Macro TechDraw AuxiliaryView

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#! python
# -*- coding: utf-8 -*-
"""
This script creates an Auxiliary View from two selectec vertices
of one base view.

What is required: an active document, a drawing page containing one
or more views with a projection of a shape.

A possible workflow:
1. Extract base view from selection (two vertices)
2. Extract work page from app objects
3. Add a new view
4. Link base view from selection to new view
5. Link base view source to new view source
6. Retrieve new view's x direction from base view's x direction
7. calculate new view's z direction from new view's x direction
    and base view's z direction
8. Set new view rotation including base view rotation
9. (Add annotations etc.)

I have tried to follow this naming rule:
 class names:    CamelCase
 function names: mixedCase
 constant names: ALL_CAPITAL + underscore
 variable names: lower_case + underscore
"""

__Name__= ""
__Comment__ = ""
__Author__ = "FBXL5"
__Version__ = "00.02"
__Date__    = "2025-06-27"
__License__ = "LGPL-2.0-or-later as FreeCAD"
__Web__ = ""
__Wiki__ = ""
__Icon__  = ""
__IconW__  = ""
__Help__ = ""
__Status__ = "Alpha"
__Requires__ = "FreeCAD >= 1.0 + Python3"
__Communication__ = "https://www.freecad.org/wiki/index.php?title=User: FBXL5"
__Files__ = ""

import math # to use some predefined conversions
from PySide.QtGui import (QMessageBox)

ARROW = """<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<svg
  xmlns="http://www.w3.org/2000/svg" version="1.1"
  width ="16.8mm"
  height="2.8mm"
  viewBox=" 0 -1.4 16.8 2.8">
    <g id="ArrowHead"
      style="fill:#000;fill-opacity:1;stroke:#000;stroke-width:0.5;stroke-linecap:round;stroke-linejoin:round;font-size:5.0;text-anchor:middle;font-family:osifont">
        <path d="m 0.3 0.0 h 16 " />
        <path d="m 0.3 0.0 l 8.0 1.05 v -2.1 z " />
    </g>
</svg>
"""

def displayMessage(title,message):
    '''
    displayMessage('Title','Messagetext')
    '''
    message_box = QMessageBox()
    message_box.setText(message)
    message_box.setWindowTitle(title)
    message_box.exec()

def getActiveDocument():
    '''
    Returns the active document or sends a message
    '''
    ado = App.activeDocument()
    if ado is not None:
        return ado
    displayMessage("AuxView", "No active document available!")
    return False

# (borrowed from TechDraw sources)
def getSelView(nSel=0):
    '''
    view = getSelView()
    nSel=0 ... number of selected view, 0 = first selected
    Return selected view, otherwise return False
    '''
    if not Gui.Selection.getSelection():
        view = None
        displayMessage('AuxView','No view selected')
    else:
        view = Gui.Selection.getSelection()[nSel]
    return view

# (borrowed from TechDraw sources)
def getSelVertexes(nVertex=1, nSel=0):
    '''
    vertexes = getSelVertexes(nVertex)
    nVertex=1 ... min. number of selected vertexes
    nSel=0 ... number of selected view, 0 = first selected
    Return a list of selected vertexes if at least nVertex vertexes are selected, otherwise return False
    '''
    if getSelView(nSel):
        view = getSelView(nSel)
    else:
        return False
    if not Gui.Selection.getSelectionEx():
        displayMessage('AuxView','No vertex selected')
        return False
    objectList = Gui.Selection.getSelectionEx()[nSel].SubElementNames

    vertexes = []
    for objectString in objectList:
        if objectString[0:6] == 'Vertex':
            vertexes.append(view.getVertexBySelection(objectString))

    if (len(vertexes) < nVertex):
        displayMessage('AuxView','Select at least '+
                        str(nVertex)+' vertices')
        return False
    else:
        return vertexes

def getPageOfSelection(doc, b_view):
    '''Retrieves the Page that holds the selected elements'''
    #- Find an object starting with 'Page' that contains the selected object
    for each in doc.Objects:
        if each.Name.startswith("Page"):  # [0:4] == 'Page':
            for item in each.OutList: # Search items belonging to a Page object
                if item.Name.startswith("ProjGroup"): # Look into projection groups
                    for view in item.OutList: # Search views belonging to a ProjGroup object
                        if view.Name == b_view.Name:
                            return each
                else:
                    if item.Name == b_view.Name:
                        return each
    return False

