On this page:
make-object
collapse
copy
equal?
get-alignment-off
get-alignment-on
get-background-add
get-background-mult
get-face
get-family
get-foreground-add
get-foreground-mult
get-size-add
get-size-in-pixels-off
get-size-in-pixels-on
get-size-mult
get-smoothing-off
get-smoothing-on
get-style-off
get-style-on
get-transparent-text-backing-off
get-transparent-text-backing-on
get-underlined-off
get-underlined-on
get-weight-off
get-weight-on
set-alignment-off
set-alignment-on
set-delta
set-delta-background
set-delta-face
set-delta-foreground
set-face
set-family
set-size-add
set-size-in-pixels-off
set-size-in-pixels-on
set-size-mult
set-smoothing-off
set-smoothing-on
set-style-off
set-style-on
set-transparent-text-backing-off
set-transparent-text-backing-on
set-underlined-off
set-underlined-on
set-weight-off
set-weight-on

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:

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:

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 : byte?
(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)

method

(send a-style-delta get-alignment-on)

  (or/c 'base 'top 'center 'bottom)

method

(send a-style-delta get-background-add)

  (is-a?/c add-color<%>)
Gets the object additive color shift for the background (applied after the multiplicative factor). Call this add-color<%> object’s methods to change the style delta’s additive background color shift.

method

(send a-style-delta get-background-mult)

  (is-a?/c mult-color<%>)
Gets the multiplicative color shift for the background (applied before the additive factor). Call this mult-color<%> object’s methods to change the style delta’s multiplicative background color shift.

method

(send a-style-delta get-face)  (or/c string? #f)

Gets the delta’s font face string. If this string is #f and the family is 'base when the delta is applied to a style, the style’s face and family are not changed. However, if the face string is #f and the family is not 'base, then the style’s face is changed to #f.

See also get-family.

method

(send a-style-delta get-family)

  
(or/c 'base 'default 'decorative 'roman 'script
      'swiss 'modern 'symbol 'system)
Returns the delta’s font family. The possible values are
  • 'base no change to family

  • 'default

  • 'decorative

  • 'roman

  • 'script

  • 'swiss

  • 'modern (fixed width)

  • 'symbol (Greek letters)

  • 'system (used to draw control labels)

See also get-face.

method

(send a-style-delta get-foreground-add)

  (is-a?/c add-color<%>)
Gets the additive color shift for the foreground (applied after the multiplicative factor). Call this add-color<%> object’s methods to change the style delta’s additive foreground color shift.

method

(send a-style-delta get-foreground-mult)

  (is-a?/c mult-color<%>)
Gets the multiplicative color shift for the foreground (applied before the additive factor). Call this mult-color<%> object’s methods to change the style delta’s multiplicative foreground color shift.

method

(send a-style-delta get-size-add)  byte?

Gets the additive font size shift (applied after the multiplicative factor).

method

(send a-style-delta get-size-in-pixels-off)  boolean?

method

(send a-style-delta get-size-in-pixels-on)  boolean?

method

(send a-style-delta get-size-mult)  real?

Gets the multiplicative font size shift (applied before the additive factor).

method

(send a-style-delta get-smoothing-off)

  (or/c 'base 'default 'partly-smoothed 'smoothed 'unsmoothed)

method

(send a-style-delta get-smoothing-on)

  (or/c 'base 'default 'partly-smoothed 'smoothed 'unsmoothed)

method

(send a-style-delta get-style-off)

  (or/c 'base 'normal 'italic 'slant)

method

(send a-style-delta get-style-on)

  (or/c 'base 'normal 'italic 'slant)

method

(send a-style-delta get-transparent-text-backing-off)

  boolean?

method

(send a-style-delta get-transparent-text-backing-on)

  boolean?

method

(send a-style-delta get-underlined-off)  boolean?

method

(send a-style-delta get-underlined-on)  boolean?

method

(send a-style-delta get-weight-off)

  (or/c 'base 'normal 'bold 'light)

method

(send a-style-delta get-weight-on)

  (or/c 'base 'normal 'bold 'light)

method

(send a-style-delta set-alignment-off v)  void?

  v : (or/c 'base 'top 'center 'bottom)

method

(send a-style-delta set-alignment-on v)  void?

  v : (or/c 'base 'top 'center 'bottom)

method

(send a-style-delta set-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
(send a-style-delta set-delta change-command 
  param) 
  (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)
  param : symbol
(send a-style-delta set-delta change-command 
  param) 
  (is-a?/c style-delta%)
  change-command : 
(or/c 'change-size
      'change-bigger
      'change-smaller)
  param : byte?
(send a-style-delta set-delta change-command 
  on?) 
  (is-a?/c style-delta%)
  change-command : 
(or/c 'change-underline
      'change-size-in-pixels)
  on? : any/c
Configures the delta with high-level specifications. The return value is the delta itself.

