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From: Reece Dunn (msclrhd_at_[hidden])
Date: 2004-12-22 05:57:58

Alan Gutierrez wrote:
> * Reece Dunn <msclrhd_at_[hidden]> [2004-12-22 05:22]:
>>Hi All,
>>In the "thoughts on a GUI component library" thread there have been
>>various discussions about the layout of a rectangle and come relating to
>>CSS. Note that point and size are stable.
>>The CSS3 Values and Units module
>>( defines various
>>units (e.g. inches, picas and em). This is a good basis for a GUI
>>library metric type. The type should store the values as a floating
>>point to allow things like 2.71cm and also to support platforms that
>>store coordinates as floating points (e.g. Cocoa).
>>The CSS3 relative values (em and ex) are dependant on the inherited
>>font-size property, so it is difficult to use these units as there is no
>>associated font-size property. Another issue relating to this is how to
>>resolve metric values between units that are not directly convertable. I
>>have suggested using a device::resolve method that takes metric, point,
>>size and rect types, but it may not always be possible to get access to
>>a device.
> Maybe, in this sense, a font is a "device" that can resolve?

Maybe what would be better is a css_device, since this would allow
font-size property inheriting and resolution of the em unit. It should
therefore be possible to extend/override the default resolution
behaviour for a device:

struct device
    virtual metric resolve_unit( metric v, metric::type t, orientation o );
    inline point resolve( const point & p, metric::type t )
       return point
          resolve_unit( p.x, t, orientation::x_axis ),
          resolve_unit( p.y, t, orientation::y_axis )
    // similar resolve method for size and rect

Therefore the css_device would override the resolve_unit method.


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