def getCcwAngle(vertex1,vertex2,view_rotation):
    '''Creates 3D vectors to calculate the 2D angle towards the x direction of the
    base view which is parallel to the page view's x direction.
    The direction of the XDirection property is not parallel to the view's
    x direction if the view is rotated! This angle also has to be taken into
    account to calculate the 3D angle'''
    #- Extract position vectors from the points
    vector_start = App.Vector(vertex1.X, vertex1.Y, vertex1.Z)
    vector_end   = App.Vector(vertex2.X, vertex2.Y, vertex2.Z)
    #- Calculate the 2D Direction vector from start vertex to end vertex
    # on the XY plane of the base view/work page (z = 0)
    direction = vector_end.sub(vector_start)
    x_direction = App.Vector(1, 0, 0)
    angle_x = math.degrees(direction.getAngle(x_direction))
    # getAngle() returns positive (absolute) values only (in rad)
    # -> convert to degrees and check orientation
    if vertex1.Y > vertex2.Y:
        angle_x *= -1  # switches angle orientation
    #- Turn back the base view rotation
    # angle_x is a float value now but view_rotation is deg
    #print('a. angle_x: ', angle_x)
    #print('b. view_rotation: ', float(view_rotation))
    angle_x -= float(view_rotation)
    return angle_x

def symbolAngle(vertex1,vertex2):
    '''
    Creates 3D vectors to calculate the 2D angle towards the x direction of the
    base view
    '''
    #- Extract position vectors from the points
    vector_start = FreeCAD.Vector(vertex1.X, vertex1.Y, vertex1.Z)
    vector_end   = FreeCAD.Vector(vertex2.X, vertex2.Y, vertex2.Z)
    #- Calculate the 2D Direction vector from start vertex to end vertex
    # on the XY plane of the base view/work page (z = 0)
    direction = vector_end.sub(vector_start)
    y_direction = FreeCAD.Vector(0, -1, 0)
    angle_y = math.degrees(direction.getAngle(y_direction))
    # getAngle() returns positive (absolute) values only (in rad)
    # -> convert to degrees and check orientation
    if vertex1.X > vertex2.X:
        angle_y *= -1  # switches angle orientation
    return angle_y

def main():
    ''' The main section, no more, no less '''
    # Operations are performed in the active document of the application
    #- Retrieve the active document
    active_doc = getActiveDocument()
    if not active_doc:  # (active_doc is None/False)
        return
    #- Retrieve the selection view and selected vertices
    if getSelView() and getSelVertexes(2):
        base_view = getSelView()
        vertices = getSelVertexes(2)  # required number of vertices
    else:
        return

    #- Retrieve the page that holds the view
    work_page = getPageOfSelection(active_doc, base_view)
    if not work_page:
        # this should always be true as selected vertices are already checked
        return
    # At this point the input elements are gathered:
    #  active_doc, work_page, base_view, and vertices

    #- Create a new view
    new_view = active_doc.addObject('TechDraw::DrawViewPart', 'AuxView')
    #- Add the new view to the page
    work_page.addView(new_view)
    #- Add a BaseView property to the new view
    new_view.addProperty('App::PropertyLink','BaseView')
    #- Link the BaseView object to the BaseView property
    new_view.BaseView = active_doc.getObject(base_view.Name)
    #- Hand over the source objects
    new_view.Source = new_view.BaseView.Source

    #- 2D: Calculate the ccw angle between the x axes of base view and new view
    turn_ccw = getCcwAngle(vertices[0],vertices[1],new_view.BaseView.Rotation)
    # Returns a float value representing degrees

    # 3D: Turn base_view.XDirection around base_view.Direction to get
    #     new_view.XDirection
    #- Create a rotation, angle input in float (for degrees), stored in rad
    around_direction = App.Rotation(new_view.BaseView.Direction, turn_ccw)
    #- Apply rotation to the base_view.XDirection
    new_view.XDirection = around_direction.multVec(new_view.BaseView.XDirection)
    #- The cross-product of base view Z and new view X gives new view Z direction
    new_view.Direction = new_view.BaseView.Direction.cross(new_view.XDirection)

    # 2D: Take base_view.Rotation into account, it has to be converted
    #     to float since it is stored in deg
    #- Add the rotation of the base view to the angle between the x axes
    new_view.Rotation = turn_ccw + float(new_view.BaseView.Rotation)
    Gui.runCommand('TechDraw_RedrawPage',0)
    # At this point the Auxiliary View is complete

    #- Create an arrow symbol
    new_symbol = active_doc.addObject('TechDraw::DrawViewSymbol', 'Symbol')
    new_symbol.Symbol = ARROW
    new_symbol.Owner = base_view
    new_symbol.Rotation = symbolAngle(vertices[0],vertices[1])
    #- Add the new symbol to the page
    work_page.addView(new_symbol)
    #- Create a direction tag
    dir_tag = active_doc.addObject('TechDraw::DrawViewAnnotation', 'DirTag')
    dir_tag.Text = "X"
    dir_tag.Owner = new_symbol
    #- Add the new symbol to the page
    work_page.addView(dir_tag)

    #- Create a view tag
    view_tag = active_doc.addObject('TechDraw::DrawViewAnnotation', 'ViewTag')
    view_tag.Text = "AuxView X"
    view_tag.Owner = new_view
    #- Add the new symbol to the page
    work_page.addView(view_tag)

    FreeCADGui.runCommand("TechDraw_RedrawPage",0)
    FreeCADGui.runCommand("TechDraw_RedrawPage",0)

    return

if __name__ == "__main__":
    # This will be true only if the file is "executed"
    # but not if imported as module
    main()