Printing¶

QWC2 supports printing to PDF via the QGIS Server GetPrint request.

The basic steps are:

• Ensure the Print plugin is enabled in the QWC2 viewer.
• Create print layouts in the QGIS project as desired. The layouts must contain one Map element.
• Generate the themes configuration.

The available print layouts will then appear in the QWC2 print plugin.

You can limit the available print scales by setting printScales (or defaultPrintScales) in the theme configuration to a list of scale denominators. If the list is empty, the print scale can be freely chosen.

Similarly, you can limit the available print resolutions by setting printResolutions (or defaultPrintResolutions) in the theme configuration to a list of resolutions. If the list is empty, the print resolution can be freely chosen.

External WMS layers are automatically printed if the Print plugin config option printExternalLayers is true (default). Note that printing external WMTS layers is currently not supported by the QGIS Server.

You can enable the option to generate a GeoPDF by setting the Print plugin config option allowGeoPdfExport to true. Note: This is only supported on QGIS Server 3.32 and newer.

You can select output format for printing layout. Default values are application/pdf, image/jpeg, image/png and image/svg. You can restrict formats to one or more of them by setting the Print plugin config option formats to an array of these formats. See QGIS Server documentation for WMS GetPrint supported formats.

Some additional tasks include:

• Configuring the print background layers
• Configuring user labels
• Configuring the print grid
• Configuring layouts with legend
• Configuring atlas printing

Configuring print background layers ¶

Background layers are handled purely client-side in QWC2. There are two options for printing the background layer:

The first option is to add a printLayer to the background layer entry when writing the themes configuration, i.e.:

{
  ...
  "backgroundLayers": [
      {"name": "<background layer name>", "printLayer": "<qgis layer name or resource string>"}
  ]
}

You can set printLayer to a QGIS layer name, or to a resource string (i.e. wms:<baseurl>#<layername>). A QGIS layer marked as printLayer will be filtered out from the QWC2 layer tree, and hence will not be displayed in QWC2.

You can also set printLayer to a list [{"maxScale": <scale>, "name": "<layer name>"}, ..., {"maxScale": null, "name": "<QGis layer name>"}], ordered in ascending order by maxScale. The last entry should have maxScale null, as the layer used for all remaining scales.

This approach allows i.e. using a WMTS background layer in the web client for higher performance, and using a WMS background layer when printing for higher quality/resolution.

The second option is to use WMS background layers, which are automatically printed as external layers.

User labels ¶

User labels appear as free-text input fields in the QWC2 print dialog. To configure user labels, it is sufficient to add item ids to layout label items in the print layout. The specified id will appear as input field label in the QWC2 print dialog.

Note: Label ids beginning with __ (two underscore characters) are ignored as user labels by QWC2.

You can can customize the input field (max length, number of rows) by setting the printLabelConfig in the theme configuration.

Also, in the theme configuration, you can also set:

• printLabelForSearchResult: The id of the label to which to write the current search result label, if any.
• printLabelForAttribution: The id of the label to which to write the current map attribution text, if any.

If you set the Print plugin config option hideAutopopulatedFields to true, these labels will not be shown in the print dialog, otherwise they will be displayed as read-only fields.

Print grid ¶

In alternative to configuring a grid directly in the print layout, one can also define a printGrid configuration in the theme configuration. For example

"printGrid": {
  "s": 1000, "x": 500, "y": 500,
  "s": 2000, "y": 1000, "y": 1000,
  "s": 10000, "y": 5000, "y": 5000,
}

will print a 500x500 (map units) grid for scales up to 1:1000, a 1000x1000 grid for scales up to 1:2000, etc.

Layouts with legend ¶

The QWC2 print dialog will expose a toggle switch to enable the legend in the print output for layout <layout_name> if the QGIS project contains a second layout named <layout_name>_legend. The layout with the _legend suffix is expected to contain a legend item.

Atlas printing ¶

To enable atlas printing in QWC2, configure the QGIS project as follows:

• Check the Generate an atlas checkbox in the desired layout in QGIS layout designer → Atlas → Atlas settings, selecting the coverage layer as desired.
• In the layout map item properties, check Controlled by Atlas.
• In the Project properties → QGIS Server, set Maximum features for Atlas print requests to the desired value.

QWC2 will then display a feature picked in the print dialog which will allow picking the desired atlas features, and QGIS Server will generate a multi-page PDF accordingly.

Layout templates ¶

The QGIS Server print templates plugin allows providing a common set of print layouts to projects to avoid having to manage potentially identical print layouts multiple times in the individual projects.

To configure it in qwc-docker, proceed as follows:

• Download the QGIS Server print templates plugin, i.e. to volumes/qgis-server-plugins/print_templates, choose a print layout folder (i.e. volumes/print-layouts) and configure the qwc-qgis-server container as follows:

  qwc-qgis-server:
    image: docker.io/sourcepole/qwc-qgis-server:<TAG>
    environment:
      FCGID_EXTRA_ENV: 'PRINT_LAYOUT_DIR'
      PRINT_LAYOUT_DIR: '/layouts'
    volumes:
      - ./volumes/qgis-server-plugins/print_templates:/usr/share/qgis/python/plugins/print_templates:ro
      - ./volumes/print-layouts:/layouts:ro
    ...

• Mount the print layout folder also into the config generator container:

qwc-config-service:
    image: docker.io/sourcepole/qwc-config-generator:<TAG>
    volumes:
      - ./volumes/print-layouts:/layouts:ro
      ...

• Extend the config generator configuration in tenantConfig.json by specifying the location of the print layouts dir:

{
  "config": {
    "qgis_print_layouts_dir": "/layouts"
    ...
  }
  ...
}

• In a multi-tenant environment, to provide separate print layouts for each tenant, organize the layouts in separate directories for each tenant below qgis_print_layouts_dir, and specify qgis_print_layouts_tenant_subdir in the respective tenantConfig.json to point to the desired subdir path.