Fix crash in indeterminate progressbars on windows

Note that this is a surgical fix for 4.7 only.
In 4.8 we will add these checks at the top
of the styling functions or in the widgets instead.

Task-number:QTBUG-15227
Reviewed-by:gabi

3 files changed, 13 insertions, 3 deletions

diff --git a/src/gui/styles/qcommonstyle.cpp b/src/gui/styles/qcommonstyle.cpp
index 039a6da..1d7c838 100644
--- a/src/gui/styles/qcommonstyle.cpp
+++ b/src/gui/styles/qcommonstyle.cpp
@@ -1403,8 +1403,9 @@ void QCommonStyle::drawControl(ControlElement element, const QStyleOption *opt,
         }
         break;
     case CE_ProgressBarGroove:
-        qDrawShadePanel(p, opt->rect, opt->palette, true, 1,
-                        &opt->palette.brush(QPalette::Window));
+        if (opt->rect.isValid())
+            qDrawShadePanel(p, opt->rect, opt->palette, true, 1,
+                            &opt->palette.brush(QPalette::Window));
         break;
     case CE_ProgressBarLabel:
         if (const QStyleOptionProgressBar *pb = qstyleoption_cast<const QStyleOptionProgressBar *>(opt)) {
diff --git a/src/gui/styles/qwindowsstyle.cpp b/src/gui/styles/qwindowsstyle.cpp
index 654be3c..32a6d8d 100644
--- a/src/gui/styles/qwindowsstyle.cpp
+++ b/src/gui/styles/qwindowsstyle.cpp
@@ -2397,8 +2397,10 @@ void QWindowsStyle::drawControl(ControlElement ce, const QStyleOption *opt, QPai
 #ifndef QT_NO_PROGRESSBAR
     case CE_ProgressBarContents:
         if (const QStyleOptionProgressBar *pb = qstyleoption_cast<const QStyleOptionProgressBar *>(opt)) {
-
             QRect rect = pb->rect;
+            if (!rect.isValid())
+                return;
+
             bool vertical = false;
             bool inverted = false;
 
diff --git a/tests/auto/qstyle/tst_qstyle.cpp b/tests/auto/qstyle/tst_qstyle.cpp
index ba24225..9c754d2 100644
--- a/tests/auto/qstyle/tst_qstyle.cpp
+++ b/tests/auto/qstyle/tst_qstyle.cpp
@@ -413,6 +413,13 @@ void tst_QStyle::testWindowsStyle()
     QWindowsStyle wstyle;
     testAllFunctions(&wstyle);
     lineUpLayoutTest(&wstyle);
+
+    // Tests drawing indeterminate progress with 0 size: QTBUG-15973
+    QStyleOptionProgressBar pb;
+    pb.rect = QRect(0,0,-9,0);
+    QPixmap surface(QSize(200, 200));
+    QPainter painter(&surface);
+    wstyle.drawControl(QStyle::CE_ProgressBar, &pb, &painter, 0);
 }
 
 void tst_QStyle::testWindowsXPStyle()