Comments on: Trying to solve compositing problems of Qt widgets as X11 windows http://myrizio.wordpress.com/2007/07/21/trying-to-solve-compositing-problems-of-qt-widgets-as-x11-windows/ Programming, KDE and more Sat, 28 Nov 2009 18:10:07 +0000 http://wordpress.com/ hourly 1 By: Maurizio http://myrizio.wordpress.com/2007/07/21/trying-to-solve-compositing-problems-of-qt-widgets-as-x11-windows/#comment-312 Maurizio Wed, 20 Feb 2008 23:06:38 +0000 http://myrizio.wordpress.com/2007/07/21/trying-to-solve-compositing-problems-of-qt-widgets-as-x11-windows/#comment-312 No need, this problem is now officially fixed in the snapshot of Qt 4.4 No need, this problem is now officially fixed in the snapshot of Qt 4.4

]]> By: Kevin Mills http://myrizio.wordpress.com/2007/07/21/trying-to-solve-compositing-problems-of-qt-widgets-as-x11-windows/#comment-311 Kevin Mills Wed, 20 Feb 2008 17:33:44 +0000 http://myrizio.wordpress.com/2007/07/21/trying-to-solve-compositing-problems-of-qt-widgets-as-x11-windows/#comment-311 I stumbled across your posting while looking for a solution for creating a transparent window in X. I am trying to do the same thing in an environment where I *know* I won't have a capable Window Manager (older AIX and Sun machines running CDE or OpenLook). Would you be willing to share the manual solution you found? And any chance you'd know how to do something like this *without* Qt? I stumbled across your posting while looking for a solution for creating a transparent window in X. I am trying to do the same thing in an environment where I *know* I won’t have a capable Window Manager (older AIX and Sun machines running CDE or OpenLook). Would you be willing to share the manual solution you found? And any chance you’d know how to do something like this *without* Qt?

]]> By: Maurizio http://myrizio.wordpress.com/2007/07/21/trying-to-solve-compositing-problems-of-qt-widgets-as-x11-windows/#comment-41 Maurizio Thu, 09 Aug 2007 15:27:32 +0000 http://myrizio.wordpress.com/2007/07/21/trying-to-solve-compositing-problems-of-qt-widgets-as-x11-windows/#comment-41 Riccardo: Yup, i already commented on that blog post too :) Riccardo: Yup, i already commented on that blog post too :)

]]> By: Riccardo Iaconelli http://myrizio.wordpress.com/2007/07/21/trying-to-solve-compositing-problems-of-qt-widgets-as-x11-windows/#comment-40 Riccardo Iaconelli Thu, 09 Aug 2007 12:43:42 +0000 http://myrizio.wordpress.com/2007/07/21/trying-to-solve-compositing-problems-of-qt-widgets-as-x11-windows/#comment-40 http://labs.trolltech.com/blogs/2007/08/09/qt-invaded-by-aliens-the-end-of-all-flicker/ :D http://labs.trolltech.com/blogs/2007/08/09/qt-invaded-by-aliens-the-end-of-all-flicker/

:D

]]> By: Enrico Ros http://myrizio.wordpress.com/2007/07/21/trying-to-solve-compositing-problems-of-qt-widgets-as-x11-windows/#comment-23 Enrico Ros Sun, 22 Jul 2007 19:47:10 +0000 http://myrizio.wordpress.com/2007/07/21/trying-to-solve-compositing-problems-of-qt-widgets-as-x11-windows/#comment-23 Just read the comments on today Zack's web-on-canvas-and-dashboard-widgets post.. seems like QWidgets on the canvas is coming in 4.4. This won't solve the general case that you outlined, but will allow anyone that based his own app on QGraphicsView to have nice overlays and animations! @maurizio: I think that the problem you're outlining is somewhat serious and should be reported to Trolltech. Con affetto, Enrico ;-) Just read the comments on today Zack’s web-on-canvas-and-dashboard-widgets post.. seems like QWidgets on the canvas is coming in 4.4. This won’t solve the general case that you outlined, but will allow anyone that based his own app on QGraphicsView to have nice overlays and animations!

@maurizio: I think that the problem you’re outlining is somewhat serious and should be reported to Trolltech.

Con affetto,
Enrico ;-)

]]> By: Top Posts « WordPress.com http://myrizio.wordpress.com/2007/07/21/trying-to-solve-compositing-problems-of-qt-widgets-as-x11-windows/#comment-22 Top Posts « WordPress.com Sat, 21 Jul 2007 23:59:03 +0000 http://myrizio.wordpress.com/2007/07/21/trying-to-solve-compositing-problems-of-qt-widgets-as-x11-windows/#comment-22 [...] Trying to solve compositing problems of Qt widgets as X11 windows Since Qt 4 all widgets are double-buffered, and every widget is drawn over the parent widget, for instance allowing it […] [...] [...] Trying to solve compositing problems of Qt widgets as X11 windows Since Qt 4 all widgets are double-buffered, and every widget is drawn over the parent widget, for instance allowing it […] [...]

