Regression: Fix setting of custom cursors for native widgets.

Currently, there is no concept of not having a cursor set on
a Window. Qt::ArrowCursor is always set instead. This causes
bugs when native child widgets are involved, for example setting
a cursor on the native widget's parent no longer works since
the child's Qt::ArrowCursor applies.

Introduce QWindowPrivate::hasCursor tracking whether a cursor
has been explicitly set and clear in QWindow::unsetCursor().

Handle 0 in QPlatformCursor::changeCursor() to mean
"unsetCursor()":
- Windows: Introduce default constructor for QWindowsWindowCursor
  meaning "0". Search for applicable parent cursor in applyCursor.
- XCB: No big changes required, set XCB_CURSOR_NONE for no cursor.
- Other platforms: Assume Qt::ArrowCursor when cursor = 0 is
  passed for now.

Task-number: QTBUG-28879
Change-Id: Id82722592f3cd5fe577a5b64dcc600c85cfea484
Reviewed-by: Jonathan Liu <net147@gmail.com>
Reviewed-by: Morten Johan Sørvig <morten.sorvig@digia.com>
Reviewed-by: Samuel Rødal <samuel.rodal@digia.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/src/platformsupport/fbconvenience/qfbcursor.cpp b/src/platformsupport/fbconvenience/qfbcursor.cpp
index bc44055721..df4fdd135e 100644
--- a/src/platformsupport/fbconvenience/qfbcursor.cpp
+++ b/src/platformsupport/fbconvenience/qfbcursor.cpp
@@ -120,7 +120,7 @@ void QFbCursor::setCursor(const uchar *data, const uchar *mask, int width, int h
 void QFbCursor::changeCursor(QCursor * widgetCursor, QWindow *window)
 {
     Q_UNUSED(window);
-    Qt::CursorShape shape = widgetCursor->shape();
+    const Qt::CursorShape shape = widgetCursor ? widgetCursor->shape() : Qt::ArrowCursor;
 
     if (shape == Qt::BitmapCursor) {
         // application supplied cursor