[Glade-devel] Future of the preview feature

[marcodiegomesquita at gmail.com (Marco Diego Aurélio Mesquita)]

Hi devs!

Now that the preview feature will finally get in, it is time to think
about future improvements for the feature. One that can be clearly
seen, is to separate the preview functions defined in glade-project to
another class. That would make the code a lot cleaner.

On the previewer side, there are many things that can be experimented
with. My main feeling is a "dynamic preview", where changes to a
project are automatically propagated to the preview. Implementing
dynamic previews would require to extend the protocol used between
glade and glade-previewer. The simplest way would be to just use a tag
like "<update>" and then send the new ui definition with the
modifications that were made.

Destroying the preview window and creating a new one to reflect the
changes is ugly and suboptimal. Another idea (richer but not simpler)
would be to extend the protocol to tell glade-previewer which changes
were made. I can see 3 types of changes that could be transformed in
tags for the protocol: property changes, removal of widget and
addition of widget.

Changing a property would be easy to propagate to glade-previewer; all
that is needed is a tag like <change_property object="object_name"
property="property_name" value="new_value">. Parsing and committing it
would not be so simple, but do-able.

Removing a widget is as simple as telling glade-previewer the widget
to be removed (maybe we'll have tell the widget to be removed and
which widget is its parent). A tag could be <remove_widget
parent="parent_name" widget="widget_name">.

Adding a new widget would be a bit more complicated, but still
do-able. The previewer would have to know which widget is the parent
of the new widget and the ui definition of the new widget. This can be
achieved by a tag like <add_widget parent="parent_name"> followed by
the ui definition of the new widget.

Also I'm thinking on other improvements that can improve usefulness of
a preview, like selecting in glade the widget that has been clicked in
the preview or adding a new widget to a container in the project if
the user clicks a widget in the palette and then on a container on a
preview.

What do you think about it? Comments? Suggestions?