Improve stencil clipping with NVPR

So that it actually performs when clipping the tiger. Add an example.

Change-Id: I7c1c6244710febdb6b02852ebca094665adec417
Reviewed-by: Andy Nichols <andy.nichols@qt.io>

6 files changed, 141 insertions, 1 deletions

diff --git a/examples/quick/pathitem/content/item17.qml b/examples/quick/pathitem/content/item17.qml
index 0197aa5fb6..7f3f06cfb8 100644
--- a/examples/quick/pathitem/content/item17.qml
+++ b/examples/quick/pathitem/content/item17.qml
@@ -70,6 +70,7 @@ Rectangle {
             source: "tiger.qml"
             asynchronous: true
             visible: status == Loader.Ready
+            scale: 0.4
         }
     }
 }
diff --git a/examples/quick/pathitem/content/pathitem.qml b/examples/quick/pathitem/content/pathitem.qml
index e3a28b2bbe..c4a86ff8b1 100644
--- a/examples/quick/pathitem/content/pathitem.qml
+++ b/examples/quick/pathitem/content/pathitem.qml
@@ -58,6 +58,7 @@ Item {
         Component.onCompleted: {
             addExample("PathItem Gallery", "Simple path rendering examples", Qt.resolvedUrl("pathitemgallery.qml"))
             addExample("Interactive paths", "Dynamic path examples", Qt.resolvedUrl("pathiteminteract.qml"))
+            addExample("Clip My Tiger!", "Clip examples, a.k.a. What Not To Do", Qt.resolvedUrl("pathitemtigers.qml"))
         }
     }
 }
diff --git a/examples/quick/pathitem/content/pathitemtigers.qml b/examples/quick/pathitem/content/pathitemtigers.qml
new file mode 100644
index 0000000000..6c8e3a19ce
--- /dev/null
+++ b/examples/quick/pathitem/content/pathitemtigers.qml
@@ -0,0 +1,137 @@
+/****************************************************************************
+**
+** Copyright (C) 2016 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the QtQuick module of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:BSD$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** BSD License Usage
+** Alternatively, you may use this file under the terms of the BSD license
+** as follows:
+**
+** "Redistribution and use in source and binary forms, with or without
+** modification, are permitted provided that the following conditions are
+** met:
+**   * Redistributions of source code must retain the above copyright
+**     notice, this list of conditions and the following disclaimer.
+**   * Redistributions in binary form must reproduce the above copyright
+**     notice, this list of conditions and the following disclaimer in
+**     the documentation and/or other materials provided with the
+**     distribution.
+**   * Neither the name of The Qt Company Ltd nor the names of its
+**     contributors may be used to endorse or promote products derived
+**     from this software without specific prior written permission.
+**
+**
+** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+import QtQuick 2.9 // to get PathItem
+
+Rectangle {
+    id: root
+    width: 1024
+    height: 768
+
+    property color col: "lightsteelblue"
+    gradient: Gradient {
+        GradientStop { position: 0.0; color: Qt.tint(root.col, "#20FFFFFF") }
+        GradientStop { position: 0.1; color: Qt.tint(root.col, "#20AAAAAA") }
+        GradientStop { position: 0.9; color: Qt.tint(root.col, "#20666666") }
+        GradientStop { position: 1.0; color: Qt.tint(root.col, "#20000000") }
+    }
+
+    Rectangle {
+        id: scissorRect
+        width: 200
+        height: 200
+        x: 150
+        property real centerY: parent.height / 2 - height / 2
+        property real dy: 0
+        y: centerY + dy
+        clip: true
+
+        Loader {
+            id: loader1
+            width: parent.width
+            height: parent.height
+            y: 25 - scissorRect.dy
+            source: "tiger.qml"
+            asynchronous: true
+            visible: status === Loader.Ready
+        }
+
+        SequentialAnimation on dy {
+            loops: Animation.Infinite
+            running: loader1.status === Loader.Ready && loader1.item.status === PathItem.Ready
+            NumberAnimation {
+                from: 0
+                to: -scissorRect.centerY
+                duration: 2000
+            }
+            NumberAnimation {
+                from: -scissorRect.centerY
+                to: scissorRect.centerY
+                duration: 4000
+            }
+            NumberAnimation {
+                from: scissorRect.centerY
+                to: 0
+                duration: 2000
+            }
+        }
+    }
+
+    // With a more complex transformation (like rotation), stenciling is used
+    // instead of scissoring, this is more expensive. It may also trigger a
+    // slower code path for PathItems, depending on the path rendering backend
+    // in use, and may affect rendering quality as well.
+    // So in short: do not do this.
+    Rectangle {
+        id: stencilRect
+        width: 300
+        height: 200
+        anchors.right: parent.right
+        anchors.rightMargin: 100
+        anchors.verticalCenter: parent.verticalCenter
+        clip: true // NB! still clips to bounding rect (not shape)
+
+        Loader {
+            id: loader2
+            width: parent.width
+            height: parent.height
+            source: "tiger.qml"
+            asynchronous: true
+            visible: status === Loader.Ready
+        }
+
+        NumberAnimation on rotation {
+            from: 0
+            to: 360
+            duration: 5000
+            loops: Animation.Infinite
+        }
+    }
+}
diff --git a/examples/quick/pathitem/content/tiger.qml b/examples/quick/pathitem/content/tiger.qml
index 7d275ba22f..a9f4abe46a 100644
--- a/examples/quick/pathitem/content/tiger.qml
+++ b/examples/quick/pathitem/content/tiger.qml
@@ -56,7 +56,6 @@ PathItem {
     asynchronous: true
 
     anchors.fill: parent
-    scale: 0.4
 
     VisualPath {
         fillColor: "#ffffff"
diff --git a/examples/quick/pathitem/pathitem.pro b/examples/quick/pathitem/pathitem.pro
index 8b606a3c50..3c12f35fd2 100644
--- a/examples/quick/pathitem/pathitem.pro
+++ b/examples/quick/pathitem/pathitem.pro
@@ -6,6 +6,7 @@ RESOURCES += pathitem.qrc
 OTHER_FILES += content/pathitem.qml \
                content/pathitemgallery.qml \
                content/pathiteminteract.qml \
+               content/pathitemtigers.qml \
                content/tiger.qml \
                content/item1.qml \
                content/item2.qml \
diff --git a/examples/quick/pathitem/pathitem.qrc b/examples/quick/pathitem/pathitem.qrc
index 5b38d90c0c..d67c918faf 100644
--- a/examples/quick/pathitem/pathitem.qrc
+++ b/examples/quick/pathitem/pathitem.qrc
@@ -7,6 +7,7 @@
         <file alias="pathitem.qml">content/pathitem.qml</file>
         <file alias="pathitemgallery.qml">content/pathitemgallery.qml</file>
         <file alias="pathiteminteract.qml">content/pathiteminteract.qml</file>
+        <file alias="pathitemtigers.qml">content/pathitemtigers.qml</file>
         <file alias="tiger.qml">content/tiger.qml</file>
         <file alias="item1.qml">content/item1.qml</file>
         <file alias="item2.qml">content/item2.qml</file>