Freecad macro to diff two step files

CompareSTEPs.FCMacro

import FreeCAD as App
import FreeCADGui as Gui

# colors from HistoryWorkbench addon (RGBA)
Color = tuple[float, float, float, float]

DIFF_FEATURE_TRANSPARENCY: int = 70

ADDED_COLOR: Color = (0.0, 0.5, 0.0, 1.0)
REMOVED_COLOR: Color = (0.9, 0.0, 0.0, 1.0)

# cyan & orange
OLD_COLOR: Color = (0.0, 0.7, 0.9, 0.0)
NEW_COLOR: Color = (1.0, 0.5, 0.0, 0.5)

# magenta & yellow
OLD_COLOR: Color = (0.8, 0.1, 0.6, 0.0)
NEW_COLOR: Color = (1.0, 0.9, 0.1, 0.5)



# Compatibility check for Qt UI bindings across FreeCAD versions
try:
    from PySide2 import QtWidgets
except ImportError:
    try:
        from PySide6 import QtWidgets
    except ImportError:
        from PySide import QtGui as QtWidgets


def compare_step_models():
    doc = App.ActiveDocument
    if not doc:
        QtWidgets.QMessageBox.warning(None, "Error", "No active document open.")
        return

    # Retrieve selected objects from Tree View
    sel = Gui.Selection.getSelection()
    if len(sel) != 2:
        QtWidgets.QMessageBox.information(
            None,
            "Selection Required",
            "Select exactly TWO objects in the Tree View:\n\n"
            "1. First selected = Old STEP\n"
            "2. Second selected = New STEP"
        )
        return

    obj_old = sel[0]
    obj_new = sel[1]

    # --- 1. Apply Appearance Settings ---
    # Old Version: Solid Red =
    obj_old.ViewObject.ShapeColor = OLD_COLOR
    obj_old.ViewObject.Visibility = True

    # New Version: Translucent Green 
    obj_new.ViewObject.ShapeColor = NEW_COLOR
    obj_new.ViewObject.Visibility = True
    
    # 2. move the orignal inside a group for easy visibility toggle
    step_group = doc.getObject("Original_STEP_Models")
    if not step_group:
        step_group = doc.addObject("App::DocumentObjectGroup", "Original_STEP_Models")

    # Add the selected objects to the group
    step_group.addObject(obj_old)
    step_group.addObject(obj_new)

    # --- 3. Perform Part Cuts using Shape Copies ---
    doc.openTransaction("Compare STEP Models")

    # Copy 1: Added Material (New - Old)
    base_added = doc.addObject("Part::Feature", "Base_New_Copy")
    base_added.Shape = obj_new.Shape.copy()
    tool_added = doc.addObject("Part::Feature", "Tool_Old_Copy")
    tool_added.Shape = obj_old.Shape.copy()

    cut_added = doc.addObject("Part::Cut", "Diff_Added_Material")
    cut_added.Base = base_added
    cut_added.Tool = tool_added

    # Hide intermediate helper copies so tree stays clean
    base_added.ViewObject.Visibility = False
    tool_added.ViewObject.Visibility = False

    # Copy 2: Removed Material (Old - New)
    base_removed = doc.addObject("Part::Feature", "Base_Old_Copy")
    base_removed.Shape = obj_old.Shape.copy()
    tool_removed = doc.addObject("Part::Feature", "Tool_New_Copy")
    tool_removed.Shape = obj_new.Shape.copy()

    cut_removed = doc.addObject("Part::Cut", "Diff_Removed_Material")
    cut_removed.Base = base_removed
    cut_removed.Tool = tool_removed

    # Hide intermediate helper copies
    base_removed.ViewObject.Visibility = False
    tool_removed.ViewObject.Visibility = False

    # Apply contrasting colors to the diff cuts for easy visual inspection
    cut_added.ViewObject.ShapeColor = (0.0, 0.8, 0.0, 0.4)    # Green for Added
    cut_removed.ViewObject.ShapeColor = (0.9, 0.1, 0.1, 0.8)  # Red for Removed

    # Keep original objects visible
    obj_old.ViewObject.Visibility = True
    obj_new.ViewObject.Visibility = True

    doc.commitTransaction()
    doc.recompute()

    # Select both output cuts in the Tree
    Gui.Selection.clearSelection()
    Gui.Selection.addSelection(cut_added)
    Gui.Selection.addSelection(cut_removed)


compare_step_models()