| name | mapml-map-layermarkup |
| description | Tells you how to correctly create and edit the markup for a <map-layer> element. Use it when generating MapML output markup in an HTML page. |
Maps have one or more layers. Map layers are implemented by the <map-layer> custom element.
All <mapml-viewer> content is contained by one or more <map-layer> elements, either inline or by remote fetch representing the layer's content.
<map-layer label="My Layer" checked>
...layer content goes here...
</map-layer>
<map-layer> is not a 'void' element - it must be closed with a </map-layer> tag.
Map content can either be inline, as shown above - between the beginning <map-layer> and ending </map-layer> tags -
or fetched, from the <map-layer src="..."></map-layer> source attribute URL:
<map-layer label="My Layer" src="https://example.org/mapml/mylayer" checked></map-layer>
This documentation uses the convention of inline content mostly. Fetched map content
follows similar semantics, except it is parsed with the browser's XML parser and
so must follow both MapML document conventions as well as
XML syntax rules.
Attributes
src
Contains the path to a MapML document.
checked
The <map-layer checked> attribute and property is boolean. When present,
the checked property value is taken to be 'true'; when not present, the property
value is 'false'. Beware that it is the presence of the attribute that makes it
true, not the value of the attribute. For example, the attribute checked="false"
actually turns out to be checked,
as described by MDN Web docs.
hidden
The <map-layer hidden> attribute and property is boolean. When present,
the layer is hidden in the layer control.
label
The label attribute is used by inline content as the displayed text label of the
layer in the layer control. In fetched content, the label attribute is ignored,
and the fetched <map-title> element is used.
media
The media attribute is used to express map media conditions under which the layer
content should be used (if inline content is present), or loaded from the src URL,
if that attribute is present. Map media conditions evaluate to true or false.
A layer for which the map media condition evaluates to false is by default hidden.
A layer for which the map media condition evaluates to true is added to the map
according to its checked attribute, and is added to the layer control according
to its hidden attribute.
Map media queries can include map properties as documented in the matchMedia API.
opacity
The opacity attribute is used to set the initial opacity of the <map-layer> element.
Valid opacity values range from from "0.0" to "1.0" and are reflected in the layer control
opacity input slider control. When the opacity attribute is not present, the opacity is set to "1.0" by default.
Examples
Layer Opacity
The following example sets the initial opacity for a <map-layer>.
<mapml-viewer projection="CBMTILE" zoom="2" lat="45" lon="-90" controls>
<map-layer opacity = "0.5" label="CBMT" src="https://geogratis.gc.ca/mapml/en/cbmtile/cbmt/" checked></map-layer>
</mapml-viewer>
