Re: Why doesn't my label show up in the window

[Emmanuele Bassi <ebassi gmail com>]

hi;

On 27 August 2012 07:40, Frank Cox <theatre melvilletheatre com> wrote:
> Both of the attached modifications of the program appears to work properly every
> time.
>
> So is my problem that the label isn't actually ready to be drawn on the first
> call to sleep() for some reason?

you still fail at understanding the basic concept of event driven
programming â i.e. you react to what the GUI tells you that happened,
not the other way around â and, more importantly, at understanding the
basic tenet of mainloop-driven toolkits, which is: Thou Shall Never
Block Thy Main Loop.

widgets are not "ready to be drawn" because you told them to: they
have internal state that has to be updated, and given that the toolkit
authors do not want to block the main loop, it will be mostly done
lazily, and along with the full tree, instead of piecemeal. that's
*the* main difference between event driven programming with graphical
toolkits and programming done on the console: the widgets will tell
*you* when they are being drawn, or when something happens. in other
words, "in event driven programming, like in Soviet Russia, the
toolkit updates you".

another thing is that if you feel you need to call sleep() anywhere in
a GUI then you are doing it wrong on an epic scale. the first rule of
mainloop-driven toolkits (such as GTK+) is: you do not block the main
loop. the second rule of mainloop-driven toolkits is: you do *not*
block the main loop. even if you're using sleep() to demonstrate the
fact that your long running operation is blocking the GUI, you're
doing it wrong.

let the main loop run; do not try and spin it yourself; do not try to
block it; do not let long running operations in the same loop as your
GUI loop, *ever*. everything I've seen from you code snippets contains
at least one violation of these rules.

stop trying to write code in GTK+ like you would do with ncurses. look
at examples on the developer.gnome.org website; look at existing GTK+
applications; read books on event-driven programming.

ciao,
 Emmanuele.

-- 
W: http://www.emmanuelebassi.name
B: http://blogs.gnome.org/ebassi/