[Qgis-user] HELP highlights points

[Ujaval Gandhi]

This can be done with an 'Action'. I was able to do it with a bit of PyQGIS
code. Change the  point_layer_name in the snippet below to match your point
name. Define the Action on the line layer. Here's how it works
https://ibb.co/vP7KRDd

line_layer = QgsProject.instance().mapLayer('[% @layer_id %]')
point_layer_name = 'points'
fid = [% $id %]
line_feature = line_layer.getFeature(fid)
line_geometry = line_feature.geometry().buffer(40, 5)
point_layer = QgsProject.instance().mapLayersByName(point_layer_name)[0]
nearby_points = [p.id() for p in point_layer.getFeatures()
    if p.geometry().intersects(line_geometry) ]
layer.selectByIds(nearby_points)


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Ujaval Gandhi
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On Thu, Dec 24, 2020 at 8:02 PM Charles Dixon-Paver <charles at kartoza.com>
wrote:

> I was very interested to see if this was possible with qgis expressions
> and symbology, and I got it to work with surprisingly little effort, albeit
> with some issues [1].
>
> I simply used the rule based symbology to highlight the relevant features
> using an expression [2].
>
> The expression I used was as follows:
>
> if(
>   distance($geometry,
>     geometry(
>       get_feature('Lines','fid','1')
>     )
>   ) < 500
> ,true,false)
>
> One caveat is that the view does not automatically update when digitizing
> a new vertice. As a result I needed to zoom in and out constantly to update
> the symbol styles. This could probably be modified by using a layer action
> though.
>
> Secondly, this expression is limited to a single feature in it's
> current state. I'm not sure if anyone has a clever workaround for including
> all geometries from another layer in an expression.
>
> Lastly, this only tracks actual features, not the cursor.
>
> There could be many other ways to achieve your result though, but I was
> interested to see how well this would function so others might find the
> result quite interesting. It's probably also quite usable for static styles
> if the objective is just for mapmaking rather than a digitizing tool.
>
> [1] https://imgur.com/a/5J0dSt3
> [2] https://imgur.com/a/E043vO7
>
> On Thu, 24 Dec 2020 at 15:31, Raffaele Ceretto <cerettoraffaele at gmail.com>
> wrote:
>
>> I need a tool that allows me to draw a line and that at the same time
>> highlights points within a certain distance (for example 40 meters).
>> I have a map with hundreds of points, I would like when I draw a line
>> what is nearby will light up.
>> There is a specific tool to do this or a simple "magnet" function?
>> Thank you for your help
>>
>> waiting for a reply
>>
>> regards
>>
>> Raffaele
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