Re: GtkSpreadTable ('spread-table' branch)

[Murray Cumming <murrayc murrayc com>]

On Fri, 2010-10-08 at 21:23 +0900, Tristan Van Berkom wrote:
> On Fri, 2010-10-08 at 14:08 +0200, Murray Cumming wrote:
> > 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.
> > 
> 
> You can use gtk_widget_translate_coordinates() for that... but it 
> will leave you with alot of guessing (observing widget allocation
> sizes in the child list etc).
> 
> I think an API will make your code much cleaner, maybe it would
> help if at least you got to step in /before/ the allocation
> actually happens.
> 
> i.e. the same API could be:
> 
> guint gtk_spread_table_get_child_line (table, child, size);
> 
> where it would return: the column 'child' would fall into
> if 'table' were allocated 'size' width.
> 
> This could potentially give you a chance to shift size groups, 
> run some tests with the above api and then actually allocate
> the table's size after you know it's safe.

So I'd start with the child's currently allocated-size?

-- 
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