6.11 style-delta%

class
style-delta% : class?

superclass: object%

A style-delta% object encapsulates a style change. The changes expressible by a delta include:

changing the font family
changing the font face
changing the font size to a new value
enlarging the font by an additive amount
enlarging the font by a multiplicative amount, etc.
changing the font style (normal, italic, or slant)
toggling the font style
changing the font to italic if it is currently slant, etc.
changing the font weight, etc.
changing the underline, etc.
changing the vertical alignment, etc.
changing the foreground color
dimming or brightening the foreground color, etc.
changing the background color, etc.
changing text backing transparency

The set-delta method is convenient for most style delta settings; it takes a high-level delta specification and sets the internal delta information.

To take full advantage of a style delta, it is necessary to understand the internal on/off settings that can be manipulated through methods such as set-weight-on. For example, the font weight change is specified through the weight-on and weight-off internal settings. Roughly, weight-on turns on a weight setting when it is not present and weight-off turns off a weight setting when it is present. These two interact precisely in the following way:

If both weight-on and weight-off are set to 'base, then the font weight is not changed.
If weight-on is not 'base, then the weight is set to weight-on.
If weight-off is not 'base, then the weight will be set back to 'normal when the base style has the weight weight-off.
If both weight-on and weight-off are set to the same value, then the weight is toggled with respect to that value: if the base style has the weight weight-on, then weight is changed to 'normal; if the base style has a different weight, it is changed to weight-on.
If both weight-on and weight-off are set, but to different values, then the weight is changed to weight-on only when the base style has the weight weight-off.

Font styles, smoothing, underlining, and alignment work in an analogous manner.

The possible values for alignment-on and alignment-off are:

'base
'top
'center
'bottom

The possible values for style-on and style-off are:

'base
'normal
'italic
'slant

The possible values for smoothing-on and smoothing-off are:

'base
'default
'partly-smoothed
'smoothed
'unsmoothed

The possible values for underlined-on and underlined-off are:

#f (acts like 'base)
#t

The possible values for size-in-pixels-on and size-in-pixels-off are:

#f (acts like 'base)
#t

The possible values for transparent-text-backing-on and transparent-text-backing-off are:

#f (acts like 'base)
#t

The possible values for weight-on and weight-off are:

'base
'normal
'bold
'light

The family and face settings in a style delta are interdependent:

When a delta’s face is #f and its family is 'base, then neither the face nor family are modified by the delta.
When a delta’s face is a string and its family is 'base, then only face is modified by the delta.
When a delta’s family is not 'base, then both the face and family are modified by the delta. If the delta’s face is #f, then applying the delta sets a style’s face to #f, so that the family setting prevails in choosing a font.

constructor
(make-object style-delta% [change-command])
→ (is-a?/c style-delta%)
   change-command :
(or/c 'change-nothing
      'change-normal
      'change-toggle-underline
      'change-toggle-size-in-pixels
      'change-normal-color
      'change-bold)
= 'change-nothing
(make-object style-delta% change-command v)
→ (is-a?/c style-delta%)
   change-command :
(or/c 'change-family
      'change-style
      'change-toggle-style
      'change-weight
      'change-toggle-weight
      'change-smoothing
      'change-toggle-smoothing
      'change-alignment)
  v : symbol
(make-object style-delta% change-command v)
→ (is-a?/c style-delta%)
   change-command :
(or/c 'change-size
      'change-bigger
      'change-smaller)
  v : exact-integer?
(make-object style-delta% change-command v)
→ (is-a?/c style-delta%)
   change-command :
(or/c 'change-underline
      'change-size-in-pixels)
  v : any/c

The initialization arguments are passed on to set-delta.

method
(send a-style-delta collapse delta) → boolean?
delta : (is-a?/c style-delta%)

Tries to collapse into a single delta the changes that would be made by applying this delta after a given delta. If the return value is #f, then it is impossible to perform the collapse. Otherwise, the return value is #t and this delta will contain the collapsed change specification.

method
(send a-style-delta copy delta) → void?
delta : (is-a?/c style-delta%)

Copies the given style delta’s settings into this one.

method
(send a-style-delta equal? delta) → boolean?
delta : (is-a?/c style-delta%)

Returns #t if the given delta is equivalent to this one in all contexts or #f otherwise.

method
(send a-style-delta get-alignment-off)
→ (or/c 'base 'top 'center 'bottom)

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2	Widget Gallery
3	Windowing Classes
4	Windowing Functions
5	Editors
6	Snip and Style Classes
7	Editor Classes
8	Editor Functions
9	WXME Decoding
10	Preferences
11	Dynamic Loading
12	Startup Actions
13	Init Libraries
14	Platform Dependencies
	Index

6.1	add-color<%>
6.2	image-snip%
6.3	mult-color<%>
6.4	readable-snip<%>
6.5	snip%
6.6	snip-admin%
6.7	snip-class%
6.8	snip-class-list<%>
6.9	string-snip%
6.10	style<%>
6.11	style-delta%
6.12	style-list%
6.13	tab-snip%