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[Fix, Test] (MG_Impl/GLImpl): an indexed buffer SIZE query reports the range that was asked for, not what the buffer currently holds

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swung0x48
2026-08-11 20:43:28 -04:00
parent 05bef7118b
commit 6dd0201bf2
2 changed files with 61 additions and 6 deletions
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MobileGL/MG_Impl/GLImpl/Getter/GL_Getter.cpp
+9 -6
View File
@@ -722,10 +722,14 @@ namespace MobileGL::MG_Impl::GLImpl {
*data = 0;
return;
}
// GL 4.6 core table 23.4/23.5: *_BUFFER_SIZE reports the size glBindBufferRange
// was ASKED for, verbatim. It is not clamped to the buffer's storage, and it does
// not follow the buffer when a later glBufferData resizes it - a range may legally
// name bytes the buffer does not have yet. Clamping it here answered 0 for the
// common conformance shape of binding a range on a buffer that has no storage
// yet (KHR-GL43.shader_storage_buffer_object.basic-binding).
const Range1D range = bindingPoint.GetRange();
const auto start = std::min(range.start, bufferObject->GetSize());
const auto end = std::min(range.end, bufferObject->GetSize());
*data = static_cast<GLint>(end - start);
*data = static_cast<GLint>(range.end - range.start);
return;
}
default:
@@ -951,9 +955,8 @@ namespace MobileGL::MG_Impl::GLImpl {
*data = 0;
return;
}
const auto start = std::min(range.start, bufferObject->GetSize());
const auto end = std::min(range.end, bufferObject->GetSize());
*data = static_cast<GLint64>(end - start);
// Verbatim, unclamped - see the GetIntegeri_v arm.
*data = static_cast<GLint64>(range.end - range.start);
return;
}
default:
MobileGL/MG_Test/Buffer/BufferTest.cpp
+52
View File
@@ -480,6 +480,58 @@ TEST_F(BufferTest, BindBufferRangeZeroUnbindsBindingPoint) {
EXPECT_EQ(MobileGL::MG_Impl::GLImpl::GetError(), GL_NO_ERROR);
}
// GL 4.6 core tables 23.4/23.5: *_BUFFER_START and *_BUFFER_SIZE report the (offset, size) pair
// glBindBufferRange was ASKED for. They are not clamped to the buffer's storage - a range may
// legally name bytes the buffer does not have, and glBufferData may resize the buffer afterwards
// without the binding's reported window moving. The size arm used to intersect the recorded range
// with the buffer's current size, so binding a range on a still-empty buffer (glGenBuffers with no
// glBufferData - exactly what KHR-GL43.shader_storage_buffer_object.basic-binding does) answered 0
// while START still answered the offset, an internally inconsistent pair no driver reports.
TEST_F(BufferTest, IndexedBufferSizeQueryReportsTheRequestedSizeNotTheBuffersStorage) {
GLint ssboAlignment = 0;
MobileGL::MG_Impl::GLImpl::GetIntegerv(GL_SHADER_STORAGE_BUFFER_OFFSET_ALIGNMENT, &ssboAlignment);
ASSERT_GT(ssboAlignment, 0);
const GLintptr offset = ssboAlignment;
const GLsizeiptr size = 512;
GLuint buffer = 0;
MobileGL::MG_Impl::GLImpl::GenBuffers(1, &buffer);
// Deliberately no glBufferData: the name exists, the storage does not.
MobileGL::MG_Impl::GLImpl::BindBufferRange(GL_SHADER_STORAGE_BUFFER, 1, buffer, offset, size);
ASSERT_EQ(MobileGL::MG_Impl::GLImpl::GetError(), GL_NO_ERROR);
GLint start32 = 0;
GLint size32 = 0;
GLint64 start64 = 0;
GLint64 size64 = 0;
MobileGL::MG_Impl::GLImpl::GetIntegeri_v(GL_SHADER_STORAGE_BUFFER_START, 1, &start32);
MobileGL::MG_Impl::GLImpl::GetIntegeri_v(GL_SHADER_STORAGE_BUFFER_SIZE, 1, &size32);
MobileGL::MG_Impl::GLImpl::GetInteger64i_v(GL_SHADER_STORAGE_BUFFER_START, 1, &start64);
MobileGL::MG_Impl::GLImpl::GetInteger64i_v(GL_SHADER_STORAGE_BUFFER_SIZE, 1, &size64);
EXPECT_EQ(start32, static_cast<GLint>(offset));
EXPECT_EQ(size32, static_cast<GLint>(size));
EXPECT_EQ(start64, static_cast<GLint64>(offset));
EXPECT_EQ(size64, static_cast<GLint64>(size));
// Giving the buffer storage afterwards does not move the window either way.
MobileGL::MG_Impl::GLImpl::BindBuffer(GL_SHADER_STORAGE_BUFFER, buffer);
MobileGL::MG_Impl::GLImpl::BufferData(GL_SHADER_STORAGE_BUFFER, offset + size, nullptr, GL_DYNAMIC_DRAW);
MobileGL::MG_Impl::GLImpl::GetIntegeri_v(GL_SHADER_STORAGE_BUFFER_SIZE, 1, &size32);
EXPECT_EQ(size32, static_cast<GLint>(size));
// glBindBufferBase binds the whole buffer and reports (0, 0), not the buffer's size.
MobileGL::MG_Impl::GLImpl::BindBufferBase(GL_SHADER_STORAGE_BUFFER, 1, buffer);
MobileGL::MG_Impl::GLImpl::GetIntegeri_v(GL_SHADER_STORAGE_BUFFER_START, 1, &start32);
MobileGL::MG_Impl::GLImpl::GetIntegeri_v(GL_SHADER_STORAGE_BUFFER_SIZE, 1, &size32);
EXPECT_EQ(start32, 0);
EXPECT_EQ(size32, 0);
MobileGL::MG_Impl::GLImpl::BindBufferBase(GL_SHADER_STORAGE_BUFFER, 1, 0);
MobileGL::MG_Impl::GLImpl::BindBuffer(GL_SHADER_STORAGE_BUFFER, 0);
MobileGL::MG_Impl::GLImpl::DeleteBuffers(1, &buffer);
EXPECT_EQ(MobileGL::MG_Impl::GLImpl::GetError(), GL_NO_ERROR);
}
TEST_F(BufferTest, GetInteger64vMaxShaderStorageBlockSize) {
GLint64 maxSsboBlockSize = 0;
MobileGL::MG_Impl::GLImpl::GetInteger64v(GL_MAX_SHADER_STORAGE_BLOCK_SIZE, &maxSsboBlockSize);