[NTG-context] Attributes

Hans Hagen pragma at wxs.nl
Wed Apr 23 11:00:27 CEST 2014


On 4/22/2014 8:10 PM, Stéphane Goujet wrote:
> On Tue, 22 Apr 2014, Hans Hagen wrote:
>
>> On 4/20/2014 3:14 PM, Stéphane Goujet wrote:
>>>     I would like to know what is the recommended way to use
>>> attributes in
>>>  Context.
>>>  What is the Context way to declare and set attributes? Is it something
>>>  like this?
>>>  \defineattribute[myattr]
>>>  \dosetattribute{myattr}{1}
>>>
>>>     And how do I then access them from Lua? Should it look like
>>>  has_attribute(mynode, attributes.myattr)
>>>     or
>>>  has_attribute(mynode, attributes.xxxxx("myattr"))
>>>     or something else?
>>
>> attributes.names[...]
>> attributes.numbers[...]
>
>    Please have a look at my example (it is a bit long because it shows
> various possibilities) and its result.
>     When I have not yet done a \defineattribute[myattr], node.has_attribute
> returns 0 when I thought it should return nil.
>    When I do \defineattribute[...], every attribute seems to get the
> same number (1024), but now node.has_attribute returns nil ...

change this is syst-ini.mkiv:

\normalprotected\def\newattribute{\syst_basics_allocate\c_syst_last_allocated_attribute\attribute\attributedef\c_syst_max_allocated_register}


> =========================
> Example
> =========================
> \starttext
>
> \startluacode
>      mycallback=function(head)
>          if attributes.names==nil then
>              print "No attribute names at all"
>          end
>          if attributes.numbers==nil then
>              print "No attribute numbers at all"
>          end
>          for mynode in node.traverse_id(node.id("glyph"), head) do
>              if string.match("0ABCDEabcdefg",
> unicode.utf8.char(mynode.char)) then
>                  print ("Glyph = "..unicode.utf8.char(mynode.char))
>                  if attributes.numbers["myattr"]==nil then
>                      print "No attribute number for myattr"
>                  else
>                      print ("myattr : number =
> "..(attributes.numbers["myattr"]))
>                  end
>                  if attributes.numbers["myattrb"]==nil then
>                      print "No attribute number for myattrb"
>                  else
>                      print ("myattrb : number =
> "..(attributes.numbers["myattrb"]))
>                  end
>                  if node.has_attribute(mynode,
> attributes.numbers["myattr"]) then
>                      print ("Attribute myattr =
> "..(node.has_attribute(mynode, attributes.numbers["myattr"])))
>                  else
>                      print "No attribute myattr"
>                  end
>                  if node.has_attribute(mynode,
> attributes.numbers["myattrb"]) then
>                      print ("Attribute myattrb =
> "..(node.has_attribute(mynode, attributes.numbers["myattrb"])))
>                  else
>                      print "No attribute myattrb"
>                  end
>                  if node.has_attribute(mynode, 111) then
>                      print ("Attribute 111 =
> "..(node.has_attribute(mynode, 111)))
>                  else
>                      print "No attribute 111"
>                  end
>              end
>          end
>          return head
>      end
>
>      nodes.tasks.appendaction("processors", "before", "mycallback")
> \stopluacode
>
> 0
>
> \attribute111=-1
> A
>
> \attribute111=200
> B
>
> \attribute111=202
> C
>
> \attribute111=-1
> D
>
> \attribute111=-"7FFFFFFF
> E
>
> \defineattribute[myattr]
> \defineattribute[myattrb]
> a
>
> \doresetattribute{myattr}
> b
>
> \dosetattribute{myattr}{500}
> c
>
> \dosetattribute{myattr}{502}
> d
>
> \doresetattribute{myattr}
> e
>
>
> \stoptext
> ======================
>
>
> ======================
> Result :
> ======================
> Glyph = 0
> No attribute number for myattr
> No attribute number for myattrb
> Attribute myattr = 0
> Attribute myattrb = 0
> No attribute 111
> Glyph = A
> No attribute number for myattr
> No attribute number for myattrb
> Attribute myattr = 0
> Attribute myattrb = 0
> Attribute 111 = -1
> Glyph = B
> No attribute number for myattr
> No attribute number for myattrb
> Attribute myattr = 0
> Attribute myattrb = 0
> Attribute 111 = 200
> Glyph = C
> No attribute number for myattr
> No attribute number for myattrb
> Attribute myattr = 0
> Attribute myattrb = 0
> Attribute 111 = 202
> Glyph = D
> No attribute number for myattr
> No attribute number for myattrb
> Attribute myattr = 0
> Attribute myattrb = 0
> Attribute 111 = -1
> Glyph = E
> No attribute number for myattr
> No attribute number for myattrb
> Attribute myattr = 0
> Attribute myattrb = 0
> No attribute 111
> Glyph = a
> myattr : number = 1024
> myattrb : number = 1024
> No attribute myattr
> No attribute myattrb
> No attribute 111
> Glyph = b
> myattr : number = 1024
> myattrb : number = 1024
> No attribute myattr
> No attribute myattrb
> No attribute 111
> Glyph = c
> myattr : number = 1024
> myattrb : number = 1024
> No attribute myattr
> No attribute myattrb
> No attribute 111
> Glyph = d
> myattr : number = 1024
> myattrb : number = 1024
> No attribute myattr
> No attribute myattrb
> No attribute 111
> Glyph = e
> myattr : number = 1024
> myattrb : number = 1024
> No attribute myattr
> No attribute myattrb
> No attribute 111
> ======================
>
> Goodbye,
>    Stéphane.
>
>
> ___________________________________________________________________________________
> If your question is of interest to others as well, please add an entry to the Wiki!
>
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> ___________________________________________________________________________________
>


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