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[Fix] (DirectGLES): apply the read buffer when one FBO is bound as both draw and read

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- SyncCurrentFBO skips the READ-target pass when the same GL FBO is bound as
  both draw and read (the common GL_FRAMEBUFFER case), but the read buffer
  (glReadBuffer) is only applied inside SyncToBackend's READ path — so the skip
  silently dropped every glReadBuffer change, leaving the backend read buffer
  stuck at COLOR_ATTACHMENT0.
- Extract the read-buffer application into BackendFramebufferObject::
  SyncReadBufferToBackend and invoke it from the skip branch (target == Read)
  as well as from SyncToBackend, so reads always target the right attachment.
- Bind the backend FBO as READ inside the helper before glReadBuffer, since the
  skip path only bound it as DRAW.
- Fixes KHR-GL3x.draw_buffers.draw_buffers_1 (reading COLOR_ATTACHMENT1 while
  the FBO stays GL_FRAMEBUFFER-bound returned attachment 0's value); the render
  was already correct, only the readback resolved the wrong attachment.
This commit is contained in:
swung0x48
2026-07-21 12:18:55 -04:00
parent 3049c4b82b
commit bc2d698b3e
3 changed files with 40 additions and 10 deletions
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MobileGL/MG_Backend/DirectGLES/Managers.cpp
+24 -10
View File
@@ -2535,6 +2535,28 @@ namespace MobileGL::MG_Backend::DirectGLES {
return false;
}
void BackendFramebufferObject::SyncReadBufferToBackend(
const SharedPtr<MG_State::GLState::FramebufferObject>& stateFBOObject) {
if (!stateFBOObject) {
return;
}
auto frontendReadBuf = stateFBOObject->GetReadBuffer();
if (frontendReadBuf == m_frontendReadBuffer) {
return;
}
m_frontendReadBuffer = frontendReadBuf;
GLenum glBackendReadBuffer = GetBackendAttachmentType(frontendReadBuf);
if (m_backendReadBuffer != glBackendReadBuffer) {
m_backendReadBuffer = glBackendReadBuffer;
// glReadBuffer targets whatever FBO is bound to GL_READ_FRAMEBUFFER. When this is
// reached from SyncCurrentFBO's "same FBO as draw" skip path the backend FBO was
// only bound as DRAW, so bind it as READ first to route the read buffer correctly.
Bind(FramebufferTarget::Read);
g_GLESFuncs.glReadBuffer(glBackendReadBuffer);
}
}
void BackendFramebufferObject::SyncToBackend(
const SharedPtr<MG_State::GLState::FramebufferObject>& stateFBOObject, FramebufferTarget asTarget) {
#ifdef TRACY_ENABLE
@@ -2616,16 +2638,8 @@ namespace MobileGL::MG_Backend::DirectGLES {
// 2. Remap read buffer. glReadBuffer writes the READ-bound FBO's state, so
// only apply (and stamp the memo) when this object is bound as READ.
auto frontendReadBuf = stateFBOObject->GetReadBuffer();
if (frontendReadBuf != m_frontendReadBuffer && asTarget == FramebufferTarget::Read) {
m_frontendReadBuffer = frontendReadBuf;
GLenum glBackendReadBuffer = GetBackendAttachmentType(frontendReadBuf);
if (m_backendReadBuffer != glBackendReadBuffer) {
m_backendReadBuffer = glBackendReadBuffer;
g_GLESFuncs.glReadBuffer(glBackendReadBuffer);
}
if (asTarget == FramebufferTarget::Read) {
SyncReadBufferToBackend(stateFBOObject);
}
// -------------------- Attach texture to backend FBO -----------------------