What is QGIS map canvas?

What is QGIS map canvas?

The Map canvas widget is probably the most important widget within QGIS because it shows the map composed from overlaid map layers and allows interaction with the map and layers. The canvas always shows a part of the map defined by the current canvas extent.

How do I import Iface?

Layers

1. Add vector layer. from qgis.
2. Get active layer. layer = iface.
3. List all layers. from qgis.core import QgsProject QgsProject.
4. Obtain layers name. layers_names = [] for layer in QgsProject.
5. Find layer by name. from qgis.core import QgsProject layer = QgsProject.
6. Set active layer.
7. Refresh layer at interval.
8. Show methods.

What do you do with the map canvas in QGIS?

The QgsMapCanvas class also controls refreshing of the rendered map. Besides this item which acts as a background, there may be more map canvas items. Typical map canvas items are rubber bands (used for measuring, vector editing etc.) or vertex markers.

What is the scope of the qgsmapcanvas class?

Returns a reference to the expression context scope for the map canvas. This scope is injected into the expression context used for rendering the map, and can be used to apply specific variable overrides for expression evaluation for the map canvas render. New in version 2.12. Emitted when the extents of the map change [signal]

How is the interaction with the map canvas done?

The interaction is done through the use of map tools : there are tools for panning, zooming, identifying layers, measuring, vector editing and others. Similar to other graphics programs, there is always one tool active and the user can switch between the available tools.

Do you have to have theme name in qgsmapcanvas?

The theme name must match a theme present in the associated project’s QgsMapThemeCollection. When the canvas is associated to a map theme, it will automatically follow the layer selection and layer styles from that theme.