blocks|key|192451|text|特别是当场景中有移动项时，QGraphicsScene的索引可能需要一些时间来更新索引，从而降低索引性能。您可以使用setItemIndexMethod()对索引进行调优。如果不依赖项目()或itemAt()，这可能有助于提高性能。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|192452|然而，这是一个很长的机会。如果你的场景中只有几个项目，那么性能上的改善可能是微乎其微的。|192453|entityMap|0|LINK|mutability|MUTABLE|url|http://doc.qt.nokia.com/latest/qgraphicsscene.html|1|http://doc.qt.nokia.com/latest/qgraphicsscene.html#itemIndexMethod-prop|2|http://doc.qt.nokia.com/latest/qgraphicsscene.html#items|3|http://doc.qt.nokia.com/latest/qgraphicsscene.html#itemAt^0|D|E|0|1M|K|1|2J|4|2|2O|8|3|0|0^^$0|@$1|2|3|4|5|6|7|T|8|@]|9|@$A|U|B|V|1|W]|$A|X|B|Y|1|Z]|$A|10|B|11|1|12]|$A|13|B|14|1|15]]|C|$]]|$1|D|3|E|5|6|7|16|8|@]|9|@]|C|$]]|$1|F|3|-4|5|6|7|17|8|@]|9|@]|C|$]]]|G|$H|$5|I|J|K|C|$L|M]]|N|$5|I|J|K|C|$L|O]]|P|$5|I|J|K|C|$L|Q]]|R|$5|I|J|K|C|$L|S]]]]

Especially when you have moving items in a scene, <a href="http://doc.qt.nokia.com/latest/qgraphicsscene.html" rel="nofollow">QGraphicsScene</a>'s indexing may need some time to update its index, decreasing performance. You can tune the indexing by using <a href="http://doc.qt.nokia.com/latest/qgraphicsscene.html#itemIndexMethod-prop" rel="nofollow">setItemIndexMethod()</a>. If you do not rely on <a href="http://doc.qt.nokia.com/latest/qgraphicsscene.html#items" rel="nofollow">items()</a> or <a href="http://doc.qt.nokia.com/latest/qgraphicsscene.html#itemAt" rel="nofollow">itemAt()</a>, this may help increase performance.

However, this is a long shot. If you have only few items in your scene, the performance improvements may be minimal.

blocks|key|2016310|text|通常最好将Graphicssystem设置为“光栅”(由于GL作为视口)，最终的输出仍然是OpenGL。您没有提到这一点，但是如果在命令行中添加"-graphicssystem光栅“会产生任何改进，您可以很容易地尝试。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2016311|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

Usually it is best to set the Graphicssystem to "raster" (final output will still be OpenGL because of the GL Widget as viewport). You don't mention it, but you can easily try if adding "-graphicssystem raster" to the command line yields any improvements.

blocks|key|2016319|text|根据我自己的经验，QGraphicsItem中的图形效果确实是内存和计算量很大。如果在动画转换期间使用它们，可能是问题所在。你应该把它们摘下来，看看它有多流畅，然后尝试实现你自己的效果。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2016320|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

From my own experience, graphics effects in QGraphicsItem is really memory and computation heavy. If you use them during the animated transitions, it could be the problem. You should take them off and see how much smoother it is then try to implement your own effects.

