Tracking Buffer state.

Reduces OpenGL call count if subsequently binding the same Buffer into
the same Target.

src/Buffer.cpp

@@ -19,6 +19,8 @@
 
 #include "Context.h"
 #include "Extensions.h"
+#include "Implementation/State.h"
+#include "Implementation/BufferState.h"
 
 namespace Magnum {
 
@@ -36,10 +38,46 @@ void Buffer::initializeContextBasedFunctionality(Context* context) {
     }
 }
 
+Buffer::~Buffer() {
+    GLuint* bindings = Context::current()->state()->buffer->bindings;
+
+    /* Remove all current bindings from the state */
+    for(std::size_t i = 1; i != Implementation::BufferState::TargetCount; ++i)
+        if(bindings[i] == _id) bindings[i] = 0;
+
+    glDeleteBuffers(1, &_id);
+}
+
+void Buffer::bind(Target target, GLuint id) {
+    GLuint& bound = Context::current()->state()->buffer->bindings[Implementation::BufferState::indexForTarget(target)];
+
+    /* Already bound, nothing to do */
+    if(bound == id) return;
+
+    /* Bind the buffer otherwise */
+    bound = id;
+    glBindBuffer(static_cast<GLenum>(target), id);
+}
+
+Buffer::Target Buffer::bindInternal(Target hint) {
+    GLuint* bindings = Context::current()->state()->buffer->bindings;
+    GLuint& hintBinding = bindings[Implementation::BufferState::indexForTarget(hint)];
+
+    /* Shortcut - if already bound to hint, return */
+    if(hintBinding == _id) return hint;
+
+    /* Return first target in which the buffer is bound */
+    for(std::size_t i = 1; i != Implementation::BufferState::TargetCount; ++i)
+        if(bindings[i] == _id) return Implementation::BufferState::targetForIndex[i];
+
+    /* Bind the buffer to hint target otherwise */
+    hintBinding = _id;
+    glBindBuffer(static_cast<GLenum>(hint), _id);
+    return hint;
+}
+
 void Buffer::copyImplementationDefault(Buffer* read, Buffer* write, GLintptr readOffset, GLintptr writeOffset, GLsizeiptr size) {
-    read->bind(Target::CopyRead);
-    write->bind(Target::CopyWrite);
-    glCopyBufferSubData(static_cast<GLenum>(Target::CopyRead), static_cast<GLenum>(Target::CopyWrite), readOffset, writeOffset, size);
+    glCopyBufferSubData(static_cast<GLenum>(read->bindInternal(Target::CopyRead)), static_cast<GLenum>(write->bindInternal(Target::CopyWrite)), readOffset, writeOffset, size);
 }
 
 void Buffer::copyImplementationDSA(Buffer* read, Buffer* write, GLintptr readOffset, GLintptr writeOffset, GLsizeiptr size) {
@@ -47,8 +85,7 @@ void Buffer::copyImplementationDSA(Buffer* read, Buffer* write, GLintptr readOff
 }
 
 void Buffer::setDataImplementationDefault(GLsizeiptr size, const GLvoid* data, Buffer::Usage usage) {
-    bind();
-    glBufferData(static_cast<GLenum>(_defaultTarget), size, data, static_cast<GLenum>(usage));
+    glBufferData(static_cast<GLenum>(bindInternal(_defaultTarget)), size, data, static_cast<GLenum>(usage));
 }
 
 void Buffer::setDataImplementationDSA(GLsizeiptr size, const GLvoid* data, Buffer::Usage usage) {
@@ -56,8 +93,7 @@ void Buffer::setDataImplementationDSA(GLsizeiptr size, const GLvoid* data, Buffe
 }
 
 void Buffer::setSubDataImplementationDefault(GLintptr offset, GLsizeiptr size, const GLvoid* data) {
-    bind();
-    glBufferSubData(static_cast<GLenum>(_defaultTarget), offset, size, data);
+    glBufferSubData(static_cast<GLenum>(bindInternal(_defaultTarget)), offset, size, data);
 }
 
 void Buffer::setSubDataImplementationDSA(GLintptr offset, GLsizeiptr size, const GLvoid* data) {

src/Buffer.h

@@ -236,9 +236,7 @@ class MAGNUM_EXPORT Buffer {
          *
          * @see @fn_gl{BindBuffer}
          */
-        inline static void unbind(Target target) {
-            glBindBuffer(static_cast<GLenum>(target), 0);
-        }
+        inline static void unbind(Target target) { bind(target, 0); }
 
         /**
          * @brief Copy one buffer to another
@@ -277,9 +275,7 @@ class MAGNUM_EXPORT Buffer {
          * Deletes associated OpenGL buffer.
          * @see @fn_gl{DeleteBuffers}
          */
-        inline virtual ~Buffer() {
-            glDeleteBuffers(1, &_id);
-        }
+        virtual ~Buffer();
 
         /** @brief Default bind type */
         inline Target defaultTarget() const { return _defaultTarget; }
@@ -301,9 +297,7 @@ class MAGNUM_EXPORT Buffer {
          *
          * @see @fn_gl{BindBuffer}
          */
-        inline void bind(Target target) {
-            glBindBuffer(static_cast<GLenum>(target), _id);
-        }
+        inline void bind(Target target) { bind(target, _id); }
 
