Initial code for better cursor_follow behavior (wip)

OP_cursor_snap_canvas.py

@@ -2,6 +2,8 @@
 import bpy
 import mathutils
 from bpy_extras import view3d_utils
+from bpy.app.handlers import persistent
+
 from .utils import get_gp_draw_plane, region_to_location, get_view_origin_position
 
 ## override all sursor snap shortcut with this in keymap
@@ -105,12 +107,12 @@ def swap_keymap_by_id(org_idname, new_idname):
             k.idname = new_idname
 
 
-# prev_matrix = mathutils.Matrix()
 prev_matrix = None
 
 # @call_once(bpy.app.handlers.frame_change_post)
 
-def cursor_follow_update(self,context):
+## used in properties file to register in boolprop update
+def cursor_follow_update(self, context):
     '''append or remove cursor_follow handler according a boolean'''
     global prev_matrix
     # imported in properties to register in boolprop update
@@ -155,6 +157,35 @@ def cursor_follow(scene):
     # store for next use
     prev_matrix = current_matrix.copy()
 
+prev_active_obj = None
+
+## Add check for object selection change
+def selection_changed():
+    """Callback function for selection changes"""
+    if not bpy.context.scene.gptoolprops.cursor_follow:
+        return
+    print('select_changed')
+    global prev_matrix, prev_active_obj
+    if prev_active_obj != bpy.context.object:
+        ## Set stored matrix to active object
+        prev_matrix = bpy.context.object.matrix_world
+        prev_active_obj = bpy.context.object
+
+## Note: Same owner as layer manager (will be removed as well)
+def subscribe_object_change():
+    subscribe_to = (bpy.types.LayerObjects, 'active')
+    bpy.msgbus.subscribe_rna(
+        key=subscribe_to,
+        # owner of msgbus subcribe (for clearing later)
+        owner=bpy.types.GreasePencilv3, # <-- attach to ID during it's lifetime.
+        args=(),
+        notify=selection_changed,
+        options={'PERSISTENT'},
+    )
+
+@persistent
+def subscribe_object_change_handler(dummy):
+    subscribe_object_change()
 
 classes = (
 GPTB_OT_cusor_snap,
@@ -163,14 +194,18 @@ GPTB_OT_cusor_snap,
 def register():
     for cls in classes:
         bpy.utils.register_class(cls)
-    
     # swap_keymap_by_id('view3d.cursor3d','view3d.cursor_snap')#auto swap to custom GP snap wrap
+    
+    ## Follow cursor matrix update on object change
+    # bpy.app.handlers.load_post.append(subscribe_object_change_handler) # select_change
+    # ## Directly set msgbus to work at first addon activation # select_change
+    # bpy.app.timers.register(subscribe_object_change, first_interval=1) # select_change
 
-    # bpy.app.handlers.frame_change_post.append(cursor_follow)
+    ## No need to frame_change_post.append(cursor_follow). Added by property update, when activating 'cursor follow'
 
 
 def unregister():
-    # bpy.app.handlers.frame_change_post.remove(cursor_follow)
+    # bpy.app.handlers.load_post.remove(subscribe_object_change_handler) # select_change
 
     # swap_keymap_by_id('view3d.cursor_snap','view3d.cursor3d')#Restore normal snap
 
@@ -179,4 +214,6 @@ def unregister():
     
     # force remove handler if it's there at unregister
     if cursor_follow.__name__ in [hand.__name__ for hand in bpy.app.handlers.frame_change_post]:
-            bpy.app.handlers.frame_change_post.remove(cursor_follow)
+            bpy.app.handlers.frame_change_post.remove(cursor_follow)
+    
+    bpy.msgbus.clear_by_owner(bpy.types.GreasePencilv3)