Apply directly to the buffer

- Add DSA abstraction to GlBuffer
- Move backing impls to their respective classes
- Remove versioned package, move impls to appropriate package
- Make fallback methods take no arguments
- Do VAO check/bind in GlStateTracker
- GlVertexArray actually checks the tracked info when binding attributes
- Add separate enable* and setup* methods in VertexArray
- Add support for DSA VAO with ARB instanced arrays incase there are
  some particularly cursed drivers out there
- Misc. cleanup

src/main/java/com/jozufozu/flywheel/backend/Backends.java

@@ -7,7 +7,7 @@ import com.jozufozu.flywheel.backend.compile.InstancingPrograms;
 import com.jozufozu.flywheel.backend.engine.batching.BatchingEngine;
 import com.jozufozu.flywheel.backend.engine.indirect.IndirectEngine;
 import com.jozufozu.flywheel.backend.engine.instancing.InstancingEngine;
-import com.jozufozu.flywheel.gl.versioned.GlCompat;
+import com.jozufozu.flywheel.gl.GlCompat;
 import com.jozufozu.flywheel.lib.backend.SimpleBackend;
 import com.jozufozu.flywheel.lib.context.Contexts;
 import com.jozufozu.flywheel.lib.util.ShadersModHandler;

src/main/java/com/jozufozu/flywheel/backend/compile/core/Compilation.java

@@ -10,9 +10,9 @@ import org.jetbrains.annotations.NotNull;
 import org.lwjgl.opengl.GL20;
 
 import com.jozufozu.flywheel.Flywheel;
+import com.jozufozu.flywheel.gl.GlCompat;
 import com.jozufozu.flywheel.gl.shader.GlShader;
 import com.jozufozu.flywheel.gl.shader.ShaderType;
-import com.jozufozu.flywheel.gl.versioned.GlCompat;
 import com.jozufozu.flywheel.glsl.GLSLVersion;
 import com.jozufozu.flywheel.glsl.SourceComponent;
 import com.jozufozu.flywheel.glsl.SourceFile;

src/main/java/com/jozufozu/flywheel/backend/engine/instancing/GPUInstancer.java

@@ -41,7 +41,7 @@ public class GPUInstancer<I extends Instance> extends AbstractInstancer<I> {
 		}
 
 		vbo = new GlBuffer(GlBufferUsage.DYNAMIC_DRAW);
-		vbo.setGrowthMargin(instanceStride * 16);
+		vbo.growthMargin(instanceStride * 16);
 	}
 
 	public void update() {

src/main/java/com/jozufozu/flywheel/backend/engine/instancing/InstancedMeshPool.java

@@ -39,7 +39,7 @@ public class InstancedMeshPool {
 		this.vertexType = vertexType;
 		int stride = vertexType.getLayout().getStride();
 		vbo = new GlBuffer();
-		vbo.setGrowthMargin(stride * 32);
+		vbo.growthMargin(stride * 32);
 	}
 
 	public VertexType getVertexType() {

src/main/java/com/jozufozu/flywheel/gl/GlCompat.java

@@ -1,4 +1,4 @@
-package com.jozufozu.flywheel.gl.versioned;
+package com.jozufozu.flywheel.gl;
 
 import java.nio.ByteBuffer;
 
@@ -8,6 +8,8 @@ import org.lwjgl.opengl.GL20C;
 import org.lwjgl.opengl.GLCapabilities;
 import org.lwjgl.system.MemoryStack;
 
+import com.jozufozu.flywheel.gl.array.GlVertexArray;
+
 import net.minecraft.Util;
 
