Re: Vertical centering an actor

["Jasper St. Pierre" <jstpierre mecheye net>]

On Thu, Jul 5, 2012 at 10:03 AM, Michele <micxgx gmail com> wrote:
> I'm facing some problems with what seemed to me a trivial thing at
> first glance. I just want to vertical align an actor to the center of
> the screen. This actor is added to Main.uiGroup and its size is
> variable. The actor at issue is the gnome shell dash that I moved out
> of the overview in the dash-to-dock extension.
>
> I've tried  to achieve this result in a lot of different ways but none
> of them is working properly.
>
> 1. Put the actor inside a container like St.Bin and use the y_align
> property to keep it at middle. This works but the extra void area
> above and below the child actor steal click events from the window
> actors. Applying a clip to the actor affects only it's visibility and
> not such events.

Set the St.Bin's reactivity to false?

> 2. Use notify::height to manually update the actor vertical position.
> This cause a lot of Clutter allocation cycles warnings.
>
> 3. Patch Main.uiGroup allocate function. Direclty replacing the
> allocate function in the shell code works like expected. However, I
> can't remove the original signal (It's a genericContainer) since I
> can't obtain it's id. I also tried obtaining it with
> 'g_signal_handler_find', but I had problems understanding what should
> be passed as the 'gpointer instance' first argument. Thus I can only
> add an additional signal and reallocate the actor at the correct
> vertical position. This seemed to work at first although I'm doubling
> the number of allocation calls, but dash popupmenus are often placed
> at the wrong position.
>
> 4.) Connect to the actor 'allocation-changed' signal and force a
> reallocation of the actor itself. This seemingly works, but I'm not
> sure if it's a good practice. I don't see any warning or error and I'm
> still allocating the actor twice as needed. Popupmenus are in the
> correct position tough.
>
> 5.) Set the actor anchor_point to CLUTTER_GRAVITY_WEST so that the
> position is always correct when it's resized. The main problem here is
> that if the dash height is even, the actor appears blurred, since
> icons positions are not integer values. I can get over this issue by
> setting the y coordinate of the dash at an half-integer value as well,
> but nobody assure me that after adding or removing an icon from the
> dash it's height will remain always even or always odd.
>
> This problem drove me mad... and now I've run out of ideas. Any
> suggestion or correction about my assumptions?
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-- 
  Jasper