blocks|key|2016386|text|好吧，我等了这么久才找到解决办法。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2016387|同时，我用QML重写了应用程序的UI，令我惊讶的是，它的性能要好得多，应用程序现在非常流畅。|2016388|一些结论：|2016389|在全屏模式下运行时，OpenGL加速效果最好.在QDeclarativeView中拥有整个UI，并将其viewPort设置为QGLWidget，并将其显示在全屏上，这使这成为可能。|unordered-list-item|2016390|QWidgets的开销似乎比我们想象的要多得多。|2016391|QML的性能比预期的要好得多。|2016392|QGraphicsDropshadowEffect的影响微乎其微，但我去掉了它，现在我使用了笔画效果。在未来，我可能会考虑使用QML着色器效果。|2016393|为QDeclarativeView设置各种优化标志是值得的|2016394|绘制具有alpha透明度的项目比不使用alpha透明的绘制项目要糟糕得多。尽可能避免阿尔法透明度。|2016395|将QGraphicsItem子类重写为QDeclarativeItem子类非常简单，值得付出努力。|2016396|源代码在这里。|offset|length|2016397|entityMap|0|LINK|mutability|MUTABLE|url|http://gitorious.org/colorful-apps/puzzle-master^0|0|0|0|0|0|0|0|0|0|0|0|7|0|0^^$0|@$1|2|3|4|5|6|7|16|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|17|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|18|8|@]|9|@]|A|$]]|$1|F|3|G|5|H|7|19|8|@]|9|@]|A|$]]|$1|I|3|J|5|H|7|1A|8|@]|9|@]|A|$]]|$1|K|3|L|5|H|7|1B|8|@]|9|@]|A|$]]|$1|M|3|N|5|H|7|1C|8|@]|9|@]|A|$]]|$1|O|3|P|5|H|7|1D|8|@]|9|@]|A|$]]|$1|Q|3|R|5|H|7|1E|8|@]|9|@]|A|$]]|$1|S|3|T|5|H|7|1F|8|@]|9|@]|A|$]]|$1|U|3|V|5|6|7|1G|8|@]|9|@$W|1H|X|1I|1|1J]]|A|$]]|$1|Y|3|-4|5|6|7|1K|8|@]|9|@]|A|$]]]|Z|$10|$5|11|12|13|A|$14|15]]]]

Okay, I've waited for this long for a solution.

In the meantime, I've rewritten the app's UI in QML, and to my surprise, the performance is a LOT better and the app is very smooth now.

Some conclusions:

<ul>
<li>OpenGL acceleration is best when running in full-screen mode. Having the whole UI in a QDeclarativeView and setting its viewPort to a QGLWidget, and displaying it in fullscreen make this possible.</li>
<li>It seems that the overhead of QWidgets is a lot more than we had thought.</li>
<li>QML can perform a lot better than expected.</li>
<li>The impact of the QGraphicsDropshadowEffect was marginal, but I removed it and now I use a stroke effect instead. In the future, I might consider using QML shader effects.</li>
<li>It's worth to set all kinds of optimalization flags for the QDeclarativeView</li>
<li>Drawing items with alpha transparency performs a lot worse than drawing them without. Avoid alpha transparency whenever possible.</li>
<li>Rewriting a QGraphicsItem subclass to be a QDeclarativeItem subclass is really easy and worth the effort.</li>
</ul>

<a href="http://gitorious.org/colorful-apps/puzzle-master" rel="noreferrer">Source code is here.</a>

blocks|key|192565|text|我的回答是那些像我刚才一样在他们的GraphicsItem::paint()方法中实现呈现模式逻辑的人。例如：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|192566|GraphicsItem::paint(QPainter+*+painter,+const+QStyleOptionGraphicsItem*,+QWidget*)
{
++++QPen+_pen+;
++++const+qreal+normalPenWidthF+=+1.5+;
++++if(isSelected())+{
++++++++_pen.setColor(Settings::s_selectionColor)+;
++++++++_pen.setWidthF(Settings::s_selectionWidth)+;
++++}
++++else
++++if(isHovered())+{
++++++++_pen.setColor(Settings::s_hoveredColor)+;
++++++++_pen.setWidthF(Settings::s_selectionWidth)+;
++++}
++++else
++++if(someOtherLogic())+{
++++++++_pen.setColor(Settings::s_otherColor)+;
++++++++_pen.setWidthF(normalPenWidthF)+;
++++}
++++else+{
++++++++_pen.setColor(TSPSettings::s_defaultColor)+;
++++++++_pen.setWidthF(normalPenWidthF)+;
++++}
++++//
++++painter->setPen(_pen)+;
++++painter->setBrush(Qt::NoBrush)+;
++++painter->drawEllipse(m_rect)+;
}|code-block|syntax|javascript|192567|下面是我如何获得良好的QGraphicsView性能，即使在涉及多个层的大型场景中。它甚至可以支持层间形状的动态裁剪。|192568|自定义GraphicsItems应该继承QAbstractGraphicsShapeItem，因此您有setPen()和setBrush()支持。|ordered-list-item|192569|公开一个接口以更新笔和画笔，并仅在需要时使用一些逻辑触发更新。|192570|.h|192571|class+AbstractGraphicsItem+:+public+QAbstractGraphicsShapeItem
{
++++private+:
++++++++bool+m_hovered+;

