Gustavo wrote:
> On Thu, Aug 14, 2008 at 9:36 PM, Jose Gonzalez <[EMAIL PROTECTED]> wrote:
>
>> Gustavo wrote:
>>
>>> Attached is a patch (txt so gmail/firefox don't think it's an
>>> octet-stream and is removed by mailman) to add pre_render() to
>>> Evas_Smart_Class. This patch applies on e17/libs and hacks edje and
>>> emotion so we can test.
>>>
>>> CAUTION: if you compile and install Evas with this patch, it will
>>> change the EVAS_SMART_CLASS_VERSION, making ALL existing binaries
>>> incompatible, so if you do this and your E or other Evas-dependent
>>> application crashes, it will not restart until you reverse the patch,
>>> compile and install the old (non-patched) Evas.
>>>
>>> USE CASE:
>>>
>>> Most users of smart objects end with nasty freeze/thaw to avoid heavy
>>> computations, this can be seen in many places, including Edje. It
>>> would be lot better if we could avoid this if we know when we need to
>>> compute, recalc, reconfigure, ... things. And we know: before drawing!
>>> So why not make this automatic?
>>>
>>> IMPLEMENTATION:
>>>
>>> I don't know this part of Evas internals that much, but I hacked it as
>>> a walk of all objects (layers, then its objects) and checking if
>>> object changed and if it is a smart and if it has the new pre_render
>>> callback. In this case, call this function. This is done BEFORE any
>>> other stuff, before obscure, dirty, etc... calcs, so it will not
>>> impact existing evas_render code at all.
>>>
>>>
>> Well, you really need both pre-render and post-render smart class funcs.
>> This is in case you want to track state (say in the smart data) via cur/prev
>> states.
>> You don't need to walk a new list - all evas objects have internal
>> render-pre and render-post fucntions which are called before and after
>> the actual obj rendering calls (during evas render). Smart objects have
>> these too, and are called.. it's just they don't do much right now.
>>
>> All you have to do is go to the "evas_object_smart.c" file (in the
>> src/lib/
>> canvas dir), and at the very bottom of that file there are these two
>> functions:
>>
>> static void
>> evas_object_smart_render_pre(Evas_Object *obj)
>>
>> static void
>> evas_object_smart_render_post(Evas_Object *obj)
>>
>> In those functions, simply add calls to the corresponding smart obj's
>> new class functions. :)
>>
>>
>>
>>> In order to mark smart objects dirty without doing any operation,
>>> I added evas_object_smart_changed(), that will call
>>> evas_object_changed(). Maybe something better could be done?
>>>
>>> Edje was changed and _edje_recalc() just calls
>>> evas_object_smart_changed(), while _edje_recalc_do() will do the
>>> actual work. THIS IS A TEMPORARY HACK.
>>>
>>> Emotion has no callback, so pre_render = NULL, just to make it compile.
>>>
>>>
>>>
>>> NEXT STEPS:
>>>
>>> If this proves to be correct, we need to patch all uses of
>>> Evas_Smart_Class. This is about 50 on current cvs e17.
>>>
>
> Ok, from Jose's mail I can see that even the experienced lack some
> details of the problem, so I'll add more to my original mail:
>
> WHY SMART OBJECTS NEEDS TO BE DIFFERENT:
>
> Evas is not an immediate render library, instead it will do all the
> calcs and render at the "render phase". Evas has a number of
> pre-defined objects, like Rectangle, Text and more, but it also have
> what we call "Smart Objects", these do not draw anything at all, it
> just call user functions that can in turn manipulate these pre-defined
> objects.
>
> Why Smart Objects can't use regular object's pre_render/post_render?
> The way Evas is implemented, existing pre_render and post_render
> cannot change the scene, that is, objects cannot move, restack, show
> or disappear, no new objects can be created and much more limits,
> otherwise the render phase could be never-ending. Since Smart Objects
> do not draw by themselves, the only way they could draw is by means of
> changing other objects, thus making them unable to join the existing
> pre_render/post_render usage. That's why Smart Object pre-renders are
> called before doing any real work painting work.
>
>
If that's what you want, to restack, move, etc.. Then the way you're doing
it is extremely bad design. It should instaed be done by adding
evas-render-pre/post
api funcs which would be called before evas render, similar to what ecore_evas
does with sub-canvases. What you want, via smart objs, is not only limited in
scope but also 'breaks' the existing semantics of such smart callbacks to some
degree.
It *is* useful to have smart class callbaks for smart objs internal
render-pre/
post functions. But you'll have to think a bit outside the needs you're looking
at right now (edje recalc) to see it. :)
> Why not add post_render? Because there is no use case for those, and
> adding just for completeness sake would add yet another O(n) walk over
> the objects.
>
> Give me some examples of Smart Object pre_render usage: You have a
> layout (ie: VBox, HBox, Grid) and you want to add multiple items
> there, but you don't want to recalculate position of every object as
> you add then, because depending on the layout algorithm you can end
> with O(n^2) or worse easily. What you usually do? You add a counter
> (frozen count) that if > 0 you avoid any calcs, then after you're done
> you make it 0 and recalc as required. But doing this everywhere is
> error prone and boring, still you might have 2 batch of these between
> scenes, doing the first recalc without need. To solve this, we could
> postpone recalcs until we actually draw the scene, we would avoid the
> counter and would avoid extra calcs.
>
>
>
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