From 2185922d384ac752ed3450e6cc6bb75c28e2b725 Mon Sep 17 00:00:00 2001
From: bjorn <tie.372@gmail.com>
Date: Mon, 8 Aug 2016 18:27:35 -0700
Subject: [PATCH] Buffer draw range;

---
 src/graphics/buffer.c   | 26 +++++++++++++++++++++++++-
 src/graphics/buffer.h   |  4 ++++
 src/graphics/graphics.c |  2 ++
 3 files changed, 31 insertions(+), 1 deletion(-)

diff --git a/src/graphics/buffer.c b/src/graphics/buffer.c
index dc6032e2..16c87989 100644
--- a/src/graphics/buffer.c
+++ b/src/graphics/buffer.c
@@ -31,7 +31,7 @@ int lovrBufferDraw(lua_State* L) {
 
   glBindVertexArray(buffer->vao);
   glEnableVertexAttribArray(0);
-  glDrawArrays(*drawMode, 0, buffer->size);
+  glDrawArrays(*drawMode, buffer->rangeStart, buffer->rangeCount);
   glDisableVertexAttribArray(0);
 
   return 0;
@@ -86,11 +86,35 @@ int lovrBufferSetVertex(lua_State* L) {
   return 0;
 }
 
+int lovrBufferGetDrawRange(lua_State* L) {
+  Buffer* buffer = luax_checkbuffer(L, 1);
+  lua_pushnumber(L, buffer->rangeStart + 1);
+  lua_pushnumber(L, buffer->rangeStart + 1 + buffer->rangeCount);
+  return 2;
+}
+
+int lovrBufferSetDrawRange(lua_State* L) {
+  Buffer* buffer = luax_checkbuffer(L, 1);
+  int rangeStart = luaL_checknumber(L, 2);
+  int rangeEnd = luaL_checknumber(L, 3);
+
+  if (rangeStart <= 0 || rangeEnd <= 0 || rangeStart > rangeEnd) {
+    return luaL_error(L, "Invalid buffer draw range (%d, %d)", rangeStart, rangeEnd);
+  }
+
+  buffer->rangeStart = rangeStart - 1;
+  buffer->rangeCount = rangeEnd - rangeStart + 1;
+
+  return 0;
+}
+
 const luaL_Reg lovrBuffer[] = {
   { "draw", lovrBufferDraw },
   { "getVertex", lovrBufferGetVertex },
   { "setVertex", lovrBufferSetVertex },
   { "getDrawMode", lovrBufferGetDrawMode },
   { "setDrawMode", lovrBufferSetDrawMode },
+  { "getDrawRange", lovrBufferGetDrawRange },
+  { "setDrawRange", lovrBufferSetDrawRange },
   { NULL, NULL }
 };
diff --git a/src/graphics/buffer.h b/src/graphics/buffer.h
index 2b5d677e..29b56711 100644
--- a/src/graphics/buffer.h
+++ b/src/graphics/buffer.h
@@ -10,6 +10,8 @@ typedef struct {
   const char* drawMode;
   GLuint vao;
   GLuint vbo;
+  int rangeStart;
+  int rangeCount;
 } Buffer;
 
 map_int_t BufferDrawModes;
@@ -23,5 +25,7 @@ int lovrBufferGetVertex(lua_State* L);
 int lovrBufferSetVertex(lua_State* L);
 int lovrBufferGetDrawMode(lua_State* L);
 int lovrBufferSetDrawMode(lua_State* L);
+int lovrBufferGetDrawRange(lua_State* L);
+int lovrBufferSetDrawRange(lua_State* L);
 
 extern const luaL_Reg lovrBuffer[];
diff --git a/src/graphics/graphics.c b/src/graphics/graphics.c
index 20d06c87..08799cb2 100644
--- a/src/graphics/graphics.c
+++ b/src/graphics/graphics.c
@@ -78,6 +78,8 @@ int lovrGraphicsNewBuffer(lua_State* L) {
   buffer->drawMode = "fan";
   buffer->size = size;
   buffer->data = malloc(buffer->size * 3 * sizeof(GLfloat));
+  buffer->rangeStart = 0;
+  buffer->rangeCount = buffer->size;
 
   glGenBuffers(1, &buffer->vbo);
   glBindBuffer(GL_ARRAY_BUFFER, buffer->vbo);