QQuickShape: override contains(QPointF); demonstrate in examples

QQuickItem::contains() only checks the Item's bounding box by default.
In the case of Shapes, that can be comically imprecise, but it's fast.
So we add a containsMode property to control whether we will do that
(the default) or actually check each of the QPainterPaths within to
see whether they contain the point (FillContains).

FillContains could be optimized later: use QRegion perhaps, or download
the rendered texture from the GPU and test whether the pixel at the
point is transparent.  It may also be appropriate to add a StrokeContains
option.

The main motivation is to detect mouse (or touch) interaction within
a shaped area.  QQuickSinglePointHandler::wantsEventPoint() already
checks whether its parent Item contains the event point.  So if a
Shape has a TapHandler for example, it will respond only within the
visible bounds of the Shape rather than within the entire rectangular
bounding box as long as containsMode is set to FillContains.

Examples quick/shapes/content/tapableTriangle.qml and tiger.qml
are modified to react when a press occurs inside, and the former
is fixed to be able to run standalone via the qml runtime.  The
latter has an offset issue when run standalone but is OK within
the shape gallery example.

As a drive-by optimization, QQuickShapePrivate's variables are
re-ordered by type so that the compiler can place the bools and
enums into bitfields; and to facilitate reordering, the
initialization is done C++11-style, in the header.

[ChangeLog][QtQuick][Shape] A containsMode property is added.
If it is set to FillContains, then Shape.contains() returns true
only within the visible bounds, so its Pointer Handlers also respond
only within those bounds.

Change-Id: I31c85a9b08aa6945c58dc07febfe89ffef21274b
Reviewed-by: Paolo Angelelli <paolo.angelelli@qt.io>

1 files changed, 101 insertions, 0 deletions

diff --git a/examples/quick/shapes/content/tapableTriangle.qml b/examples/quick/shapes/content/tapableTriangle.qml
new file mode 100644
index 0000000000..ba1fa1e460
--- /dev/null
+++ b/examples/quick/shapes/content/tapableTriangle.qml
@@ -0,0 +1,101 @@
+/****************************************************************************
+**
+** Copyright (C) 2018 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the QtQuick module of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:BSD$
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+** accordance with the commercial license agreement provided with the
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+** BSD License Usage
+** Alternatively, you may use this file under the terms of the BSD license
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+****************************************************************************/
+
+import QtQuick 2.11
+import QtQuick.Shapes 1.11
+import Qt.labs.handlers 1.0
+
+Rectangle {
+    width: 120
+    height: 120
+    color: th.pressed ? "steelBlue" : "lightGray"
+
+    Shape {
+        id: ctr
+        anchors.fill: parent
+        containsMode: Shape.FillContains
+
+        TapHandler { id: th }
+
+        ShapePath {
+            strokeColor: "red"
+            fillColor: "blue"
+
+            SequentialAnimation on strokeWidth {
+                loops: Animation.Infinite
+                NumberAnimation { from: 1; to: 30; duration: 5000 }
+                NumberAnimation { from: 30; to: 1; duration: 5000 }
+                PauseAnimation { duration: 2000 }
+            }
+
+            startX: 30; startY: 30
+            PathLine { x: ctr.width - 30; y: ctr.height - 30 }
+            PathLine { x: 30; y: ctr.height - 30 }
+            PathLine { x: 30; y: 30 }
+        }
+
+        // Besides ShapePath, Shape supports visual and non-visual objects too, allowing
+        // free mixing without going through extra hoops:
+        Rectangle {
+            id: testRect
+            color: "green"
+            opacity: 0.3
+            width: 20
+            height: 20
+            anchors.right: parent.right
+        }
+        Timer {
+            interval: 100
+            repeat: true
+            onTriggered: testRect.width = testRect.width > 1 ? testRect.width - 1 : 20
+            running: true
+        }
+    }
+}