From 5ad9ef56f4488be254d278aeaab4a5d50c60ce47 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Vladim=C3=ADr=20Vondru=C5=A1?= <mosra@centrum.cz>
Date: Sun, 24 Aug 2014 18:39:57 +0200
Subject: [PATCH] Added Buffer::uniformOffsetAlignment() limit query.

---
 doc/opengl-mapping.dox                    |  2 +-
 src/Magnum/Buffer.cpp                     | 14 ++++++++++++++
 src/Magnum/Buffer.h                       | 11 +++++++++++
 src/Magnum/Implementation/BufferState.cpp |  2 +-
 src/Magnum/Implementation/BufferState.h   |  1 +
 src/Magnum/Platform/magnum-info.cpp       |  1 +
 6 files changed, 29 insertions(+), 2 deletions(-)

diff --git a/doc/opengl-mapping.dox b/doc/opengl-mapping.dox
index 4fbb3b5cf..7f99a768d 100644
--- a/doc/opengl-mapping.dox
+++ b/doc/opengl-mapping.dox
@@ -377,7 +377,7 @@ OpenGL function                        | Matching API
 @def_gl{TEXTURE_BUFFER_OFFSET_ALIGNMENT} | @ref BufferTexture::offsetAlignment()
 @def_gl{TIMESTAMP}                     | |
 @def_gl{TRANSFORM_FEEDBACK_BUFFER_BINDING}, \n @def_gl{TRANSFORM_FEEDBACK_BUFFER_SIZE}, \n @def_gl{TRANSFORM_FEEDBACK_BUFFER_START} | not queryable
-@def_gl{UNIFORM_BUFFER_OFFSET_ALIGNMENT} | |
+@def_gl{UNIFORM_BUFFER_OFFSET_ALIGNMENT} | @ref Buffer::uniformOffsetAlignment()
 @def_gl{UNIFORM_BUFFER_BINDING}, \n @def_gl{UNIFORM_BUFFER_SIZE}, \n @def_gl{UNIFORM_BUFFER_START} | not queryable
 @def_gl{VERTEX_BINDING_DIVISOR}, \n @def_gl{VERTEX_BINDING_OFFSET}, \n @def_gl{VERTEX_BINDING_STRIDE} | not queryable
 @def_gl{VERTEX_PROGRAM_POINT_SIZE}     | not queryable
diff --git a/src/Magnum/Buffer.cpp b/src/Magnum/Buffer.cpp
index 03696dc1b..b42b95d09 100644
--- a/src/Magnum/Buffer.cpp
+++ b/src/Magnum/Buffer.cpp
@@ -99,6 +99,20 @@ Int Buffer::shaderStorageOffsetAlignment() {
     return value;
 }
 
+Int Buffer::uniformOffsetAlignment() {
+    #ifndef MAGNUM_TARGET_GLES
+    if(!Context::current()->isExtensionSupported<Extensions::GL::ARB::uniform_buffer_object>())
+        return 1;
+    #endif
+
+    GLint& value = Context::current()->state().buffer->uniformOffsetAlignment;
+
+    if(value == 0)
+        glGetIntegerv(GL_UNIFORM_BUFFER_OFFSET_ALIGNMENT, &value);
+
+    return value;
+}
+
 Int Buffer::maxUniformBindings() {
     #ifndef MAGNUM_TARGET_GLES
     if(!Context::current()->isExtensionSupported<Extensions::GL::ARB::uniform_buffer_object>())
diff --git a/src/Magnum/Buffer.h b/src/Magnum/Buffer.h
index af196e214..f04773764 100644
--- a/src/Magnum/Buffer.h
+++ b/src/Magnum/Buffer.h
@@ -471,6 +471,17 @@ class MAGNUM_EXPORT Buffer: public AbstractObject {
          */
         static Int maxShaderStorageBindings();
 
+        /**
+         * @brief Alignment of uniform buffer binding offset
+         *
+         * The result is cached, repeated queries don't result in repeated
+         * OpenGL calls. If extension @extension{ARB,uniform_buffer_object}
+         * (part of OpenGL 3.1) is not available, returns `1`.
+         * @see @fn_gl{Get} with @def_gl{UNIFORM_BUFFER_OFFSET_ALIGNMENT}
+         * @requires_gles30 Uniform buffers are not available in OpenGL ES 2.0
+         */
+        static Int uniformOffsetAlignment();
+
         /**
          * @brief Alignment of shader storage buffer binding offset
          *
diff --git a/src/Magnum/Implementation/BufferState.cpp b/src/Magnum/Implementation/BufferState.cpp
index 618dff7f0..7d285ed78 100644
--- a/src/Magnum/Implementation/BufferState.cpp
+++ b/src/Magnum/Implementation/BufferState.cpp
@@ -83,7 +83,7 @@ BufferState::BufferState(Context& context, std::vector<std::string>& extensions)
     #ifndef MAGNUM_TARGET_GLES
     , minMapAlignment(0)
     #endif
-    , maxAtomicCounterBindings(0), maxShaderStorageBindings(0), shaderStorageOffsetAlignment(0), maxUniformBindings(0)
+    , maxAtomicCounterBindings{0}, maxShaderStorageBindings{0}, shaderStorageOffsetAlignment{0}, uniformOffsetAlignment{0}, maxUniformBindings{0}
     #endif
 {
     #ifndef MAGNUM_TARGET_GLES
diff --git a/src/Magnum/Implementation/BufferState.h b/src/Magnum/Implementation/BufferState.h
index 48ccba415..38d9e101e 100644
--- a/src/Magnum/Implementation/BufferState.h
+++ b/src/Magnum/Implementation/BufferState.h
@@ -74,6 +74,7 @@ struct BufferState {
         maxAtomicCounterBindings,
         maxShaderStorageBindings,
         shaderStorageOffsetAlignment,
+        uniformOffsetAlignment,
         maxUniformBindings;
     #endif
 };
diff --git a/src/Magnum/Platform/magnum-info.cpp b/src/Magnum/Platform/magnum-info.cpp
index 52016ab2b..d36e4e059 100644
--- a/src/Magnum/Platform/magnum-info.cpp
+++ b/src/Magnum/Platform/magnum-info.cpp
@@ -513,6 +513,7 @@ MagnumInfo::MagnumInfo(const Arguments& arguments): Platform::WindowlessApplicat
         _h(ARB::uniform_buffer_object)
         #endif
 
+        _l(Buffer::uniformOffsetAlignment())
         _l(Shader::maxUniformBlocks(Shader::Type::Vertex))
         #ifndef MAGNUM_TARGET_GLES
         _l(Shader::maxUniformBlocks(Shader::Type::TessellationControl))