++++public+:
++++++++AbstractGraphicsItem()+;
++++++++virtual+~AbstractGraphicsItem()+;

++++++++bool+isHovered()+const+{+return+m_hovered+;+}
++++++++void+setIsHovered(bool+state)+;

++++++++//+control+render+mode+update
++++++++virtual+void+updatePenAndBrush()=0+;

++++protected+:
++++++++virtual+QVariant+itemChange(GraphicsItemChange+change,+const+QVariant+&value)+;
++++++++virtual+void+hoverEnterEvent(QGraphicsSceneHoverEvent+*e);
++++++++virtual+void+hoverLeaveEvent(QGraphicsSceneHoverEvent+*e);
};|192572|.cpp|192573|AbstractGraphicsItem::AbstractGraphicsItem()
++++:+QAbstractGraphicsShapeItem()
++++,+m_hovered(false)
{
}

AbstractGraphicsItem::~AbstractGraphicsItem()
{
}

void+AbstractGraphicsItem::setHovered(bool+state)
{
++++if+(h!=isHovered())+{
++++++++m_hovered+=+h+;
++++++++updatePenAndBrush()+;
++++++++update()+;
++++}
}

void+AbstractGraphicsItem::hoverEnterEvent(QGraphicsSceneHoverEvent*)
{
++++setHovered(true)+;
}

void+AbstractGraphicsItem::hoverLeaveEvent(QGraphicsSceneHoverEvent*)
{
++++setHovered(false)+;
}

QVariant+AbstractGraphicsItem::itemChange(GraphicsItemChange+change,+const+QVariant+&value)
{
++++switch(change)+{
++++++++case+ItemSelectedHasChanged+:
++++++++++++updatePenAndBrush()+;
++++++++++++break+;
++++}

++++return+QAbstractGraphicsShapeItem::itemChange(change,+value);
}|192574|然后您的GraphicsItem+(继承了AbstractGraphicsItem)变成：|192575|void+GraphicsItem::updatePenAndBrush()
{
++++QPen+_pen+;
++++if(isSelected())+{
++++++++_pen.setColor(Settings::s_selectionColor)+;
++++++++_pen.setWidthF(Settings::s_selectionWidth)+;
++++}+else
++++if(isHovered())+{
++++++++_pen.setColor(Settings::s_hoveredColor)+;
++++++++_pen.setWidthF(Settings::s_selectionWidth)+;
++++}+else
++++if(someOtherLogic())+{
++++++++_pen.setColor(Settings::s_otherColor)+;
++++++++_pen.setWidthF(normalPenWidthF)+;
++++}+else+{
++++++++_pen.setColor(Settings::s_defaultColor)+;
++++++++_pen.setWidthF(normalPenWidthF)+;
++++}
++++_pen.setCosmetic(true)+;
++++setPen(_pen)+;
}

void+GraphicsItem::paint(QPainter+*painter,+const+QStyleOptionGraphicsItem*,+QWidget+*)
{
++++painter->setPen(pen())+;
++++painter->setBrush(brush())+;
++++painter->drawEllipse(s_rect)+;
}|192576|旧的GraphicsItem::paint()方法的内容现在在GraphicsItem::updatePenAndBrush()中，并且时不时地被调用，但不是每次调用时都调用。另一方面，油漆方法达到了基本的水平。显然，你必须亲自打电话给updatePenAndBrush()，但在我的情况下，这并不难。这不是我唯一为提高表现所做的事。我搜索了很多，图形视图系统也有很多调整的可能，但是我的应用程序从几乎没有用到实时(终于！)|192577|entityMap^0|H|L|0|0|0|0|0|0|0|0|0|4|C|L|K|0|0|2|L|V|X|3A|J|0^^$0|@$1|2|3|4|5|6|7|17|8|@$9|18|A|19|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|1A|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|1B|8|@]|D|@]|E|$]]|$1|M|3|N|5|O|7|1C|8|@]|D|@]|E|$]]|$1|P|3|Q|5|O|7|1D|8|@]|D|@]|E|$]]|$1|R|3|S|5|6|7|1E|8|@]|D|@]|E|$]]|$1|T|3|U|5|H|7|1F|8|@]|D|@]|E|$I|J]]|$1|V|3|W|5|6|7|1G|8|@]|D|@]|E|$]]|$1|X|3|Y|5|H|7|1H|8|@]|D|@]|E|$I|J]]|$1|Z|3|10|5|6|7|1I|8|@$9|1J|A|1K|B|C]|$9|1L|A|1M|B|C]]|D|@]|E|$]]|$1|11|3|12|5|H|7|1N|8|@]|D|@]|E|$I|J]]|$1|13|3|14|5|6|7|1O|8|@$9|1P|A|1Q|B|C]|$9|1R|A|1S|B|C]|$9|1T|A|1U|B|C]]|D|@]|E|$]]|$1|15|3|-4|5|6|7|1V|8|@]|D|@]|E|$]]]|16|$]]

