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Subject: [boost] [gui] Help with a little experiment.
From: Germán Diago (germandiago_at_[hidden])
Date: 2011-06-18 07:05:08

Hello. I'm trying to implement a little experiment of what I see should
be the future of c++ guis. For that I'm going to need a handful of
proto and fusion, and I have some questions. Besides that, there
have been many times that a GUI for boost has been discussed.
As I have some questions and something to expose, I thought it would
be a good idea to post this message in both boost users and boost developers.

I don't have an entire proposal for this, but for now I'm experimenting
how a GUI framework should look like in my opinion.

My opinion is that it should be AS declarative as possible, so, taking
as a backend the gtk framework, I came with a syntax like the following

#define CONTROLLER_CLASS GuiController
#include <Gui/Layout.h>
#include <iostream>

class GuiController {
        void onEntryChanged(Entry & entry) {
                auto text = entry.getText();
                std::cout << text << std::endl;

        void onButtonClick(Button & button) {
                std::cout << "Button was clicked" << std::endl;

auto gui_definition =
Window(title="Hello, world!") <<
        VBox(expand=true) <<
                HBox(expand=true) <<
                        Label(text="Name:") && Entry[SLOT(onEntryChanged)])
                << End(HBox);
                << Button(text="hello")[SLOT(onButtonClick)];
        << End(VBox)
<< End(Window);

The properties are mapped to objects like title corresponding to the gtk
properties. The << operator means insert into and the << End(WidgetName)
means that no more widgets should be inserted inside that closed widget.
The && operator means put widgets at the same level. Regarding signals,
they're put inside operator[]. That gui definition would be used like this

template <class UI, class Controller>
?? createGUI(UIDefinition & ui_def, Controller & controller);

int main(int argc, char * argv[]) {
        GuiController controller;
        auto window = createGUI(gui_definition, controller);


The function createGUI would generate a GUI from the definition and
 it would bind SLOTS automagically. It's very little code making use of
a DSEL. The problem is that I must learn a lot of proto to code this,
but if it works, do you think it would be an improvement? It's all
and the code is very short. After this first step I could start
thinking beyond gtk
and separate the library in backend and frotend so that not just gtk+ is used.

My question is:

Can I make something like End(VBox) work with boost.proto? I mean if it's
possible to close the expression for a VBox with end and insert the next widget
to the same level that the HBox.

Thanks for your time and feedback is welcome.

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