[reportlab-users] SVG font-size values lack units (invalid CSS)

[Robin Becker]

Peter wrote:
........

> 

> The images don't look identical to those from the PNG output from

> renderPM (the fonts sizes differ a little), but this does look pretty

> close and it now works on all the browsers I have tested.

> 

well I just looked at the definitions currently being talked about for svg 1.1 
and font-size appears here

http://www.w3.org/TR/SVG11/propidx.html

there the allowed value types for font-size are

  <absolute-size>  |  <relative-size>  | <length>  |  <percentage>  |  inherit


and following the link for length gives this definition



> <length>: A length is a distance measurement. The format of a <length> is a <number>  optionally followed immediately by a unit identifier. (Note that the specification of a <number> is different for property  values than for XML attribute values.)

> If the <length> is expressed as a value without a unit identifier (e.g., 48), then the <length> represents a distance in the current user coordinate system.

> If one of the unit identifiers is provided (e.g., 12mm), then the <length> is processed according to the description in Units.

> Percentage values (e.g., 10%) depend on the particular property or attribute to which the percentage value has been assigned. Two common cases are: (a) when a percentage value represents a percent of the viewport (refer to the section that discusses Units in general), and (b) when a percentage value represents a percent of the bounding box on a given object (refer to the section that describes Object bounding box units).

> Within the SVG DOM, a <length> is represented as an SVGLength or an SVGAnimatedLength.




I take the definition to allow font-size to be allowed not to be followed by a unit.

That said it's not at all obvious how these lengths should be properly interpreted.

For PDF the default coordinate system is certainly defined in point units ie 
1=1pt. For our bitmaps we decided to make 1 pixel == 1point, but I believe you 
can specify a dpi value. For SVG I'm not sure. According to

http://www.w3.org/TR/SVG11/coords.html#InitialCoordinateSystem

the SVG User agent (browser?) is supposed to set up the default view port and 
the default coordinate system consistently so that 1unit=1pixel. That should be 
consistent with our current usage. However, looking at the standard examples 
it's obvious that SVG is not obeying these rules. I believe the default unit 
should be pixels.

Has anyone else got any better ideas?
-- 
Robin Becker