[QGIS-Developer] Calculate area/perimtere/length of polygon/line while editing (Sylvain Th?ry)

Philipe Borba philipeborba at gmail.com
Tue Mar 11 11:02:29 PDT 2025 

In the Brazilian Army plugin, we have a tool to calculate the line length or the polygon area upon digitalization, like shown in the gif below:



The code used in this tool is available at: https://github.com/dsgoficial/DsgTools/blob/master/DsgTools/gui/ProductionTools/MapTools/MeasureTool/measureTool.py

> On 11 Mar 2025, at 13:37, qgis-developer-request at lists.osgeo.org wrote:
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> Today's Topics:
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>   1. Re: Calculate area/perimtere/length of polygon/line while
>      editing (Sylvain Th?ry)
>   2. Re: Calculate area/perimtere/length of polygon/line while
>      editing (Catania, Luke A ERDC-RDE-GRL-VA CIV)
> 
> 
> ----------------------------------------------------------------------
> 
> Message: 1
> Date: Tue, 11 Mar 2025 17:05:15 +0100
> From: Sylvain Th?ry <sylvain.thery at cnrs.fr>
> To: "Catania, Luke A ERDC-RDE-GRL-VA CIV"
> 	<Luke.A.Catania at erdc.dren.mil>, DelazJ <delazj at gmail.com>
> Cc: "qgis-developer at lists.osgeo.org" <qgis-developer at lists.osgeo.org>
> Subject: Re: [QGIS-Developer] Calculate area/perimtere/length of
> 	polygon/line while editing
> Message-ID: <a9f6f86d-4d22-4a2f-97c6-fa7e89e4b03b at cnrs.fr>
> Content-Type: text/plain; charset="utf-8"; Format="flowed"
> 
> Hello,
> 
> It seems there is a fix here : 
> https://github.com/agiudiceandrea/calcarea2/blob/a6a3d7c5a98e64573731cd6a005da4e2d9836fdd/calcareaevent.py
> 
> All the best,
> S.
> 
> 
> Le 11/03/2025 ? 16:14, Catania, Luke A ERDC-RDE-GRL-VA CIV via 
> QGIS-Developer a ?crit?:
>> 
>> Thanks. Plugin installed but will not run.? I get the error below. I 
>> have QGIS 3.34.4.
>> 
>> *TypeError: QgisInterface missing 'mActionDigitizeWithCurve' action *
>> 
>> Traceback (most recent call last):
>> ? File "C:\PROGRA~1/QGIS33~1.4/apps/qgis-ltr/./python\qgis\utils.py", 
>> line 423, in _startPlugin
>> ? ? plugins[packageName] = package.classFactory(iface)
>> ? File 
>> "C:\Users/RDTECLAC/AppData/Roaming/QGIS/QGIS3\profiles\default/python/plugins\calcarea2\__init__.py", 
>> line 29, in classFactory
>> ? ? return CalcAreaPlugin( iface )
>> ? File 
>> "C:\Users/RDTECLAC/AppData/Roaming/QGIS/QGIS3\profiles\default/python/plugins\calcarea2\plugin.py", 
>> line 66, in __init__
>> ? ? self.toolEvent = CalcAreaEvent( self.iface )
>> ? File 
>> "C:\Users/RDTECLAC/AppData/Roaming/QGIS/QGIS3\profiles\default/python/plugins\calcarea2\calcareaevent.py", 
>> line 478, in __init__
>> ? ? self.addFeatureEvent = AddFeatureEvent( iface )
>> ? File 
>> "C:\Users/RDTECLAC/AppData/Roaming/QGIS/QGIS3\profiles\default/python/plugins\calcarea2\calcareaevent.py", 
>> line 213, in __init__
>> ? ? self.geomPolygon = self.GeomPolygon( iface )
>> ? File 
>> "C:\Users/RDTECLAC/AppData/Roaming/QGIS/QGIS3\profiles\default/python/plugins\calcarea2\calcareaevent.py", 
>> line 316, in __init__
>> ? ? self.actionDigitizeWithCurve = getActionDigitizeWithCurve( iface )
>> ? File 
>> "C:\Users/RDTECLAC/AppData/Roaming/QGIS/QGIS3\profiles\default/python/plugins\calcarea2\calcareaevent.py", 
>> line 308, in getActionDigitizeWithCurve
>> ? ? raise TypeError(f"QgisInterface missing '{name}' action")
>> TypeError: QgisInterface missing 'mActionDigitizeWithCurve' action
>> 
>> *From:*DelazJ <delazj at gmail.com>
>> *Sent:* Tuesday, March 11, 2025 11:08 AM
>> *To:* Catania, Luke A ERDC-RDE-GRL-VA CIV <Luke.A.Catania at erdc.dren.mil>
>> *Cc:* qgis-developer at lists.osgeo.org
>> *Subject:* Re: [QGIS-Developer] Calculate area/perimtere/length of 
>> polygon/line while editing
>> 
>> Hi,
>> 
>> There is a CalcArea2 plugin whose description mentions it should be 
>> doing that for polygons. You might want to take ispiration from their 
>> code.
