From a5395e4298ddd0d9fef39347a4557b95e5f57959 Mon Sep 17 00:00:00 2001
From: Zac Zhang <zac.z.zhang@outlook.com>
Date: Fri, 22 Dec 2023 14:38:53 +0100
Subject: [PATCH 1/4] update ready for the review

---
 src/compas/scene/context.py | 22 +++++++++-------------
 src/compas/scene/scene.py   |  7 +++++--
 2 files changed, 14 insertions(+), 15 deletions(-)

diff --git a/src/compas/scene/context.py b/src/compas/scene/context.py
index 564f588b476d..0a2265ffc5a7 100644
--- a/src/compas/scene/context.py
+++ b/src/compas/scene/context.py
@@ -1,10 +1,12 @@
-from compas.plugins import pluggable
+import inspect
+from collections import defaultdict
+
+import compas
 from compas.plugins import PluginValidator
+from compas.plugins import pluggable
+
 from .exceptions import NoSceneObjectContextError
 from .exceptions import SceneObjectNotRegisteredError
-import inspect
-import compas
-from collections import defaultdict
 
 ITEM_SCENEOBJECT = defaultdict(dict)
 
@@ -62,15 +64,9 @@ def is_viewer_open():
     bool
 
     """
-    # TODO: implement [without introducing compas_view2 as a dependency..?]
-    # make the viewer app a singleton
-    # check for the exitence of an instance of the singleton
-    # if the instance exists, return True
-    # in this case, the viewer is the current context
-    # to do this without introducing compas_view2 as a dependency,
-    # creating the singleton instance should modify a class attribute of the SceneObject
-    # (or potentially a module level attribute of compas itself)
-    return False
+    from compas.scene import Scene
+
+    return Scene.viewerinstance is not None
 
 
 def _detect_current_context():
diff --git a/src/compas/scene/scene.py b/src/compas/scene/scene.py
index b4001a0423dd..b66f2a01c2f7 100644
--- a/src/compas/scene/scene.py
+++ b/src/compas/scene/scene.py
@@ -1,12 +1,15 @@
 from compas.data import Data
 from compas.datastructures import Tree
 from compas.datastructures import TreeNode
-from .sceneobject import SceneObject
-from .context import redraw
+
 from .context import clear
+from .context import redraw
+from .sceneobject import SceneObject
 
 
 class Scene(Data):
+    viewerinstance = None
+
     def __init__(self, name=None, context=None):
         super(Scene, self).__init__(name)
         self._tree = Tree("Scene")

From 09c52d86910f821d0a844b6cada62155e095ae67 Mon Sep 17 00:00:00 2001
From: Zac Zhang <zac.z.zhang@outlook.com>
Date: Fri, 22 Dec 2023 14:41:23 +0100
Subject: [PATCH 2/4] changelog

---
 CHANGELOG.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 7b3e78f84fa6..27170de75c51 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -8,7 +8,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ## Unreleased
 
 ### Added
-
+* Added `viewerinstance ` in  `compas.scene.Scene` to support viewers context detection.
 * Added `compas_rhino8` as starting point for Rhino8 support.
 * Added tutorial for `compas.datastructures.Tree`.
 

From cc5ba1e6c72851456403cc40b3c910d807e7e554 Mon Sep 17 00:00:00 2001
From: Zac Zhang <zac.z.zhang@outlook.com>
Date: Wed, 3 Jan 2024 16:03:33 +0100
Subject: [PATCH 3/4] lint

---
 src/compas/scene/scene.py | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/compas/scene/scene.py b/src/compas/scene/scene.py
index c407b639dbb6..ec351213a9ab 100644
--- a/src/compas/scene/scene.py
+++ b/src/compas/scene/scene.py
@@ -178,7 +178,9 @@ class Scene(Data):
     >>> scene.redraw()
 
     """
+
     viewerinstance = None
+
     def __init__(self, name=None, context=None):
         super(Scene, self).__init__(name)
         self._tree = SceneTree("Scene")

From 1de9b1313213d30817ce079e270754dc18c2bb7c Mon Sep 17 00:00:00 2001
From: Zac Zhang <zac.z.zhang@outlook.com>
Date: Wed, 3 Jan 2024 16:30:43 +0100
Subject: [PATCH 4/4] superfluous spaces

---
 CHANGELOG.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index de2039d0a4d7..020e1f216d78 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -8,7 +8,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ## Unreleased
 
 ### Added
-* Added `viewerinstance ` in  `compas.scene.Scene` to support viewers context detection.
+* Added `viewerinstance` in `compas.scene.Scene` to support viewers context detection.
 * Added `compas_rhino8` as starting point for Rhino8 support.
 * Added `compas.scene.SceneObjectNode`.
 * Added `compas.scene.SceneTree`.