[Drawkit] changing font

[Graham Cox]

On 27 Jun 2008, at 11:28 am, James Maxwell wrote:

> Okay, I don't see +drawableShapeWithBezierPath: but there is  
> +drawableShapeWithPath:, which I'm assuming is what you mean. I'll  
> give that a try later. I was basically hand-building my path from  
> the glyph, using -appendBezierPathWithGlyph:, then using -setPath:  
> from DK, but as I say, that leaves me to mess around with the  
> bounds... I'll try the convenience method a little later.


Yes, it's + drawableShapeWithPath: in beta 3, the name got/will be  
changed ;-)

using setPath: will be a pain in the neck, as you have found. I'll  
explain why, for the benefit of the list.

Shapes store their paths bounded by a square 1.0 units on each side,  
centred at the origin (i.e. they extend from -0.5 to +0.5 in each  
dimension). The path is then transformed to the real size, position  
and angle on the screen. The -setPath: method expects a path in this  
form, what I call a "canonical path". If it's not, you'll get  
incorrect results. In fact the latest code doesn't even let you pass  
an arbitrary path, it will assert if the bounds is non-canonical. The  
use of a canonical path makes the various transforms to and from the  
screen much easier to handle.

That isn't terribly convenient in many cases, so there is another  
method -adoptPath: which works with any path. It inversely transforms  
the path into canonical form for storage. So by passing your glyph  
path to adoptPath: you should eliminate all the mucking about needed  
to "fit" the glyph to the bounds. The convenience constructor does the  
same.

By the way I know the dearth of documentation isn't helping, but the  
comment headers for these methods does actually explain this. FWIW, if  
you use a method, you should probably read any notes for it in the  
code just in case there's something unexpected hidden there, as there  
is in this case. While I try to name things as well as I can,  
sometimes assuming behaviour from the name alone is going to get you  
into trouble. This is also why names get changed, which is in itself  
often a pain in the neck, I know.


cheers, Graham