cam: attempt to fix issue #26652 ie. fix issue with state of recompute button for tool bit (#26884)

* cam: attempt to fix issue #26652 ie. fix issue with state of recompute button for tool bit

* add unit test for issue #26652

* run precommit

* relocate `purgeTouched()` call to end of `_update_visual_representation` function

src/Mod/CAM/CAMTests/TestToolBitRecomputeState.py

@@ -0,0 +1,51 @@
+# ***************************************************************************
+# *   Copyright (c) 2026 Chris Jones github.com/ipatch                      *
+# *                                                                         *
+# *   This file is part of the FreeCAD CAx development system.              *
+# *                                                                         *
+# *   This program is free software; you can redistribute it and/or modify  *
+# *   it under the terms of the GNU Lesser General Public License (LGPL)    *
+# *   as published by the Free Software Foundation; either version 2 of     *
+# *   the License, or (at your option) any later version.                   *
+# ***************************************************************************
+
+import FreeCAD
+from CAMTests.PathTestUtils import PathTestWithAssets
+from Path.Tool.toolbit import ToolBitEndmill
+
+
+class TestToolBitRecomputeState(PathTestWithAssets):
+    """Test toolbit recompute state handling (issue #26652)"""
+
+    def setUp(self):
+        """Set up test fixtures"""
+        super().setUp()
+        self.doc = FreeCAD.newDocument("TestToolbitState")
+
+    def tearDown(self):
+        """Clean up after tests"""
+        FreeCAD.closeDocument(self.doc.Name)
+        super().tearDown()
+
+    def testToolbitExpressionRecomputeState(self):
+        """Test that toolbit with unitless expression doesn't stay touched after recompute"""
+        # create an endmill shape and toolbit
+        shape = self.assets.get("toolbitshape://endmill")
+        toolbit = ToolBitEndmill(shape, id="test_endmill")
+
+        # attach to document
+        obj = toolbit.attach_to_doc(self.doc, label="TestEndmill")
+
+        # set initial diameter
+        obj.Diameter = FreeCAD.Units.Quantity("5 mm")
+        self.doc.recompute()
+
+        # now set expression without unit - this triggers issue #26652
+        obj.setExpression("Diameter", "5")
+        self.doc.recompute()
+
+        # after recompute, toolbit should not be in touched state
+        self.assertFalse(
+            "Touched" in obj.State,
+            "Toolbit with unitless expression should not be touched after recompute",
+        )

src/Mod/CAM/CMakeLists.txt

@@ -585,6 +585,7 @@ SET(Tests_SRCS
     CAMTests/Tools/Bit/test-path-tool-bit-bit-00.fctb
     CAMTests/Tools/Library/test-path-tool-bit-library-00.fctl
     CAMTests/Tools/Shape/test-path-tool-bit-shape-00.fcstd
+    CAMTests/TestToolBitRecomputeState.py
 )
 
 SET(Tests_Fixtures

src/Mod/CAM/Path/Tool/toolbit/models/base.py

@@ -914,6 +914,9 @@ class ToolBit(Asset, ABC):
             )
             raise
 
+        # clear the touched state since visual updates shouldn't require recompute
+        self.obj.purgeTouched()
+
     def to_dict(self):
         """
         Returns a dictionary representation of the tool bit.

src/Mod/CAM/TestCAMApp.py

@@ -80,6 +80,7 @@ from CAMTests.TestPathToolAssetManager import TestPathToolAssetManager
 from CAMTests.TestPathToolAssetStore import TestPathToolFileStore, TestPathToolMemoryStore
 from CAMTests.TestPathToolAssetUri import TestPathToolAssetUri
 from CAMTests.TestPathToolBit import TestPathToolBit
+from CAMTests.TestToolBitRecomputeState import TestToolBitRecomputeState
 from CAMTests.TestPathToolShapeClasses import TestPathToolShapeClasses
 from CAMTests.TestPathToolShapeDoc import TestPathToolShapeDoc
 from CAMTests.TestPathToolShapeIcon import (