Fixed floating point overflow issues in QRasterizer::rasterizeLine

Change 7c673a4cf64ba04 introduced some autotest failures in the
fpe_steepSlopes test in QPainter.

Since the other rasterizers all deal in a 26.6 fixed point coordinate
space we should snap the line vertices to this to prevent floating point
overflows due to very steep slopes.

This also necessitates keeping track of four different slope / inverse
slope increments for each of the four edges.

This also fixes a previously QEXPECT_FAIL'ed test case.

Task-number: QTBUG-13429
Reviewed-by: Trond
(cherry picked from commit 93199a5b7082fd484b7f21ad4825d71693ecead2)

1 files changed, 0 insertions, 1 deletions

diff --git a/tests/auto/qpainter/tst_qpainter.cpp b/tests/auto/qpainter/tst_qpainter.cpp
index a94c300..45f5c3e 100644
--- a/tests/auto/qpainter/tst_qpainter.cpp
+++ b/tests/auto/qpainter/tst_qpainter.cpp
@@ -3172,7 +3172,6 @@ void fpe_steepSlopes()
     p.setRenderHint(QPainter::Antialiasing, antialiased);
     p.setTransform(transform);
 
-    QEXPECT_FAIL("steep line 3 aa", "needs to be fixed", Continue);
     p.drawLine(line);
 }