[PyQt] Composite widgets?

[Hans-Peter Jansen]

On Monday 06 September 2010, 03:13:29 Peter Milliken wrote:
> Prior to embarking on learning PyQt, I wrote my GUI applications using
> Tkinter and Pmw. The Pmw widget set is quite nice and provides a library
> of composite classes using the Tkinter widgets.
>
> My question is:
>
> Is there any (similar) composite widgets in PyQt? i.e. Pmw has the
> EntryField widget, which combines the (commonly used case) of a Label and
> a LineEdit into the one class - much more convenient than always having
> to specify the two entities separately, which seems to be the case with
> PyQt? The EntryField widget offers far more than just conveniently
> creating a Label and a LineEdit in the one class, it also allows
> definition of entry validation as well, so you can see that the composite
> classes provide quite a high level of functional behaviour to the user.

Well, the powers of Pmw are undoubted, as long as you keep on the well 
prepared route. The reason, why Qt and therefore PyQt doesn't follow this 
route is flexibility. E.g. a label/editfield composite: usually you want 
the labels and editfields align to some grid, where they all align 
vertically, otherwise the UI looks pretty crowded. Given, I need more 
editors, e.g. a date and a combo for a single item, I tend to combine them 
ad hoc by a hbox layout from within designer instead of creating some 
composite widgets.

> Pmw defines other composite widgets like: RadioSelect - which groups
> radio buttons (well, you have the choice of defining it to handle radio
> buttons, check buttons or "normal" buttons). Of course in PyQt I have
> found the QGroupBox class, but this only performs a (small) part of what
> the Pmw RadioSelect widget does.

All these exist as single items, just add them to your UI interactively in 
designer, but there's no such thing in Pmw. In a very old project, where I 
used Pmw until lately for historical reasons, I suffered from crashes in 
newer versions of tix, that where related to unicode issues of edit 
widgets. Such problems can drive you crazy, since looking into tix might 
damage one's brain. 

Try to create a table like window and different editors for all columns and 
say 100000 rows with Pmw. Let it update hundreds of cells every second. 
Will it still be usable? 

I replaced that Pmw database frontend with a PyQt based one, where I halved 
the number of lines, but _added_ a bulk of functionality, that simply 
wouldn't been able with Pmw. Needless to say, it starts ten times quicker, 
it has a quick full text search facility in _huge_ tables at nearly zero 
cost, a table query tool, that creates persistent queries by dynamically 
creating the widgets (field, operation, argument, join) in a dummy prove 
way (this is an application where custom widgets make sense), print the 
tables nicely, the app looks good and the usability improved greatly.

> Do such composite widgets exist? am I missing something in the PyQt
> documentation?

Start browsing the Qt documentation. Yes, it's a bit arkward to ignore the 
C++ decoration, but after getting used to, you start to enjoy to be able to 
ignore all the C++ related complexities and regret all those poor C++ 
hackers: hack, compile, link, crash, hack, compile, link, just for entering 
the event loop two or three hundred microseconds earlier then us (on an 
average system) when they finally fixed their self created headaches. 

Pete