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I am interested in making reproducible PDF figures in QGIS3, and therefore want to work from the console/PyQGIS.

Using some previous helpful advice from PDF Output with Python the problem is successfully reduced to setting up the QgsPrintLayout. I am not sure how to do this, below is my best attempt so far:

#setup the background classes for managing the project
canvas =iface.mapCanvas()
manager = project.layoutManager()
#new layout
layout = QgsPrintLayout(project)
layout.initializeDefaults()
layout.setName('console')
itemMap = QgsLayoutItemMap(layout)
itemMap.setExtent(canvas.extent())
layout.addLayoutItem(itemMap)
#add the layout to the manager
manager.addLayout(layout)

The "console" layout is successfully added to QGIS 3 and I can open it to see if the content is satisfactory. The map does not render and its extent is nan,nan,nan,nan.

How do I setup the extent and size of the map object in the layout?

SOLVED. The following code produces a map without issues.

#get a reference to the layout manager
manager = project.layoutManager()
#make a new print layout object
layout = QgsPrintLayout(project)
#needs to call this according to API documentaiton
layout.initializeDefaults()
#cosmetic
layout.setName('console')
#add layout to manager
manager.addLayout(layout)
#create a map item to add
itemMap = QgsLayoutItemMap.create(layout)
#using ndawson's answer below, do this before setting extent
itemMap.attemptResize(QgsLayoutSize(6,4, QgsUnitTypes.LayoutInches))
#set an extent
itemMap.setExtent(canvas.extent())
#add the map to the layout
layout.addLayoutItem(itemMap)
PolyGeo
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lobgoblin
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  • Thanks for including the "solved" code. I'd like to ask about one thing. Where in the documentation did you find that you need to initializeDefaults()? I can't find this anywhere. – Erich Purpur Jan 17 '19 at 14:51
  • I was not able to find the API documentation on why initializeDefaults() is required, but try this example without it: https://gis.stackexchange.com/a/309551/75563

    I found that not only is the PDF way off, but QGIS crashed as well when pressing Export to PDF ...

     – RobLabs Jan 22 '19 at 20:51

1 Answers1

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You need to set a size for the map item (usually you do this before setting the extent):

itemMap.attemptResize(QgsLayoutSize(50, 60, QgsUnitTypes.LayoutMillimeters)) itemMap.attemptMove(QgsLayoutPoint(1,2,QgsUnitTypes.LayoutMillimeters)) itemMap.setExtent(...)

ndawson
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