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[Feat] (MG_Impl, MG_State): implement the direct state access transform feedback API

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glCreateTransformFeedbacks, glTransformFeedbackBufferBase, glTransformFeedbackBufferRange
and the three glGetTransformFeedback* queries were all stubs, so a transform feedback
object could only be configured and inspected by binding it first - the exact thing
direct state access exists to avoid. The queries were the worse half: they returned
nothing and raised no error, so an application could not tell that it had learned
nothing.

glCreateTransformFeedbacks creates the objects outright. glGenTransformFeedbacks only
reserves names, and a reserved name becomes an object when it is first bound
(GL 4.6 core 13.2.1); the DSA form has no bind step to create them from.

The queries and the buffer bindings read and write a named object's state. That state
lives in two places: the context keeps one live copy of the capture bindings and the
active/paused flags for whichever object is bound, and every other object's copy sits in
its saved state until a bind swaps it in. The by-name accessors added to the context
resolve that, so a query for the bound object reads the live copy rather than a stale
save.

GL_TRANSFORM_FEEDBACK_BUFFER_START and _SIZE are answered as zero unless the binding was
made by the range form, matching what the buffer object binding points already do.

Takes direct_state_access.xfb_* from 0 to 4 of 5 on both backends; xfb_functional still
fails on the capture itself, which is a separate defect.
This commit is contained in:
BZLZHH
2026-08-05 02:16:48 +00:00
parent 42fd02d82f
commit dac02ca044
6 changed files with 258 additions and 6 deletions
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MobileGL/MG_State/GLState/Core.h
+19
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@@ -45,6 +45,14 @@ namespace MobileGL {
// translates the result into its own API call.
VertexAttribTypeInfo ClassifyVertexAttribType(GLenum glType);
// One indexed capture binding of a transform feedback object, as the by-name queries
// report it. An empty Buffer means the binding point is unbound.
struct NamedTransformFeedbackBinding {
SharedPtr<BufferObject> Buffer;
Range1D Range{};
Bool HasExplicitRange = false;
};
class GLContext {
public:
GLContext() = default;
@@ -299,6 +307,17 @@ namespace MobileGL {
// cannot express: an empty completed span is legal and draws nothing.
Bool HasTransformFeedbackCompletedSpan(Uint index) const;
// The by-name (direct state access) view. A named object that happens to be the
// bound one is answered from the live copy, since that is where its state actually
// is until a bind swaps it out.
void CreateTransformFeedbackObject(Uint index);
Bool IsNamedTransformFeedbackActive(Uint index) const;
Bool IsNamedTransformFeedbackPaused(Uint index) const;
NamedTransformFeedbackBinding GetNamedTransformFeedbackBinding(Uint index, Uint bufferIndex) const;
void SetNamedTransformFeedbackBinding(Uint index, Uint bufferIndex,
const SharedPtr<BufferObject>& buffer, Range1D range,
Bool hasExplicitRange);
// Framebuffer
void GenFramebufferNames(Uint number, Vector<Uint>& framebuffers);
const SharedPtr<FramebufferObject>& GetFramebufferObject(Uint index);