Workspaces: Store an active view-layer per scene

Instead of storing a single active view-layer in the workspace, one is
stored for each scene the workspace showed before.
With this, some things become possible:
* Multiple windows in the same workspace but showing different scenes.
* Toggling back and forth scene keeps same active view-layer for each scene.
* Activating workspace which didn't show current scene before, the current view-layer is kept.

A necessary evil for this is that accessing view-layer and object mode
from .py can't be done via workspace directly anymore. It has to be done
through the window, so RNA can use the correct scene.
So instead of `workspace.view_layer`, it's `window.view_layer` now (same
with mode) even though it's still workspace data.

Fixes T53432.

1 files changed, 4 insertions, 3 deletions

diff --git a/release/scripts/startup/bl_ui/space_info.py b/release/scripts/startup/bl_ui/space_info.py
index 8c7fcb29ad2..f032f6a899b 100644
--- a/release/scripts/startup/bl_ui/space_info.py
+++ b/release/scripts/startup/bl_ui/space_info.py
@@ -48,15 +48,16 @@ class INFO_HT_header(Header):
             layout.template_ID(window, "workspace", new="workspace.workspace_add_menu", unlink="workspace.workspace_delete")
             layout.template_search_preview(window, "screen", workspace, "screens", new="screen.new", unlink="screen.delete", rows=2, cols=6)
 
-        if hasattr(workspace, 'object_mode'):
-            act_mode_item = bpy.types.Object.bl_rna.properties['mode'].enum_items[workspace.object_mode]
+        if hasattr(window, 'object_mode'):
+            act_mode_item = bpy.types.Object.bl_rna.properties['mode'].enum_items[window.object_mode]
         else:
             act_mode_item = bpy.types.Object.bl_rna.properties['mode'].enum_items[layer.objects.active.mode]
         layout.operator_menu_enum("object.mode_set", "mode", text=act_mode_item.name, icon=act_mode_item.icon)
 
         row = layout.row()
         row.active = not workspace.use_scene_settings
-        row.template_search(workspace, "view_layer", scene, "view_layers")
+        # Active workspace view-layer is retrieved through window, not through workspace.
+        row.template_search(window, "view_layer", scene, "view_layers")
 
         if view_render.has_multiple_engines:
             row.prop(view_render, "engine", text="")