how to make temporary entity?

[war16641]

I need temporary entities to help user to better understand the context. these temporary entities will retain when move or scale the autocad window, but will disappear when REDRAW called or reopen the file.
for example, there are 3 lines. i need to show their length on the center. just make 3 TEXT to show length. but i donot need these 3 TEXT show permanently.
how to do this?

[CEXT-Dan]

Not easy, best bet is to use Gi.TransientManager if you want to draw text. You can try to hook this up to Ed.EditorReactor to handle REGEN. Here’s a quick sample, note I only created Gi.TransientManager as a proof of concept, it’s not well tested.

If you are working with multiple documents, I’m pretty sure that both Gi.TransientManager and Ed.EditorReactor are per session, so you’re probably doing to need the add a document reactor to clear TransientEntities if documents are switched

import traceback
from pyrx import Ap, Db, Ed, Ge, Gi

def OnPyReload():
    pass

def OnPyUnloadApp():
    endit()

class TransientEntities:
    def __init__(self):
        self.vpids = []
        self.markers = []
        
    def draw(self):
        self.vpids.append(Ed.Core.getVar("CVPORT"))
        
        dbl = Db.Line(Ge.Point3d(0, 0, 0), Ge.Point3d(100, 100, 0))
        dbl.setDatabaseDefaults()
        dbl.setColorIndex(1)
        self.markers.append(dbl)
        
        dbt = Db.Text(dbl.midPoint(), "Hello world")
        dbt.setDatabaseDefaults()
        dbt.setRotation(dbl.direction().angleTo(Ge.Vector3d.kYAxis,Ge.Vector3d.kZAxis))
        self.markers.append(dbt)
        
        tm = Gi.TransientManager.current()
        tm.addTransient(dbl, Gi.TransientDrawingMode.kAcGiDirectShortTerm, 128, self.vpids)
        tm.addTransient(dbt, Gi.TransientDrawingMode.kAcGiDirectShortTerm, 128, self.vpids)
        Ed.Core.vportTableRecords2Vports()
        
    def clear(self):
        tm = Gi.TransientManager.current()
        for marker in self.markers:
            tm.eraseTransient(marker, self.vpids)
        self.vpids.clear()
        self.markers.clear()
        

class GeometryReactor(Ed.EditorReactor):
    def __init__(self):
        Ed.EditorReactor.__init__(self)
        self.te = TransientEntities()
       
    def startDraw(self):
        self.te.draw()
        
    def commandEnded(self, cmdStr: str, /) -> None:
        if cmdStr.casefold() == "REGEN".casefold():
            self.te.clear()
        
@Ap.Command()
def startit():
    try:
        global inst
        inst = GeometryReactor()
        inst.addReactor()
        inst.startDraw()
    except Exception:
        traceback.print_exc()
     
@Ap.Command()   
def restartit():
    try:
        global inst
        inst.startDraw()
    except Exception:
        traceback.print_exc()

@Ap.Command()
def endit():
    try:
        global inst
        inst.removeReactor()
        del inst
    except Exception:
        traceback.print_exc()