Charles, thanks very much. This looks promising.
I'm out all day but will check it later and advise . . . . .
-----
Cheers, Spring
On 14/Apr/2021 07:34, Charles Dixon-Paver wrote:
If you want the layer dependant label visibility to be applied to the
entire layer, then indeed using an expression in the "Show label"
rendering option should do what you are asking. By the sounds of
things though, you should probably just be using a simple expression
like:
if (is_layer_visible( 'toggle_layer_name' ), 1, 0)
Invert it to only display the labels when a certain layer is /not/
visible by simply switching the true/ false statement order, e.g. if
(is_layer_visible( 'toggle_layer_name' ),false,true)
If you are wanting the behaviour to be applied to a specific rule you
can specify a similar context within the rule using an expression like
if (is_layer_visible( 'toggle_layer_name' ),{expression when true}, false)
Note, however, that although the map canvas will automatically toggle
the display of the visible layers, it probably isn't going to
automatically update the label rendering... So even with these
expressions working properly you may have to refresh the map or pan a
little to check that it's working after changing the layer visibility.
As I'm sure you can imagine, labeling can be quite a computationally
expensive resource so there are likely very good reasons for this
behaviour, although you can probably work around it using some python
code or similar. An example might be the following:
def redrawWhenToggled(layerTreeNode):
canvas = iface.mapCanvas()
canvas.redrawAllLayers()
toggle_layer =
QgsProject.instance().layerTreeRoot().findLayer('toggle_layer_name_76f7c585_xxxxx')
toggle_layer.visibilityChanged.connect(redrawWhenToggled)
That should redraw the canvas each time you toggle the visibility on
that particular layer. Note that 'toggle_layer_name_76f7c585_xxxxx' is
of course the layerID. You can easily get the layer id by selecting/
highlighting the item in the layers tab and using
iface.activeLayer().id() in the python console.
I would probably also use a layer id, rather than a name, in the
"is_layer_visible" expression, so that the expression continues to
work even when a layer is renamed or duplicated etc.
On Tue, 13 Apr 2021 at 23:27, Springfield Harrison
<stellar...@gmail.com <mailto:stellar...@gmail.com>> wrote:
Hello Folks, back again!
I'm trying to have labels display only when that "layer" is turned
on (visible). BUT my layers are actually rule based symbology and
apply only to selected records in the layer (as per the rules),
(sub-layers?).
Under the Rendering tab for labels I find:
/With data-defined expressions in//Show label//and//Always
Show//you can fine tune which labels should be rendered./
but there is no explanation of how to implement this feature.
I would expect that something like this may be in the right
direction:
/if (is_layer_visible( @layer_name ) = 0, ("Tree_Tag" || ' - '
|| ' (' || "More" || ') ') , '*')/
Any thoughts on how to selectively make labels visible would be great.
-----
Cheers, Spring
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