"Render layers as a group" still applies after you unchecked it

[DelazJ]

What is the bug or the crash?

Create group with layers
Set the group to "render layers as a group"
In a layer symbology properties, under the layer rendering group, set the blending mode to any of the clipping modes (mask below, masked in below,...): you might get some effect on the map
Uncheck the group to property to NOT "render layers as a group"
The effect on the map is still applied; check the blending mode of the layer you previously set: the combobox is now empty. No idea what value should populate the widget but... looks like an issue to me.

Kazam_screencast_00004.webm

Steps to reproduce the issue

see above

Versions

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QGIS version	3.29.0-Master	QGIS code revision	7e2e622
Qt version	5.15.3
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Supported QGIS version

• I'm running a supported QGIS version according to the roadmap.

New profile

• I tried with a new QGIS profile

Additional context

No response

[roya0045]

Does the issue happens if you go through the property menu and not the styling panel?

[DelazJ]

@roya0045 I'm not sure I understand what you want me to check but... anyway...

1. I unchecked the group option in the layer styling panel (groups do not have "Properties" dialog)
2. I opened the layer properties dialog: the blending combobox is empty (same as in the Layer Styling panel).

• If I press OK, it is reset to "Normal"
• If I press Cancel, it is kept empty

Something that I forgot to say in my earlier message is that, if you do not edit the combobox, and later turned on the "render layers as a group" option, the combobox takes the blends clipping mode you initially set. The issues I can see:

• if "render layers as a group" is unchecked, the clipping mode continues to apply while to my understanding it shouldn't (but this helps workaround Render Layers as a Group not working with Themes in Layout #50391)
• the empty combobox is confusing; i guess it is an intermediate state to allow retrieving user setting when render... is back to ON and avoid overwriting with "Normal". This is IMHO the root of the issues: mixing hard blending options (normal, lighten,...) with contextual ones (mask...) that can disappear anytime.

Given that clipping blending modes are possible only in group context, I'd suggest to add a dedicated "group blending" combobox in the layer properties with only the clipping modes + (normal or empty/not set entry):

• if the layer is not in a group or the layer is in a group with "render..." OFF, setting this to whatever has no effect (or we could just gray the option, but showing the value the user selected when it was ON)
• if the layer is in a group with "render..." ON and a clipping mode is set, then it clips what it has to (and I guess, takes precedence on the common blending options)

[roya0045]

@DelazJ My mistake, I assume that since the group could be modified in the layer styling, it was also accessible in a standalone window (the properties for normal layers). I guess that could be a bug to only have it accessible through layer styling.

[DelazJ]

I guess that could be a bug to only have it accessible through layer styling.

Not sure. Apart from the "render..." options, groups have (yet) no properties. So not sure it is worth a Properties dialog.