sw_engine shape: change of the rectangle fast tracking algorithm

The algorithm erroneously treated some shapes (like isosceles trapezoids
and specifically arranged zero width parallelograms) as rectangles,
which causes the whole bbox to be filled.

Change-Id: If5aa87c53cf174367841323ac813b28ead4871b4

diff --git a/src/lib/sw_engine/tvgSwShape.cpp b/src/lib/sw_engine/tvgSwShape.cpp
index a0cbce1..44066f3 100644 (file)
--- a/src/lib/sw_engine/tvgSwShape.cpp
+++ b/src/lib/sw_engine/tvgSwShape.cpp
@@ -430,13 +430,14 @@ bool _fastTrack(const SwOutline* outline)
     auto pt3 = outline->pts + 2;
     auto pt4 = outline->pts + 3;
 
-    auto min1 = pt1->y < pt3->y ? pt1 : pt3;
-    auto min2 = pt2->y < pt4->y ? pt2 : pt4;
-    if (min1->y != min2->y) return false;
-
-    SwCoord len1 = pow(pt1->x - pt3->x, 2) + pow(pt1->y - pt3->y, 2);
-    SwCoord len2 = pow(pt2->x - pt4->x, 2) + pow(pt2->y - pt4->y, 2);
-    if (len1 == len2) return true;
+    SwPoint a;
+    SwPoint b;
+    a.x = pt1->x;
+    a.y = pt3->y;
+    b.x = pt3->x;
+    b.y = pt1->y;
+
+    if ((*pt2 == a && *pt4 == b) || (*pt2 == b && *pt4 == a)) return true;
 
     return false;
 }