 /**
@@ -17,17 +19,9 @@ import net.minecraft.Util;
  * system.
  */
 public class GlCompat {
-	private static final GLCapabilities caps;
-	public static final VertexArray vertexArray;
-	public static final boolean amd;
-	public static final boolean supportsIndirect;
-
-	static {
-		caps = GL.createCapabilities();
-		vertexArray = VertexArray.DSA.INSTANCE.fallback(caps);
-		supportsIndirect = _decideIfWeSupportIndirect();
-		amd = _decideIfWeAreAMDWindows();
-	}
+	public static final GLCapabilities CAPABILITIES = GL.createCapabilities();
+	private static final boolean amd = _decideIfWeAreAMDWindows();
+	private static final boolean supportsIndirect = _decideIfWeSupportIndirect();
 
 	private GlCompat() {
 	}
@@ -37,7 +31,7 @@ public class GlCompat {
 	}
 
 	public static boolean supportsInstancing() {
-		return caps.OpenGL33 || caps.GL_ARB_instanced_arrays;
+		return GlVertexArray.IMPL != null;
 	}
 
 	public static boolean supportsIndirect() {
@@ -45,12 +39,7 @@ public class GlCompat {
 	}
 
 	private static boolean _decideIfWeSupportIndirect() {
-		return caps.OpenGL46 || (
-				caps.GL_ARB_compute_shader &&
-				caps.GL_ARB_shader_draw_parameters &&
-				caps.GL_ARB_base_instance &&
-				caps.GL_ARB_multi_draw_indirect &&
-				caps.GL_ARB_direct_state_access);
+		return CAPABILITIES.OpenGL46 || (CAPABILITIES.GL_ARB_compute_shader && CAPABILITIES.GL_ARB_shader_draw_parameters && CAPABILITIES.GL_ARB_base_instance && CAPABILITIES.GL_ARB_multi_draw_indirect && CAPABILITIES.GL_ARB_direct_state_access);
 	}
 
 	/**

src/main/java/com/jozufozu/flywheel/gl/GlStateTracker.java

@@ -39,6 +39,12 @@ public class GlStateTracker {
 		return new State(BUFFERS.clone(), vao, program);
 	}
 
+	public static void bindVao(int vao) {
+		if (vao != GlStateTracker.vao) {
+			GlStateManager._glBindVertexArray(vao);
+		}
+	}
+
 	public record State(int[] buffers, int vao, int program) implements AutoCloseable {
 		public void restore() {
 			if (vao != GlStateTracker.vao) {

src/main/java/com/jozufozu/flywheel/gl/array/GlVertexArray.java

@@ -1,18 +1,14 @@
 package com.jozufozu.flywheel.gl.array;
 
-import java.util.List;
-
 import org.lwjgl.opengl.GL32;
 
 import com.jozufozu.flywheel.api.layout.BufferLayout;
 import com.jozufozu.flywheel.gl.GlObject;
 import com.jozufozu.flywheel.gl.GlStateTracker;
-import com.jozufozu.flywheel.gl.versioned.GlCompat;
 import com.mojang.blaze3d.platform.GlStateManager;
 
-@SuppressWarnings("MismatchedReadAndWriteOfArray")
 public class GlVertexArray extends GlObject {
-
+	public static final VertexArray IMPL = new VertexArray.DSA().fallback();
 	private static final int MAX_ATTRIBS = GL32.glGetInteger(GL32.GL_MAX_VERTEX_ATTRIBS);
 
 	/**
@@ -42,57 +38,61 @@ public class GlVertexArray extends GlObject {
 
 	private int elementBufferBinding = 0;
 
-
 	public GlVertexArray() {
-		setHandle(GlCompat.vertexArray.create());
+		setHandle(IMPL.create());
 	}
 
 	public void bindForDraw() {
-		if (!isBound()) {
-			GlStateManager._glBindVertexArray(handle());
-		}
-	}
-
-	private boolean isBound() {
-		return handle() == GlStateTracker.getVertexArray();
+		GlStateTracker.bindVao(handle());
 	}
 
 	public static void unbind() {
 		GlStateManager._glBindVertexArray(0);
 	}
 
-	public void bindAttributes(BufferLayout type, int vbo, int startAttrib, long startOffset) {
+	public void bindAttributes(BufferLayout type, final int vbo, final int startAttrib, final long startOffset) {
+		final int vao = handle();
 		final int stride = type.getStride();
 
-		List<VertexAttribute> vertexAttributes = type.attributes();
-		for (int i = 0; i < vertexAttributes.size(); i++) {
-			var attribute = vertexAttributes.get(i);
-			int index = i + startAttrib;
-			targets[index] = vbo;
-			attributes[index] = attribute;
-			offsets[index] = startOffset;
-			strides[index] = stride;
+		int index = startAttrib;
+		long offset = startOffset;
+		for (var attribute : type.attributes()) {
+			if (!enabled[index]) {
+				IMPL.enableAttrib(vao, index);
+				enabled[index] = true;
+			}
 
