<html xmlns:v="urn:schemas-microsoft-com:vml" xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word" xmlns:m="http://schemas.microsoft.com/office/2004/12/omml" xmlns="http://www.w3.org/TR/REC-html40"><head><meta http-equiv=Content-Type content="text/html; charset=us-ascii"><meta name=Generator content="Microsoft Word 12 (filtered medium)"><style><!--
/* Font Definitions */
@font-face
{font-family:"Cambria Math";
panose-1:2 4 5 3 5 4 6 3 2 4;}
@font-face
{font-family:Calibri;
panose-1:2 15 5 2 2 2 4 3 2 4;}
/* Style Definitions */
p.MsoNormal, li.MsoNormal, div.MsoNormal
{margin:0cm;
margin-bottom:.0001pt;
font-size:11.0pt;
font-family:"Calibri","sans-serif";}
a:link, span.MsoHyperlink
{mso-style-priority:99;
color:blue;
text-decoration:underline;}
a:visited, span.MsoHyperlinkFollowed
{mso-style-priority:99;
color:purple;
text-decoration:underline;}
span.E-MailFormatvorlage17
{mso-style-type:personal-compose;
font-family:"Calibri","sans-serif";
color:windowtext;}
.MsoChpDefault
{mso-style-type:export-only;}
@page WordSection1
{size:612.0pt 792.0pt;
margin:70.85pt 70.85pt 2.0cm 70.85pt;}
div.WordSection1
{page:WordSection1;}
--></style><!--[if gte mso 9]><xml>
<o:shapedefaults v:ext="edit" spidmax="1026" />
</xml><![endif]--><!--[if gte mso 9]><xml>
<o:shapelayout v:ext="edit">
<o:idmap v:ext="edit" data="1" />
</o:shapelayout></xml><![endif]--></head><body lang=DE link=blue vlink=purple><div class=WordSection1><p class=MsoNormal><span lang=EN-US>Hello,<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US>after reading the tutorials and How-to’s for writing ParaView Plugins I’ve started with the Autostart-Example project. My goal was to create a plugin which is executed in an external thread. It might happens that I need this in the near future. <o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US>Well, it works quit well, I guess. But to avoid some errors and miss-behaviors I need a confirmation that I am on the right way.<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US>My approach is to use the signal-slot-pattern to communicate between the main thread of ParaView and my own plugin-thread. The class </span><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New"'>pqMyApplicationStarter </span><span lang=EN-US>represents the ParaView-plugin (which is running in the main thread of ParaView?). There is an object in this class which executes a loop within an external thread ( class </span><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New"'>Thread</span><span lang=EN-US> ), which extends QThread. <o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US>As I read somewhere that vtk isn’t implemented threaded-safe at all (at least the rendering stuff) I decided to do all render calls in</span><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New"'> pqMyApplicationStarter.</span><span lang=EN-US> When the </span><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New"'>UpdatedData()</span><span lang=EN-US>signal is fired the active view needs to re-rendered. </span><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New"'><o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New"'><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US>The question I want to ask is very simple: Is this the right / best way to create a thread and communicate with it via signals?<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New"'>/////////////// Thread.h ////////////////////////////</span><span lang=EN-US><o:p></o:p></span></p><p class=MsoNormal style='text-autospace:none'><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New";color:blue'>class</span><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New"'> Thread : <span style='color:blue'>public</span> QThread<o:p></o:p></span></p><p class=MsoNormal style='text-autospace:none'><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New"'>{<o:p></o:p></span></p><p class=MsoNormal style='text-indent:35.4pt;text-autospace:none'><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New"'>Q_OBJECT<o:p></o:p></span></p><p class=MsoNormal style='text-autospace:none'><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New";color:blue'>public</span><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New"'>:<o:p></o:p></span></p><p class=MsoNormal style='text-indent:35.4pt;text-autospace:none'><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New"'>Thread(QObject* parent = 0);<o:p></o:p></span></p><p class=MsoNormal style='text-indent:35.4pt;text-autospace:none'><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New";color:blue'>virtual</span><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New"'> ~Thread();<o:p></o:p></span></p><p class=MsoNormal style='text-indent:35.4pt;text-autospace:none'><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New";color:blue'>virtual</span><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New"'> <span style='color:blue'>void</span> run();<o:p></o:p></span></p><p class=MsoNormal style='text-autospace:none'><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New"'>signals:<o:p></o:p></span></p><p class=MsoNormal style='text-autospace:none'><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New"'> <span style='color:blue'>void</span> UpdatedData();<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New"'>};<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New"'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New"'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New"'><o:p> </o:p></span></p><p class=MsoNormal style='text-autospace:none'><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New";color:blue'>void</span><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New"'> Thread::run()<o:p></o:p></span></p><p class=MsoNormal style='text-autospace:none'><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New"'>{<o:p></o:p></span></p><p class=MsoNormal style='text-autospace:none'><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New"'> running = <span style='color:blue'>true</span>;<o:p></o:p></span></p><p class=MsoNormal style='text-autospace:none'><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New"'><o:p> </o:p></span></p><p class=MsoNormal style='text-autospace:none'><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New"'> <span style='color:blue'>while</span>( running )<o:p></o:p></span></p><p class=MsoNormal style='text-autospace:none'><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New"'> {<o:p></o:p></span></p><p class=MsoNormal style='margin-left:35.4pt;text-indent:35.4pt;text-autospace:none'><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New";color:green'>// Sleep awhile<o:p></o:p></span></p><p class=MsoNormal style='text-autospace:none'><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New"'> msleep( 800 );<o:p></o:p></span></p><p class=MsoNormal style='text-autospace:none'><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New"'> <span style='color:green'>// Fire the signal<o:p></o:p></span></span></p><p class=MsoNormal