kc3-lang/angle

2025-03-03T16:43:33

Reland "Dont use Subject/Observer for SwapchainImageChanged" This is reland of the following CL https://chromium-review.googlesource.com/c/angle/angle/+/6319893 Because we do deferred ANI (VkAcquireNextImage) call until image is needed, we need a way to force Context to go through FramebufferVk::syncState call (FramebufferVk::syncState calls WindowSurfaceVk::getAttachmentRenderTarget, which end up calling ANI. Right now we uses subject/observer mechanism, by sending angle::SubjectMessage::SwapchainImageChanged to all observers of WindowSurfaceVk. In this case it is egl::Surface. Then eglSurface redirects this message to its observers, which are all gl::Framebuffer's attachments: color, depth, stencil. Even though only color attachment needs to be notified, but because we don't have a separate list of observers, depth/stencil attachment also receive the notification and they early out. Then gl::Framebuffer sets DIRTY_BIT_COLOR_BUFFER_CONTENTS_0 dirty bit and send the angle::SubjectMessage::DirtyBitsFlagged to Context, which dirty DrawFBO and ReadFBO and dirty cached state. Note that this is specific for swap image changed case, there is no surface property change (surface property change will still trigger the subject/observer message with SubjectMessage::SubjectChanged message, but this occurs rarely). This gets worse for apps that uses multiple contexts, for the example pokemon_masters_ex has three contexts, each context has its own default frame buffer that attach to the same surface, and we never remove non-current context from the observer list. This end up with egl::Surface has 12 observers and for every frame, it loop over the list of 12 observers and send message (virtual function call) to each of them. Color attachment also ends up sending two messages to Context, one for Read FBO and another for Draw FBO. There are total 21 virtual function calls. Even for single context usage, you have 6 virtual function calls, for every frame. EGL spec says "an EGLSurface must be current on only one thread at a time", any other context must call EGLMakeCurrent in order to use this surface, which will add all necessary dirty bits at that time. So we really only need to notify current context. In this CL, SwapchainImageChanged no longer uses subject/observer mechanism, so this message is removed. This CL still uses subject/observer mechanism to send DirtyBitsFlagged from Framebuffer back to context. We could call setDrawFramebufferDirty and setReadFramebufferDirty directly, but that will require to remove the "const" decoration out of gl::Context which generates too much code diff, so onStateChange(angle::SubjectMessage::DirtyBitsFlagged) is still used. Bug: angleproject:400711938 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/6319893 Commit-Queue: Charlie Lao <cclao@google.com> Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org> Reviewed-by: Yuxin Hu <yuxinhu@google.com> Change-Id: I017b0e8934b5194a520828fa5c4af1d6e3ef9aac Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/6404621