-			GlCompat.vertexArray.setupAttrib(handle(), index, vbo, stride, startOffset, attribute);
+			if (shouldSetupAttrib(index, vbo, stride, offset, attribute)) {
+				IMPL.setupAttrib(vao, index, vbo, stride, offset, attribute);
+				targets[index] = vbo;
+				attributes[index] = attribute;
+				offsets[index] = offset;
+				strides[index] = stride;
+			}
 
-			startOffset += attribute.getByteWidth();
+			index++;
+			offset += attribute.getByteWidth();
 		}
 	}
 
+	private boolean shouldSetupAttrib(int index, int vbo, int stride, long offset, VertexAttribute attribute) {
+		return targets[index] != vbo || offsets[index] != offset || strides[index] != stride || !attribute.equals(attributes[index]);
+	}
+
 	protected void deleteInternal(int handle) {
 		GlStateManager._glDeleteVertexArrays(handle);
 	}
 
 	public void setAttributeDivisor(int index, int divisor) {
 		if (divisors[index] != divisor) {
-			GlCompat.vertexArray.setAttribDivisor(handle(), index, divisor);
+			IMPL.setAttribDivisor(handle(), index, divisor);
 			divisors[index] = divisor;
 		}
 	}
 
 	public void setElementBuffer(int ebo) {
 		if (elementBufferBinding != ebo) {
-			GlCompat.vertexArray.setElementBuffer(handle(), ebo);
+			IMPL.setElementBuffer(handle(), ebo);
 			elementBufferBinding = ebo;
 		}
 	}

src/main/java/com/jozufozu/flywheel/gl/array/VertexArray.java

@@ -1,23 +1,23 @@
-package com.jozufozu.flywheel.gl.versioned;
+package com.jozufozu.flywheel.gl.array;
 
 import org.lwjgl.opengl.ARBInstancedArrays;
 import org.lwjgl.opengl.GL20C;
 import org.lwjgl.opengl.GL30C;
 import org.lwjgl.opengl.GL33C;
 import org.lwjgl.opengl.GL45C;
-import org.lwjgl.opengl.GLCapabilities;
 import org.lwjgl.system.Checks;
 
+import com.jozufozu.flywheel.gl.GlCompat;
 import com.jozufozu.flywheel.gl.GlStateTracker;
-import com.jozufozu.flywheel.gl.array.VertexAttribute;
 import com.jozufozu.flywheel.gl.buffer.GlBufferType;
-import com.mojang.blaze3d.platform.GlStateManager;
 
 public interface VertexArray {
 	int create();
 
 	void setElementBuffer(int vao, int elementBuffer);
 
+	void enableAttrib(int vao, int index);
+
 	void setupAttrib(int vao, int index, int vbo, int stride, long offset, VertexAttribute attribute);
 
 	void setAttribDivisor(int vao, int attrib, int divisor);
@@ -30,69 +30,58 @@ public interface VertexArray {
 
 		@Override
 		public void setElementBuffer(int vao, int elementBuffer) {
-			if (vao != GlStateTracker.getVertexArray()) {
-				GlStateManager._glBindVertexArray(vao);
-			}
+			GlStateTracker.bindVao(vao);
 			GlBufferType.ELEMENT_ARRAY_BUFFER.bind(elementBuffer);
 		}
 
 		@Override
-		public void setupAttrib(int vao, int index, int vbo, int stride, long offset, VertexAttribute attribute) {
-			if (vao != GlStateTracker.getVertexArray()) {
-				GlStateManager._glBindVertexArray(vao);
-			}
-			GlBufferType.ARRAY_BUFFER.bind(vbo);
-
+		public void enableAttrib(int vao, int index) {
+			GlStateTracker.bindVao(vao);
 			GL20C.glEnableVertexAttribArray(index);
-			attribute.setup(offset, index, stride);
 		}
 