style='text-autospace:none'><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New"'> emit UpdatedData(); <o:p></o:p></span></p><p class=MsoNormal style='text-autospace:none'><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New"'> </span><span style='font-size:10.0pt;font-family:"Courier New"'>} <o:p></o:p></span></p><p class=MsoNormal style='text-autospace:none'><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New"'>}<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New"'>/////////////////////////////////////////////////////<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New"'><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New"'><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New"'>/////////////// pqMyApplicationStarter //////////////<o:p></o:p></span></p><p class=MsoNormal style='text-autospace:none'><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New";color:blue'>class</span><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New"'> pqMyApplicationStarter : <span style='color:blue'>public</span> QObject<o:p></o:p></span></p><p class=MsoNormal style='text-autospace:none'><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New"'>{<o:p></o:p></span></p><p class=MsoNormal style='text-autospace:none'><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New"'> Q_OBJECT<o:p></o:p></span></p><p class=MsoNormal style='text-autospace:none'><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New"'> <span style='color:blue'>typedef</span> QObject Superclass;<o:p></o:p></span></p><p class=MsoNormal style='text-autospace:none'><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New"'><o:p> </o:p></span></p><p class=MsoNormal style='text-autospace:none'><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New";color:blue'>public</span><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New"'>:<o:p></o:p></span></p><p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;font-family:"Courier New"'> pqMyApplicationStarter(QObject* p=0);<o:p></o:p></span></p><p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;font-family:"Courier New"'> ~pqMyApplicationStarter();<o:p></o:p></span></p><p class=MsoNormal style='text-autospace:none'><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New"'><o:p> </o:p></span></p><p class=MsoNormal style='text-autospace:none'><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New"'> </span><span style='font-size:10.0pt;font-family:"Courier New";color:green'>// Callback for startup.<o:p></o:p></span></p><p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;font-family:"Courier New"'> <span style='color:blue'>void</span> onStartup();</span><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New"'><o:p></o:p></span></p><p class=MsoNormal style='text-autospace:none'><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New"'><o:p> </o:p></span></p><p class=MsoNormal style='text-autospace:none'><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New";color:blue'>public</span><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New"'> slots:<o:p></o:p></span></p><p class=MsoNormal style='text-autospace:none'><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New"'> <span style='color:blue'>void</span> Trigger();<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New"'>};<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New"'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New"'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New"'><o:p> </o:p></span></p><p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;font-family:"Courier New";color:blue'>void</span><span style='font-size:10.0pt;font-family:"Courier New"'> pqMyApplicationStarter::onStartup()<o:p></o:p></span></p><p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;font-family:"Courier New"'>{<o:p></o:p></span></p><p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;font-family:"Courier New"'> </span><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New"'>myThread = <span style='color:blue'>new</span> Thread();<o:p></o:p></span></p><p class=MsoNormal style='text-autospace:none'><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New"'> myThread->start();<o:p></o:p></span></p><p class=MsoNormal style='text-autospace:none'><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New"'><o:p> </o:p></span></p><p class=MsoNormal style='text-autospace:none'><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New"'> pqActiveObjects::instance().connect( myThread, SIGNAL(UpdatedData()), <span style='color:blue'>this</span>, SLOT(Trigger()) ); <o:p></o:p></span></p><p class=MsoNormal style='text-autospace:none'><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New"'>}<o:p></o:p></span></p><p class=MsoNormal style='text-autospace:none'><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New"'><o:p> </o:p></span></p><p class=MsoNormal style='text-autospace:none'><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New";color:blue'>void</span><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New"'> pqMyApplicationStarter::Trigger()<o:p></o:p></span></p><p class=MsoNormal style='text-autospace:none'><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New"'>{ <span style='color:green'><o:p></o:p></span></span></p><p class=MsoNormal style='text-autospace:none'><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New"'> pqActiveObjects* object = &(pqActiveObjects::instance());<o:p></o:p></span></p><p class=MsoNormal style='text-autospace:none'><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New"'> pqView* view = object->activeView();<o:p></o:p></span></p><p class=MsoNormal style='text-autospace:none'><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New"'><o:p> </o:p></span></p><p class=MsoNormal style='text-autospace:none'><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New"'> <span style='color:blue'>if</span> (view)<o:p></o:p></span></p><p class=MsoNormal style='text-autospace:none'><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New"'> {<o:p></o:p></span></p><p class=MsoNormal style='text-autospace:none'><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New"'> view->render();<o:p></o:p></span></p><p class=MsoNormal style='text-autospace:none'><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New"'> }<o:p></o:p></span></p><p class=MsoNormal style='text-autospace:none'><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New"'><o:p> </o:p></span></p><p class=MsoNormal style='text-autospace:none'><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New"'> view = NULL;<o:p></o:p></span></p><p class=MsoNormal style='text-autospace:none'><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New"'>}<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New"'><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New"'><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US>Thanks a lot.<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US>Cheers,<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US>Stephan<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p></div></body></html>