From 052b85720688900bc36f8844a94269cb1c0cdd52 Mon Sep 17 00:00:00 2001
From: Mikko Rasa <tdb@tdb.fi>
Date: Fri, 1 Oct 2021 12:51:31 +0300
Subject: [PATCH] Add an abstraction for queries

---
 source/core/commands.cpp   | 14 ++++++++
 source/core/commands.h     |  4 +++
 source/core/query.cpp      | 73 ++++++++++++++++++++++++++++++++++++++
 source/core/query.h        | 54 ++++++++++++++++++++++++++++
 source/render/renderer.cpp | 10 ++++++
 source/render/renderer.h   |  4 +++
 6 files changed, 159 insertions(+)
 create mode 100644 source/core/query.cpp
 create mode 100644 source/core/query.h

diff --git a/source/core/commands.cpp b/source/core/commands.cpp
index 19ff1011..a0a4336a 100644
--- a/source/core/commands.cpp
+++ b/source/core/commands.cpp
@@ -1,6 +1,7 @@
 #include <algorithm>
 #include <msp/gl/extensions/arb_direct_state_access.h>
 #include <msp/gl/extensions/arb_draw_instanced.h>
+#include <msp/gl/extensions/arb_occlusion_query.h>
 #include <msp/gl/extensions/ext_framebuffer_blit.h>
 #include <msp/gl/extensions/ext_framebuffer_object.h>
 #include <msp/gl/extensions/msp_clear_buffer.h>
@@ -9,6 +10,7 @@
 #include "error.h"
 #include "gl.h"
 #include "pipelinestate.h"
+#include "query.h"
 
 using namespace std;
 
@@ -107,5 +109,17 @@ void Commands::resolve_multisample(Framebuffer &target)
 	}
 }
 
+void Commands::begin_query(const QueryPool &pool, unsigned index)
+{
+	if(index>=pool.queries.size())
+		throw out_of_range("OpenGLCommands::begin_query");
+	glBeginQuery(pool.gl_type, pool.queries[index]);
+}
+
+void Commands::end_query(const QueryPool &pool, unsigned)
+{
+	glEndQuery(pool.gl_type);
+}
+
 } // namespace GL
 } // namespace Msp
diff --git a/source/core/commands.h b/source/core/commands.h
index ca10f784..d290e34e 100644
--- a/source/core/commands.h
+++ b/source/core/commands.h
@@ -8,6 +8,7 @@ namespace GL {
 
 class Batch;
 class PipelineState;
+class QueryPool;
 
 class Commands
 {
@@ -22,6 +23,9 @@ public:
 	void draw(const Batch &);
 	void draw_instanced(const Batch &, unsigned);
 	void resolve_multisample(Framebuffer &);
+
+	void begin_query(const QueryPool &, unsigned);
+	void end_query(const QueryPool &, unsigned);
 };
 
 } // namespace GL
diff --git a/source/core/query.cpp b/source/core/query.cpp
new file mode 100644
index 00000000..a6d77eda
--- /dev/null
+++ b/source/core/query.cpp
@@ -0,0 +1,73 @@
+#include <stdexcept>
+#include <msp/gl/extensions/arb_occlusion_query.h>
+#include <msp/gl/extensions/arb_occlusion_query2.h>
+#include "query.h"
+#include "renderer.h"
+
+using namespace std;
+
+namespace Msp {
+namespace GL {
+
+QueryPool::QueryPool(QueryType t, unsigned s):
+	type(t),
+	gl_type(get_gl_query_type(type))
+{
+	if(type==OCCLUSION_QUERY)
+	{
+		static Require req(ARB_occlusion_query);
+		static Require req2(ARB_occlusion_query2);
+	}
+
+	resize(s);
+}
+
+QueryPool::~QueryPool()
+{
+	glDeleteQueries(queries.size(), queries.data());
+}
+
+void QueryPool::resize(unsigned s)
+{
+	if(s<queries.size())
+		glDeleteQueries(queries.size()-s, queries.data()+s);
+
+	unsigned old_size = queries.size();
+	queries.resize(s);
+	if(s>old_size)
+		glGenQueries(s-old_size, queries.data()+old_size);
+}
+
+unsigned QueryPool::get_result(unsigned i) const
+{
+	unsigned result = 0;
+	glGetQueryObjectuiv(queries[i], GL_QUERY_RESULT, &result);
+	return result;
+}
+
+
+QueryPool::Activate::Activate(Renderer &r, const QueryPool &p, unsigned i):
+	renderer(r),
+	pool(p),
+	index(i)
+{
+	renderer.begin_query(pool, index);
+}
+
+QueryPool::Activate::~Activate()
+{
+	renderer.end_query(pool, index);
+}
+
+
+unsigned get_gl_query_type(QueryType t)
+{
+	switch(t)
+	{
+	case OCCLUSION_QUERY: return GL_ANY_SAMPLES_PASSED;
+	default: throw invalid_argument("get_gl_query_type");
+	}
+}
+
+} // namespace GL
+} // namespace Msp
diff --git a/source/core/query.h b/source/core/query.h
new file mode 100644
index 00000000..aaa993e3
--- /dev/null
+++ b/source/core/query.h
@@ -0,0 +1,54 @@
+#ifndef MSP_GL_QUERY_H_
+#define MSP_GL_QUERY_H_
+
+#include <vector>
+#include <msp/core/noncopyable.h>
+
+namespace Msp {
+namespace GL {
+
+class Renderer;
+
+enum QueryType
+{
+	OCCLUSION_QUERY
+};
+
+class QueryPool: public Msp::NonCopyable
+{
+	friend class Commands;
+
+public:
+	class Activate
+	{
+	private:
+		Renderer &renderer;
+		const QueryPool &pool;
+		unsigned index;
+
+	public:
+		Activate(Renderer &, const QueryPool &, unsigned);
+		~Activate();
+	};
+
+private:
+	QueryType type;
+	unsigned gl_type;
+	std::vector<unsigned> queries;
+
+public:
+	QueryPool(QueryType type, unsigned);
+	~QueryPool();
+
+	void resize(unsigned);
+	unsigned get_size() const { return queries.size(); }
+
+	unsigned get_result(unsigned) const;
+};
+
+unsigned get_gl_query_type(QueryType);
+
+} // namespace Msp
+} // namespace GL
+
+#endif
diff --git a/source/render/renderer.cpp b/source/render/renderer.cpp
index 19148a4d..1d729200 100644
--- a/source/render/renderer.cpp
+++ b/source/render/renderer.cpp
@@ -280,6 +280,16 @@ void Renderer::resolve_multisample(Framebuffer &target)
 	commands.resolve_multisample(target);
 }
 
+void Renderer::begin_query(const QueryPool &pool, unsigned index)
+{
+	commands.begin_query(pool, index);
+}
+
+void Renderer::end_query(const QueryPool &pool, unsigned index)
+{
+	commands.end_query(pool, index);
+}
+
 void Renderer::apply_state()
 {
 	if(!state->shprog)
diff --git a/source/render/renderer.h b/source/render/renderer.h
index 5139c4ce..3e0e50d8 100644
--- a/source/render/renderer.h
+++ b/source/render/renderer.h
@@ -21,6 +21,7 @@ class Material;
 class Mesh;
 class Lighting;
 class Program;
+class QueryPool;
 class Renderable;
 class Sampler;
 class Texture;
@@ -203,6 +204,9 @@ public:
 
 	void resolve_multisample(Framebuffer &);
 
+	void begin_query(const QueryPool &, unsigned);
+	void end_query(const QueryPool &, unsigned);
+
 private:
 	void apply_state();
 };
-- 
2.43.0