در حال ویرایش الگو:Px/توضیحات (بخش)

=== Default values ===

It used to be a bit tricky to handle empty but defined image size values in a template, since the MediaWiki pipetrick doesn't return the default value for empty parameters. That is, <code>
<nowiki>{{{width|250px}}}</nowiki> </code> does not return "250px" if the template was called like this: <code>
<nowiki>{{template|width=}}</nowiki> </code>

The usual workaround was to do like this:
:<code>
<nowiki>{{#if:{{{width|}}}|{{{width}}}|250px}}</nowiki> </code>

When at the same time handling the "pxpx" bug this became even more messy code:
:<code>
<nowiki>[[Image:{{{image}}} | {{#if:{{{width|}}}|{{px|{{{width}}}}}|250px}} ]]</nowiki> </code>

To simplify the coding, {{tl|px}} allows for an optional default value to be defined allowing for the following:

:<code>
<nowiki>[[Image:{{{image}}} | {{px|{{{width|}}}|250}} ]]</nowiki> </code>

'''Note!''' The parameters to {{tlf|px}} must use the pipe "|", like this: <code>
<nowiki>{{{width|}}}</nowiki> </code>. Or else {{tlf|px}} will be fed and return the string "<code>
<nowiki>{{{width}}}</nowiki> </code>" if ''width'' was not defined.