From 9ea45d05951ead69fee978000cda90f9cf5f0c81 Mon Sep 17 00:00:00 2001
From: Mikko Rasa <tdb@tdb.fi>
Date: Tue, 26 Jan 2021 01:17:52 +0200
Subject: [PATCH] Better way of refreshing VertexSetup

It can now disable attribute arrays which are no longer used.
---
 source/mesh.cpp         |  4 ++--
 source/vertexformat.cpp |  7 ++++++
 source/vertexformat.h   |  2 ++
 source/vertexsetup.cpp  | 53 +++++++++++++++++++++++++++++++++++------
 source/vertexsetup.h    | 10 +++++++-
 5 files changed, 66 insertions(+), 10 deletions(-)

diff --git a/source/mesh.cpp b/source/mesh.cpp
index 51468f2f..ae08fd83 100644
--- a/source/mesh.cpp
+++ b/source/mesh.cpp
@@ -230,7 +230,7 @@ void Mesh::Loader::vertices(const vector<VertexComponent> &c)
 	if(allow_gl_calls)
 	{
 		obj.check_buffers(VERTEX_BUFFER);
-		obj.vtx_setup.set_vertex_array(obj.vertices);
+		obj.vtx_setup.refresh();
 	}
 }
 
@@ -285,7 +285,7 @@ bool Mesh::AsyncLoader::process()
 	else if(phase==1)
 	{
 		mesh.resize_buffers();
-		mesh.vtx_setup.set_vertex_array(vertices);
+		mesh.vtx_setup.refresh();
 		vertex_updater = mesh.vertices.refresh_async();
 		if(!mesh.batches.empty())
 			index_updater = mesh.batches.front().refresh_async();
diff --git a/source/vertexformat.cpp b/source/vertexformat.cpp
index 037305f8..6c2e2933 100644
--- a/source/vertexformat.cpp
+++ b/source/vertexformat.cpp
@@ -43,6 +43,13 @@ VertexFormat VertexFormat::operator,(unsigned i) const
 	return r;
 }
 
+bool VertexFormat::operator==(const VertexFormat &other) const
+{
+	if(count!=other.count)
+		return false;
+	return equal(components, components+count, other.components);
+}
+
 unsigned VertexFormat::stride() const
 {
 	unsigned s = 0;
diff --git a/source/vertexformat.h b/source/vertexformat.h
index bcb5b925..35612922 100644
--- a/source/vertexformat.h
+++ b/source/vertexformat.h
@@ -44,6 +44,8 @@ public:
 
 	VertexFormat operator,(VertexComponent c) const;
 	VertexFormat operator,(unsigned i) const;
+	bool operator==(const VertexFormat &) const;
+	bool operator!=(const VertexFormat &other) const { return !(*this==other); }
 
 	bool empty() const { return !count; }
 	const unsigned char *begin() const { return components; }
diff --git a/source/vertexsetup.cpp b/source/vertexsetup.cpp
index 19edfb39..d50406a1 100644
--- a/source/vertexsetup.cpp
+++ b/source/vertexsetup.cpp
@@ -42,7 +42,8 @@ void VertexSetup::set_vertex_array(const VertexArray &a)
 		throw invalid_argument("VertexSetup::set_vertex_array");
 
 	vertex_array = &a;
-	update(VERTEX_ARRAY);
+	update(get_update_mask(VERTEX_ARRAY, vertex_format, *vertex_array));
+	vertex_format = vertex_array->get_format();
 }
 
 void VertexSetup::set_instance_array(const VertexArray *a)
@@ -56,7 +57,8 @@ void VertexSetup::set_instance_array(const VertexArray *a)
 	}
 
 	inst_array = a;
-	update(INSTANCE_ARRAY);
+	update(get_update_mask(INSTANCE_ARRAY, inst_format, *inst_array));
+	inst_format = inst_array->get_format();
 }
 
 void VertexSetup::set_index_buffer(const Buffer &ibuf)
@@ -65,6 +67,34 @@ void VertexSetup::set_index_buffer(const Buffer &ibuf)
 	update(INDEX_BUFFER);
 }
 
