From a0c6318eeaba2d25c8f9e1438c0ff26f8f91531d Mon Sep 17 00:00:00 2001
From: Lee Salzman <lsalzman@gmail.com>
Date: Thu, 18 Sep 2008 01:43:44 +0000
Subject: [PATCH] backported polygon offset replacement from sauer

git-svn-id: svn://svn.code.sf.net/p/actiongame/code/trunk/ac@2673 e016b1c5-ed68-44aa-a2f7-31cac88cffde
---
 source/src/protos.h     |  2 ++
 source/src/rendergl.cpp | 45 ++++++++++++++++++++++++++++++++++++++---
 2 files changed, 44 insertions(+), 3 deletions(-)

diff --git a/source/src/protos.h b/source/src/protos.h
index 4aaefdc4..f3f12b7f 100644
--- a/source/src/protos.h
+++ b/source/src/protos.h
@@ -208,6 +208,8 @@ extern GLdouble mvmatrix[16], projmatrix[16], mvpmatrix[16], invmvmatrix[16];
 extern void gl_checkextensions();
 extern void gl_init(int w, int h, int bpp, int depth, int fsaa);
 extern void cleangl();
+extern void enablepolygonoffset(GLenum type);
+extern void disablepolygonoffset(GLenum type, bool restore = true);
 extern void line(int x1, int y1, float z1, int x2, int y2, float z2);
 extern void line(int x1, int y1, int x2, int y2, color *c = NULL);
 extern void box(block &b, float z1, float z2, float z3, float z4);
diff --git a/source/src/rendergl.cpp b/source/src/rendergl.cpp
index 3ae1ed67..02040862 100644
--- a/source/src/rendergl.cpp
+++ b/source/src/rendergl.cpp
@@ -114,7 +114,6 @@ void gl_init(int w, int h, int bpp, int depth, int fsaa)
 
     glEnable(GL_LINE_SMOOTH);
     glHint(GL_LINE_SMOOTH_HINT, GL_NICEST);
-    glPolygonOffset(-3.0, -3.0);
 
     glCullFace(GL_FRONT);
     glEnable(GL_CULL_FACE);
@@ -126,6 +125,44 @@ void gl_init(int w, int h, int bpp, int depth, int fsaa)
     camera1 = player1;
 }
 
+FVAR(polygonoffsetfactor, -3.0f);
+FVAR(polygonoffsetunits, -3.0f);
+FVAR(depthoffset, 0.005f);
+
+void enablepolygonoffset(GLenum type)
+{
+    if(!depthoffset)
+    {
+        glPolygonOffset(polygonoffsetfactor, polygonoffsetunits);
+        glEnable(type);
+        return;
+    }
+
+    GLdouble offsetmatrix[16];
+    memcpy(offsetmatrix, projmatrix, 16*sizeof(GLdouble));
+    offsetmatrix[14] += depthoffset * projmatrix[10];
+
+    glMatrixMode(GL_PROJECTION);
+    glLoadMatrixd(offsetmatrix);
+    glMatrixMode(GL_MODELVIEW);
+}
+
+void disablepolygonoffset(GLenum type, bool restore)
+{
+    if(!depthoffset)
+    {
+        glDisable(type);
+        return;
+    }
+
+    if(restore)
+    {
+        glMatrixMode(GL_PROJECTION);
+        glLoadMatrixd(projmatrix);
+        glMatrixMode(GL_MODELVIEW);
+    }
+}
+
 void line(int x1, int y1, float z1, int x2, int y2, float z2)
 {
     glBegin(GL_POLYGON);
@@ -948,11 +985,13 @@ void gl_drawframe(int w, int h, float changelod, float curfps)
     if(editmode)
     {
         if(cursordepth==1.0f) worldpos = camera1->o;
-        glEnable(GL_POLYGON_OFFSET_LINE);
+        enablepolygonoffset(GL_POLYGON_OFFSET_LINE);
         glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
+        glDepthMask(GL_FALSE);
         cursorupdate();
+        glDepthMask(GL_TRUE);
         glPolygonMode(GL_FRONT_AND_BACK, GL_FILL);
-        glDisable(GL_POLYGON_OFFSET_LINE);
+        disablepolygonoffset(GL_POLYGON_OFFSET_LINE, false);
     }
 
     extern vector<vertex> verts;