+		@Override
+		public void setupAttrib(int vao, int index, int vbo, int stride, long offset, VertexAttribute attribute) {
+			GlStateTracker.bindVao(vao);
+			GlBufferType.ARRAY_BUFFER.bind(vbo);
+			attribute.setup(offset, index, stride);
+		}
 	}
 
 	class InstancedArraysARB extends GL3 {
-		public static InstancedArraysARB INSTANCE = new InstancedArraysARB();
-
 		@Override
 		public void setAttribDivisor(int vao, int attrib, int divisor) {
-			if (vao != GlStateTracker.getVertexArray()) {
-				GlStateManager._glBindVertexArray(vao);
-			}
+			GlStateTracker.bindVao(vao);
 			ARBInstancedArrays.glVertexAttribDivisorARB(attrib, divisor);
 		}
 
-		public VertexArray fallback(GLCapabilities caps) {
-			return isSupported(caps) ? this : null;
-		}
-
-		private boolean isSupported(GLCapabilities caps) {
-			return Checks.checkFunctions(caps.glVertexAttribDivisorARB);
+		public VertexArray fallback() {
+			if (Checks.checkFunctions(GlCompat.CAPABILITIES.glVertexAttribDivisorARB)) {
+				return this;
+			}
+			// null signals that we don't support instancing.
+			return null;
 		}
 	}
 
 	class InstancedArraysCore extends GL3 {
-		public static InstancedArraysCore INSTANCE = new InstancedArraysCore();
-
 		@Override
 		public void setAttribDivisor(int vao, int attrib, int divisor) {
-			if (vao != GlStateTracker.getVertexArray()) {
-				GlStateManager._glBindVertexArray(vao);
-			}
+			GlStateTracker.bindVao(vao);
 			GL33C.glVertexAttribDivisor(attrib, divisor);
 		}
 
-		public VertexArray fallback(GLCapabilities caps) {
-			return isSupported(caps) ? this : InstancedArraysARB.INSTANCE.fallback(caps);
+		public VertexArray fallback() {
+			// We know vertex arrays are supported because minecraft required GL32.
+			if (Checks.checkFunctions(GlCompat.CAPABILITIES.glVertexAttribDivisor)) {
+				return this;
+			}
+			return new InstancedArraysARB().fallback();
 		}
 
-		private static boolean isSupported(GLCapabilities caps) {
-			// We know vertex arrays are supported because minecraft required GL32.
-			return Checks.checkFunctions(caps.glVertexAttribDivisor);
-		}
 	}
 
 	class DSA implements VertexArray {
-		public static final DSA INSTANCE = new DSA();
-
 		@Override
 		public int create() {
 			return GL45C.glCreateVertexArrays();
@@ -104,8 +93,12 @@ public interface VertexArray {
 		}
 
 		@Override
-		public void setupAttrib(int vao, int index, int vbo, int stride, long offset, VertexAttribute attribute) {
+		public void enableAttrib(int vao, int index) {
 			GL45C.glEnableVertexArrayAttrib(vao, index);
+		}
+
+		@Override
+		public void setupAttrib(int vao, int index, int vbo, int stride, long offset, VertexAttribute attribute) {
 			GL45C.glVertexArrayVertexBuffer(vao, index, vbo, offset, stride);
 			attribute.setupDSA(vao, index);
 		}
@@ -115,12 +108,26 @@ public interface VertexArray {
 			GL45C.glVertexArrayBindingDivisor(vao, attrib, divisor);
 		}
 
-		public VertexArray fallback(GLCapabilities caps) {
-			return isSupported(caps) ? this : InstancedArraysCore.INSTANCE.fallback(caps);
-		}
+		public VertexArray fallback() {
+			var c = GlCompat.CAPABILITIES;
+			if (Checks.checkFunctions(c.glCreateVertexArrays, c.glVertexArrayElementBuffer, c.glEnableVertexArrayAttrib, c.glVertexArrayVertexBuffer, c.glVertexArrayAttribFormat, c.glVertexArrayAttribIFormat)) {
 