+void VertexSetup::refresh()
+{
+	if(vertex_array && vertex_array->get_format()!=vertex_format)
+		set_vertex_array(*vertex_array);
+
+	if(inst_array && inst_array->get_format()!=inst_format)
+		set_instance_array(inst_array);
+}
+
+unsigned VertexSetup::get_attribs(const VertexFormat &fmt)
+{
+	unsigned mask = 0;
+	for(const unsigned char *c=fmt.begin(); c!=fmt.end(); ++c)
+	{
+		unsigned t = get_component_type(*c);
+		if(t>=get_component_type(ATTRIB1))
+			t -= get_component_type(ATTRIB1);
+		mask |= 1<<t;
+	}
+	return mask;
+}
+
+unsigned VertexSetup::get_update_mask(unsigned base, const VertexFormat &cur_fmt, const VertexArray &new_array)
+{
+	unsigned unused = get_attribs(cur_fmt)&~get_attribs(new_array.get_format());
+	return base | (unused ? UNUSED_ATTRIBS | (unused<<ATTRIB_SHIFT) : 0);
+}
+
 void VertexSetup::update(unsigned mask) const
 {
 	static bool direct = ARB_direct_state_access && ARB_vertex_attrib_binding;
@@ -74,14 +104,23 @@ void VertexSetup::update(unsigned mask) const
 		return;
 	}
 
+	if(mask&UNUSED_ATTRIBS)
+	{
+		for(unsigned i=0, am=mask>>ATTRIB_SHIFT; am; ++i, am>>=1)
+			if(am&1)
+			{
+				if(direct)
+					glDisableVertexArrayAttrib(id, i);
+				else
+					glDisableVertexAttribArray(i);
+			}
+	}
+
 	if(mask&VERTEX_ARRAY)
 		update_vertex_array(*vertex_array, 0, 0, direct);
 
-	if(mask&INSTANCE_ARRAY)
-	{
-		if(inst_array)
-			update_vertex_array(*inst_array, 1, 1, direct);
-	}
+	if((mask&INSTANCE_ARRAY) && inst_array)
+		update_vertex_array(*inst_array, 1, 1, direct);
 
 	if(mask&INDEX_BUFFER)
 	{
diff --git a/source/vertexsetup.h b/source/vertexsetup.h
index 9e7409ac..bae4c5f3 100644
--- a/source/vertexsetup.h
+++ b/source/vertexsetup.h
@@ -2,6 +2,7 @@
 #define MSP_GL_VERTEXSETUP_H_
 
 #include "bindable.h"
+#include "vertexformat.h"
 
 namespace Msp {
 namespace GL {
@@ -19,13 +20,17 @@ private:
 	{
 		VERTEX_ARRAY = 1,
 		INSTANCE_ARRAY = 2,
-		INDEX_BUFFER = 4
+		INDEX_BUFFER = 4,
+		UNUSED_ATTRIBS = 8,
+		ATTRIB_SHIFT = 4
 	};
 
 	unsigned id;
 	mutable unsigned dirty;
 	const VertexArray *vertex_array;
+	VertexFormat vertex_format;
 	const VertexArray *inst_array;
+	VertexFormat inst_format;
 	const Buffer *index_buffer;
 
 public:
@@ -35,11 +40,14 @@ public:
 	void set_vertex_array(const VertexArray &);
 	void set_instance_array(const VertexArray *);
 	void set_index_buffer(const Buffer &);
+	void refresh();
 	const VertexArray *get_vertex_array() const { return vertex_array; }
 	const VertexArray *get_instance_array() const { return inst_array; }
 	const Buffer *get_index_buffer() const { return index_buffer; }
 
 private:
+	static unsigned get_attribs(const VertexFormat &);
+	static unsigned get_update_mask(unsigned, const VertexFormat &, const VertexArray &);
 	void update(unsigned) const;
 	void update_vertex_array(const VertexArray &, unsigned, unsigned, bool) const;
 
-- 
2.43.0