Fix polygon OOB reads and config macro

include/raylib-nuklear.h

@@ -157,6 +157,15 @@ extern "C" {
 #define RAYLIB_NUKLEAR_FONT_SPACING_RATIO 0.01f
 #endif // RAYLIB_NUKLEAR_FONT_SPACING_RATIO
 
+#ifndef RAYLIB_NUKLEAR_POLYGON_FILL_MAX_POINTS
+/**
+ * The maximum amount of points allowed when drawing a filled polygon.
+ *
+ * @see NK_COMMAND_POLYGON_FILLED
+ */
+#define RAYLIB_NUKLEAR_POLYGON_FILL_MAX_POINTS 64
+#endif  // RAYLIB_NUKLEAR_POLYGON_FILL_MAX_POINTS
+
 #ifndef RAYLIB_NUKLEAR_DEFAULT_ARC_SEGMENTS
 /**
  * The amount of segments used when drawing an arc.
@@ -563,9 +572,6 @@ NuklearImageToTexture(struct nk_image img)
  */
 static void raylib_nuklear_draw_polygon_fill(float scale, const struct nk_vec2i *pnts, int count, Color col) {
     int i = 0;
-    #ifndef RAYLIB_NUKLEAR_POLYGON_FILL_MAX_POINTS
-    #define RAYLIB_NUKLEAR_POLYGON_FILL_MAX_POINTS 64
-    #endif
     int left = 10000, top = 10000, bottom = 0, right = 0;
     int nodes, nodeX[RAYLIB_NUKLEAR_POLYGON_FILL_MAX_POINTS], pixelX, pixelY, j, swap ;
 
@@ -620,7 +626,7 @@ static void raylib_nuklear_draw_polygon_fill(float scale, const struct nk_vec2i
             } else i++;
         }
         /*  Fill the pixels between node pairs. */
-        for (i = 0; i < nodes; i += 2) {
+        for (i = 0; i + 1 < nodes; i += 2) {
             if (nodeX[i+0] >= right) break;
             if (nodeX[i+1] > left) {
                 if (nodeX[i+0] < left) nodeX[i+0] = left ;
@@ -632,7 +638,6 @@ static void raylib_nuklear_draw_polygon_fill(float scale, const struct nk_vec2i
             }
         }
     }
-    #undef RAYLIB_NUKLEAR_POLYGON_FILL_MAX_POINTS
 }
 
 /**
@@ -829,9 +834,11 @@ DrawNuklear(struct nk_context * ctx)
                     Vector2 end = {(float)p->points[i + 1].x * scale, (float)p->points[i + 1].y * scale};
                     DrawLineEx(start, end, thickness, color);
                 }
-                Vector2 last = {(float)p->points[p->point_count - 1].x * scale, (float)p->points[p->point_count - 1].y * scale};
-                Vector2 first = {(float)p->points[0].x * scale, (float)p->points[0].y * scale};
-                DrawLineEx(last, first, thickness, color);
+                if (p->point_count >= 2) {
+                    Vector2 last = {(float)p->points[p->point_count - 1].x * scale, (float)p->points[p->point_count - 1].y * scale};
+                    Vector2 first = {(float)p->points[0].x * scale, (float)p->points[0].y * scale};
+                    DrawLineEx(last, first, thickness, color);
+                }
             } break;
 
             case NK_COMMAND_POLYGON_FILLED: {

test/raylib-nuklear-test.c

@@ -202,6 +202,51 @@ int main(int argc, char *argv[]) {
         UnloadNuklear(ctx);
     }
 
+    // Degenerate polygons must not crash DrawNuklear().
+    // https://github.com/RobLoach/raylib-nuklear/issues/131
+    {
+        ctx = InitNuklear(10);
+        Assert(ctx);
+
+        UpdateNuklear(ctx);
+
+        if (nk_begin(ctx, "PolygonTest", nk_rect(0, 0, 100, 100),
+                NK_WINDOW_NO_SCROLLBAR)) {
+            struct nk_command_buffer* canvas = nk_window_get_canvas(ctx);
+            struct nk_color color = nk_rgb(230, 20, 20);
+
+            // No points.
+            nk_fill_polygon(canvas, NULL, 0, color);
+            nk_stroke_polygon(canvas, NULL, 0, 1.0f, color);
+
+            // A single point.
+            float single[] = {10.0f, 10.0f};
+            nk_fill_polygon(canvas, single, 1, color);
+            nk_stroke_polygon(canvas, single, 1, 1.0f, color);
+
+            // A self-touching polygon, where a repeated vertex touches the
+            // outline and can leave the scanline fill with an odd node count.
+            float touching[] = {
+                10.0f, 10.0f,
+                30.0f, 10.0f,
+                20.0f, 20.0f,
+                30.0f, 30.0f,
+                10.0f, 30.0f,
+                20.0f, 20.0f
+            };
+            nk_fill_polygon(canvas, touching, 6, color);
+            nk_stroke_polygon(canvas, touching, 6, 1.0f, color);
+        }
+        nk_end(ctx);
+
+        BeginDrawing();
+            ClearBackground(RAYWHITE);
+            DrawNuklear(ctx);
+        EndDrawing();
+
+        UnloadNuklear(ctx);
+    }
+
     // A NULL context must not crash any of the public entry points.
     {
         UpdateNuklear(NULL);