, bitmap);
if (!success) {
std::lock_guard<std::mutex> autoLock(renderLocker);
success = renderFrame(composition, index, bitmap);
if (success) {
success = sequenceFile->writeFrame(index, bitmap);
Expand Down
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