Added BufferTexture::offsetAlignment() limit query.

src/BufferTexture.cpp

@@ -29,11 +29,27 @@
 #include "Context.h"
 #include "Extensions.h"
 
+#include "Implementation/State.h"
+#include "Implementation/TextureState.h"
+
 namespace Magnum {
 
 BufferTexture::SetBufferImplementation BufferTexture::setBufferImplementation = &BufferTexture::setBufferImplementationDefault;
 BufferTexture::SetBufferRangeImplementation BufferTexture::setBufferRangeImplementation = &BufferTexture::setBufferRangeImplementationDefault;
 
+Int BufferTexture::offsetAlignment() {
+    if(!Context::current()->isExtensionSupported<Extensions::GL::ARB::texture_buffer_range>())
+        return 0;
+
+    GLint& value = Context::current()->state().texture->bufferOffsetAlignment;
+
+    /* Get the value, if not already cached */
+    if(value == 0)
+        glGetIntegerv(GL_TEXTURE_BUFFER_OFFSET_ALIGNMENT, &value);
+
+    return value;
+}
+
 void BufferTexture::initializeContextBasedFunctionality(Context& context) {
     if(context.isExtensionSupported<Extensions::GL::EXT::direct_state_access>()) {
         Debug() << "BufferTexture: using" << Extensions::GL::EXT::direct_state_access::string() << "features";

src/BufferTexture.h

@@ -205,6 +205,16 @@ class MAGNUM_EXPORT BufferTexture: private AbstractTexture {
         /** @copydoc AbstractTexture::maxLabelLength() */
         static Int maxLabelLength() { return AbstractTexture::maxLabelLength(); }
 
+        /**
+         * @brief Minimum required alignment for texture buffer offsets
+         *
+         * The result is cached, repeated queries don't result in repeated
+         * OpenGL calls. If extension @extension{ARB,texture_buffer_range}
+         * (part of OpenGL 4.3) is not available, returns `0`.
+         * @see @fn_gl{Get} with @def_gl{TEXTURE_BUFFER_OFFSET_ALIGNMENT}
+         */
+        static Int offsetAlignment();
+
         explicit BufferTexture(): AbstractTexture(GL_TEXTURE_BUFFER) {}
 
         /** @copydoc AbstractTexture::id() */

src/Implementation/TextureState.cpp

@@ -28,7 +28,7 @@ namespace Magnum { namespace Implementation {
 
 TextureState::TextureState(): maxAnisotropy(0.0f), currentLayer(0)
     #ifndef MAGNUM_TARGET_GLES
-    , maxColorSamples(0), maxDepthSamples(0), maxIntegerSamples(0)
+    , maxColorSamples(0), maxDepthSamples(0), maxIntegerSamples(0), bufferOffsetAlignment(0)
     #endif
     {}
 

src/Implementation/TextureState.h

@@ -39,7 +39,8 @@ struct TextureState {
     #ifndef MAGNUM_TARGET_GLES
     GLint maxColorSamples,
         maxDepthSamples,
-        maxIntegerSamples;
+        maxIntegerSamples,
+        bufferOffsetAlignment;
     #endif
 
     std::vector<GLuint> bindings;