[Qgis-developer] QgsLayerTreeViewMenuProvider and default values

Richard Duivenvoorde rdmailings at duif.net
Mon Nov 21 23:10:14 PST 2016

On 21-11-16 16:40, Martin Dobias wrote:
> On Mon, Nov 21, 2016 at 6:09 PM, Richard Duivenvoorde <richard at duif.net> wrote:
>> On 2016-11-21 03:02, Martin Dobias wrote:
>> Ah, thanks Martin for your anwers.
>>>> Q3: looking at the possibility to add a 'Transparency slider' in the
>>>> layertree (see layer props bottom item): how difficult is it to add a
>>>> 'refresh data' button (with custom refresh data code) in the layer tree
>>> See the original pull request for some example code:
>>> https://github.com/qgis/QGIS/pull/3170
>> I tried this, and indeed can create such a widget (QToolButton or
>> QPushBtuuon) with a handle to a layer to do things with it.
>> But I can only add it to a layer in the legend via the properties dialog?
> Here is how to configure an embedded widget without properties dialog:
> my_layer.setCustomProperty("embeddedWidgets/count", 1)
> my_layer.setCustomProperty("embeddedWidgets/0/id", "transparency")
> Finally one needs to call refreshLayerLegend(), e.g.:
> view = iface.layerTreeView()
> view.model().refreshLayerLegend(view.currentNode())
> The methods from QgsLegendInterface only affect the actions in context
> menu for the layer tree, they are not related to embedded widgets
> functionality.

Hi Martin,

a cool thanks. Will try.

I think having this kind of functionality has a lot of potential 
specially for plugin writers (examples taken from Martin's blogs or PR's):
- change transparency with a slider widget
- refresh data for this layer via a button widget
- let user choose between x predefined styles with a dropdown widget
- create a timebased subquery via a datetime-widget
- do 'something' on this layer
- layer based timeslider?
etc etc

This kind of 'components' could easily be exchanged via plugins isn't 
it? Or do you envision some other exchange mechanism?

The api for using a widget via python/code could have some love I think.

Also do you think it is usefull to have the same type of widget 2 times 
for a layer in the legend?

I'll try to add this new knowledge in the python cookbook too.

Thanks & Regards,

Richard Duivenvoorde

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