I'm new here, and here to cause some trouble. I just wrote my first
GTK+3 app - or rather, I adapted an existing C++ program to give it a
GUI with GTK+3, and the distinction is important for reasons I'll make
clear. It wasn't a fun experience, and I'll try to keep ranting to a
minimum, but I'm here to ask people to seriously and thoughtfully
consider that gtk+4 embrace some new ideas.
1. Threads are here to stay
A number of years ago I was doing something in python and tkinter, and
got a crash out of tkinter. I dug a bit and realized I'd found a tkinter
issue, and there wasn't a workaround. Since I was stuck - and annoyed -
I wrote my own GUI toolkit, specific to Windows (but using openGL) and
python. Frankly it looked like crap, but it had the feature of features
I'd always dreamed of - thread safety. Complete thread safety, invisible
to the coder. You could delete a widget from any thread at any time,
including from the click callback of the widget itself, and it sorted
everything out for you. No explicit locking, no hangs or crashes.
I can't tell you how freeing this was or how much I've missed it since.
Widgets are just resources and should be like any other resource. Think
of files on linux. If one thread is writing to a file and another
decides to delete the file, well, maybe you got what you wanted or maybe
you didn't, but the operating system does not refuse your request, hang
or crash. The file is your resource, and as such, you do what you want
with it, from any thread at any time. The resource manager, in this case
the OS, deals with it all, leaving you free to Just Code(tm).
My C++ application is now riddled with gdk_threads_add_idle calls. It
has to be. It has a lot of threads, each doing independent tasks with
sockets and things, and sometimes they want to update a label with new
text or new colors. And instead of calling GTK and saying "do this", I
now have a bunch of functions that have to get injected into GTK, each
returning false. Now the code is ugly. And I'm not going to redesign it
around some central GTK world view; the fact that it paints a screen
with status is not the main point of the application and GTK shouldn't
demand a starring role.
Abolish the concept of a main gtk thread. "Anything anywhere and real
soon now" should be the motto.
2. My pixels, not yours. Hands off.
I know that Gtk has huge investment in flowing, springy, widget layout.
Yay adaptability to new screen sizes. But sometimes, you know, I just
want a widget to stay where I put it.
Sure, if you're writing an app that has to adapt to a 2x3" phone's
screen or a 20x8' foot, twenty billion pixel wall screen, having the GUI
engine manage sizing is nice. And monitors keep getting bigger, so...
Except wait. They don't anymore. These days, there's small screens,
desktop screens, and massive wall displays, and applications rarely
cross from one to the other. When they do, they're already coded to
adapt, because layout is philosophically different for a phone and a
huge screen, and different in ways that the GUI engine isn't likely to
be smart about without help.
In other words there's a place in the world for the ability to
Visual-Basic-Style-I-said-This-Big-And-Right-Here-and-no-backtalk-out-of-you
nailing down of widgets, for specific niche applications. Maybe Glade
can do this, but every time I Googled, I found threads saying "that's
not the Gtk way".
One True Wayism can have merits, but not in GUIs. Make a GTK API that
makes it easy to draw exactly what I want. My application is a fixed
display on a wall, and I'm not happy to see fields shifting around
because the very large Current Time field ticked over to skinnier
numbers. (I'm sure this is fixable using the current toolkit - but
apparently not trivially.)
3. I have to do what? Just to control colors and text in labels?
Maybe I did this wrong, but my goal was a black background, and then a
bunch of labels of various sizes. I need to be able to update the text
color and background color of the labels on the fly; everything from
slow adjustment of text color to indicate changing states, to
ohMyGoshAProblem! flashing labels at 4/sec because something's badly
wrong. Simple, no?
Simple not. It took a few days and I still didn't get exactly what I
wanted.
First of all, I learned the hard way that if you specify a widget's
background color in Glade, nothing you do at runtime can change it.
(That's probably overstated, but none of the existing or depreciated
calls I tried did anything.) That's just a weird bug or documentation
failure, but the upshot is that it's critical to specify as little as
possible in Glade and do as much as possible in code. That's simply
weird. And since Glade isn't making it easy to get the layout I wanted
anyway, why did I bother with it?
Second, in other to get a black background everywhere, I had to use css.
Not a lot of it: *{background-color: black;} got it done. But then there
was learning curve with providers and those are tricker than they should
be; it was a great moment when the window finally turned black. It
should have taken ten seconds boring seconds in Glade. Why did I need a
css file? What is this stuff about providers and screens?
And then there's coloring the text itself. In the end I generated markup
strings on the fly: <span yadda yadda>My carefully escaped text because
& happens</span>. They worked (once I cleared all the attributes out of
Glade). But why am I generating instructions in a clumsy markup
language, to be grokked by some underlying interpreter (that can only
run in a thread that's not me)? I'm on a raspberry pi - I'd rather not
use cycles for unnecessary parsing. You used to have override functions
for this stuff. Simple, clear, here's the color I want and I don't have
to generate a goofy string to get it. Why on earth are they depreciated?
And I still haven't gotten the entire label to change to the background
color I want - just the background of the text itself, which doesn't
always fill the label. Good enough for now I guess.
So here's the upshot.
Simple things should be simple; setting colors of anything should be
trivial. Sometimes the programmer needs to be in control of all the
aspects of everything. CSS and markup languages are great and all, and
if you're coding apps that need to play in a user-tweakable thematic
playpen and be easy for non-programmers to customize, they're great. But
not everything does or /should/ work that way. Gtk+ 3 makes it hard to
do it any other way.
I realize this may be contentious. But while I'm not fundamentally a GUI
designer, I've been writing applications for decades and have a pretty
good idea what happens inside GUI engines. I've used commercial ones
(Visual Basic, Java), written a couple, messed around with openGL. I
know what I need to get things done, and I've come to the conclusion
that packages like Gtk are designed around the convenience of the
library coder (make the user bring all his work to MY thread, muhahaha).
I think it's time for that to change, so I propose the change starts
with Gtk+4. Bring back simplicity and control and give me true thread
safety or give me, alright, not death, but maybe a sympathetic
implementation.
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