UXCharAttr

UXCharAttr is the style of a single character: four fields, and the equality test that makes runs possible.

#use <UXKit>            // or #import "UXAttributedString.xc"

Overview

class UXCharAttr : Object {
    bool bold;
    bool italic;
    i32  pen;      // colour pen; 1 = ink, the default
    i16  size;     // point size; 0 = the view's default
}

UXAttributedString keeps one of these per character. This costs memory, and it makes setting and querying a style trivially correct: there is no run list to split, merge or keep in order.

The runs a drawing pass wants are derived on demand by coalescing neighbours that compare equal.

`sameAs` is what makes a run

bool sameAs(UXCharAttr* o)

Compares all four fields by value. This is the coalescing rule: two adjacent characters belong to the same run when their attributes are sameAs each other.

Adding a field to this class therefore changes what counts as a run, in one place. If you add a field and do not compare it in sameAs, spans that should draw differently are silently merged. Change the two together.

`dup` is what keeps runs independent

UXCharAttr* dup(void)

A run carries a copy of the attributes, not a pointer into the string’s per-character array. A run you hold stays valid and unchanged if the string is restyled underneath you.

Writing to a run’s attr changes nothing in the string. To restyle, use the string’s setBold/setItalic/setColor/setSize.

The defaults are meaningful

pen  = 1     // ink
size = 0     // "whatever the view is using"

size == 0 means unset, not a zero-point font. The drawing code falls back to the view’s font. This lets you colour a span without fixing its size, which matters when the same text is drawn at two zoom levels.

pen == 1 is ink. Pen 0 is the background in the GEM model these pens come from, so a default-constructed attribute is visible.

Fields

bold

bool bold

italic

bool italic

The two combine freely. A character can be both, which is a third distinct run style.

pen

i32 pen         // 1 = ink

A colour pen index, not an RGB value. The indirection lets the same model drive a 16-colour GEM palette and a true-colour backend.

size

i16 size        // 0 = inherit

Point size, or 0 to inherit.

Conforms to

Inherits Object