-		private static boolean isSupported(GLCapabilities caps) {
-			return Checks.checkFunctions(caps.glCreateVertexArrays, caps.glVertexArrayElementBuffer, caps.glEnableVertexArrayAttrib, caps.glVertexArrayVertexBuffer, caps.glVertexArrayBindingDivisor, caps.glVertexArrayAttribFormat, caps.glVertexArrayAttribIFormat);
+				if (Checks.checkFunctions(c.glVertexArrayBindingDivisor)) {
+					return this;
+				} else if (Checks.checkFunctions(c.glVertexArrayVertexAttribDivisorEXT)) {
+					// Seems like this may happen when a driver supports
+					// ARB_direct_state_access but not core instanced arrays?
+					return new InstancedArraysEXTDSA();
+				}
+			}
+			return new InstancedArraysCore().fallback();
+		}
+	}
+
+	class InstancedArraysEXTDSA extends DSA {
+		@Override
+		public void setAttribDivisor(int vao, int attrib, int divisor) {
+			ARBInstancedArrays.glVertexArrayVertexAttribDivisorEXT(vao, attrib, divisor);
 		}
 	}
 }

src/main/java/com/jozufozu/flywheel/gl/array/VertexAttributeF.java

@@ -13,7 +13,6 @@ import com.jozufozu.flywheel.gl.GlNumericType;
  * @param normalized Whether the data is normalized.
  */
 public record VertexAttributeF(GlNumericType type, int size, boolean normalized) implements VertexAttribute {
-
 	@Override
 	public int getByteWidth() {
 		return size * type.getByteWidth();

src/main/java/com/jozufozu/flywheel/gl/array/VertexAttributeI.java

@@ -12,7 +12,6 @@ import com.jozufozu.flywheel.gl.GlNumericType;
  * @param size The number of components in the attribute, e.g. 3 for a vec3.
  */
 public record VertexAttributeI(GlNumericType type, int size) implements VertexAttribute {
-
 	@Override
 	public int getByteWidth() {
 		return size * type.getByteWidth();

src/main/java/com/jozufozu/flywheel/gl/buffer/Buffer.java

@@ -0,0 +1,89 @@
+package com.jozufozu.flywheel.gl.buffer;
+
+import org.lwjgl.opengl.GL15;
+import org.lwjgl.opengl.GL30;
+import org.lwjgl.opengl.GL31;
+import org.lwjgl.opengl.GL45C;
+import org.lwjgl.system.Checks;
+
+import com.jozufozu.flywheel.gl.GlCompat;
+
+public interface Buffer {
+	int create();
+
+	void data(int vbo, long size, long ptr, int glEnum);
+
+	void copyData(int src, int dst, long srcOffset, long dstOffset, long size);
+
+	long mapRange(int handle, int offset, long size, int access);
+
+	void unmap(int handle);
+
+	class DSA implements Buffer {
+		@Override
+		public int create() {
+			return GL45C.glCreateBuffers();
+		}
+
+		@Override
+		public void data(int vbo, long size, long ptr, int glEnum) {
+			GL45C.nglNamedBufferData(vbo, size, ptr, glEnum);
+		}
+
+		@Override
+		public void copyData(int src, int dst, long srcOffset, long dstOffset, long size) {
+			GL45C.glCopyNamedBufferSubData(src, dst, srcOffset, dstOffset, size);
+		}
+
+		@Override
+		public long mapRange(int handle, int offset, long size, int access) {
+			return GL45C.nglMapNamedBufferRange(handle, offset, size, access);
+		}
+
+		@Override
+		public void unmap(int handle) {
+			GL45C.glUnmapNamedBuffer(handle);
+		}
+
+		public Buffer fallback() {
+			var c = GlCompat.CAPABILITIES;
+			if (Checks.checkFunctions(c.glCreateBuffers, c.glNamedBufferData, c.glCopyNamedBufferSubData, c.glMapNamedBufferRange, c.glUnmapNamedBuffer)) {
+				return this;
+			}
+			return new Core();
+		}
+	}
+
+	class Core implements Buffer {
+		@Override
+		public int create() {
+			return GL15.glGenBuffers();
+		}
+
+		@Override
+		public void data(int vbo, long size, long ptr, int glEnum) {
+			GlBufferType.COPY_WRITE_BUFFER.bind(vbo);
+			GL15.nglBufferData(GlBufferType.COPY_WRITE_BUFFER.glEnum, size, ptr, glEnum);
+		}
+
+		@Override
+		public void copyData(int src, int dst, long size, long srcOffset, long dstOffset) {
+			GlBufferType.COPY_READ_BUFFER.bind(src);
+			GlBufferType.COPY_WRITE_BUFFER.bind(dst);
+
+			GL31.glCopyBufferSubData(GlBufferType.COPY_READ_BUFFER.glEnum, GlBufferType.COPY_WRITE_BUFFER.glEnum, srcOffset, dstOffset, size);
+		}
+
+		@Override
+		public long mapRange(int handle, int offset, long size, int access) {
+			GlBufferType.COPY_READ_BUFFER.bind(handle);
+			return GL30.nglMapBufferRange(GlBufferType.COPY_READ_BUFFER.glEnum, 0, size, access);
+		}
+
+		@Override
+		public void unmap(int handle) {
+			GlBufferType.COPY_READ_BUFFER.bind(handle);
+			GL15.glUnmapBuffer(GlBufferType.COPY_READ_BUFFER.glEnum);
+		}
+	}
+}

