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function layer_property takes a layer name/id and a property (eg 'crs') and returns the matching value. This approach is more flexible than having all these values as variables, since it allows retrieval of properties of a layer from contexts which aren't layer-aware (eg a composer label showing the metadata of a layer).
35 lines
1.4 KiB
Plaintext
35 lines
1.4 KiB
Plaintext
<h3>layer_property function</h3>
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Returns a matching layer property or metadata value.
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<h4>Syntax</h4>
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<pre>layer_property(layer,property)</pre>
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<h4>Arguments</h4>
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layer → a string, representing either a layer name or layer ID<br />
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property → a string corresponding to the property to return. Valid options are:<br />
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<ul>
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<li>name: layer name</li>
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<li>id: layer ID</li>
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<li>title: metadata title string</li>
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<li>abstract: metadata abstract string</li>
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<li>keywords: metadata keywords</li>
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<li>data_url: metadata URL</li>
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<li>attribution: metadata attribution string</li>
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<li>attribution_url: metadata attribution URL</li>
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<li>source: layer source</li>
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<li>min_scale: minimum display scale for layer</li>
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<li>max_scale: maximum display scale for layer</li>
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<li>crs: layer CRS</li>
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<li>crs_definition: layer CRS full definition</li>
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<li>extent: layer extent (as a geometry object)</li>
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<li>type: layer type, eg Vector or Raster</li>
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<li>storage_type: storage format (vector layers only)</li>
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<li>geometry_type: geometry type, eg Point (vector layers only)</li>
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<li>feature_count: approximate feature count for layer (vector layers only)</li>
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</ul>
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<h4>Example</h4>
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<pre> layer_property('streets','title') → 'Basemap Streets'</pre><br />
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<pre> layer_property('airports','feature_count') → 120</pre><br />
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<pre> layer_property('landsat','crs') →'EPSG:4326'</pre>
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