Except for 'change-nothing and 'change-normal, the command only changes part of the delta. Thus, applying 'change-bold and then 'change-italic sets the delta for both the style and weight change.

The change-command argument specifies how the delta is changed; the possible values are:
  • 'change-nothing reset all changes

  • 'change-normal turn off all styles and resizings

  • 'change-toggle-underline underline regions that are currently not underlined, and vice versa

  • 'change-toggle-size-in-pixels interpret sizes in pixels for regions that are currently interpreted in points, and vice versa

  • 'change-normal-color change the foreground and background to black and white, respectively

  • 'change-italic change the style of the font to italic

  • 'change-bold change the weight of the font to bold

  • 'change-family change the font family (param is a family; see font%); see also get-family

  • 'change-style change the style of the font (param is a style; see font%)

  • 'change-toggle-style toggle the style of the font (param is a style; see font%)

  • 'change-weight change the weight of the font (param is a weight; see font%)

  • 'change-toggle-weight toggle the weight of the font (param is a weight; see font%)

  • 'change-smoothing change the smoothing of the font (param is a smoothing; see font%)

  • 'change-toggle-smoothing toggle the smoothing of the font (param is a smoothing; see font%)

  • 'change-alignment change the alignment (param is an alignment; see style-delta%)

  • 'change-size change the size to an absolute value (param is a size)

  • 'change-bigger make the text larger (param is an additive amount)

  • 'change-smaller make the text smaller (param is an additive amount)

  • 'change-underline set the underline status to either underlined or plain

  • 'change-size-in-pixels set the size interpretation to pixels or points

method

(send a-style-delta set-delta-background name)

  (is-a?/c style-delta%)
  name : string?
(send a-style-delta set-delta-background color)
  (is-a?/c style-delta%)
  color : (is-a?/c color%)
Makes the delta encode a background color change to match the absolute color given; that is, it sets the multiplicative factors to 0.0 in the result of get-background-mult, and it sets the additive values in the result of get-background-add to the specified color’s values. In addition, it also disables transparent text backing by setting transparent-text-backing-on to #f and transparent-text-backing-off to #t. The return value of the method is the delta itself.

For the case that a string color name is supplied, see color-database<%>.

method

(send a-style-delta set-delta-face name 
  [family]) 
  (is-a?/c style-delta%)
  name : string?
  family : 
(or/c 'base 'default 'decorative 'roman
      'script 'swiss 'modern 'symbol 'system)
   = 'default
Like set-face, but sets the family at the same time.

The return value is a-style-delta.

method

(send a-style-delta set-delta-foreground name)

  (is-a?/c style-delta%)
  name : string?
(send a-style-delta set-delta-foreground color)
  (is-a?/c style-delta%)
  color : (is-a?/c color%)
Makes the delta encode a foreground color change to match the absolute color given; that is, it sets the multiplicative factors to 0.0 in the result of get-foreground-mult, and it sets the additive values in the result of get-foreground-add to the specified color’s values. The return value of the method is the delta itself.

For the case that a string color name is supplied, see color-database<%>.

method

(send a-style-delta set-face v)  void?

  v : (or/c string? #f)
See get-face. See also set-delta-face.

method

(send a-style-delta set-family v)  void?

  v : 
(or/c 'base 'default 'decorative 'roman 'script
      'swiss 'modern 'symbol 'system)
Sets the delta’s font family. See get-family.

method

(send a-style-delta set-size-add v)  void?

  v : byte?
Sets the additive font size shift (applied after the multiplicative factor).

method

(send a-style-delta set-size-in-pixels-off v)  void?

  v : any/c

method

(send a-style-delta set-size-in-pixels-on v)  void?

  v : any/c

method

(send a-style-delta set-size-mult v)  void?

  v : real?
Sets the multiplicative font size shift (applied before the additive factor).

method

(send a-style-delta set-smoothing-off v)  void?

  v : 
(or/c 'base 'default 'partly-smoothed
      'smoothed 'unsmoothed)

method

(send a-style-delta set-smoothing-on v)  void?

  v : 
(or/c 'base 'default 'partly-smoothed
      'smoothed 'unsmoothed)

method

(send a-style-delta set-style-off v)  void?

  v : (or/c 'base 'normal 'italic 'slant)

method

(send a-style-delta set-style-on v)  void?

  v : (or/c 'base 'normal 'italic 'slant)

method

(send a-style-delta set-transparent-text-backing-off v)  void?

  v : any/c

method

(send a-style-delta set-transparent-text-backing-on v)  void?

  v : any/c

method

(send a-style-delta set-underlined-off v)  void?

  v : any/c

method

(send a-style-delta set-underlined-on v)  void?

  v : any/c

method

(send a-style-delta set-weight-off v)  void?

  v : (or/c 'base 'normal 'bold 'light)

method

(send a-style-delta set-weight-on v)  void?

  v : (or/c 'base 'normal 'bold 'light)