W3C home > Mailing lists > Public > www-html@w3.org > September 1998

Re: Image Map spec is incomplete. Any Gurus?

From: Murray Macdonald <murray@mha.ca>
Date: Mon, 07 Sep 1998 23:08:23 -0700
Message-ID: <35F4C9D7.4E1CB6BD@mha.ca>
To: "www-html@w3.org" <www-html@w3.org>
C:Nicholas Owens wrote:
> 
> i have seen your message before.  part of the reason you aren't
> receiving an answer is b/c maybe nobody understands what you are
> asking.

A few people DO understand what I am asking and are agreeing that the
spec is incomplete.  Nobody (including you) has been able to actually
answer the question.

> the imagemap spec is complete.  

WRONG.  The spec does not specify legal ranges for "coordinates" nor
does it specify how many "coordinates" a polygon may have.  Can a
polygon have 43 million "coordinates" all of which are huge enough to
require 128 bit values?  

To refresh your memory here is what the HTML4.0 spec says for the <AREA>
tag:

====SNIP====

AREA attribute definitions

shape = default|rect|circle|poly [CI] 
     This attribute specifies the shape of a region. Possible values: 
          default: Specifies the entire region. 
          rect: Define a rectangular region. 
          circle: Define a circular region. 
          poly: Define a polygonal region. 
coords = coordinates [CN] 
     This attribute specifies the position a shape on the screen. The
number and order of values depends on the shape being defined. Possible
combinations: 
          rect: left-x, top-y, right-x, bottom-y. 
          circle: center-x, center-y, radius. Note. When the radius
value is a percentage value, user agents should calculate the final
radius value based on the
          associated object's width and height. The radius should be the
smaller value of the two. 
          poly: x1, y1, x2, y2, ..., xN, yN. 

     Coordinates are relative to the top, left corner of the object. All
values are lengths. All values are separated by commas. 
nohref [CI] 
     When set, this boolean attribute specifies that a region has no
associated link. 

====SNIP====

If you follow up the definition of "lengths" it tells you there are
pixel or percentage definitions of size.  Again this is ambiguous.

> you don't need to specify any negative coordinates, or maybe i'm not 
> understanding your question.  you can always specify an area 'pixel by 
> 'pixel' if it is stated as a polygon. 

Its not a matter of what I need to do, its a matter of the specification
needing to be specific.  Although it is true that a polygon could
represent the visible portion of any circle area (or of a more complex
polygon) it seems stupid to have to calculate a polygon that plots the
visible points of a more complex object just to accommodate an under
developed specification.

Presumably I can create circles centered on the map that have a radius
larger than the map.  What if the center of a circle area was located at
1,1 and the radius was 100.  Even though some of this circle's area was
off the page, you would expect this to work, right?  What if the
circle's center was moved 10 pixels to the left?  Then the circle would
be centered at a pixel location of -9,1.  Are you suggesting that at
this point it should stop being a circle and be replotted as a polygon?
This seems silly and the html 4.0 specification does not state this.  It
is simply ambiguous.

> trust me, there is no need for neg. coordinates.

trust me.  the spec needs to be "SPECIFIC" in this regard or it is not a
complete SPEC, and negative values have practical uses.  Who are the
people who actually resolve these issues?  How do I get a definitive
answer from the gods?

--M.
Received on Tuesday, 8 September 1998 02:08:17 GMT

This archive was generated by hypermail 2.2.0+W3C-0.50 : Tuesday, 27 March 2012 18:15:37 GMT