Valeri Fine writes: > Qt provides very attractive base class QCanvasItem: > > http://doc.trolltech.com/3.0/qcanvasitemlist.html > http://doc.trolltech.com/3.0/qcanvasitem.html I get a little nervous when QCanvas is suggested as something to emulate. I works okay for some things but the fact that it is integer pixel based makes it difficult to use for things like event displays. The user must take care of the world coordinate abstraction. As an alternative, I think GnomeCanvas is a better role model. It treats objects as a heirarchy of items and groups (similar to how TPad can hold TPads and other TObjects) each with their own affine transformation and either world or absolute pixel drawing. You can also put Gtk Widgets into a GnomeCanvas (although, I am not sure if that means one can have postscript output of the widget). Some reading: GnomeCanvas white paper: http://developer.gnome.org/doc/whitepapers/canvas/canvas.html Chapter from GGAD book: http://developer.gnome.org/doc/GGAD/cha-canvas.html Another thing I haven't mentioned in my Gnome/Gtk/Gdk cheer-leading is that since all the underlying libraries are C, but follow an object oriented design, they lend themselves to easy wrapping in other languages. For example, the Gnome--/Gtk--/Gdk-- effort. I mention this because one could consider writing ROOT/CINT wrappers for the underlying C libraries as well. But, another big long project.... GnomeCanvas does lack some things that QCanvas supplies, such as the setting an item's "velocity" to provide default movement. This is not so useful for event displays but probably good for 2D games, and arguably better handled by the user. > Qt provides the base QPaintDevice class with some subclasses like > QPrinter, QWidget, QPixmap, QPicture etc > > http://doc.trolltech.com/3.0/qpaintdevice.html > http://doc.trolltech.com/3.0/qpicture.html#details > http://doc.trolltech.com/3.0/qprinter.html > > > I'd like to call your attention to QPrinter / QPicture classes. > That is what one needs for the batch job. > > See: http://doc.trolltech.com/3.0/qprinter.html#setOutputToFile The QPainter idea is interesting. To put it in ROOT terms, it essentially lets you swap out the implimentation of TVirtualX at run time from paint-to-X11 to paint-to-Postscript. I used this when I tried to make Qt widgets draw themselves to postscript, along with the QCanvas for a proto-MIDAD event display. It worked fairly well, although not perfect, I think due to internal Qt bugs (some widgets drew themselves wrong in Postscript). I didn't get enough help from the Qt guys to find it desirable to get it working 100% and in the end, due to the QCanvas limitations, the QCanvas based display was abandoned for TCanvas based one. -Brett.
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