src/main/java/com/jozufozu/flywheel/gl/buffer/GlBuffer.java

@@ -1,16 +1,16 @@
 package com.jozufozu.flywheel.gl.buffer;
 
-import static org.lwjgl.opengl.GL15.glBufferData;
 import static org.lwjgl.opengl.GL15.glDeleteBuffers;
-import static org.lwjgl.opengl.GL15.glGenBuffers;
-import static org.lwjgl.opengl.GL15.nglBufferData;
-import static org.lwjgl.opengl.GL31.glCopyBufferSubData;
+
+import org.lwjgl.system.MemoryUtil;
 
 import com.jozufozu.flywheel.gl.GlObject;
 import com.jozufozu.flywheel.lib.memory.FlwMemoryTracker;
 import com.jozufozu.flywheel.lib.memory.MemoryBlock;
+import com.mojang.blaze3d.platform.GlStateManager;
 
 public class GlBuffer extends GlObject {
+	public static final Buffer IMPL = new Buffer.DSA().fallback();
 	protected final GlBufferUsage usage;
 	/**
 	 * The size (in bytes) of the buffer on the GPU.
@@ -26,64 +26,67 @@ public class GlBuffer extends GlObject {
 	}
 
 	public GlBuffer(GlBufferUsage usage) {
-		setHandle(glGenBuffers());
+		setHandle(IMPL.create());
 		this.usage = usage;
 	}
 
 	/**
 	 * @return true if the buffer was recreated.
 	 */
-	public boolean ensureCapacity(long size) {
-		if (size < 0) {
-			throw new IllegalArgumentException("Size " + size + " < 0");
+	public boolean ensureCapacity(long capacity) {
+		if (capacity < 0) {
+			throw new IllegalArgumentException("Size " + capacity + " < 0");
 		}
 
-		if (size == 0) {
+		if (capacity == 0) {
 			return false;
 		}
 
-		if (this.size == 0) {
-			this.size = size;
-			GlBufferType.COPY_WRITE_BUFFER.bind(handle());
-			glBufferData(GlBufferType.COPY_WRITE_BUFFER.glEnum, size, usage.glEnum);
-			FlwMemoryTracker._allocGPUMemory(size);
-
+		if (size == 0) {
+			alloc(capacity);
 			return true;
 		}
 
-		if (size > this.size) {
-			var oldSize = this.size;
-			this.size = size + growthMargin;
-
-			realloc(oldSize, this.size);
-
+		if (capacity > size) {
+			realloc(capacity);
 			return true;
 		}
 
 		return false;
 	}
 
-	private void realloc(long oldSize, long newSize) {
-		FlwMemoryTracker._freeGPUMemory(oldSize);
-		FlwMemoryTracker._allocGPUMemory(newSize);
-		var oldHandle = handle();
-		var newHandle = glGenBuffers();
+	private void alloc(long capacity) {
+		increaseSize(capacity);
+		IMPL.data(handle(), size, MemoryUtil.NULL, usage.glEnum);
+		FlwMemoryTracker._allocGPUMemory(size);
+	}
 
