From df3cdf0ebbb66639eebe8b18183a97842a0a2c95 Mon Sep 17 00:00:00 2001
From: Luke Benstead <kazade@gmail.com>
Date: Thu, 7 Mar 2019 21:41:25 +0000
Subject: [PATCH] Fix drawing polygons. Fixes #35

---
 GL/draw.c             | 31 ++++++++++++++++---------------
 samples/nehe02/main.c | 35 ++++++++++++++++++++++++-----------
 2 files changed, 40 insertions(+), 26 deletions(-)

diff --git a/GL/draw.c b/GL/draw.c
index b922d21..0ca5b88 100644
--- a/GL/draw.c
+++ b/GL/draw.c
@@ -756,6 +756,8 @@ static void genArraysTriangleStrip(
     output[count - 1].flags = PVR_CMD_VERTEX_EOL;
 }
 
+#define MAX_POLYGON_SIZE 10
+
 static void genArraysTriangleFan(
     ClipVertex* output,
     GLsizei count,
@@ -772,25 +774,23 @@ static void genArraysTriangleFan(
         doTexture, doMultitexture, doLighting
     );
 
+    assert(count < MAX_POLYGON_SIZE);
+    static ClipVertex buffer[MAX_POLYGON_SIZE];
+
+    memcpy(buffer, output, sizeof(ClipVertex) * count);
+
+    // First 3 vertices are in the right place, just end early
     swapVertex(&output[1], &output[2]);
     output[2].flags = PVR_CMD_VERTEX_EOL;
 
-    GLsizei i = 3;
+    GLsizei i = 3, target = 3;
     ClipVertex* first = &output[0];
 
-    for(; i < count - 1; ++i) {
-        ClipVertex* next = &output[i + 1];
-        ClipVertex* previous = &output[i - 1];
-        ClipVertex* vertex = &output[i];
-
-        *next = *first;
-
-        swapVertex(next, vertex);
-
-        vertex = next + 1;
-        *vertex = *previous;
-
-        vertex->flags = PVR_CMD_VERTEX_EOL;
+    for(; i < count; ++i) {
+        output[target++] = *first;
+        output[target++] = buffer[i];
+        output[target] = buffer[i - 1];
+        output[target++].flags = PVR_CMD_VERTEX_EOL;
     }
 }
 
@@ -838,6 +838,7 @@ static void generate(ClipVertex* output, const GLenum mode, const GLsizei first,
                 doTexture, doMultitexture, doLighting
             );
             break;
+        case GL_POLYGON:
         case GL_TRIANGLE_FAN:
             genArraysTriangleFan(
                 output,
@@ -887,7 +888,7 @@ static void generate(ClipVertex* output, const GLenum mode, const GLsizei first,
             nptr, nstride,
             doTexture, doMultitexture, doLighting
         );
-    } else if(mode == GL_TRIANGLE_FAN) {
+    } else if(mode == GL_TRIANGLE_FAN || mode == GL_POLYGON) {
         genElementsTriangleFan(
             output,
             count,
diff --git a/samples/nehe02/main.c b/samples/nehe02/main.c
index 1f40acb..e8ec6f1 100644
--- a/samples/nehe02/main.c
+++ b/samples/nehe02/main.c
@@ -7,7 +7,7 @@ void InitGL(int Width, int Height)	        // We call this right after our OpenG
 {
     glClearColor(0.0f, 0.0f, 0.0f, 0.0f);		// This Will Clear The Background Color To Black
     glClearDepth(1.0);				// Enables Clearing Of The Depth Buffer
-    glDepthFunc(GL_LESS);				// The Type Of Depth Test To Do
+    glDepthFunc(GL_LEQUAL);				// The Type Of Depth Test To Do
     glEnable(GL_DEPTH_TEST);			// Enables Depth Testing
     glShadeModel(GL_SMOOTH);			// Enables Smooth Color Shading
 
@@ -41,23 +41,36 @@ void DrawGLScene()
     glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);		// Clear The Screen And The Depth Buffer
     glLoadIdentity();				// Reset The View
 
-    glTranslatef(-1.5f,0.0f,-6.0f);		// Move Left 1.5 Units And Into The Screen 6.0
+    glTranslatef(-3.0f, 0.0f, -10.0f);		// Move Left 1.5 Units And Into The Screen 6.0
 
     // draw a triangle
-    glBegin(GL_POLYGON);				// start drawing a polygon
-    glVertex3f( 0.0f, 1.0f, 0.0f);		// Top
-    glVertex3f( 1.0f,-1.0f, 0.0f);		// Bottom Right
-    glVertex3f(-1.0f,-1.0f, 0.0f);		// Bottom Left
+    glBegin(GL_TRIANGLES);				// start drawing a polygon
+        glVertex3f( 0.0f, 1.0f, 0.0f);		// Top
+        glVertex3f( 1.0f,-1.0f, 0.0f);		// Bottom Right
+        glVertex3f(-1.0f,-1.0f, 0.0f);		// Bottom Left
     glEnd();					// we're done with the polygon
 
-    glTranslatef(3.0f,0.0f,0.0f);		        // Move Right 3 Units
+    glTranslatef(3.0f, 0.0f, 0.0f);		        // Move Right 3 Units
 
     // draw a square (quadrilateral)
     glBegin(GL_QUADS);				// start drawing a polygon (4 sided)
-    glVertex3f(-1.0f, 1.0f, 0.0f);		// Top Left
-    glVertex3f( 1.0f, 1.0f, 0.0f);		// Top Right
-    glVertex3f( 1.0f,-1.0f, 0.0f);		// Bottom Right
-    glVertex3f(-1.0f,-1.0f, 0.0f);		// Bottom Left
+        glVertex3f(-1.0f, 1.0f, 0.0f);		// Top Left
+        glVertex3f( 1.0f, 1.0f, 0.0f);		// Top Right
+        glVertex3f( 1.0f,-1.0f, 0.0f);		// Bottom Right
+        glVertex3f(-1.0f,-1.0f, 0.0f);		// Bottom Left
+    glEnd();					// done with the polygon
+
+    glTranslatef(3.0f, 0.0f, 0.0f);
+
+    glBegin(GL_POLYGON);				// start drawing a polygon (4 sided)
+        glVertex3f(-0.0f, 1.0f, 0.0f);		// Top Left
+        glVertex3f(-0.75f, 0.75f, 0.0f);
+        glVertex3f(-1.0f, 0.0f, 0.0f);		// Top Right
+        glVertex3f(-0.75f,-0.75f, 0.0f);		// Bottom Right
+        glVertex3f(-0.0f,-1.0f, 0.0f);		// Bottom Left
+        glVertex3f( 0.75f,-0.75f, 0.0f);		// Bottom Right
+        glVertex3f( 1.0f, 0.0f, 0.0f);		// Top Right
+        glVertex3f( 0.75f, 0.75f, 0.0f);
     glEnd();					// done with the polygon
 
     // swap buffers to display, since we're double buffered.