Re: GTK & Pango string measurement

[Piñeiro <apinheiro igalia com>]

From: Wesley Smith <wesley hoke gmail com>

> >> In the situation I'm talking about, there is no GtkWidget object so
> >> your technique won't work.  This is the code I'm going off of
> >> actually.  Thus my question is how can I get a pango context from  a
> >> GtkCellRendererText?
> >
> > AFAIK, the pango context used by the GtkCellRenderer is the same used
> > by the treeview, so try to make something like:
> >
> 
> 
> Hmmm.  But then I'm allowed to add many GtkCellRendererText views to
> GtkTreeView and each of those can have different font settings, so
> what would happen then?  I might not be getting the correct
> measurements from the PangoContext in GtkTreeView.

Hmm, yes, looking a litte deeper on that, it seems that my previous
pseudocode was just a rough estimation.

(And about the different font settings, I guess that you configure it
with the other GtkCellRendererText properties):

http://library.gnome.org/devel/gtk/stable/GtkCellRendererText.html#GtkCellRendererText.properties

So looking in the current GTK+ code, my advice is check
gtk_tree_view_column_cell_get_size, as it tries to solve a similar
problem to ours. After a quick review:

* gtk_tree_view_column_cell_get_size: C&P the documentation:
  > * Obtains the width and height needed to render the column.  This is used
  > *primarily by the #GtkTreeView.

* internally it calls gtk_cell_renderer_get_size, for each cell
  renderer in this column. Their doc:
  > * Obtains the width and height needed to render the cell. Used by view 
  > * widgets to determine the appropriate size for the cell_area passed to
  > * gtk_cell_renderer_render().  If @cell_area is not %NULL, fills in the
  > * x and y offsets (if set) of the cell relative to this location. 

* And the call to this function is that:
      gtk_cell_renderer_get_size (info->cell,
				  tree_column->tree_view,
				  cell_area,
				  x_offset,
				  y_offset,
				  &new_width,
				  &new_height);

  So is using the tree_view as widget.

* In the specific case of gtk_cell_renderer_text_get_size, it calls a
  internal get_size, passing NULL as layout. Looking at that function,
  as it is receiving a NULL layout, then it creates a new pango_layout,
  based on treeview layout, the cell_renderer attributtes and so on.


BR

===
API (apinheiro igalia com)