# Styling Layers

Using QGIS, you can control many visual aspects of your layer. You may apply a common style for all the features in a layer (Single Symbol) or apply a thematic style that displays features according to any of its attributes (Categorized).

# WMS Layers

When Pozi fetches a layer using WMS (ie, not vector), QGIS Server renders the layer exactly as configured in QGIS.

# Vector Layers

When using vector layers (ie, WFS-enabled), the rendering is done by Pozi in the browser, which can cause the layer to appear differently compared to QGIS for some styling options.

When styling vector layers, use only the supported styles specified below.

(If you need Pozi to display layers using a QGIS style that doesn't appear in the below lists of supported styles, disable WFS for the layer to force Pozi to retrieve the layer via WMS, which uses the QGIS Server renderer.)

# Points

Supported marker symbols:

Note that diamond, cross2, cross_fill, star_diamond symbols are not currently supported. Symbol rotation is also not supported.

Suggested sizes:

  • set size to 4mm or greater enable to easier interaction for users in the browser
  • set stroke to white, 0.5mm or greater to provide separation from the background

# Lines

Supported lines:

  • Simple Line
    • Solid Line
    • No Pen
    • Custom Dash Pattern

Set line thicknesses to 2mm or greater to enable users to easily select line features.

To style a line with dots and/or dashes:

  • set the cap style to flat
  • tick "Use custom dash pattern"
  • specify a dash pattern (eg, 4 2) in millimeters.

# Polygons

Supported fills:

  • Simple Fill
    • Solid
    • No brush (see note below)
    • Cross
    • Diagonal X
  • Point Pattern Fill

Note that the 'No brush' fill will prevent users from being able to select a polygon by clicking within the polygon. If you want to display a polygon with an empty fill while still enabling users to select the polygon, use the 'Solid' fill, and set the opacity of the fill colour to a low or zero value.

# Labels

Point, line and polygon features can optionally be configured to display labels.

Labelling in QGIS
https://docs.qgis.org/latest/en/docs/user_manual/working_with_vector/vector_properties.html#labels-properties

Not yet supported in Pozi:

  • label offsets
  • buffer transparency
  • text expressions
    • combining values from multiple fields
    • find-and-replace operations
    • converting to upper or lower case
    • etc

Instead of using text expressions to manipulate text, use virtual fields to achieve the same effect.

To improve legibility, set label text size to 10 points or greater and a white 1.8mm buffer.

# Embedded Symbology

MapInfo tables sometimes contain embedded styles. QGIS Desktop may recognise and display the map features using these styles, but QGIS Server is unable to pass on the styling information to Pozi for styling vector layers.

If the layer appears in QGIS Symbology mode "Embedded Symbols", switch it to "Single Symbol" or "Categorized", and style it according to your preference.


# Categorized Symbology

Layers can be styled using the Categorized option. Pick the field to use for the category from the drop-down list, then click the Classify button.

Categorized styling
Categorized styling

# Limitations

When publishing the layer as a vector layer, the field used for categorisation must be a field that that is exposed (ie, not hidden).

An addition, the following limitations apply:

  • the symbology must be based on a field (real or virtual), not an expression
  • the values must not be merged (ie, only one value per row)
  • the field name must not contain any spaces

You can work around these limitations by creating a suitably named virtual field that contains the required logic.

For instance, the virtual field can contain a case statement to accept any number of input values (from one or more fields) and generate specific values for use in subsequent styling.

See Virtual Fields for more information.

# Fallback Style

When using the Classify button to generate styles for each unique value, QGIS automatically generates an additional fallback style for "all other values". However this function is not supported in Pozi - this style category will be ignored by Pozi.

# Opacity

Layer Styling > Layer Rendering > Opacity

Layers are initially displayed in Pozi using the opacity value you've set - the user may then adjust the opacity up or down from the initial value.


# Bubble Symbols

Pozi Enterprise Cloud customers can display their vector point layers using Pozi's popular bubble symbols.

Ensure the PC on which the QGIS project is being maintained has the Font Awesome icon library installed and configured in QGIS.

Configuring Font Awesome
../setting-up-qgis/#font-awesome

# Customise Bubble Symbol

  1. download sample SLD file
    Sample SLD file
    bubble-and-font-awesome-example.sld 5.15KB
  2. go to Layer Properties > Symbology > Style > Load Style > ... (select downloaded SLD file) > Load Style
  3. pick icon
    • select top SVG Marker item
    • in SVG browser, select Pozi SVGs
    • browse icons or use search box to find icon
    • select icon
  4. pick bubble colour
    • select middle SVG Marker item
    • click Fill Color to change colour
  5. OK

Save your project, and preview the layer in Pozi.

Note that the vertical alignment of the icon within the bubble in QGIS may differ slightly to what you see in the Pozi app. What's important is that the icon displays appropriately in Pozi, even if it looks slightly misaligned in QGIS.


# Troubleshooting

Ensure that the field used for categorisation is exposed (ie, not hidden). See above.

Pozi will display layers in a generic style (often purple) if it cannot process the style that was configured in QGIS.

Simplify the style in the QGIS project and try again. For point features, replace custom point symbols with one of the standard symbols specified above. For polygon features, replace hatch styles with semi-opaque fills or any of the supported fill styles specified above.

It's possible that the GetFeatureInfo response coordinates do not have enough precision.

Open the affected QGIS project(s), go to Project > Properties > QGIS Server > WMS Capabilities > GetFeatureInfo geometry precision, and set it to 8 decimal places.

There are some limitations for labels on vector features in Pozi:

  • labels are always placed in the centre of the feature, regardless of any placement rules
  • complex text expressions may not generate the expected text

The issue with text expressions can be easily overcome by using a virtual field for the label.

Otherwise, for complete control of how the layer appears in Pozi, consider switching the layer to WMS by disabling WFS for the layer.