Zoom in layer with PyQGIS

Question

I am working on creating a plugin on QGIS 3.10. This plugin loads two layers in my QGIS project. I would like to zoom in the layer extent of AEE_layer. Unfortunately despite the code that specifies to zoom the canvas on the AEE_layer extent, it does not work. The canvas systematically zooms in on the extent of all the layers that are loaded in my project.

project = QgsProject.instance()
canvas = iface.mapCanvas()
project.write('C:/CartoIni/Projet/Projet.qgs')
groupe_aire = root.addGroup("Aires d'étude")
AEE_layer = QgsVectorLayer("C:/Users/Thysma/Documents/Stage/Data/AEE.shp", 'AEE','ogr')
QgsProject.instance().addMapLayer(AEE_layer, False)
groupe_aire.addLayer(AEE_layer)
reg_layer = QgsVectorLayer("C:/Users/Thysma/Documents/Stage/Data/REGION.shp", 'Limites régionales','ogr')
QgsProject.instance().addMapLayer(reg_layer, False)
groupe_aire.addLayer(reg_layer)
extent = AEE_layer.extent()
canvas.setExtent(extent)
canvas.refresh()

Try by replacing : canvas = iface.mapCanvas(), and welcome to GIS SE ! — J. Monticolo, Mar 29 '21 at 13:01
the result of AEE_layer.extent() : <QgsRectangle: 610783.06441810820251703 6745293.08760993927717209, 623023.31778933946043253 6757083.76099352352321148> — Mathys WOHL, Apr 01 '21 at 08:48
With a canvas CRS configured to Lambert 93 (EPSG: 2154), I tried in the QGIS Python console iface.mapCanvas().setExtent(QgsRectangle(610783.06441810820251703, 6745293.08760993927717209, 623023.31778933946043253, 6757083.76099352352321148)) and it zooms perfectly to the Orléans - Olivet area. Check your canvas coordinate system. — J. Monticolo, Apr 01 '21 at 09:20
I tried also in the QGIS Python console. I have the same result as you but when i load my plugin in QGIS it doesn't work — Mathys WOHL, Apr 01 '21 at 12:50
is the layer loaded in the QGIS main canvas with your plugin ? — J. Monticolo, Apr 01 '21 at 13:21
I uptaded my code in the post above. I use QgsLayerTreeMapCanvas() when I load my project. Is this the right way to go ? — Mathys WOHL, Apr 01 '21 at 13:53
like my first comment, change your 2nd line into canvas = iface.mapCanvas() (even if it didn't produce the good result now, because here, you create your own canvas and you don't display it). — J. Monticolo, Apr 01 '21 at 14:19
I change my second line. How can I display the canvas created in this case ? — Mathys WOHL, Apr 01 '21 at 14:25

J. Monticolo · Accepted Answer · 2021-04-03T08:14:44.180

You have to load layers and before set the new extent, tell to your canvas to wait before rendering. An important thing too is to set your project or canvas CRS. In the code, I left the two but only one work.

Try the code below :

project = QgsProject.instance()
canvas = iface.mapCanvas()
modifications
crs_l93 = QgsCoordinateReferenceSystem("EPSG:2154")
project.setCrs(crs_l93)
canvas.setDestinationCrs(crs_l93)

project.write('C:/CartoIni/Projet/Projet.qgs')
root = QgsProject.instance().layerTreeRoot()  # add the root object, as your original code
groupe_aire = root.addGroup("Aires d'étude")
AEE_layer = QgsVectorLayer("C:/Users/Thysma/Documents/Stage/Data/AEE.shp", 'AEE','ogr')
QgsProject.instance().addMapLayer(AEE_layer, False)
groupe_aire.addLayer(AEE_layer)
reg_layer = QgsVectorLayer("C:/Users/Thysma/Documents/Stage/Data/REGION.shp", 'Limites régionales','ogr')
QgsProject.instance().addMapLayer(reg_layer, False)
groupe_aire.addLayer(reg_layer)
canvas.waitWhileRendering()  # modification here
extent = AEE_layer.extent()
canvas.setExtent(extent)
canvas.refresh()

EDIT: if the first code doesn't work

You can set the extent once the canvas is refreshed a first time :

def set_aee_extent():
    extent = AEE_layer.extent()
    canvas.setExtent(extent)
    # disconnect the signal to avoid calling set_aee_extent again
    canvas.mapCanvasRefreshed.disconnect(set_aee_extent)
    canvas.refresh()
project = QgsProject.instance()
canvas = iface.mapCanvas()
modifications
crs_l93 = QgsCoordinateReferenceSystem("EPSG:2154")
project.setCrs(crs_l93)
canvas.setDestinationCrs(crs_l93)

project.write("C:/CartoIni/Projet/Projet.qgs")
root = QgsProject.instance().layerTreeRoot()  # add the root object, as your original code
groupe_aire = root.addGroup("Aires d'étude")
AEE_layer = QgsVectorLayer("C:/Users/Thysma/Documents/Stage/Data/AEE.shp", 'AEE','ogr')
reg_layer = QgsVectorLayer("C:/Users/Thysma/Documents/Stage/Data/REGION.shp", 'Limites régionales','ogr')
canvas.mapCanvasRefreshed.connect(set_aee_extent)
canvas.setLayers([AEE_layer, reg_layer])
groupe_aire.addLayer(AEE_layer)
groupe_aire.addLayer(reg_layer)

score 4 · Answer 2 · answered Mar 29 '21 at 13:05

Try replacing QgsMapCanvas() with iface.mapCanvas()

AEE_layer = QgsVectorLayer("C:/Users/Thysma/Documents/Stage/Data/AEE.shp", 'AEE','ogr')
QgsProject.instance().addMapLayer(AEE_layer, False)
canvas = iface.mapCanvas()
extent = AEE_layer.extent()
canvas.setExtent(extent)
canvas.refresh()

Check out https://gis.stackexchange.com/a/363373/107424

Zoom in layer with PyQGIS

2 Answers2

modifications

modifications