rhi: Expose the maximum uniform buffer range limit

Task-number: QTBUG-97715
Change-Id: I7f0a52c410b9b77f735fb3b7fd33141674bb0cda
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Andy Nichols <andy.nichols@qt.io>
(cherry picked from commit a8be40bd64b9258334d6936b1775bc6631fd158d)
Reviewed-by: Laszlo Agocs <laszlo.agocs@qt.io>

8 files changed, 62 insertions, 1 deletions

diff --git a/src/gui/rhi/qrhi.cpp b/src/gui/rhi/qrhi.cpp
index f8b3eab218..4c61aa259b 100644
--- a/src/gui/rhi/qrhi.cpp
+++ b/src/gui/rhi/qrhi.cpp
@@ -767,6 +767,12 @@ Q_LOGGING_CATEGORY(QRHI_LOG_INFO, "qt.rhi.general")
     \value MaxThreadGroupZ The maximum size of a work/thread group in the Z
     dimension. Effectively the maximum value of \c local_size_z in the compute
     shader. Typically 64 or 256.
+
+    \value MaxUniformBufferRange The number of bytes that can be exposed from a
+    uniform buffer to the shaders at once. On OpenGL ES 2.0 and 3.0
+    implementations this may be as low as 3584 bytes (224 four component, 32
+    bits per component vectors). Elsewhere the value is typically 16384 (1024
+    vec4s) or 65536 (4096 vec4s).
  */
 
 /*!
@@ -3208,6 +3214,9 @@ bool QRhiShaderResourceBinding::isLayoutCompatible(const QRhiShaderResourceBindi
     suitable for creating pipelines. Such a pipeline must then always be used
     together with another, layout compatible QRhiShaderResourceBindings with
     resources present passed to QRhiCommandBuffer::setShaderResources().
+
+    \note If the size of \a buf exceeds the limit reported for
+    QRhi::MaxUniformBufferRange, unexpected errors may occur.
  */
 QRhiShaderResourceBinding QRhiShaderResourceBinding::uniformBuffer(
         int binding, StageFlags stage, QRhiBuffer *buf)
@@ -3242,6 +3251,9 @@ QRhiShaderResourceBinding QRhiShaderResourceBinding::uniformBuffer(
     suitable for creating pipelines. Such a pipeline must then always be used
     together with another, layout compatible QRhiShaderResourceBindings with
     resources present passed to QRhiCommandBuffer::setShaderResources().
+
+    \note If \a size exceeds the limit reported for QRhi::MaxUniformBufferRange,
+    unexpected errors may occur.
  */
 QRhiShaderResourceBinding QRhiShaderResourceBinding::uniformBuffer(
         int binding, StageFlags stage, QRhiBuffer *buf, int offset, int size)
@@ -3276,6 +3288,9 @@ QRhiShaderResourceBinding QRhiShaderResourceBinding::uniformBuffer(
     suitable for creating pipelines. Such a pipeline must then always be used
     together with another, layout compatible QRhiShaderResourceBindings with
     resources present passed to QRhiCommandBuffer::setShaderResources().
+
+    \note If \a size exceeds the limit reported for QRhi::MaxUniformBufferRange,
+    unexpected errors may occur.
  */
 QRhiShaderResourceBinding QRhiShaderResourceBinding::uniformBufferWithDynamicOffset(
         int binding, StageFlags stage, QRhiBuffer *buf, int size)
diff --git a/src/gui/rhi/qrhi_p.h b/src/gui/rhi/qrhi_p.h
index 17b170203b..506e36d3ce 100644
--- a/src/gui/rhi/qrhi_p.h
+++ b/src/gui/rhi/qrhi_p.h
@@ -1605,7 +1605,8 @@ public:
         MaxThreadsPerThreadGroup,
         MaxThreadGroupX,
         MaxThreadGroupY,
-        MaxThreadGroupZ
+        MaxThreadGroupZ,
+        MaxUniformBufferRange
     };
 
     ~QRhi();
diff --git a/src/gui/rhi/qrhid3d11.cpp b/src/gui/rhi/qrhid3d11.cpp
index 8e94d70502..ab9d915ece 100644
--- a/src/gui/rhi/qrhid3d11.cpp
+++ b/src/gui/rhi/qrhid3d11.cpp
@@ -576,6 +576,8 @@ int QRhiD3D11::resourceLimit(QRhi::ResourceLimit limit) const
         return D3D11_CS_THREAD_GROUP_MAX_Y;
     case QRhi::MaxThreadGroupZ:
         return D3D11_CS_THREAD_GROUP_MAX_Z;
+    case QRhi::MaxUniformBufferRange:
+        return 65536;
     default:
         Q_UNREACHABLE();
         return 0;
diff --git a/src/gui/rhi/qrhigles2.cpp b/src/gui/rhi/qrhigles2.cpp
index 7d7e8a9226..ad134c7352 100644
--- a/src/gui/rhi/qrhigles2.cpp
+++ b/src/gui/rhi/qrhigles2.cpp
@@ -397,6 +397,22 @@ QT_BEGIN_NAMESPACE
 #define GL_TEXTURE_RECTANGLE              0x84F5
 #endif
 
+#ifndef GL_MAX_VERTEX_UNIFORM_COMPONENTS
+#define GL_MAX_VERTEX_UNIFORM_COMPONENTS  0x8B4A
+#endif
+
+#ifndef GL_MAX_FRAGMENT_UNIFORM_COMPONENTS
+#define GL_MAX_FRAGMENT_UNIFORM_COMPONENTS 0x8B49
+#endif
+
+#ifndef GL_MAX_VERTEX_UNIFORM_VECTORS
+#define GL_MAX_VERTEX_UNIFORM_VECTORS     0x8DFB
+#endif
+
+#ifndef GL_MAX_FRAGMENT_UNIFORM_VECTORS
+#define GL_MAX_FRAGMENT_UNIFORM_VECTORS   0x8DFD
+#endif
+
 /*!
     Constructs a new QRhiGles2InitParams.
 
