QGIS master: is_layer_visible () does not update automatically

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Author Name: salvatore fiandaca (salvatore fiandaca)
Original Redmine Issue: 17617
Affected QGIS version: master
Redmine category:expressions

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I used the function is_layer_visible () to change the appearance of the labels, but you need to do a manual refresc, it does not update automatically.

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• N3.jpg (salvatore fiandaca)

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Author Name: Giovanni Manghi (@gioman)

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Is this a regression (works as expected in 2.18.* or earlier)?

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• status_id was changed from Open to Feedback

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Author Name: Giovanni Manghi (@gioman)

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• subject was changed from QGIS master d0e927a - is_layer_visible () does not update automatically to QGIS master: is_layer_visible () does not update automatically

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Author Name: Giovanni Manghi (@gioman)

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• category_id was changed from Symbology to Labelling

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Author Name: Giovanni Manghi (@gioman)

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Feedback needed here. Is a regression in QGIS 3 (did it worked as expected in QGIS 2)?

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Author Name: salvatore fiandaca (salvatore fiandaca)

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In QGIS 2, the is_layer_visible function does not exist; so it's not a regression.

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Author Name: Giovanni Manghi (@gioman)

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Still true on the latest master?

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Author Name: salvatore fiandaca (salvatore fiandaca)

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Giovanni Manghi wrote:

Still true on the latest master?

yes, it is still true in the last master - gnu / linux mint 19
as soon as I can I try in win 10

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Author Name: Giovanni Manghi (@gioman)

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• category_id was changed from Labelling to Expressions
• operating_system was changed from win 10 64b to
• status_id was changed from Feedback to Open

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Author Name: Nyall Dawson (@nyalldawson)

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I think this is a "wont fix". Expressions in QGIS can be very complex and adding a method to determine the dependencies of an expression would be almost impossible. For instance, there's also expressions which fetch features from other layers, expressions which calculate aggregates from other layers, expressions which use related features, etc. We'd also need to consider all these cases and force a refresh whenever any of the dependencies change. But then there's also expressions which rely on variables too. Then there's also the need to consider everywhere expressions can be used which may need refreshing... e.g. canvas renders, layout items, virtual fields, data defined properties, etc.

I think given the extreme complexity of solving this and the easy workaround (refresh the canvas manually) it should be tagged as "wontfix"

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Author Name: salvatore fiandaca (salvatore fiandaca)

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Nyall Dawson wrote:

I think this is a "wont fix". Expressions in QGIS can be very complex and adding a method to determine the dependencies of an expression would be almost impossible. For instance, there's also expressions which fetch features from other layers, expressions which calculate aggregates from other layers, expressions which use related features, etc. We'd also need to consider all these cases and force a refresh whenever any of the dependencies change. But then there's also expressions which rely on variables too. Then there's also the need to consider everywhere expressions can be used which may need refreshing... e.g. canvas renders, layout items, virtual fields, data defined properties, etc.

I think given the extreme complexity of solving this and the easy workaround (refresh the canvas manually) it should be tagged as "wontfix"

Thanks for the reply

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Author Name: Giovanni Manghi (@gioman)

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So... closing?

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Author Name: salvatore fiandaca (salvatore fiandaca)

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Giovanni Manghi wrote:

So... closing?

for me, Nyall explanation is ok

[qgib]

Author Name: Giovanni Manghi (@gioman)

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• resolution was changed from to wontfix
• status_id was changed from Open to Closed