From 8b99547d099c96bd8cc6037e2026db123b2523c1 Mon Sep 17 00:00:00 2001
From: Mikko Rasa <tdb@tdb.fi>
Date: Sat, 21 Dec 2013 13:30:02 +0200
Subject: [PATCH] Present Mesh's index buffer as current while the Mesh is
 bound

This simplifies the internal update operations.
---
 source/batch.cpp  | 15 +--------------
 source/buffer.cpp | 19 ++++++++++++++++---
 source/buffer.h   |  2 +-
 source/mesh.cpp   | 22 +++++++++-------------
 source/mesh.h     |  1 +
 5 files changed, 28 insertions(+), 31 deletions(-)

diff --git a/source/batch.cpp b/source/batch.cpp
index bca33484..7f9adff7 100644
--- a/source/batch.cpp
+++ b/source/batch.cpp
@@ -248,25 +248,12 @@ void Batch::draw() const
 
 	if(Buffer *ibuf = get_buffer())
 	{
-		bool have_vao = Mesh::current();
-		const Buffer *old_ibuf = 0;
-		if(!have_vao)
-		{
-			old_ibuf = Buffer::current(ELEMENT_ARRAY_BUFFER);
-			ibuf->bind_to(ELEMENT_ARRAY_BUFFER);
-		}
+		BindRestore _bind_ibuf(ibuf, ELEMENT_ARRAY_BUFFER);
 
 		if(dirty)
 			update_buffer();
 
 		glDrawRangeElements(prim_type, min_index, max_index, size(), data_type, reinterpret_cast<void *>(get_offset()));
-		if(!have_vao)
-		{
-			if(old_ibuf)
-				old_ibuf->bind_to(ELEMENT_ARRAY_BUFFER);
-			else
-				Buffer::unbind_from(ELEMENT_ARRAY_BUFFER);
-		}
 	}
 	else
 		glDrawRangeElements(prim_type, min_index, max_index, size(), data_type, &data[0]);
diff --git a/source/buffer.cpp b/source/buffer.cpp
index 61670cf9..9fa03c12 100644
--- a/source/buffer.cpp
+++ b/source/buffer.cpp
@@ -65,13 +65,26 @@ void Buffer::bind_to(BufferType t) const
 {
 	if(t!=type)
 		require_buffer_type(t);
-	// Don't change the binding in a mesh's vertex array object
-	if(t==ELEMENT_ARRAY_BUFFER && Mesh::current())
-		throw invalid_operation("Buffer::bind_to(ELEMENT_ARRAY_BUFFER)");
+	if(t==ELEMENT_ARRAY_BUFFER)
+		if(const Mesh *m = Mesh::current())
+		{
+			// Don't change the binding in a mesh's vertex array object
+			if(this==m->get_index_buffer())
+				return;
+			throw invalid_operation("Buffer::bind_to(ELEMENT_ARRAY_BUFFER)");
+		}
 	if(set_current(t, this))
 		glBindBuffer(t, id);
 }
 
+const Buffer *Buffer::current(BufferType t)
+{
+	if(t==ELEMENT_ARRAY_BUFFER)
+		if(const Mesh *m = Mesh::current())
+			return m->get_index_buffer();
+	return binding(t);
+}
+
 void Buffer::unbind_from(BufferType type)
 {
 	if(type==ELEMENT_ARRAY_BUFFER && Mesh::current())
diff --git a/source/buffer.h b/source/buffer.h
index bfbfd148..a7d4c2ba 100644
--- a/source/buffer.h
+++ b/source/buffer.h
@@ -89,7 +89,7 @@ public:
 	/** Unbinds the buffer from its default slot. */
 	void unbind() const { unbind_from(type); }
 
-	static const Buffer *current(BufferType t) { return binding(t); }
+	static const Buffer *current(BufferType);
 	static void unbind_from(BufferType);
 private:
 	static const Buffer *&binding(BufferType);
diff --git a/source/mesh.cpp b/source/mesh.cpp
index c9819ae9..413986f4 100644
--- a/source/mesh.cpp
+++ b/source/mesh.cpp
@@ -80,16 +80,18 @@ void Mesh::refresh() const
 	{
 		if(dirty&1)
 		{
-			unbind();
 			for(list<Batch>::const_iterator i=batches.begin(); i!=batches.end(); ++i)
 				i->refresh();
 		}
 
 		if(dirty&2)
 		{
-			glBindVertexArray(vao_id);
 			Bind bind_vbuf(vbuf, ARRAY_BUFFER);
 
+			bool bind_here = !current();
+			if(bind_here)
+				glBindVertexArray(vao_id);
+
 			const VertexFormat &fmt = vertices.get_format();
 			unsigned stride = get_stride(fmt)*sizeof(float);
 			float *ptr = 0;
@@ -107,7 +109,9 @@ void Mesh::refresh() const
 				ptr += sz;
 			}
 			glBindBuffer(ELEMENT_ARRAY_BUFFER, ibuf->get_id());
-			glBindVertexArray(0);
+
+			if(bind_here)
+				glBindVertexArray(0);
 		}
 
 		dirty = 0;
@@ -184,16 +188,8 @@ void Mesh::bind() const
 	called.  Thus unbind won't try to call a null function either. */
 	if(!vao_id)
 		unbind();
-	else
-	{
-		if(Buffer::current(ELEMENT_ARRAY_BUFFER))
-		{
-			unbind();
-			Buffer::unbind_from(ELEMENT_ARRAY_BUFFER);
-		}
-		if(set_current(this))
-			glBindVertexArray(vao_id);
-	}
+	else if(set_current(this))
+		glBindVertexArray(vao_id);
 }
 
 void Mesh::unbind()
diff --git a/source/mesh.h b/source/mesh.h
index 2aba273e..ba21f256 100644
--- a/source/mesh.h
+++ b/source/mesh.h
@@ -55,6 +55,7 @@ private:
 
 public:
 	const VertexArray &get_vertices() const { return vertices; }
+	const Buffer *get_index_buffer() const { return ibuf; }
 	unsigned get_n_vertices() const;
 	float *modify_vertex(unsigned);
 
-- 
2.43.0