backport cursor follow fix from gpv3 - add msg_bus on selection change owned by GreasePencil type

3.3.2

- added: fix cursor follow and add optional target object (backported from gpv3)

CHANGELOG.md

@@ -1,10 +1,15 @@
 # Changelog
 
-GPv2
+3.3.2
+
+- added: fix cursor follow and add optional target object (backported from gpv3)
+
 3.3.1
 
 - added: improve file checker and visibility conflict feature (backported from gpv3)
 
+-- GPv2 code - Above this line, version is separated from 4.3+ version (using GPv3) --
+
 3.3.0
 
 - added: `Move Material To Layer` has now option to copy instead of moving in pop-up menu.

OP_cursor_snap_canvas.py

@@ -3,6 +3,7 @@ import bpy
 import mathutils
 from bpy_extras import view3d_utils
 from .utils import get_gp_draw_plane, region_to_location, get_view_origin_position
+from bpy.app.handlers import persistent
 
 ## override all sursor snap shortcut with this in keymap
 class GPTB_OT_cusor_snap(bpy.types.Operator):
@@ -110,15 +111,20 @@ 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'''
+    ob = bpy.context.object
+    if bpy.context.scene.gptoolprops.cursor_follow_target:
+        ## override with target object is specified
+        ob = bpy.context.scene.gptoolprops.cursor_follow_target
     global prev_matrix
     # imported in properties to register in boolprop update
     if self.cursor_follow:#True
+        if ob:
+            # out of below condition to be called when setting target as well
+            prev_matrix = ob.matrix_world.copy()
         if not cursor_follow.__name__ in [hand.__name__ for hand in bpy.app.handlers.frame_change_post]:
-            if context.object:
-                prev_matrix = context.object.matrix_world
-            
             bpy.app.handlers.frame_change_post.append(cursor_follow)
     
     else:#False
@@ -129,11 +135,13 @@ def cursor_follow_update(self,context):
 
 def cursor_follow(scene):
     '''Handler to make the cursor follow active object matrix changes on frame change'''
-    ## TODO update global prev_matrix to equal current_matrix on selection change (need another handler)... 
-    if not bpy.context.object:
+    ob = bpy.context.object
+    if bpy.context.scene.gptoolprops.cursor_follow_target:
+        ## override with target object is specified
+        ob = bpy.context.scene.gptoolprops.cursor_follow_target
+    if not ob:
         return
     global prev_matrix
-    ob = bpy.context.object
     current_matrix = ob.matrix_world
     if not prev_matrix:
         prev_matrix = current_matrix.copy()
@@ -146,9 +154,7 @@ def cursor_follow(scene):
     
     ## translation only
     # scene.cursor.location += (current_matrix - prev_matrix).to_translation()
-    
-    # print('offset:', (current_matrix - prev_matrix).to_translation())
-    
+        
     ## full
     scene.cursor.location = current_matrix @ (prev_matrix.inverted() @ scene.cursor.location)
     
@@ -156,6 +162,38 @@ def cursor_follow(scene):
     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
+    if bpy.context.scene.gptoolprops.cursor_follow_target:
+        # we are following a target, nothing to update on selection change
+        return
+    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.copy()
+        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.GreasePencil, # <-- 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 +201,18 @@ 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 +221,6 @@ 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.GreasePencil)

UI_tools.py

@@ -279,7 +279,8 @@ class GPTB_PT_anim_manager(Panel):
         col.use_property_split = False
         text, icon = ('Cursor Follow On', 'PIVOT_CURSOR') if context.scene.gptoolprops.cursor_follow else ('Cursor Follow Off', 'CURSOR')
         col.prop(context.scene.gptoolprops, 'cursor_follow', text=text, icon=icon)
-        
+        if context.scene.gptoolprops.cursor_follow:
+            col.prop(context.scene.gptoolprops, 'cursor_follow_target', text='Target', icon='OBJECT_DATA')
 
 class GPTB_PT_toolbox_playblast(Panel):
     bl_label = "Playblast"

__init__.py

@@ -4,7 +4,7 @@ bl_info = {
 "name": "GP toolbox",
 "description": "Tool set for Grease Pencil in animation production",
 "author": "Samuel Bernou, Christophe Seux",
-"version": (3, 3, 1),
+"version": (3, 3, 2),
 "blender": (4, 0, 0),
 "location": "Sidebar (N menu) > Gpencil > Toolbox / Gpencil properties",
 "warning": "",

properties.py

@@ -177,6 +177,11 @@ class GP_PG_ToolsSettings(PropertyGroup):
         name='Cursor Follow', description="3D cursor follow active object animation when activated",
         default=False, update=cursor_follow_update)
 
+    cursor_follow_target : bpy.props.PointerProperty(
+        name='Cursor Follow Target',
+        description="Optional target object to follow for cursor instead of active object",
+        type=bpy.types.Object, update=cursor_follow_update)
+
     edit_lines_opacity : FloatProperty(
         name="Edit Lines Opacity", description="Change edit lines opacity for all grease pencils", 
         default=0.5, min=0.0, max=1.0, step=3, precision=2, update=change_edit_lines_opacity)