OVERVIEW
* In 2.7 terminology, all layers and groups are now collection datablocks.
* These collections are nestable, linkable, instanceable, overrideable, ..
which opens up new ways to set up scenes and link + override data.
* Viewport/render visibility and selectability are now a part of the collection
and shared across all view layers and linkable.
* View layers define which subset of the scene collection hierarchy is excluded
for each. For many workflows one view layer can be used, these are more of an
advanced feature now.
OUTLINER
* The outliner now has a "View Layer" display mode instead of "Collections",
which can display the collections and/or objects in the view layer.
* In this display mode, collections can be excluded with the right click menu.
These will then be greyed out and their objects will be excluded.
* To view collections not linked to any scene, the "Blender File" display mode
can be used, with the new filtering option to just see Colleciton datablocks.
* The outliner right click menus for collections and objects were reorganized.
* Drag and drop still needs to be improved. Like before, dragging the icon or
text gives different results, we'll unify this later.
LINKING AND OVERRIDES
* Collections can now be linked into the scene without creating an instance,
with the link/append operator or from the collections view in the outliner.
* Collections can get static overrides with the right click menu in the outliner,
but this is rather unreliable and not clearly communicated at the moment.
* We still need to improve the make override operator to turn collection instances
into collections with overrides directly in the scene.
PERFORMANCE
* We tried to make performance not worse than before and improve it in some
cases. The main thing that's still a bit slower is multiple scenes, we have to
change the layer syncing to only updated affected scenes.
* Collections keep a list of their parent collections for faster incremental
updates in syncing and caching.
* View layer bases are now in a object -> base hash to avoid quadratic time
lookups internally and in API functions like visible_get().
VERSIONING
* Compatibility with 2.7 files should be improved due to the new visibility
controls. Of course users may not want to set up their scenes differently
now to avoid having separate layers and groups.
* Compatibility with 2.8 is mostly there, and was tested on Eevee demo and Hero
files. There's a few things which are know to be not quite compatible, like
nested layer collections inside groups.
* The versioning code for 2.8 files is quite complicated, and isolated behind
#ifdef so it can be removed at the end of the release cycle.
KNOWN ISSUES
* The G-key group operators in the 3D viewport were left mostly as is, they
need to be modified still to fit better.
* Same for the groups panel in the object properties. This needs to be updated
still, or perhaps replaced by something better.
* Collections must all have a unique name. Less restrictive namespacing is to
be done later, we'll have to see how important this is as all objects within
the collections must also have a unique name anyway.
* Full scene copy and delete scene are exactly doing the right thing yet.
Differential Revision: https://developer.blender.org/D3383https://code.blender.org/2018/05/collections-and-groups/
This commit does the main integration of workspaces, which is a design we agreed on during the 2.8 UI workshop (see https://wiki.blender.org/index.php/Dev:2.8/UI/Workshop_Writeup)
Workspaces should generally be stable, I'm not aware of any remaining bugs (or I've forgotten them :) ). If you find any, let me know!
(Exception: mode switching button might get out of sync with actual mode in some cases, would consider that a limitation/ToDo. Needs to be resolved at some point.)
== Main Changes/Features
* Introduces the new Workspaces as data-blocks.
* Allow storing a number of custom workspaces as part of the user configuration. Needs further work to allow adding and deleting individual workspaces.
* Bundle a default workspace configuration with Blender (current screen-layouts converted to workspaces).
* Pressing button to add a workspace spawns a menu to select between "Duplicate Current" and the workspaces from the user configuration. If no workspaces are stored in the user configuration, the default workspaces are listed instead.
* Store screen-layouts (`bScreen`) per workspace.
* Store an active screen-layout per workspace. Changing the workspace will enable this layout.
* Store active mode in workspace. Changing the workspace will also enter the mode of the new workspace. (Note that we still store the active mode in the object, moving this completely to workspaces is a separate project.)
* Store an active render layer per workspace.
* Moved mode switch from 3D View header to Info Editor header.
* Store active scene in window (not directly workspace related, but overlaps quite a bit).
* Removed 'Use Global Scene' User Preference option.
* Compatibility with old files - a new workspace is created for every screen-layout of old files. Old Blender versions should be able to read files saved with workspace support as well.
* Default .blend only contains one workspace ("General").
* Support appending workspaces.
Opening files without UI and commandline rendering should work fine.
Note that the UI is temporary! We plan to introduce a new global topbar
that contains the workspace options and tabs for switching workspaces.
== Technical Notes
* Workspaces are data-blocks.
* Adding and removing `bScreen`s should be done through `ED_workspace_layout` API now.
* A workspace can be active in multiple windows at the same time.
* The mode menu (which is now in the Info Editor header) doesn't display "Grease Pencil Edit" mode anymore since its availability depends on the active editor. Will be fixed by making Grease Pencil an own object type (as planned).
* The button to change the active workspace object mode may get out of sync with the mode of the active object. Will either be resolved by moving mode out of object data, or we'll disable workspace modes again (there's a `#define USE_WORKSPACE_MODE` for that).
* Screen-layouts (`bScreen`) are IDs and thus stored in a main list-base. Had to add a wrapper `WorkSpaceLayout` so we can store them in a list-base within workspaces, too. On the long run we could completely replace `bScreen` by workspace structs.
* `WorkSpace` types use some special compiler trickery to allow marking structs and struct members as private. BKE_workspace API should be used for accessing those.
* Added scene operators `SCENE_OT_`. Was previously done through screen operators.
== BPY API Changes
* Removed `Screen.scene`, added `Window.scene`
* Removed `UserPreferencesView.use_global_scene`
* Added `Context.workspace`, `Window.workspace` and `BlendData.workspaces`
* Added `bpy.types.WorkSpace` containing `screens`, `object_mode` and `render_layer`
* Added Screen.layout_name for the layout name that'll be displayed in the UI (may differ from internal name)
== What's left?
* There are a few open design questions (T50521). We should find the needed answers and implement them.
* Allow adding and removing individual workspaces from workspace configuration (needs UI design).
* Get the override system ready and support overrides per workspace.
* Support custom UI setups as part of workspaces (hidden panels, hidden buttons, customizable toolbars, etc).
* Allow enabling add-ons per workspace.
* Support custom workspace keymaps.
* Remove special exception for workspaces in linking code (so they're always appended, never linked). Depends on a few things, so best to solve later.
* Get the topbar done.
* Workspaces need a proper icon, current one is just a placeholder :)
Reviewed By: campbellbarton, mont29
Tags: #user_interface, #bf_blender_2.8
Maniphest Tasks: T50521
Differential Revision: https://developer.blender.org/D2451
Issue here was that py API code was keeping references (pointers) to the
liniked data-blocks, which can actually be duplicated and then deleted
during the 'make local' process...
Would have like to find a better way than passing optional GHash to get
the oldid->newid mapping, but could not think of a better idea.
