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.

3 files changed, 28 insertions, 11 deletions

diff --git a/source/blender/blenloader/intern/readfile.c b/source/blender/blenloader/intern/readfile.c
index 5d170960158..323586b66b2 100644
--- a/source/blender/blenloader/intern/readfile.c
+++ b/source/blender/blenloader/intern/readfile.c
@@ -2843,6 +2843,14 @@ static void lib_link_workspaces(FileData *fd, Main *bmain)
 		IDP_LibLinkProperty(id->properties, fd);
 		id_us_ensure_real(id);
 
+		for (WorkSpaceDataRelation *relation = workspace->scene_viewlayer_relations.first;
+		     relation != NULL;
+		     relation = relation->next)
+		{
+			relation->parent = newlibadr(fd, id->lib, relation->parent);
+			/* relation->value is set in direct_link_workspace_link_scene_data */
+		}
+
 		for (WorkSpaceLayout *layout = layouts->first, *layout_next; layout; layout = layout_next) {
 			bScreen *screen = newlibadr(fd, id->lib, BKE_workspace_layout_screen_get(layout));
 
@@ -2868,6 +2876,7 @@ static void direct_link_workspace(FileData *fd, WorkSpace *workspace, const Main
 {
 	link_list(fd, BKE_workspace_layouts_get(workspace));
 	link_list(fd, &workspace->hook_layout_relations);
+	link_list(fd, &workspace->scene_viewlayer_relations);
 	link_list(fd, BKE_workspace_transform_orientations_get(workspace));
 
 	for (WorkSpaceDataRelation *relation = workspace->hook_layout_relations.first;
@@ -2881,7 +2890,7 @@ static void direct_link_workspace(FileData *fd, WorkSpace *workspace, const Main
 	if (ID_IS_LINKED(&workspace->id)) {
 		/* Appending workspace so render layer is likely from a different scene. Unset
 		 * now, when activating workspace later we set a valid one from current scene. */
-		BKE_workspace_view_layer_set(workspace, NULL);
+		BKE_workspace_relations_free(&workspace->scene_viewlayer_relations);
 	}
 
 	/* Same issue/fix as in direct_link_workspace_link_scene_data: Can't read workspace data
@@ -6134,13 +6143,19 @@ static void direct_link_layer_collections(FileData *fd, ListBase *lb)
  * Workspaces store a render layer pointer which can only be read after scene is read.
  */
 static void direct_link_workspace_link_scene_data(
-        FileData *fd, const Scene *scene, const ListBase *workspaces)
+        FileData *fd, Scene *scene, const ListBase *workspaces)
 {
 	for (WorkSpace *workspace = workspaces->first; workspace; workspace = workspace->id.next) {
-		ViewLayer *layer = newdataadr(fd, BKE_workspace_view_layer_get(workspace));
-		/* only set when layer is from the scene we read */
-		if (layer && (BLI_findindex(&scene->view_layers, layer) != -1)) {
-			BKE_workspace_view_layer_set(workspace, layer);
+		for (WorkSpaceDataRelation *relation = workspace->scene_viewlayer_relations.first;
+		     relation != NULL;
+		     relation = relation->next)
+		{
+			ViewLayer *layer = newdataadr(fd, relation->value);
+			if (layer) {
+				BLI_assert(BLI_findindex(&scene->view_layers, layer) != -1);
+				/* relation->parent is set in lib_link_workspaces */
+				relation->value = layer;
+			}
 		}
 	}
 }
@@ -7175,7 +7190,7 @@ void blo_lib_link_restore(Main *newmain, wmWindowManager *curwm, Scene *curscene
 		for (WorkSpaceLayout *layout = layouts->first; layout; layout = layout->next) {
 			lib_link_workspace_layout_restore(id_map, newmain, layout);
 		}
-		BKE_workspace_view_layer_set(workspace, cur_view_layer);
+		BKE_workspace_view_layer_set(workspace, cur_view_layer, curscene);
 	}
 
 	for (wmWindow *win = curwm->windows.first; win; win = win->next) {
diff --git a/source/blender/blenloader/intern/versioning_280.c b/source/blender/blenloader/intern/versioning_280.c
index 8da4fef7b21..3b5e248f58b 100644
--- a/source/blender/blenloader/intern/versioning_280.c
+++ b/source/blender/blenloader/intern/versioning_280.c
@@ -86,8 +86,9 @@ static void do_version_workspaces_create_from_screens(Main *bmain)
 {
 	for (bScreen *screen = bmain->screen.first; screen; screen = screen->id.next) {
 		const bScreen *screen_parent = screen_parent_find(screen);
+		Scene *scene = screen->scene;
 		WorkSpace *workspace;
-		ViewLayer *layer = BKE_view_layer_from_scene_get(screen->scene);
+		ViewLayer *layer = BKE_view_layer_from_scene_get(scene);
 		ListBase *transform_orientations;
 
 		if (screen_parent) {
@@ -100,7 +101,7 @@ static void do_version_workspaces_create_from_screens(Main *bmain)
 			workspace = BKE_workspace_add(bmain, screen->id.name + 2);
 		}
 		BKE_workspace_layout_add(workspace, screen, screen->id.name + 2);
-		BKE_workspace_view_layer_set(workspace, layer);
+		BKE_workspace_view_layer_set(workspace, layer, scene);
 
 #ifdef WITH_CLAY_ENGINE
 		BLI_strncpy(workspace->view_render.engine_id, RE_engine_id_BLENDER_CLAY,
@@ -111,7 +112,7 @@ static void do_version_workspaces_create_from_screens(Main *bmain)
 #endif
 
 		transform_orientations = BKE_workspace_transform_orientations_get(workspace);
-		BLI_duplicatelist(transform_orientations, &screen->scene->transform_spaces);
+		BLI_duplicatelist(transform_orientations, &scene->transform_spaces);
 	}
 }
 
diff --git a/source/blender/blenloader/intern/writefile.c b/source/blender/blenloader/intern/writefile.c
index b20f12e7e70..08ec2231e38 100644
--- a/source/blender/blenloader/intern/writefile.c
+++ b/source/blender/blenloader/intern/writefile.c
@@ -1138,7 +1138,7 @@ static void current_screen_compat(
 
 	*r_screen = (window) ? BKE_workspace_active_screen_get(window->workspace_hook) : NULL;
 	*r_scene = (window) ? window->scene : NULL;
-	*r_render_layer = (window) ? BKE_workspace_view_layer_get(workspace) : NULL;
+	*r_render_layer = (window) ? BKE_workspace_view_layer_get(workspace, *r_scene) : NULL;
 }
 
 typedef struct RenderInfo {
@@ -3778,6 +3778,7 @@ static void write_workspace(WriteData *wd, WorkSpace *workspace)
 	writestruct(wd, ID_WS, WorkSpace, 1, workspace);
 	writelist(wd, DATA, WorkSpaceLayout, layouts);
 	writelist(wd, DATA, WorkSpaceDataRelation, &workspace->hook_layout_relations);
+	writelist(wd, DATA, WorkSpaceDataRelation, &workspace->scene_viewlayer_relations);
 	writelist(wd, DATA, TransformOrientation, transform_orientations);
 }