Re: [gtkmm] writing a custom cellrenderer

[Roel Vanhout <rvanhout riks nl>]

Hi,

These examples are very useful, especially cellrenderertoggle.cc in the 
gtkmm examples. What I don't understand in the cellrendererpopup and 
cellrendererlist is that they don't have any code (as far as I see) that 
does some actual drawing (ie, they don't override either render() or 
render_vfunc(). Is that because the only custom thing about them is that 
they emit different signals? Anyway, thanks a lot, I think I can get 
things to work with the cellrenderertoggle.cc example.

cheers,


roel




Daniel Sundberg wrote:

> Roel Vanhout wrote:
>  > Hello all,
>  >
> 
> Hi,
> 
> have you looked at the example located in examples/customcellrenderer in
> the gtkmm source distribution. I have successfully created a custom cell
> renderer in my program GSpeakers based on this example. Please have a
> look at:
> 
>
http://cvs.sourceforge.net/viewcvs.py/gspeakers/gspeakers2/src/cellrendererp
opup.h?view=markup 
> 
>
http://cvs.sourceforge.net/viewcvs.py/gspeakers/gspeakers2/src/cellrendererp
opup.cc?view=markup 
> 
> 
>
http://cvs.sourceforge.net/viewcvs.py/gspeakers/gspeakers2/src/cellitemcross
over.h?view=markup 
> 
>
http://cvs.sourceforge.net/viewcvs.py/gspeakers/gspeakers2/src/cellitemcross
over.cc?view=markup 
> 
> 
> Regards
> 
> Daniel Sundberg
> 
> ---
> http://sumpan.com
> 
>  > I spend the bigger part of yesterday evening trying to write a custom
>  > cellrenderer for Gtk::TreeView but I didn't get it to work. I'm porting
>  > an application from plain C Gtk to C++ with gtkmm. In the original
>  > application I used the code from
>  > http://scentric.net/tutorial/sec-custom-cell-renderers.html, which was
>  > luckily exactly what I needed (in C). I thought that for a C++ version
>  > all I'd have to is derive my own class from Gtk::CellRenderer, override
>  > a few methods (that would have been declare pure virtual so that the
>  > compiler would point me to them) and that would be it. Turns out I was
>  > wrong.
>  > I started by looking at
>  > 
>
http://www.gtkmm.org/docs/gtkmm-2.4/docs/reference/html/classGtk_1_1CellRend

> 
>  > erer.html.
>  > I didn't see anything there that indicated what functions I had to
>  > override to make my own so I just write a small class, overriding
>  > get_size(), _property_renderable() and render() and copied the code
from
>  > my original C renderer to the corresponding functions. I had to massage
>  > it a bit to get it into C++ format and then it compiled. I used the
>  > add_column() method that takes a custom renderer and when all of that
>  > compiled I thought it'd work, but all I saw was a blank cell. So I
>  > looked at the implementation of the CellRendererText and -Pixbut in the
>  > gtkmm source and to my horror I found all the structs from the C
version
>  > in there - the init thing and a sort of virtual vtable and all the
>  > things I hoped I would never have to bother with again when I switched
>  > to gtkmm. I'm still hoping that this is only because they wrap the C
>  > version and that it is possible to write one in pure C++.
>  > Ok so sorry if this sounds frustrated (it's because I am), but here are
>  > a few questions that I have:
>  >
>  > - What functions do I have to override and what do I have to implement
>  > to get a custom cellrenderer, a complete new one and not one that just
>  > wraps a C version? I think I'm missing two things: first, registering a
>  > custom property ('progress' in my case), and secondly registring the
>  > cellrenderer itself somewhere.
>  > - All properties (like property_xalign()) have comments like "You
rarely
>  > need to use properties because there are get_ and set_ methods for
>  > almost all of them.". But are there really? Where are they declared?
How
>  > should I use those properties?
>  > - What are the protected methods in CellRenderer (like get_size_vfunc()
>  > ) used for? Should I override them?
>  > - Why are there two versions of get_size? Is there an easy way to
>  > implement the one in terms of the other or should I write full
>  > implementations for both?
>  >
>  > I've attached the code that I have so far. Some of it is commented out,
>  > that's what I was trying after I got everything to compile but when it
>  > didn't work. It's mostly copied from CellRendererText, but that one
>  > wraps the C version so it's not quite the same as what I try to do.
>  > Thanks in advance.
>  >
>  >
>  > cheers,
>  >
>  > roel
>  >
>  >
>  >
>  >
>  >
>  >
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