* Reece Dunn <msclrhd@hotmail.com> [2004-12-22 06:42]:
Alan Gutierrez wrote:
* Reece Dunn <msclrhd@hotmail.com> [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 (http://www.w3.org/TR/2001/WD-css3-values-20010713/) 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.
Would the css_device be implemented as a device decorator? -- Alan Gutierrez - alan@engrm.com