From b1474cb085eab4b23d951b1716b67e0c4bfd55c5 Mon Sep 17 00:00:00 2001
From: Nick Gasson <nick@nickg.me.uk>
Date: Sun, 7 Feb 2010 13:50:05 +0000
Subject: [PATCH] Render tree to display list

---
 include/OpenGLHelper.hpp |  1 +
 src/LTree.cpp            | 35 +++++++++++++++++++++++++++++++++--
 src/OpenGLHelper.cpp     | 17 ++++++++++++-----
 3 files changed, 46 insertions(+), 7 deletions(-)

diff --git a/include/OpenGLHelper.hpp b/include/OpenGLHelper.hpp
index 25375f9..84a24ed 100644
--- a/include/OpenGLHelper.hpp
+++ b/include/OpenGLHelper.hpp
@@ -31,6 +31,7 @@ void initGL();
 void drawGLScene(IWindowPtr aWindow, IGraphicsPtr aContext, IScreenPtr aScreen);
 void resizeGLScene(IWindowPtr aWindow);
 void printGLVersion();
+void checkGLError();
 
 // Wrappers for OpenGL picking features
 void beginPick(IWindowPtr aWindow, unsigned* aBuffer, int x, int y);
diff --git a/src/LTree.cpp b/src/LTree.cpp
index 92cd735..b06378f 100644
--- a/src/LTree.cpp
+++ b/src/LTree.cpp
@@ -125,6 +125,7 @@ using namespace lsystem;
 class LTree : public IScenery {
 public:
     LTree();
+    ~LTree();
 
     // IScenery interface
     void render() const;
@@ -140,9 +141,12 @@ private:
     };
    
     void interpret(Token t, RenderState& rs) const;
+    void renderToDisplayList() const;
 
     LSystem ls;
     Vector<float> position;
+
+    GLuint displayList;
    
     static const Rule rules[];
 };
@@ -165,6 +169,14 @@ LTree::LTree()
 	evolve(ls);
 	//debug() << "n=" << n << ": " << ls;
     }
+
+    displayList = glGenLists(1);
+    renderToDisplayList();
+}
+
+LTree::~LTree()
+{
+    glDeleteLists(displayList, 1);
 }
 
 void LTree::interpret(Token t, RenderState& rs) const
@@ -220,11 +232,28 @@ void LTree::interpret(Token t, RenderState& rs) const
 
 void LTree::render() const
 {
-    using namespace placeholders;
+    glPushAttrib(GL_ENABLE_BIT);
 
-    glPushMatrix();
+    glDisable(GL_BLEND);
+    glDisable(GL_TEXTURE_2D);
 
+    glPushMatrix();
+    
     gl::translate(position);
+    glCallList(displayList);
+
+    glPopMatrix();
+    
+    glPopAttrib();
+}
+
+void LTree::renderToDisplayList() const
+{
+    using namespace placeholders;
+
+    glNewList(displayList, GL_COMPILE);
+
+    glPushMatrix();
 
     gl::colour(makeRGB(159, 71, 17));
    
@@ -233,6 +262,8 @@ void LTree::render() const
 	bind(&LTree::interpret, this, _1, rs));
 
     glPopMatrix();
+
+    glEndList();
 }
 
 void LTree::setPosition(float x, float y, float z)
diff --git a/src/OpenGLHelper.cpp b/src/OpenGLHelper.cpp
index 628f311..273edb8 100644
--- a/src/OpenGLHelper.cpp
+++ b/src/OpenGLHelper.cpp
@@ -28,6 +28,17 @@
 
 #include <boost/lexical_cast.hpp>
 
+void checkGLError()
+{
+    using namespace boost;
+   
+    GLenum error = glGetError();
+    if (error != GL_NO_ERROR) {   
+	throw runtime_error
+	    ("OpenGL error: " + lexical_cast<string>(gluErrorString(error)));
+    }
+}
+
 void drawGLScene(IWindowPtr aWindow, IGraphicsPtr aContext, IScreenPtr aScreen)
 {
     using namespace boost;
@@ -80,11 +91,7 @@ void drawGLScene(IWindowPtr aWindow, IGraphicsPtr aContext, IScreenPtr aScreen)
     aScreen->overlay();
 
     // Check for OpenGL errors
-    GLenum error = glGetError();
-    if (error != GL_NO_ERROR) {   
-	throw runtime_error
-	    ("OpenGL error: " + lexical_cast<string>(gluErrorString(error)));
-    }
+    checkGLError();
 }
 
 // Report the current OpenGL version
-- 
2.39.2