-		GlBufferType.COPY_READ_BUFFER.bind(oldHandle);
-		GlBufferType.COPY_WRITE_BUFFER.bind(newHandle);
-
-		glBufferData(GlBufferType.COPY_WRITE_BUFFER.glEnum, newSize, usage.glEnum);
-		glCopyBufferSubData(GlBufferType.COPY_READ_BUFFER.glEnum, GlBufferType.COPY_WRITE_BUFFER.glEnum, 0, 0, oldSize);
+	private void realloc(long capacity) {
+		FlwMemoryTracker._freeGPUMemory(size);
+		var oldSize = size;
+		increaseSize(capacity);
 
+		int oldHandle = handle();
+		int newHandle = IMPL.create();
+		IMPL.data(newHandle, size, MemoryUtil.NULL, usage.glEnum);
+		IMPL.copyData(oldHandle, newHandle, 0, 0, oldSize);
 		glDeleteBuffers(oldHandle);
 		setHandle(newHandle);
+
+		FlwMemoryTracker._allocGPUMemory(size);
+	}
+
+	/**
+	 * Increase the size of the buffer to at least the given capacity.
+	 */
+	private void increaseSize(long capacity) {
+		size = capacity + growthMargin;
 	}
 
 	public void upload(MemoryBlock directBuffer) {
 		FlwMemoryTracker._freeGPUMemory(size);
-		GlBufferType.COPY_WRITE_BUFFER.bind(handle());
-		nglBufferData(GlBufferType.COPY_WRITE_BUFFER.glEnum, directBuffer.size(), directBuffer.ptr(), usage.glEnum);
-		this.size = directBuffer.size();
+		IMPL.data(handle(), directBuffer.size(), directBuffer.ptr(), usage.glEnum);
+		size = directBuffer.size();
 		FlwMemoryTracker._allocGPUMemory(size);
 	}
 
@@ -91,16 +94,16 @@ public class GlBuffer extends GlObject {
 		return new MappedBuffer(handle(), size);
 	}
 
-	public void setGrowthMargin(int growthMargin) {
+	public void growthMargin(int growthMargin) {
 		this.growthMargin = growthMargin;
 	}
 
-	public long getSize() {
+	public long size() {
 		return size;
 	}
 
 	protected void deleteInternal(int handle) {
-		glDeleteBuffers(handle);
+		GlStateManager._glDeleteBuffers(handle);
 		FlwMemoryTracker._freeGPUMemory(size);
 	}
 }

src/main/java/com/jozufozu/flywheel/gl/buffer/MappedBuffer.java

@@ -1,10 +1,8 @@
 package com.jozufozu.flywheel.gl.buffer;
 
 import static org.lwjgl.opengl.GL30.GL_MAP_WRITE_BIT;
-import static org.lwjgl.opengl.GL30.nglMapBufferRange;
 import static org.lwjgl.system.MemoryUtil.NULL;
 
-import org.lwjgl.opengl.GL15;
 import org.lwjgl.system.MemoryUtil;
 
 import com.jozufozu.flywheel.gl.error.GlError;
@@ -17,8 +15,7 @@ public class MappedBuffer implements AutoCloseable {
 	public MappedBuffer(int glBuffer, long size) {
 		this.glBuffer = glBuffer;
 
-		GlBufferType.COPY_READ_BUFFER.bind(glBuffer);
-		ptr = nglMapBufferRange(GlBufferType.COPY_READ_BUFFER.glEnum, 0, size, GL_MAP_WRITE_BIT);
+		ptr = GlBuffer.IMPL.mapRange(glBuffer, 0, size, GL_MAP_WRITE_BIT);
 
 		if (ptr == MemoryUtil.NULL) {
 			throw new GlException(GlError.poll(), "Could not map buffer");
@@ -35,8 +32,7 @@ public class MappedBuffer implements AutoCloseable {
 			return;
 		}
 
-		GlBufferType.COPY_READ_BUFFER.bind(glBuffer);
-		GL15.glUnmapBuffer(GlBufferType.COPY_READ_BUFFER.glEnum);
+		GlBuffer.IMPL.unmap(glBuffer);
 		ptr = NULL;
 	}
 }