]]> By: Maurizio http://myrizio.wordpress.com/2007/07/21/trying-to-solve-compositing-problems-of-qt-widgets-as-x11-windows/#comment-21 Maurizio Sat, 21 Jul 2007 21:17:43 +0000 http://myrizio.wordpress.com/2007/07/21/trying-to-solve-compositing-problems-of-qt-widgets-as-x11-windows/#comment-21 @clee: XComposite works with a double buffer for each window it will compose, and this would be a huge waste of memory. At the moment Qt do compositing in its own stack, and it works well in this way *except* for bad interactions of the X server when a widget/window is moved/destroyed withing its parent. A compositing manager is useful when the windows being composed are created by different application that cannot easily interact, in this case it is really not required because each application can succesfully take care of its own widgets. @clee: XComposite works with a double buffer for each window it will compose, and this would be a huge waste of memory.

At the moment Qt do compositing in its own stack, and it works well in this way *except* for bad interactions of the X server when a widget/window is moved/destroyed withing its parent.

A compositing manager is useful when the windows being composed are created by different application that cannot easily interact, in this case it is really not required because each application can succesfully take care of its own widgets.

]]> By: iax http://myrizio.wordpress.com/2007/07/21/trying-to-solve-compositing-problems-of-qt-widgets-as-x11-windows/#comment-20 iax Sat, 21 Jul 2007 20:37:50 +0000 http://myrizio.wordpress.com/2007/07/21/trying-to-solve-compositing-problems-of-qt-widgets-as-x11-windows/#comment-20 @clee: Qt already uses the compositing features of X. Pixmaps and widgets are stored in X. It is my understanding (can be wrong) that the main problem is that they use still window hierarchy for distribuiting input, and that this way X associates the windows with the on screen pixmap in the same area. So moving the window moves the pixmap area around, instead of just triggering a redraw in the Qt. The flag InputOnly that Leon speaks of could change this behaviour, explaining to X the true purpose of the window. X would not try and redraw the child window when it moves but leave it to Qt. This avoids flicker. To sum it up: Qt already uses the XRender extension, so it should be just a matter of putting X to sleep. @clee: Qt already uses the compositing features of X. Pixmaps and widgets are stored in X.

It is my understanding (can be wrong) that the main problem is that they use still window hierarchy for distribuiting input, and that this way X associates the windows with the on screen pixmap in the same area. So moving the window moves the pixmap area around, instead of just triggering a redraw in the Qt.

The flag InputOnly that Leon speaks of could change this behaviour, explaining to X the true purpose of the window. X would not try and redraw the child window when it moves but leave it to Qt. This avoids flicker.

To sum it up: Qt already uses the XRender extension, so it should be just a matter of putting X to sleep.

]]> By: clee http://myrizio.wordpress.com/2007/07/21/trying-to-solve-compositing-problems-of-qt-widgets-as-x11-windows/#comment-19 clee Sat, 21 Jul 2007 20:13:44 +0000 http://myrizio.wordpress.com/2007/07/21/trying-to-solve-compositing-problems-of-qt-widgets-as-x11-windows/#comment-19 @Maurizio: On the contrary, what you're saying is that Qt is creating a new window, which is *exactly* what Composite is for. Please read more on it before dismissing it. @Maurizio: On the contrary, what you’re saying is that Qt is creating a new window, which is *exactly* what Composite is for.

Please read more on it before dismissing it.

]]> By: Maurizio http://myrizio.wordpress.com/2007/07/21/trying-to-solve-compositing-problems-of-qt-widgets-as-x11-windows/#comment-18 Maurizio Sat, 21 Jul 2007 14:21:18 +0000 http://myrizio.wordpress.com/2007/07/21/trying-to-solve-compositing-problems-of-qt-widgets-as-x11-windows/#comment-18 @clee, @iax: no, XComposite is not the solution for this problem, because compositing is done internally by Qt and we do not want X to waste additional memory for child widgets (don't misunderstand me, for toplevel windows XComposite is the way to go), it should just behave in the correct way. @Leon Bottou: interesting, i didn't know about this (i don't know X very well). If so, maybe some troll could let us know if what i proposed would be feasible. @Enrico Ros: ciao Enrico! Happy to see your reply here, and to see that you solved your problem. Unluckily your solution cannot work in the most general settings, because for instance i may want to place some animation over already implemented standard Qt widgets (such as buttons, checkboxes, etc). @clee, @iax: no, XComposite is not the solution for this problem, because compositing is done internally by Qt and we do not want X to waste additional memory for child widgets (don’t misunderstand me, for toplevel windows XComposite is the way to go), it should just behave in the correct way.

@Leon Bottou: interesting, i didn’t know about this (i don’t know X very well). If so, maybe some troll could let us know if what i proposed would be feasible.

@Enrico Ros: ciao Enrico! Happy to see your reply here, and to see that you solved your problem. Unluckily your solution cannot work in the most general settings, because for instance i may want to place some animation over already implemented standard Qt widgets (such as buttons, checkboxes, etc).

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