From 25376ba3107d36567a30a995fcaf3fd99937ed9d Mon Sep 17 00:00:00 2001
From: Alex Szpakowski <slime73@gmail.com>
Date: Wed, 21 Sep 2016 20:03:39 -0300
Subject: [PATCH] Added SpriteBatch:setDrawRange(start, count) and
 SpriteBatch:getDrawRange.

--HG--
branch : minor
---
 src/modules/graphics/opengl/Mesh.cpp          |  5 ++-
 src/modules/graphics/opengl/SpriteBatch.cpp   | 39 ++++++++++++++++++-
 src/modules/graphics/opengl/SpriteBatch.h     |  7 ++++
 .../graphics/opengl/wrap_SpriteBatch.cpp      | 32 +++++++++++++++
 4 files changed, 81 insertions(+), 2 deletions(-)

diff --git a/src/modules/graphics/opengl/Mesh.cpp b/src/modules/graphics/opengl/Mesh.cpp
index 64877ce0b..e28768f44 100644
--- a/src/modules/graphics/opengl/Mesh.cpp
+++ b/src/modules/graphics/opengl/Mesh.cpp
@@ -533,7 +533,7 @@ void Mesh::setDrawRange()
 
 bool Mesh::getDrawRange(int &start, int &count) const
 {
-	if (rangeStart < 0 || rangeCount < 0)
+	if (rangeStart < 0 || rangeCount <= 0)
 		return false;
 
 	start = rangeStart;
@@ -576,6 +576,9 @@ int Mesh::bindAttributeToShaderInput(int attributeindex, const std::string &inpu
 
 void Mesh::draw(float x, float y, float angle, float sx, float sy, float ox, float oy, float kx, float ky)
 {
+	if (vertexCount <= 0)
+		return;
+
 	OpenGL::TempDebugGroup debuggroup("Mesh draw");
 
 	uint32 enabledattribs = 0;
diff --git a/src/modules/graphics/opengl/SpriteBatch.cpp b/src/modules/graphics/opengl/SpriteBatch.cpp
index 27671dbd8..dcf9e8eac 100644
--- a/src/modules/graphics/opengl/SpriteBatch.cpp
+++ b/src/modules/graphics/opengl/SpriteBatch.cpp
@@ -48,6 +48,8 @@ SpriteBatch::SpriteBatch(Texture *texture, int size, Mesh::Usage usage)
 	, color(0)
 	, array_buf(nullptr)
 	, quad_indices(size)
+	, range_start(-1)
+	, range_count(-1)
 {
 	if (size <= 0)
 		throw love::Exception("Invalid SpriteBatch size.");
@@ -223,6 +225,30 @@ void SpriteBatch::attachAttribute(const std::string &name, Mesh *mesh)
 	attached_attributes[name] = newattrib;
 }
 
+void SpriteBatch::setDrawRange(int start, int count)
+{
+	if (start < 0 || count <= 0)
+		throw love::Exception("Invalid draw range.");
+
+	range_start = start;
+	range_count = count;
+}
+
+void SpriteBatch::setDrawRange()
+{
+	range_start = range_count = -1;
+}
+
+bool SpriteBatch::getDrawRange(int &start, int &count) const
+{
+	if (range_start < 0 || range_count <= 0)
+		return false;
+
+	start = range_start;
+	count = range_count;
+	return true;
+}
+
 void SpriteBatch::draw(float x, float y, float angle, float sx, float sy, float ox, float oy, float kx, float ky)
 {
 	const size_t pos_offset   = offsetof(Vertex, x);
@@ -279,8 +305,19 @@ void SpriteBatch::draw(float x, float y, float angle, float sx, float sy, float
 
 	gl.prepareDraw();
 
+	int start = std::min(std::max(0, range_start), next - 1);
+
+	int count = next;
+	if (range_count > 0)
+		count = std::min(count, range_count);
+
+	count = std::min(count, next - start);
+
 	GLBuffer::Bind element_bind(*quad_indices.getBuffer());
-	gl.drawElements(GL_TRIANGLES, (GLsizei) quad_indices.getIndexCount(next), quad_indices.getType(), quad_indices.getPointer(0));
+	const void *indices = quad_indices.getPointer(start * quad_indices.getElementSize());
+
+	if (count > 0)
+		gl.drawElements(GL_TRIANGLES, (GLsizei) quad_indices.getIndexCount(count), quad_indices.getType(), indices);
 }
 
 void SpriteBatch::addv(const Vertex *v, const Matrix3 &m, int index)
diff --git a/src/modules/graphics/opengl/SpriteBatch.h b/src/modules/graphics/opengl/SpriteBatch.h
index 8a40581dd..9e865b1b2 100644
--- a/src/modules/graphics/opengl/SpriteBatch.h
+++ b/src/modules/graphics/opengl/SpriteBatch.h
@@ -101,6 +101,10 @@ public:
 	 **/
 	void attachAttribute(const std::string &name, Mesh *mesh);
 
+	void setDrawRange(int start, int count);
+	void setDrawRange();
+	bool getDrawRange(int &start, int &count) const;
+
 	// Implements Drawable.
 	void draw(float x, float y, float angle, float sx, float sy, float ox, float oy, float kx, float ky);
 
@@ -146,6 +150,9 @@ private:
 
 	std::unordered_map<std::string, AttachedAttribute> attached_attributes;
 
+	int range_start;
+	int range_count;
+
 }; // SpriteBatch
 
 } // opengl
diff --git a/src/modules/graphics/opengl/wrap_SpriteBatch.cpp b/src/modules/graphics/opengl/wrap_SpriteBatch.cpp
index 325a6949b..e1eed3773 100644
--- a/src/modules/graphics/opengl/wrap_SpriteBatch.cpp
+++ b/src/modules/graphics/opengl/wrap_SpriteBatch.cpp
@@ -205,6 +205,36 @@ int w_SpriteBatch_attachAttribute(lua_State *L)
 	return 0;
 }
 
+int w_SpriteBatch_setDrawRange(lua_State *L)
+{
+	SpriteBatch *t = luax_checkspritebatch(L, 1);
+
+	if (lua_isnoneornil(L, 2))
+		t->setDrawRange();
+	else
+	{
+		int start = (int) luaL_checknumber(L, 2) - 1;
+		int count = (int) luaL_checknumber(L, 3);
+		luax_catchexcept(L, [&](){ t->setDrawRange(start, count); });
+	}
+
+	return 0;
+}
+
+int w_SpriteBatch_getDrawRange(lua_State *L)
+{
+	SpriteBatch *t = luax_checkspritebatch(L, 1);
+
+	int start = 0;
+	int count = 1;
+	if (!t->getDrawRange(start, count))
+		return 0;
+
+	lua_pushnumber(L, start + 1);
+	lua_pushnumber(L, count);
+	return 2;
+}
+
 static const luaL_Reg w_SpriteBatch_functions[] =
 {
 	{ "add", w_SpriteBatch_add },
@@ -218,6 +248,8 @@ static const luaL_Reg w_SpriteBatch_functions[] =
 	{ "getCount", w_SpriteBatch_getCount },
 	{ "getBufferSize", w_SpriteBatch_getBufferSize },
 	{ "attachAttribute", w_SpriteBatch_attachAttribute },
+	{ "setDrawRange", w_SpriteBatch_setDrawRange },
+	{ "getDrawRange", w_SpriteBatch_getDrawRange },
 	{ 0, 0 }
 };