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2eebae13dd
Move most of the QtQuick code to its own directory, so that it can be reused in the future for the chart. Signed-off-by: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>
100 lines
3.1 KiB
C++
100 lines
3.1 KiB
C++
// SPDX-License-Identifier: GPL-2.0
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// QSGNode template jugglery to overcome API flaws.
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#ifndef CHARTITEM_HELPER_H
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#define CHARTITEM_HELPER_H
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#include <memory>
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#include <QSGNode>
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// In general, we want chart items to be hideable. For example to show/hide
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// labels on demand. Very sadly, the QSG API is absolutely terrible with
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// respect to temporarily disabling. Instead of simply having a flag,
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// a QSGNode is queried using the "isSubtreeBlocked()" virtual function(!).
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//
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// Not only is this a slow operation performed on every single node, it
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// also is often not possible to override this function: For improved
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// performance, the documentation recommends to create QSG nodes via
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// QQuickWindow. This provides nodes optimized for the actual hardware.
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// However, this obviously means that these nodes cannot be derived from!
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//
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// In that case, there are two possibilities: Add a proxy node with an
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// overridden "isSubtreeBlocked()" function or remove the node from the
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// scene. The former was chosen here, because it is less complex.
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//
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// The following slightly cryptic templates are used to unify the two
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// cases: The QSGNode is generated by our own code or the QSGNode is
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// obtained from QQuickWindow.
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//
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// The "HideableQSGNode<Node>" template augments the QSGNode "Node"
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// by a "setVisible()" function and overrides "isSubtreeBlocked()"
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//
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// The "QSGProxyNode<Node>" template is a QSGNode with a single
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// child of type "Node".
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//
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// Thus, if the node can be created, use:
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// HideableQSGNode<NodeTypeThatCanBeCreated> node
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// and if the node can only be obtained from QQuickWindow, use:
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// HideableQSGNode<QSGProxyNode<NodeThatCantBeCreated>> node
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// The latter should obviously be typedef-ed.
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//
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// Yes, that's all horrible, but if nothing else it teaches us about
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// composition.
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template <typename Node>
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class HideableQSGNode : public Node {
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bool hidden;
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bool isSubtreeBlocked() const override final;
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public:
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template<class... Args>
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HideableQSGNode(bool visible, Args&&... args);
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void setVisible(bool visible);
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};
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template <typename Node>
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class QSGProxyNode : public QSGNode {
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public:
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std::unique_ptr<Node> node;
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QSGProxyNode(Node *node);
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};
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// Implementation detail of templates - move to serparate header file
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template <typename Node>
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QSGProxyNode<Node>::QSGProxyNode(Node *node) : node(node)
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{
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appendChildNode(node);
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}
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template <typename Node>
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bool HideableQSGNode<Node>::isSubtreeBlocked() const
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{
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return hidden;
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}
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template <typename Node>
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template<class... Args>
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HideableQSGNode<Node>::HideableQSGNode(bool visible, Args&&... args) :
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Node(std::forward<Args>(args)...),
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hidden(!visible)
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{
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}
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template <typename Node>
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void HideableQSGNode<Node>::setVisible(bool visible)
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{
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hidden = !visible;
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Node::markDirty(QSGNode::DirtySubtreeBlocked);
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}
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// Helper function to set points
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inline void setPoint(QSGGeometry::Point2D &v, const QPointF &p)
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{
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v.set(static_cast<float>(p.x()), static_cast<float>(p.y()));
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}
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inline void setPoint(QSGGeometry::TexturedPoint2D &v, const QPointF &p, const QPointF &t)
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{
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v.set(static_cast<float>(p.x()), static_cast<float>(p.y()),
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static_cast<float>(t.x()), static_cast<float>(t.y()));
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}
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#endif
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