qt: add patch for QTBUG-31579 to fix polyline drawing

From b7029fbd12c32e851ed7d81b692197176eb71d9e Mon Sep 17 00:00:00 2001

From: Gunnar Sletta <gunnar.sletta@digia.com>

Date: Thu, 4 Jul 2013 16:20:40 +1000

Subject: [PATCH] Fix drawing of 0-width polylines from outside the devicerect.

This was broken by a previous fix which aimed to fix gaps in

polylines with tiny line segments. The result was that we

skipped updating the origin point when stroke() didn't produce

pixels which accidentally included the case of the line

being completely outside the deviceRect. I fixed this

by returning the value of clipLine in drawLine to the caller

so we could still update the origin for this case.

Task-number: QTBUG-31579

Change-Id: Iac29436f042da7658bbeaf9370351dc6f2c95065

(cherry picked from qtbase/900cccfd459fcbdbc4aa3d313afe12cfbf68fd87)

---

 src/gui/painting/qcosmeticstroker.cpp | 42 ++++++++++++++++++++++-------------

 src/gui/painting/qcosmeticstroker_p.h |  2 +-

 2 files changed, 27 insertions(+), 17 deletions(-)

diff --git a/src/gui/painting/qcosmeticstroker.cpp b/src/gui/painting/qcosmeticstroker.cpp

index 0061ecb..4413170 100644

--- a/src/gui/painting/qcosmeticstroker.cpp

+++ b/src/gui/painting/qcosmeticstroker.cpp

@@ -133,10 +133,15 @@ struct NoDasher {

 };

+/*

+ * The return value is the result of the clipLine() call performed at the start

+ * of each of the two functions, aka "false" means completely outside the devices

+ * rect.

+ */

 template<DrawPixel drawPixel, class Dasher>

-static void drawLine(QCosmeticStroker *stroker, qreal x1, qreal y1, qreal x2, qreal y2, int caps);

+static bool drawLine(QCosmeticStroker *stroker, qreal x1, qreal y1, qreal x2, qreal y2, int caps);

 template<DrawPixel drawPixel, class Dasher>

-static void drawLineAA(QCosmeticStroker *stroker, qreal x1, qreal y1, qreal x2, qreal y2, int caps);

+static bool drawLineAA(QCosmeticStroker *stroker, qreal x1, qreal y1, qreal x2, qreal y2, int caps);

 inline void drawPixel(QCosmeticStroker *stroker, int x, int y, int coverage)

 {

@@ -602,17 +607,20 @@ void QCosmeticStroker::drawPath(const QVectorPath &path)

                 caps |= CapEnd;

             QCosmeticStroker::Point last = this->lastPixel;

-            stroke(this, p.x(), p.y(), p2.x(), p2.y(), caps);

+            bool unclipped = stroke(this, p.x(), p.y(), p2.x(), p2.y(), caps);

             /* fix for gaps in polylines with fastpen and aliased in a sequence

                of points with small distances: if current point p2 has been dropped

-               out, keep last non dropped point p. */

-            if (fastPenAliased) {

-                if (last.x != lastPixel.x || last.y != lastPixel.y ||

-                    points == begin + 2 || points == end - 2 ) {

-                    {

-                        p = p2;

-                    }

+               out, keep last non dropped point p.

+

+               However, if the line was completely outside the devicerect, we

+               still need to update p to avoid drawing the line after this one from

+               a bad starting position.

+            */

+            if (fastPenAliased && unclipped) {

+                if (last.x != lastPixel.x || last.y != lastPixel.y

+                    || points == begin + 2 || points == end - 2) {

+                    p = p2;

                 }

             } else {

                 p = p2;

@@ -720,10 +728,10 @@ static inline void capAdjust(int caps, int &x1, int &x2, int &y, int yinc)

   the drawing shifts from horizontal to vertical or back.

   */

 template<DrawPixel drawPixel, class Dasher>

-static void drawLine(QCosmeticStroker *stroker, qreal rx1, qreal ry1, qreal rx2, qreal ry2, int caps)

+static bool drawLine(QCosmeticStroker *stroker, qreal rx1, qreal ry1, qreal rx2, qreal ry2, int caps)

 {

     if (stroker->clipLine(rx1, ry1, rx2, ry2))

-        return;

+        return false;

     static const int half = 31;

     int x1 = toF26Dot6(rx1) + half;

@@ -813,7 +821,7 @@ static void drawLine(QCosmeticStroker *stroker, qreal rx1, qreal ry1, qreal rx2,

     } else {

         // horizontal

         if (!dx)

-            return;

+            return true;

         QCosmeticStroker::Direction dir = QCosmeticStroker::LeftToRight;

@@ -886,14 +894,15 @@ static void drawLine(QCosmeticStroker *stroker, qreal rx1, qreal ry1, qreal rx2,

         }

     }

     stroker->lastPixel = last;

+    return true;

 }

 template<DrawPixel drawPixel, class Dasher>

-static void drawLineAA(QCosmeticStroker *stroker, qreal rx1, qreal ry1, qreal rx2, qreal ry2, int caps)

+static bool drawLineAA(QCosmeticStroker *stroker, qreal rx1, qreal ry1, qreal rx2, qreal ry2, int caps)

 {

     if (stroker->clipLine(rx1, ry1, rx2, ry2))

-        return;

+        return false;

     int x1 = toF26Dot6(rx1);

     int y1 = toF26Dot6(ry1);

@@ -967,7 +976,7 @@ static void drawLineAA(QCosmeticStroker *stroker, qreal rx1, qreal ry1, qreal rx

     } else {

         // horizontal

         if (!dx)

-            return;

+            return true;

         int yinc = F16Dot16FixedDiv(dy, dx);

@@ -1029,6 +1038,7 @@ static void drawLineAA(QCosmeticStroker *stroker, qreal rx1, qreal ry1, qreal rx

             drawPixel(stroker, x, (y>>16) + 1, alpha * alphaEnd >> 6);

         }

     }

+    return true;

 }

 QT_END_NAMESPACE

diff --git a/src/gui/painting/qcosmeticstroker_p.h b/src/gui/painting/qcosmeticstroker_p.h

index 870738b..3216856 100644

--- a/src/gui/painting/qcosmeticstroker_p.h

+++ b/src/gui/painting/qcosmeticstroker_p.h

@@ -56,7 +56,7 @@ QT_MODULE(Gui)

 class QCosmeticStroker;

-typedef void (*StrokeLine)(QCosmeticStroker *stroker, qreal x1, qreal y1, qreal x2, qreal y2, int caps);

+typedef bool (*StrokeLine)(QCosmeticStroker *stroker, qreal x1, qreal y1, qreal x2, qreal y2, int caps);

 class QCosmeticStroker

 {

-- 

1.8.3.2