>> 
>> Regards,
>> 
>> Harrissou
>> 
>> Le?mar. 11 mars 2025 ??15:55, Catania, Luke A ERDC-RDE-GRL-VA CIV via 
>> QGIS-Developer <qgis-developer at lists.osgeo.org> a ?crit?:
>> 
>>    I need to calculate these values on the fly while I am in an edit
>>    session resizing a polygon or a line.? I need the user to see this
>>    calculation while they are editing not after the edits are
>>    committed. I already have the UI set up to capture after commit,
>>    but I need to capture while they are moving vertices and update
>>    the values in the UI, so they don?t keep editing and then
>>    committing just to see if they are close.? I want them to know
>>    before they commit.
>> 
>>    Any idea how to achieve this?
>> 
>>    Luke Catania
>> 
>>    US Army ERDC-GRL
>> 
>>    JCMS Site Planning Developer
>> 
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> 
> -- 
> Sylvain TH?RY - Ing?nieur d'?tudes CNRS en g?omatique
> UMR 5281 ART-Dev - Acteurs, Ressources et Territoires dans le D?veloppementhttps://art-dev.cnrs.fr/
> sylvain.thery at cnrs.fr  - +33.4.11.75.70.98
> Universit? Paul-Val?ry Montpellier 3 - Site St Charles - Bureau 239
> @ postale : ART-Dev - St Charles - Route de Mende - 34 199 Montpellier Cedex 5
> https://www.researchgate.net/profile/Sylvain-Thery
> 
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> ------------------------------
> 
> Message: 2
> Date: Tue, 11 Mar 2025 16:37:45 +0000
> From: "Catania, Luke A ERDC-RDE-GRL-VA CIV"
> 	<Luke.A.Catania at erdc.dren.mil>
> To: Sylvain Th?ry <sylvain.thery at cnrs.fr>, DelazJ <delazj at gmail.com>
> Cc: "qgis-developer at lists.osgeo.org" <qgis-developer at lists.osgeo.org>
> Subject: Re: [QGIS-Developer] Calculate area/perimtere/length of
> 	polygon/line while editing
> Message-ID: <29d216cf35a34103ac67038c14846614 at erdc.dren.mil>
> Content-Type: text/plain; charset="utf-8"
> 
> Thanks.  That works.   But looks like it only works when initially drawing the polygon as opposed to also working when editing an existing polygon.  I have a similar tool to this that shows the area when drawing, just trying to figure out how to get it to work when editing an existing polygon.  I was hoping to build on my own tool if there was an easy what to get a hold of some other signal that gets fired while editing.
> 
> 
> 
> From: Sylvain Th?ry <sylvain.thery at cnrs.fr> 
> Sent: Tuesday, March 11, 2025 12:05 PM
> To: Catania, Luke A ERDC-RDE-GRL-VA CIV <Luke.A.Catania at erdc.dren.mil>; DelazJ <delazj at gmail.com>
> Cc: qgis-developer at lists.osgeo.org
> Subject: Re: [QGIS-Developer] Calculate area/perimtere/length of polygon/line while editing
> 
> 
> 
> Hello, 
> 
> It seems there is a fix here : https://github.com/agiudiceandrea/calcarea2/blob/a6a3d7c5a98e64573731cd6a005da4e2d9836fdd/calcareaevent.py <Blockedhttps://github.com/agiudiceandrea/calcarea2/blob/a6a3d7c5a98e64573731cd6a005da4e2d9836fdd/calcareaevent.pyBlocked> 
> 
> All the best, 
> S.
> 
> 
> 
> Le 11/03/2025 ? 16:14, Catania, Luke A ERDC-RDE-GRL-VA CIV via QGIS-Developer a ?crit :
> 
> Thanks. Plugin installed but will not run.  I get the error below.  I have QGIS 3.34.4.
