From d72df2f3e26a7db186b8bdd2c5f0cadb611553c4 Mon Sep 17 00:00:00 2001
From: Roy-043 <info@b-k-g.nl>
Date: Sun, 5 Nov 2023 21:42:23 +0100
Subject: [PATCH] Draft: PlaneGui: view observer to update the Tray

Related issue:
#5603.

The view observer starts/stops when the Draft workbench is activated/deactivated.

Additionally:
* Minor improvements to _update_grid and _update_gui.
---
 src/Mod/Draft/InitGui.py      |  4 ++
 src/Mod/Draft/WorkingPlane.py | 82 ++++++++++++++++++++++++++++++-----
 2 files changed, 75 insertions(+), 11 deletions(-)

diff --git a/src/Mod/Draft/InitGui.py b/src/Mod/Draft/InitGui.py
index 4fc11245cc..de49d310dc 100644
--- a/src/Mod/Draft/InitGui.py
+++ b/src/Mod/Draft/InitGui.py
@@ -151,6 +151,8 @@ class DraftWorkbench(FreeCADGui.Workbench):
             FreeCADGui.Snapper.show()
             import draftutils.init_draft_statusbar as dsb
             dsb.show_draft_statusbar()
+        import WorkingPlane
+        WorkingPlane._view_observer_start()  # Updates the draftToolBar when switching views.
         FreeCAD.Console.PrintLog("Draft workbench activated.\n")
 
     def Deactivated(self):
@@ -161,6 +163,8 @@ class DraftWorkbench(FreeCADGui.Workbench):
             FreeCADGui.Snapper.hide()
             import draftutils.init_draft_statusbar as dsb
             dsb.hide_draft_statusbar()
+        import WorkingPlane
+        WorkingPlane._view_observer_stop()
         FreeCAD.Console.PrintLog("Draft workbench deactivated.\n")
 
     def ContextMenu(self, recipient):
diff --git a/src/Mod/Draft/WorkingPlane.py b/src/Mod/Draft/WorkingPlane.py
index c1791d8fc8..c580235033 100644
--- a/src/Mod/Draft/WorkingPlane.py
+++ b/src/Mod/Draft/WorkingPlane.py
@@ -1716,19 +1716,23 @@ class PlaneGui(PlaneBase):
         FreeCAD.DraftWorkingPlane.weak = self.auto
 
     def _update_grid(self):
-        if FreeCAD.GuiUp and self._view is not None:
-            if hasattr(FreeCADGui, "Snapper"):
-                FreeCADGui.Snapper.setGrid()
-                FreeCADGui.Snapper.restack()  # Required??
+        # Check for draftToolBar because the trackers (grid) depend on it for its colors.
+        if FreeCAD.GuiUp \
+                and hasattr(FreeCADGui, "draftToolBar") \
+                and hasattr(FreeCADGui, "Snapper") \
+                and self._view is not None:
+            FreeCADGui.Snapper.setGrid()
+            FreeCADGui.Snapper.restack()  # Required??
 
     def _update_gui(self):
-        if FreeCAD.GuiUp:
-            if hasattr(FreeCADGui, "draftToolBar"):
-                from PySide import QtGui
-                button = FreeCADGui.draftToolBar.wplabel
-                button.setIcon(QtGui.QIcon(self.icon))
-                button.setText(self.label)
-                button.setToolTip(self.tip)
+        if FreeCAD.GuiUp \
+                and hasattr(FreeCADGui, "draftToolBar") \
+                and self._view is not None:
+            from PySide import QtGui
+            button = FreeCADGui.draftToolBar.wplabel
+            button.setIcon(QtGui.QIcon(self.icon))
+            button.setText(self.label)
+            button.setToolTip(self.tip)
 
 
 def get_working_plane(update=True):
@@ -1759,6 +1763,62 @@ def get_working_plane(update=True):
     return wp
 
 
+# View observer code to update the Draft Tray:
+if FreeCAD.GuiUp:
+    from PySide2 import QtWidgets
+    from draftutils.todo import ToDo
+
+    def _update_gui():
+        try:
+            view = gui_utils.get_3d_view()
+            if view is None:
+                return
+            if not hasattr(FreeCAD, "draft_working_planes"):
+                FreeCAD.draft_working_planes = [[], []]
+            if view in FreeCAD.draft_working_planes[0]:
+                i = FreeCAD.draft_working_planes[0].index(view)
+                wp = FreeCAD.draft_working_planes[1][i]
+                wp._update_gui()
+            else:
+                get_working_plane()
+        except Exception:
+            pass
+
+    def _view_observer_callback(sub_win):
+        if sub_win is None:
+            return
+        view = gui_utils.get_3d_view()
+        if view is None:
+            return
+        if not hasattr(FreeCADGui, "draftToolBar"):
+            return
+        tray = FreeCADGui.draftToolBar.tray
+        if tray is None:
+            return
+        if FreeCADGui.draftToolBar.tray.isVisible() is False:
+            return
+        ToDo.delay(_update_gui, None)
+
+    _view_observer_active = False
+
+    def _view_observer_start():
+        mw = FreeCADGui.getMainWindow()
+        mdi = mw.findChild(QtWidgets.QMdiArea)
+        global _view_observer_active
+        if not _view_observer_active:
+            mdi.subWindowActivated.connect(_view_observer_callback)
+            _view_observer_active = True
+            _view_observer_callback(mdi.activeSubWindow())  # Trigger initial update.
+
+    def _view_observer_stop():
+        mw = FreeCADGui.getMainWindow()
+        mdi = mw.findChild(QtWidgets.QMdiArea)
+        global _view_observer_active
+        if _view_observer_active:
+            mdi.subWindowActivated.disconnect(_view_observer_callback)
+            _view_observer_active = False
+
+
 # Compatibility function (V0.22, 2023):
 def getPlacementFromPoints(points):
     """Return a placement from a list of 3 or 4 points. The 4th point is no longer used.