         /**
          * @brief Set buffer data
@@ -390,6 +384,9 @@ class MAGNUM_EXPORT Buffer {
     private:
         static void initializeContextBasedFunctionality(Context* context);
 
+        static void bind(Target hint, GLuint id);
+        Target bindInternal(Target hint);
+
         typedef void(*CopyImplementation)(Buffer*, Buffer*, GLintptr, GLintptr, GLsizeiptr);
         static void MAGNUM_LOCAL copyImplementationDefault(Buffer* read, Buffer* write, GLintptr readOffset, GLintptr writeOffset, GLsizeiptr size);
         static void MAGNUM_LOCAL copyImplementationDSA(Buffer* read, Buffer* write, GLintptr readOffset, GLintptr writeOffset, GLsizeiptr size);

src/CMakeLists.txt

@@ -37,6 +37,7 @@ set(Magnum_SRCS
     Timeline.cpp
     TypeTraits.cpp
 
+    Implementation/BufferState.cpp
     Implementation/State.cpp
 
     Trade/AbstractImporter.cpp

src/Implementation/BufferState.cpp

@@ -0,0 +1,63 @@
+/*
+    Copyright © 2010, 2011, 2012 Vladimír Vondruš <mosra@centrum.cz>
+
+    This file is part of Magnum.
+
+    Magnum is free software: you can redistribute it and/or modify
+    it under the terms of the GNU Lesser General Public License version 3
+    only, as published by the Free Software Foundation.
+
+    Magnum is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+    GNU Lesser General Public License version 3 for more details.
+*/
+
+#include "BufferState.h"
+
+#include <Utility/Debug.h>
+
+namespace Magnum { namespace Implementation {
+
+const Buffer::Target BufferState::targetForIndex[] = {
+    Buffer::Target::Array,
+    Buffer::Target::CopyRead,
+    Buffer::Target::CopyWrite,
+    Buffer::Target::ElementArray,
+    Buffer::Target::PixelPack,
+    Buffer::Target::PixelUnpack,
+    Buffer::Target::TransformFeedback,
+    Buffer::Target::Uniform,
+    #ifndef MAGNUM_TARGET_GLES
+    Buffer::Target::AtomicCounter,
+    Buffer::Target::DispatchIndirect,
+    Buffer::Target::DrawIndirect,
+    Buffer::Target::ShaderStorage,
+    Buffer::Target::Texture
+    #endif
+};
+
+std::size_t BufferState::indexForTarget(Buffer::Target target) {
+    switch(target) {
+        case Buffer::Target::Array:             return 1;
+        case Buffer::Target::CopyRead:          return 2;
+        case Buffer::Target::CopyWrite:         return 3;
+        case Buffer::Target::ElementArray:      return 4;
+        case Buffer::Target::PixelPack:         return 5;
+        case Buffer::Target::PixelUnpack:       return 6;
+        case Buffer::Target::TransformFeedback: return 7;
+        case Buffer::Target::Uniform:           return 8;
+        #ifndef MAGNUM_TARGET_GLES
+        case Buffer::Target::AtomicCounter:     return 9;
+        case Buffer::Target::DispatchIndirect:  return 10;
+        case Buffer::Target::DrawIndirect:      return 11;
+        case Buffer::Target::ShaderStorage:     return 12;
+        case Buffer::Target::Texture:           return 13;
+        #endif
+    }
+
+    CORRADE_ASSERT(false, "Unknown Buffer target", 0);
+    return 0;
+}
+
+}}

src/Implementation/BufferState.h

@@ -0,0 +1,43 @@
+#ifndef Magnum_Implementation_BufferState_h
+#define Magnum_Implementation_BufferState_h
+/*
+    Copyright © 2010, 2011, 2012 Vladimír Vondruš <mosra@centrum.cz>
+
+    This file is part of Magnum.
+
+    Magnum is free software: you can redistribute it and/or modify
+    it under the terms of the GNU Lesser General Public License version 3
+    only, as published by the Free Software Foundation.
+
+    Magnum is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+    GNU Lesser General Public License version 3 for more details.
+*/
+
+#include "Magnum.h"
+
+#include "Buffer.h"
+
+namespace Magnum { namespace Implementation {
+
+struct BufferState {
+    #ifndef MAGNUM_TARGET_GLES
+    static const std::size_t TargetCount = 13+1;
+    #else
+    static const std::size_t TargetCount = 8+1;
+    #endif
+
+    /* Target <-> index mapping */
+    static std::size_t indexForTarget(Buffer::Target target);
+    static const Buffer::Target targetForIndex[TargetCount-1];
+
+    inline constexpr BufferState(): bindings() {}
+
+    /* Currently bound buffer for all targets */
+    GLuint bindings[TargetCount];
+};
+
+}}
+
+#endif

src/Implementation/State.cpp

@@ -15,11 +15,14 @@
 
 #include "State.h"
 
+#include "BufferState.h"
+
 namespace Magnum { namespace Implementation {
 
-State::State() {}
+State::State(): buffer(new BufferState) {}
 
 State::~State() {
+    delete buffer;
 }
 
 }}

src/Implementation/State.h

@@ -19,11 +19,13 @@
 
 namespace Magnum { namespace Implementation {
 
-class BufferState;
+struct BufferState;
 
 struct State {
     State();
     ~State();
+
+    BufferState* const buffer;
 };
 
 }}