Re: GtkSpreadTable ('spread-table' branch)

[Murray Cumming <murrayc murrayc com>]

On Fri, 2010-10-08 at 20:36 +0900, Tristan Van Berkom wrote:
> On Fri, 2010-10-08 at 12:13 +0200, Murray Cumming wrote:
> > On Thu, 2010-10-07 at 12:37 +0900, Tristan Van Berkom wrote:
> > > Hello list again,
> > >    Now for the introduction of GtkSpreadTable (still open for
> > > a better name for this widget).
> > > 
> > > What the spread table container does is takes a linear list
> > > of widgets, which can be of variable size and spread/distribute
> > > the widgets as evenly as possible according to their size
> > > across a fixed number of rows or columns. Thus requiring the
> > > smallest size possible while maintaining the fixed number
> > > of columns or rows.
> > > 
> > > For instance when oriented vertically, widgets will be listed
> > > top-down with the first widget in the top-left corner and the 
> > > last widget on the bottom right; widgets will be lined up in 
> > > such a way to require the least height as possible.
> > > 
> > > This widget is the one that actually meets the requirements 
> > > for Glom[0].
> > > 
> > > To get a better idea of how this works you can checkout and 
> > > build the 'spread-table' branch I added to GTK+ yesterday... 
> > > fire up the ./tests/testspreadlayout demo.
> > 
> > Some quick links might be helpful
> > http://git.gnome.org/browse/gtk+/log/?h=spread-table
> > http://git.gnome.org/browse/gtk
> > +/tree/gtk/gtkspreadtable.h?h=spread-table
> > 
> > I have already wrapped this in a branch of gtkmm, and even used it in
> > Glom instead of my custom code. It seems to work fine for me.
> > 
> > Some small suggestions:
> > 1.
> > I think lines should be lines_count.
> > 
> > 2.
> > I'd like a get_widget_line(GtkWidget*) function so I can discover what
> > line (column in my case) the widget is currently in. I'd like to query
> > that whenever the allocation changes, so that I can align some child
> > widgets (children of HBoxes in columns of the GtkSpreadTable) via a
> > GtkSizeGroup. Obviously I only want widgets in a GtkSizeGroup (so they
> > have the same width) that are in the same column.
> 
> I suppose they could even be read-only child properties,
> in this way we could cache the current line number and 
> notify the changes when one widget gets placed on an new line
> (an unallocated widget would always be on line -1).
> 
> Then you could just watch when the widget jumps from line to line.
> 
> However I wonder if changing some if the internal widget's size
> groups may effect the overall requested width of that column...
> and in the worst case you end up with a situation where:
>   - Allocation happens
>   - Change size groups in consequence
>   - Size group changes widget requests
>   - Widget's get reorganized into different
>     columns as a result of the new size-grouping. 
> 
> Maybe it wont happen so long as you are playing with smaller
> sizes, but it may be recommendable to just size group widgets
> in all columns equally (I suppose experimentation will tell).

Yeah, I saw the risk of an endless loop, but maybe I can prevent that in
my code. Or maybe it will just be one extra relayout. My existing code
actually has a hard-coded concept of two horizontally-aligned items in
each column, so it knows about that constraint already. But that's very
specific behaviour.

Alternatively, is there just some way to find a child GtkWidget's
position in a GtkContainer? Then I wouldn't need extra API.

-- 
murrayc murrayc com
www.murrayc.com
www.openismus.com