@@ -678,6 +694,23 @@ bool QRhiGles2::create(QRhi::Flags flags)
 
     caps.texture3D = caps.ctxMajor >= 3; // 3.0
 
+    // The ES 2.0 spec only has MAX_xxxx_VECTORS. ES 3.0 and up has both
+    // *VECTORS and *COMPONENTS. OpenGL 2.0-4.0 only has MAX_xxxx_COMPONENTS.
+    // 4.1 and above has both. What a mess.
+    if (caps.gles) {
+        GLint maxVertexUniformVectors = 0;
+        f->glGetIntegerv(GL_MAX_VERTEX_UNIFORM_VECTORS, &maxVertexUniformVectors);
+        GLint maxFragmentUniformVectors = 0;
+        f->glGetIntegerv(GL_MAX_FRAGMENT_UNIFORM_VECTORS, &maxFragmentUniformVectors);
+        caps.maxUniformVectors = qMin(maxVertexUniformVectors, maxFragmentUniformVectors);
+    } else {
+        GLint maxVertexUniformComponents = 0;
+        f->glGetIntegerv(GL_MAX_VERTEX_UNIFORM_COMPONENTS, &maxVertexUniformComponents);
+        GLint maxFragmentUniformComponents = 0;
+        f->glGetIntegerv(GL_MAX_FRAGMENT_UNIFORM_COMPONENTS, &maxFragmentUniformComponents);
+        caps.maxUniformVectors = qMin(maxVertexUniformComponents, maxFragmentUniformComponents) / 4;
+    }
+
     if (!caps.gles) {
         f->glEnable(GL_VERTEX_PROGRAM_POINT_SIZE);
         f->glEnable(GL_POINT_SPRITE);
@@ -1105,6 +1138,8 @@ int QRhiGles2::resourceLimit(QRhi::ResourceLimit limit) const
         return caps.maxThreadGroupsY;
     case QRhi::MaxThreadGroupZ:
         return caps.maxThreadGroupsZ;
+    case QRhi::MaxUniformBufferRange:
+        return int(qMin<qint64>(INT_MAX, caps.maxUniformVectors * qint64(16)));
     default:
         Q_UNREACHABLE();
         return 0;
diff --git a/src/gui/rhi/qrhigles2_p_p.h b/src/gui/rhi/qrhigles2_p_p.h
index 4d18e9c60f..6dcf374b90 100644
--- a/src/gui/rhi/qrhigles2_p_p.h
+++ b/src/gui/rhi/qrhigles2_p_p.h
@@ -915,6 +915,7 @@ public:
               maxThreadGroupsX(0),
               maxThreadGroupsY(0),
               maxThreadGroupsZ(0),
+              maxUniformVectors(4096),
               msaaRenderBuffer(false),
               multisampledTexture(false),
               npotTextureFull(true),
@@ -956,6 +957,7 @@ public:
         int maxThreadGroupsX;
         int maxThreadGroupsY;
         int maxThreadGroupsZ;
+        int maxUniformVectors;
         // Multisample fb and blit are supported (GLES 3.0 or OpenGL 3.x). Not
         // the same as multisample textures!
         uint msaaRenderBuffer : 1;
diff --git a/src/gui/rhi/qrhimetal.mm b/src/gui/rhi/qrhimetal.mm
index d37a130d15..da3bd03bb1 100644
--- a/src/gui/rhi/qrhimetal.mm
+++ b/src/gui/rhi/qrhimetal.mm
@@ -646,6 +646,8 @@ int QRhiMetal::resourceLimit(QRhi::ResourceLimit limit) const
 #else
         return 512;
 #endif
+    case QRhi::MaxUniformBufferRange:
+        return 65536;
     default:
         Q_UNREACHABLE();
         return 0;
diff --git a/src/gui/rhi/qrhinull.cpp b/src/gui/rhi/qrhinull.cpp
index 894caf8f35..f7f8f21ba7 100644
--- a/src/gui/rhi/qrhinull.cpp
+++ b/src/gui/rhi/qrhinull.cpp
@@ -162,6 +162,8 @@ int QRhiNull::resourceLimit(QRhi::ResourceLimit limit) const
         return 0;
     case QRhi::MaxThreadGroupZ:
         return 0;
+    case QRhi::MaxUniformBufferRange:
+        return 65536;
     default:
         Q_UNREACHABLE();
         return 0;
diff --git a/src/gui/rhi/qrhivulkan.cpp b/src/gui/rhi/qrhivulkan.cpp
index 5dd7b088be..f34388a126 100644
--- a/src/gui/rhi/qrhivulkan.cpp
+++ b/src/gui/rhi/qrhivulkan.cpp
@@ -4299,6 +4299,8 @@ int QRhiVulkan::resourceLimit(QRhi::ResourceLimit limit) const
         return int(physDevProperties.limits.maxComputeWorkGroupSize[1]);
     case QRhi::MaxThreadGroupZ:
         return int(physDevProperties.limits.maxComputeWorkGroupSize[2]);
+    case QRhi::MaxUniformBufferRange:
+        return int(qMin<uint32_t>(INT_MAX, physDevProperties.limits.maxUniformBufferRange));
     default:
         Q_UNREACHABLE();
         return 0;