> 
> 
> 
> TypeError: QgisInterface missing 'mActionDigitizeWithCurve' action 
> 
> Traceback (most recent call last):
>  File "C:\PROGRA~1/QGIS33~1.4/apps/qgis-ltr/./python\qgis\utils.py", line 423, in _startPlugin
>    plugins[packageName] = package.classFactory(iface)
>  File "C:\Users/RDTECLAC/AppData/Roaming/QGIS/QGIS3\profiles\default/python/plugins\calcarea2\__init__.py", line 29, in classFactory
>    return CalcAreaPlugin( iface )
>  File "C:\Users/RDTECLAC/AppData/Roaming/QGIS/QGIS3\profiles\default/python/plugins\calcarea2\plugin.py", line 66, in __init__
>    self.toolEvent = CalcAreaEvent( self.iface )
>  File "C:\Users/RDTECLAC/AppData/Roaming/QGIS/QGIS3\profiles\default/python/plugins\calcarea2\calcareaevent.py", line 478, in __init__
>    self.addFeatureEvent = AddFeatureEvent( iface )
>  File "C:\Users/RDTECLAC/AppData/Roaming/QGIS/QGIS3\profiles\default/python/plugins\calcarea2\calcareaevent.py", line 213, in __init__
>    self.geomPolygon = self.GeomPolygon( iface )
>  File "C:\Users/RDTECLAC/AppData/Roaming/QGIS/QGIS3\profiles\default/python/plugins\calcarea2\calcareaevent.py", line 316, in __init__
>    self.actionDigitizeWithCurve = getActionDigitizeWithCurve( iface )
>  File "C:\Users/RDTECLAC/AppData/Roaming/QGIS/QGIS3\profiles\default/python/plugins\calcarea2\calcareaevent.py", line 308, in getActionDigitizeWithCurve
>    raise TypeError(f"QgisInterface missing '{name}' action")
> TypeError: QgisInterface missing 'mActionDigitizeWithCurve' action
> 
> 
> 
> From: DelazJ  <mailto:delazj at gmail.com> <delazj at gmail.com> 
> Sent: Tuesday, March 11, 2025 11:08 AM
> To: Catania, Luke A ERDC-RDE-GRL-VA CIV  <mailto:Luke.A.Catania at erdc.dren.mil> <Luke.A.Catania at erdc.dren.mil>
> Cc: qgis-developer at lists.osgeo.org <mailto:qgis-developer at lists.osgeo.org> 
> Subject: Re: [QGIS-Developer] Calculate area/perimtere/length of polygon/line while editing
> 
> 
> 
> Hi,
> 
> There is a CalcArea2 plugin whose description mentions it should be doing that for polygons. You might want to take ispiration from their code.
> 
> 
> 
> Regards,
> 
> Harrissou
> 
> 
> 
> Le mar. 11 mars 2025 ? 15:55, Catania, Luke A ERDC-RDE-GRL-VA CIV via QGIS-Developer <qgis-developer at lists.osgeo.org <mailto:qgis-developer at lists.osgeo.org> > a ?crit :
> 
> I need to calculate these values on the fly while I am in an edit session resizing a polygon or a line.  I need the user to see this calculation while they are editing not after the edits are committed. I already have the UI set up to capture after commit, but I need to capture while they are moving vertices and update the values in the UI, so they don?t keep editing and then committing just to see if they are close.  I want them to know before they commit.
> 
> 
> 
> Any idea how to achieve this?
> 
> 
> 
> Luke Catania
> 
> US Army ERDC-GRL
> 
> JCMS Site Planning Developer
> 
> 
> 
> _______________________________________________
> QGIS-Developer mailing list
> QGIS-Developer at lists.osgeo.org <mailto:QGIS-Developer at lists.osgeo.org> 
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> 
> 
> 
> 
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> 
> -- 
> Sylvain TH?RY - Ing?nieur d'?tudes CNRS en g?omatique
> UMR 5281 ART-Dev - Acteurs, Ressources et Territoires dans le D?veloppement https://art-dev.cnrs.fr/ <Blockedhttps://art-dev.cnrs.fr/Blocked> 
> sylvain.thery at cnrs.fr <mailto:sylvain.thery at cnrs.fr>   - +33.4.11.75.70.98
> Universit? Paul-Val?ry Montpellier 3 - Site St Charles - Bureau 239
> @ postale : ART-Dev - St Charles - Route de Mende - 34 199 Montpellier Cedex 5 
> https://www.researchgate.net/profile/Sylvain-Thery <Blockedhttps://www.researchgate.net/profile/Sylvain-TheryBlocked> 
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