From 5df9e64424dd157da1410b4498f53a4ac21e6aee Mon Sep 17 00:00:00 2001
From: Mikko Rasa <tdb@tdb.fi>
Date: Sat, 1 Nov 2014 02:20:27 +0200
Subject: [PATCH] Add begin() method to make Renderer reusable

---
 source/renderer.cpp | 52 ++++++++++++++++++++++++++++++---------------
 source/renderer.h   | 11 ++++++++--
 2 files changed, 44 insertions(+), 19 deletions(-)

diff --git a/source/renderer.cpp b/source/renderer.cpp
index 2f253e2a..2d262e73 100644
--- a/source/renderer.cpp
+++ b/source/renderer.cpp
@@ -22,10 +22,10 @@ namespace GL {
 
 Renderer::Renderer(const Camera *c):
 	mtx_stack(*this),
-	changed(MATRIX),
+	changed(0),
 	matrices_loaded(false),
 	shdata_applied(0),
-	camera(c),
+	camera(0),
 	state_stack(1),
 	element_buffer(0)
 {
@@ -33,6 +33,23 @@ Renderer::Renderer(const Camera *c):
 	shdata_stack.reserve(32);
 	state = &state_stack.back();
 
+	begin(c);
+}
+
+Renderer::~Renderer()
+{
+	end();
+}
+
+void Renderer::begin(const Camera *c)
+{
+	if(state_stack.size()>1)
+		throw invalid_operation("Renderer::begin");
+
+	reset_state();
+	excluded.clear();
+	camera = c;
+
 	if(camera)
 	{
 		mtx_stack.load(camera->get_matrix());
@@ -40,16 +57,11 @@ Renderer::Renderer(const Camera *c):
 	}
 	else
 	{
-		standard_shdata.uniform("projection_matrix", MatrixStack::projection().top());
 		mtx_stack.load(MatrixStack::modelview().top());
+		standard_shdata.uniform("projection_matrix", MatrixStack::projection().top());
 	}
 }
 
-Renderer::~Renderer()
-{
-	end();
-}
-
 void Renderer::set_texture(const Texture *t)
 {
 	state->texture = t;
@@ -158,13 +170,7 @@ void Renderer::end()
 	if(state_stack.size()>1)
 		throw invalid_operation("Renderer::end");
 
-	if(matrices_loaded)
-	{
-		if(camera)
-			MatrixStack::projection().pop();
-		MatrixStack::modelview().pop();
-		matrices_loaded = false;
-	}
+	reset_state();
 
 	Mesh::unbind();
 	Texturing::unbind();
@@ -174,8 +180,6 @@ void Renderer::end()
 	Program::unbind();
 	Buffer::unbind_from(ELEMENT_ARRAY_BUFFER);
 	WindingTest::unbind();
-
-	*state = State();
 }
 
 void Renderer::exclude(const Renderable &renderable)
@@ -331,6 +335,20 @@ void Renderer::apply_state()
 	}
 }
 
+void Renderer::reset_state()
+{
+	if(!matrices_loaded)
+		return;
+
+	if(camera)
+		MatrixStack::projection().pop();
+	MatrixStack::modelview().pop();
+	matrices_loaded = false;
+	changed |= MATRIX;
+
+	*state = State();
+}
+
 
 Renderer::State::State():
 	texture(0),
diff --git a/source/renderer.h b/source/renderer.h
index dd946412..1f198dae 100644
--- a/source/renderer.h
+++ b/source/renderer.h
@@ -114,6 +114,11 @@ public:
 	Renderer(const Camera *);
 	~Renderer();
 
+	/** Resets all internal state and restarts rendering.  There must be no
+	unpopped state in the stack.  It is permissible to call begin() multiple
+	times without an intervening end(). */
+	void begin(const Camera *);
+
 	MatrixStack &matrix_stack() { return mtx_stack; }
 
 	const Camera *get_camera() const { return camera; }
@@ -151,8 +156,9 @@ public:
 	Renderer.  DEPRECATED. */
 	void escape();
 
-	/** Ends rendering, unbinding all objects and resetting state.  There must
-	be no unpopped state in the stack. */
+	/** Unbinds all objects and resets related state.  There must be no unpopped
+	state in the stack.  Rendering with the same camera can be restarted without
+	an explicit begin() call. */
 	void end();
 
 	void exclude(const Renderable &);
@@ -163,6 +169,7 @@ public:
 
 private:
 	void apply_state();
+	void reset_state();
 };
 
 } // namespace GL
-- 
2.45.2