Hello,
Here is a snipped of code that can help you.
To test this you have to:
- Show python console
- enable the polygonal digitizing tool (must be the active tool before
launching this snippet)
- execute the code in the python editor
- start digitizing
- see the area printing in the console
Don't hesitate if you have further questions.
Regards,
Jacky Volpes - Djedouas - Oslandia
---
# Measurement object (adapt with crs/transform context/ellipsoid)
da = QgsDistanceArea()
da.setSourceCrs(QgsProject.instance().crs(),
QgsProject.instance().transformContext())
# If distance measurement must use ellipsoid
da.setEllipsoid(QgsProject.instance().ellipsoid())
# This is a demonstration function to adapt with your needs
def showArea(current_point):
if not isinstance(iface.mapCanvas().mapTool(),
QgsMapToolDigitizeFeature):
return
# Snapping
snapped_point =
iface.mapCanvas().snappingUtils().snapToMap(current_point).point()
if not snapped_point.isEmpty():
current_point = snapped_point
# Coordinates in map coordinates
points = [QgsPointXY(point) for point in
iface.mapCanvas().mapTool().pointsZM()]
points.append(current_point)
# Show area
print(da.measurePolygon(points))
# Must be handled correctly in the final code, but here is for testing
iface.mapCanvas().xyCoordinates.connect(showArea)
Le 05/04/2023 à 17:56, Catania, Luke A ERDC-RDE-GRL-VA CIV via
QGIS-Developer a écrit :
Looking for something like
canvas.xyCoordinates.connect( self.canvasMoveEvent )
but that’s from a 7 year old post so looks like xyCoordinates is not
in QGIS 3.x
*From:* QGIS-Developer <qgis-developer-boun...@lists.osgeo.org> *On
Behalf Of *Catania, Luke A ERDC-RDE-GRL-VA CIV via QGIS-Developer
*Sent:* Wednesday, April 5, 2023 11:53 AM
*To:* qgis-developer@lists.osgeo.org
*Subject:* Re: [QGIS-Developer] Detect a Map Canvas Mouse Event
I found
QgsMapToolEmitPoint, QgsMapTooland |canvas.setMapTool(…)|
||
|So I declared my class as |AoiSizeValidator(QgsMapToolEmitPoint)
||
|But gave that a try and it gets me x,y, initially but when I select
an add layer from the qgis edit menu, I guess it sets a new map tool
so mine gets overridden. So looks like I need a different approach to
get xy from the map canvas. |
*From:* QGIS-Developer <qgis-developer-boun...@lists.osgeo.org> *On
Behalf Of *Catania, Luke A ERDC-RDE-GRL-VA CIV via QGIS-Developer
*Sent:* Wednesday, April 5, 2023 11:27 AM
*To:* qgis-developer@lists.osgeo.org
*Subject:* [QGIS-Developer] Detect a Map Canvas Mouse Event
Trying to get a map canvas event when canvas is clicked and mouse is
dragged. I have code that creates an empty layer, but I use the QGIS
edit menu to add the actually layer. I want to be able to track the
mouse movement so I can calculated the area of the feature being drawn
in real time so I can make sure the area is within a defined range.
Is there an event I can connect to so I can run my custom code when
the even occurs?
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--
Jacky Volpes
Ingénieur SIG - Oslandia
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