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POProducer Accessing GUI outside GUI thread using service Pattern
 

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  1. POProducer Accessing GUI outside GUI thread using service Pattern
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    <p>My <code>Producer</code>(<em>which is running on a different thread</em>) needs access to <code>QDesktopWidget</code>, some QWidget, it also needs to work with <code>QPixmap</code>. So I designing the polling like this.</p> <p>Producer, Consumer, Transmitter are <code>boost::thread</code>. This is how I've planned.</p> <p>I've a <code>device::Service</code> class that is an <code>QObject</code> and lives in GUI thread. It is the base of all Service Classes. There is <code>device::PixmapService</code> that inherits <code>device::Service</code></p> <p>There is a method with the follwoing signature, that is called by <code>Producer</code> Thread. <code>ProxyTray&lt;QImage, device::PixmapService&gt; device::PixmapService::requestPixmap()</code> </p> <p><code>requestPixmap()</code> creates a tray <code>ProxyTray&lt;QImage, device::PixmapService&gt; blankTray</code><br /> and emit a <code>this-&gt;pixmapRequestedSignal(tray)</code> and returns the same <code>tray</code> immedietly.</p> <p><code>device::PixmapService::pixmapRequestedSlot</code> gets the request with Qt's Signal-Slot Mechanism. and resolves the tray by <code>tray.resolve(image)</code>.</p> <p>In the mean time Producer waits by doing. </p> <pre><code>while(!tray.released()); QImage image = tray.data(); </code></pre> <p>Is the design Okay ? Would It even work ? Am I reinventing some Wheel ?</p> <pre><code>template &lt;typename T, typename Manipulator&gt; class ProxyTray: public AbstractProxyTray{ friend class Manipulator; private: T _data; public: ProxyTray(); public: T&amp; data() const; ~ProxyTray(); private: void resolve(T&amp; data); }; class AbstractProxyTray{ private: bool _busy; public: AbstractProxyTray(); public: bool released() const;//returns !_busy virtual ~AbstractProxyTray() = 0; }; </code></pre> <p>also I need to write a copy con for the ProxyTray. and copying should be okay cause tray will be holding Qt types that is based on <code>QSharedData</code> which implements <code>copy on write</code>.</p>
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    1. USNeel Basu
    1. USNeel Basu
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    1. COI'm a big fan of boost threads when not using Qt but is there any reason that you are selecting to mix boost threads with Qt signal/slots versus using QThread?
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      1. POProducer Accessing GUI outside GUI thread using service Pattern
      1. USMatthew
    2. COWell the excuses are pretty lame. 1) I've never used boost threads before. so I am using it here to learn. and 2) boost::thread is supposed-to/has become the C++ standard in near future, So why use this from Qt if `std` supports it. 3) using boost thread its easy to keep the core of the application strictly separate from the GUI Toolkit, such that migration to any other (may be System Specific) GUI toolkit would be easier.
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      1. POProducer Accessing GUI outside GUI thread using service Pattern
      1. USNeel Basu
    3. COThe reason I ask is you may have to carefully consider the configuration of your slots/signals since you are not using QThread.
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      1. USMatthew
 

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