Fix FT glyph outline to path conversion

When the start point is not on the curve, the end point will be
used as starting point for the QPainterPath, if it is on the curve -
if it is not on the curve, the mid point between start and end point
will be used. The origianl start point will still be used as a control
point for the first bezier curve.

Task-number: QTBUG-38601
Change-Id: I90e07f1141288873263f1f12fa51e6a248d0804f
Reviewed-by: Fabian Bumberger <fbumberger@rim.com>
Reviewed-by: Lars Knoll <lars.knoll@digia.com>

1 files changed, 24 insertions, 12 deletions

diff --git a/src/gui/text/qfontengine_ft.cpp b/src/gui/text/qfontengine_ft.cpp
index fe38755ffd..f5ca559d62 100644
--- a/src/gui/text/qfontengine_ft.cpp
+++ b/src/gui/text/qfontengine_ft.cpp
@@ -450,6 +450,7 @@ static void scaleOutline(FT_Face face, FT_GlyphSlot g, FT_Fixed x_scale, FT_Fixe
     }
 }
 
+#define GLYPH2PATH_DEBUG QT_NO_QDEBUG_MACRO // qDebug
 void QFreetypeFace::addGlyphToPath(FT_Face face, FT_GlyphSlot g, const QFixedPoint &point, QPainterPath *path, FT_Fixed x_scale, FT_Fixed y_scale)
 {
     const qreal factor = 1/64.;
@@ -461,22 +462,32 @@ void QFreetypeFace::addGlyphToPath(FT_Face face, FT_GlyphSlot g, const QFixedPoi
     int i = 0;
     for (int j = 0; j < g->outline.n_contours; ++j) {
         int last_point = g->outline.contours[j];
-        QPointF start = cp + QPointF(g->outline.points[i].x*factor, -g->outline.points[i].y*factor);
-        if(!(g->outline.tags[i] & 1)) {
-            start += cp + QPointF(g->outline.points[last_point].x*factor, -g->outline.points[last_point].y*factor);
-            start /= 2;
+        GLYPH2PATH_DEBUG() << "contour:" << i << "to" << last_point;
+        QPointF start = QPointF(g->outline.points[i].x*factor, -g->outline.points[i].y*factor);
+        if (!(g->outline.tags[i] & 1)) {               // start point is not on curve:
+            if (!(g->outline.tags[last_point] & 1)) {  // end point is not on curve:
+                GLYPH2PATH_DEBUG() << "  start and end point are not on curve";
+                start = (QPointF(g->outline.points[last_point].x*factor,
+                                -g->outline.points[last_point].y*factor) + start) / 2.0;
+            } else {
+                GLYPH2PATH_DEBUG() << "  end point is on curve, start is not";
+                start = QPointF(g->outline.points[last_point].x*factor,
+                               -g->outline.points[last_point].y*factor);
+            }
+            --i;   // to use original start point as control point below
         }
-//         qDebug("contour: %d -- %d", i, g->outline.contours[j]);
-//         qDebug("first point at %f %f", start.x(), start.y());
-        path->moveTo(start);
+        start += cp;
+        GLYPH2PATH_DEBUG() << "  start at" << start;
 
+        path->moveTo(start);
         QPointF c[4];
         c[0] = start;
         int n = 1;
         while (i < last_point) {
             ++i;
             c[n] = cp + QPointF(g->outline.points[i].x*factor, -g->outline.points[i].y*factor);
-//             qDebug() << "    i=" << i << " flag=" << (int)g->outline.tags[i] << "point=" << c[n];
+            GLYPH2PATH_DEBUG() << "    " << i << c[n] << "tag =" << (int)g->outline.tags[i]
+                               << ": on curve =" << (bool)(g->outline.tags[i] & 1);
             ++n;
             switch (g->outline.tags[i] & 3) {
             case 2:
@@ -498,7 +509,7 @@ void QFreetypeFace::addGlyphToPath(FT_Face face, FT_GlyphSlot g, const QFixedPoi
             case 1:
             case 3:
                 if (n == 2) {
-//                     qDebug() << "lineTo" << c[1];
+                    GLYPH2PATH_DEBUG() << "  lineTo" << c[1];
                     path->lineTo(c[1]);
                     c[0] = c[1];
                     n = 1;
@@ -510,13 +521,14 @@ void QFreetypeFace::addGlyphToPath(FT_Face face, FT_GlyphSlot g, const QFixedPoi
                 }
                 break;
             }
-//             qDebug() << "cubicTo" << c[1] << c[2] << c[3];
+            GLYPH2PATH_DEBUG() << "  cubicTo" << c[1] << c[2] << c[3];
             path->cubicTo(c[1], c[2], c[3]);
             c[0] = c[3];
             n = 1;
         }
+
         if (n == 1) {
-//             qDebug() << "closeSubpath";
+            GLYPH2PATH_DEBUG() << "  closeSubpath";
             path->closeSubpath();
         } else {
             c[3] = start;
@@ -524,7 +536,7 @@ void QFreetypeFace::addGlyphToPath(FT_Face face, FT_GlyphSlot g, const QFixedPoi
                 c[2] = (2*c[1] + c[3])/3;
                 c[1] = (2*c[1] + c[0])/3;
             }
-//             qDebug() << "cubicTo" << c[1] << c[2] << c[3];
+            GLYPH2PATH_DEBUG() << "  close cubicTo" << c[1] << c[2] << c[3];
             path->cubicTo(c[1], c[2], c[3]);
         }
         ++i;