Is filter an internal variable?

#1 
<<filter>>
  • Save, it shows

  -webkit-filter: ;
     -moz-filter: ;
          filter: ;

Why? Is filter an internal variable?

You get strange output when you write

<$list filter=<<filter>> >

</$list>

output

filter:
;

it is because filter seems to be a variable why?

#2

It is used in the core stylesheets which by nessasity are global, but you can safely ignore it and simply set it again, use it as a parameter name etc… but don’t assume its empty unless you make it empty.

Perhaps some of the developers could fix it?

#3

Hi @atronoush the core does indeed define a macro called “filter” for generating CSS filter properties (see the definition here). Therefore it is not recommended to create a global with the name “filter” because it will prevent those CSS filters from working correctly.

#4

Thank you Jeremy!
I have heard/read from official doc, the TW variables are prefixed with tv-
So, it seems there are exceptions.

#5

If the macro is an internal one and should not be called outside the host tiddler, does it make sense to make it nested macro/procedure?

#6

Macros (and procedures and functions) are actually variables but unfortunately the core global macros do not use the tv- prefix.

It is not the case that this is purely an internal macro. It’s part of the suite of CSS macros that the core uses, and that 3rd party stylesheets can also use.

#7

Thank you! I noted this and will avoid using filter as variable.

#8

To be clear, it is using filter as a global variable/macro/procedure/function that you need to avoid, it’s not a problem to have a regular variable called “filter”.