[Bf-python] Addon's can no longer access context on activation.

[dimitris chloupis]

No idea what you talking about . No idea how to access bpy.context.scene while the addon loads.

my access to bpy.context.scene happens here -> 
https://github.com/kilon/Gyes/blob/master/gyes/random_material_generator.py#L67

and here -> https://github.com/kilon/Gyes/blob/master/gyes/random_material_generator.py#L622


in first case I check whether there is a historybak prop in scene , so there is no assumptions here 

and blender has no reason to crash. Because I check if it exists in the first place.
If the prop does not exists it gets created in the process. 


in second case the history is restored when the user clicks the button.

In any cases there is no chance that the addon would access non existant properties
because I like to leave nothing to chance ;)


unless you try to tell me something else here that I dont understand
or I missed a possible scenario . I am all ears :)



________________________________
 From: Campbell Barton <ideasman42 at gmail.com>
To: dimitris chloupis <thekilon at yahoo.co.uk>; Blender Foundation Python list <bf-python at blender.org> 
Sent: Thursday, 20 December 2012, 14:33
Subject: Re: [Bf-python] Addon's can no longer access context on activation.
 
On Thu, Dec 20, 2012 at 12:09 PM, dimitris chloupis
<thekilon at yahoo.co.uk> wrote:
> I am the developer of Gyes ( random material and texture generator). The
> reason why Gyes
> use bpy.context.scene is to store a property that store presets of
> randomised materials / textures.
> I wanted the data to be stored/saved with the blend file and be associated
> with the scene curently loaded
> as global scene presets and not specific presets to objects or any other 3d
> asset.
>
> I am not sure if removing bpy.context.scene is a good idea in the first
> place, unless there is another way to save
> , store scene presets together with the blend file. If so , then gladly I
> will update my addon. But if not , it basically
> cripples / makes useless my history tool ->
> http://wiki.blender.org/index.php/Extensions:2.6/Py/Scripts/System/Gyes/History-Tool
>
>
> ________________________________
> From: Campbell Barton <ideasman42 at gmail.com>
> To: Blender Foundation Python list <bf-python at blender.org>; bf-blender
> developers <bf-committers at blender.org>
> Sent: Thursday, 20 December 2012, 4:38
> Subject: [Bf-python] Addon's can no longer access context on activation.
>
> Recently I've noticed addons using bpy.context.scene when being
> imported or in the register() function.
>
> This is really bad practice and will cause inconsistency if the addon
> is enabled and a different blend file is loaded.
> In the worst case accessing a removed datablock can crash which is
> likely if a datablock is stored as a global variable on activation -
> object_laplace_lightning.py does this.
>
> I've changed addon loading so that they only get access to a
> restricted context which only exposes 'window_manager' - needed for
> adding keymaps.
>
>
> Accessing other attributes now errors out with...
>
>   AttributeError: '_RestrictedContext' object has no attribute 'scene'
>
> The addons distributed with blender don't do this but some contrib
> addons do, so they will need updating
> (release/scripts/addons_contrib).
>
> ----
>     add_mesh_clusters
>     gyes
>     io_atomblend_utilities
>     io_export_marmalade
>     io_import_LRO_Lola_MGS_Mola_img
>     io_import_lipSync_Importer
>     mesh_edgetools
>     mesh_fiber
>     mesh_show_vgroup_weights
>     node_categories
>     object_laplace_lightning
>     online_mat_lib
>     sequencer_extra_actions
>     space_view3d_quickPrefs
>
> If any devs want some help updating their addons you can ask on
> bf-python mailing list, though in all cases I've seen its quite
> straightforward.
>
> --
> - Campbell

Access has only been removed on loading the addon.

The solution is just not to access presets when the addon loads and
register()'s,
during execution you still have regular access to the context
(operators, panels etc).

Since the scene at load time may very well not be the same scene when
the script executes (if the user loads a new file), whatever changes
made at load time are likely lost.

-- 
- Campbell
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