QGIS display 'name' or 'title' of the active layer only (view-decorations-title)

Question

I want to display the 'name' or 'title' of the active layer in View-Decorations-Title, I found in "Automatically create an array of all visible layer names in QGIS" the answer:

array_to_string(
  array_foreach ( 
    @map_layers,
    layer_property(@element,'name')
  )
)

but, it shows all visible layers, and I can't find an expression for the current layer that can use in something like:

layer_property('active_layer???','title')

I'm using QGIS 3.26.3 in LinuxMint 20.2.

Answer 1

there is no predefined function or expression for that, you will have to write a python function in the Function editor:

with following code

from qgis.core import *
from qgis.gui import *
from qgis.utils import iface

@qgsfunction(group='Custom', referenced_columns=[])
def active_Layer(feature, parent):
    """
    returns the active Layer name.
    """
    s = iface.activeLayer().name()
    return s

then you will a a new expression which returns the active Layers name