My answer is for people who, like I did for a while, implement render mode logic in their <code>GraphicsItem::paint()</code> method.
For example :

<pre><code>GraphicsItem::paint(QPainter * painter, const QStyleOptionGraphicsItem*, QWidget*)
{
 QPen _pen ;
 const qreal normalPenWidthF = 1.5 ;
 if(isSelected()) {
 _pen.setColor(Settings::s_selectionColor) ;
 _pen.setWidthF(Settings::s_selectionWidth) ;
 }
 else
 if(isHovered()) {
 _pen.setColor(Settings::s_hoveredColor) ;
 _pen.setWidthF(Settings::s_selectionWidth) ;
 }
 else
 if(someOtherLogic()) {
 _pen.setColor(Settings::s_otherColor) ;
 _pen.setWidthF(normalPenWidthF) ;
 }
 else {
 _pen.setColor(TSPSettings::s_defaultColor) ;
 _pen.setWidthF(normalPenWidthF) ;
 }
 //
 painter-&gt;setPen(_pen) ;
 painter-&gt;setBrush(Qt::NoBrush) ;
 painter-&gt;drawEllipse(m_rect) ;
}
</code></pre>

Here is how I achieved good QGraphicsView performance, even with large scenes involving multiple layers. It could even support dynamic clipping of shapes between layers.

<ol>
<li>Custom GraphicsItems should inherit of QAbstractGraphicsShapeItem,
so you have setPen() and setBrush() support.</li>
<li>Expose an interface to update pen and brush, and use some logic to
trigger an update only when needed.</li>
</ol>

.h

<pre><code>class AbstractGraphicsItem : public QAbstractGraphicsShapeItem
{
 private :
 bool m_hovered ;

 public :
 AbstractGraphicsItem() ;
 virtual ~AbstractGraphicsItem() ;

 bool isHovered() const { return m_hovered ; }
 void setIsHovered(bool state) ;

 // control render mode update
 virtual void updatePenAndBrush()=0 ;

 protected :
 virtual QVariant itemChange(GraphicsItemChange change, const QVariant &amp;value) ;
 virtual void hoverEnterEvent(QGraphicsSceneHoverEvent *e);
 virtual void hoverLeaveEvent(QGraphicsSceneHoverEvent *e);
};
</code></pre>

.cpp

<pre><code>AbstractGraphicsItem::AbstractGraphicsItem()
 : QAbstractGraphicsShapeItem()
 , m_hovered(false)
{
}

AbstractGraphicsItem::~AbstractGraphicsItem()
{
}

void AbstractGraphicsItem::setHovered(bool state)
{
 if (h!=isHovered()) {
 m_hovered = h ;
 updatePenAndBrush() ;
 update() ;
 }
}

void AbstractGraphicsItem::hoverEnterEvent(QGraphicsSceneHoverEvent*)
{
 setHovered(true) ;
}

void AbstractGraphicsItem::hoverLeaveEvent(QGraphicsSceneHoverEvent*)
{
 setHovered(false) ;
}

QVariant AbstractGraphicsItem::itemChange(GraphicsItemChange change, const QVariant &amp;value)
{
 switch(change) {
 case ItemSelectedHasChanged :
 updatePenAndBrush() ;
 break ;
 }

 return QAbstractGraphicsShapeItem::itemChange(change, value);
}
</code></pre>

And then your <code>GraphicsItem</code> (which inherits of <code>AbstractGraphicsItem</code>) becomes :

