rhi: Expose the maximum uniform buffer range limit

Pick-to: 6.2
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>

1 files changed, 35 insertions, 0 deletions

diff --git a/src/gui/rhi/qrhigles2.cpp b/src/gui/rhi/qrhigles2.cpp
index 5259be270c..4512acb969 100644
--- a/src/gui/rhi/qrhigles2.cpp
+++ b/src/gui/rhi/qrhigles2.cpp
@@ -405,6 +405,22 @@ QT_BEGIN_NAMESPACE
 #define GL_MAX_ARRAY_TEXTURE_LAYERS       0x88FF
 #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.
 
@@ -694,6 +710,23 @@ bool QRhiGles2::create(QRhi::Flags flags)
         caps.maxTextureArraySize = 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);
@@ -1125,6 +1158,8 @@ int QRhiGles2::resourceLimit(QRhi::ResourceLimit limit) const
         return caps.maxThreadGroupsZ;
     case QRhi::TextureArraySizeMax:
         return 2048;
+    case QRhi::MaxUniformBufferRange:
+        return int(qMin<qint64>(INT_MAX, caps.maxUniformVectors * qint64(16)));
     default:
         Q_UNREACHABLE();
         return 0;