From 18909268059dc76911223636b24767c1b8f53181 Mon Sep 17 00:00:00 2001
From: themancalledjakob <jakob@jrkb.land>
Date: Tue, 19 Sep 2023 12:44:16 +0200
Subject: [PATCH] more robust outline flipping

---
 src/gpufont/font.hpp | 52 ++++++++++++++++++++++++--------------------
 1 file changed, 29 insertions(+), 23 deletions(-)

diff --git a/src/gpufont/font.hpp b/src/gpufont/font.hpp
index 5890e64..1e9cd25 100644
--- a/src/gpufont/font.hpp
+++ b/src/gpufont/font.hpp
@@ -714,6 +714,7 @@ class Font {
                     //cout << "but charcode is r or n" << endl;
                     continue;
                 }
+                // if does exist already
                 if(glyphs.count(glyphIdentity) != 0){
                     continue;
                 }
@@ -936,33 +937,38 @@ class Font {
                     convertContour(curves[i], directions[i], bbs[i], &face->glyph->outline, start, face->glyph->outline.contours[i], emSize);
                     start = face->glyph->outline.contours[i] + 1;
                 }
+                // outmost outline must be clock-wise
+                // then flip direction the deeper we go inside
                 for(int i = 0; i < n_contours; i++){
-                    if(directions[i] < 0){
-                        bool flip = true;
-                        for(int j = 0; j < n_contours; j++){
-                            if(i != j){
-                                bool inside = bbs[j].xMin <= bbs[i].xMin
-                                              && bbs[j].xMax >= bbs[i].xMax
-                                              && bbs[j].yMin <= bbs[i].yMin
-                                              && bbs[j].yMax >= bbs[i].yMax;
-                                if(inside){
-                                    flip = false;
-                                    break;
-                                }
+                    int insideAnother = 0;
+                    for(int j = 0; j < n_contours; j++){
+                        if(i != j){
+                            bool inside = bbs[j].xMin <= bbs[i].xMin
+                                          && bbs[j].xMax >= bbs[i].xMax
+                                          && bbs[j].yMin <= bbs[i].yMin
+                                          && bbs[j].yMax >= bbs[i].yMax;
+                            if(inside){
+                                insideAnother++;
                             }
                         }
-                        if(flip){
-                            for(BufferCurve & curve : curves[i]){
-                                float tmp_x = curve.x0;
-                                float tmp_y = curve.y0;
-                                curve.x0 = curve.x2;
-                                curve.y0 = curve.y2;
-                                curve.x2 = tmp_x;
-                                curve.y2 = tmp_y;
-                            }
-                            std::reverse(curves[i].begin(), curves[i].end());
-                        }
                     }
+                    bool flip = false;
+                    if((insideAnother % 2 == 0 && directions[i] < 0)
+                       || (insideAnother % 2 == 1 && directions[i] > 0)){
+                        flip = true;
+                    }
+                    if(flip){
+                        for(BufferCurve & curve : curves[i]){
+                            float tmp_x = curve.x0;
+                            float tmp_y = curve.y0;
+                            curve.x0 = curve.x2;
+                            curve.y0 = curve.y2;
+                            curve.x2 = tmp_x;
+                            curve.y2 = tmp_y;
+                        }
+                        std::reverse(curves[i].begin(), curves[i].end());
+                    }
+                    //}
                     bufferCurves.insert(bufferCurves.end(), curves[i].begin(), curves[i].end());
                 }
             }else{