<pre><code>void GraphicsItem::updatePenAndBrush()
{
 QPen _pen ;
 if(isSelected()) {
 _pen.setColor(Settings::s_selectionColor) ;
 _pen.setWidthF(Settings::s_selectionWidth) ;
 } else
 if(isHovered()) {
 _pen.setColor(Settings::s_hoveredColor) ;
 _pen.setWidthF(Settings::s_selectionWidth) ;
 } else
 if(someOtherLogic()) {
 _pen.setColor(Settings::s_otherColor) ;
 _pen.setWidthF(normalPenWidthF) ;
 } else {
 _pen.setColor(Settings::s_defaultColor) ;
 _pen.setWidthF(normalPenWidthF) ;
 }
 _pen.setCosmetic(true) ;
 setPen(_pen) ;
}

void GraphicsItem::paint(QPainter *painter, const QStyleOptionGraphicsItem*, QWidget *)
{
 painter-&gt;setPen(pen()) ;
 painter-&gt;setBrush(brush()) ;
 painter-&gt;drawEllipse(s_rect) ;
}
</code></pre>

The contents of the old <code>GraphicsItem::paint()</code> method is now in <code>GraphicsItem::updatePenAndBrush()</code> and is called every now and then, but not at every paint call. On the other side, the paint method gets to the basics.
Obviously you'll have to call <code>updatePenAndBrush()</code> yourself, but it was not hard in my case.
It's not the only thing I did to improve performance. I searched a lot, and there is a lot of tweaking possible for a Graphics View system, but with this one my app went from barely usable to real-time (finally!)

I have an app which is based on the Qt Graphics View framework. 
It's a jigsaw puzzle game which basically cuts a pixmap into smaller pixmaps (puzzle pieces) and displays them as <code>QGraphicsItem</code>s in a <code>QGraphicsView</code>. I want this app to run on smartphones and tablets. (It already runs on the Nokia N900 and some Symbian phones. Not optimized for Symbian^3 yet.) 
The source is <a href="https://gitorious.org/colorful-apps/puzzle-master" rel="nofollow">on Gitorious</a>.

The items inherit <code>QGraphicsItem</code> and <code>QObject</code>, and have <code>Q_PROPERTY</code> macros for the <code>pos()</code> and <code>rotation()</code> of the <code>QGraphicsItem</code> to enable animating them with the Qt Animation framework. 
I perform transformations on the items, such as scaling and rotating (the latter only in the in-development multitouch branch), and I also use <code>QGraphicsDropShadowEffect</code> on them.

I use a <code>QGLWidget</code> as viewport of the <code>QGraphicsView</code> in order to enable OpenGL acceleration for the app.

The problem is that despite being OpenGL-accelerated, the app is not smooth at all. (Especially the animations and especially since I added the rotation transform to the multitouch branch.) There are not many graphics items displayed, and there are no 3D operations or anything serious, just 2D drawing. 
I'm not a graphics expert at all, so I have no idea why this app runs slowly. I've seen other games with lot more complicated effects run a lot smoother than this.

What's the secret? How could I optimize this app?

How can I optimize the performance of a QGraphicsView-based app?

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

文章

问答

视频

学习中心

腾讯云实验室

直播

竞赛

腾讯云代码分析专区

腾讯iOA零信任安全管理系统专区

腾讯云架构师技术同盟交流圈

腾讯云数据库专区

腾讯云顾问专区

腾讯云原生专区

腾讯混元专区

腾讯云TCE专区

腾讯云Lighthouse专区

腾讯云HAI专区

腾讯云Edgeone专区

腾讯云存储专区

腾讯云智能专区

腾讯轻联专区 

腾讯云开发专区

TAPD专区

腾讯轻量云游戏服专区

腾讯云最具价值专家

腾讯云架构师技术同盟

腾讯云创作之星

腾讯云开发者先锋 

腾讯云代码助手

CODING DevOps

Cloud Studio

SDK中心

API中心

命令行工具

我有一个基于框架的应用程序。这是一个拼图拼图游戏，它基本上把一个像素图切成更小的像素图(拼图)，并将它们作为QGraphicsItems显示在QGraphicsView中。我希望这个应用程序能在智能手机和平板电脑上运行。(它已经在诺基亚N900和一些塞班手机上运行。尚未为Symbian^3进行优化。)来源是。这些项继承...

问如何优化基于QGraphicsView的应用程序的性能？
EN

Stack Overflow用户

社区

活动

圈层

关于

腾讯云开发者

热门产品

热门推荐

更多推荐

问如何优化基于QGraphicsView的应用程序的性能？EN