6.11 style-delta%

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▼ | 6 | Snip and Style Classes

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%

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

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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)

See style-delta%.

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

See style-delta%.

> 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?

See style-delta%.

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

See style-delta%.

> 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)

See style-delta%.

> method (send a-style-delta get-smoothing-on)
> → (or/c 'base 'default 'partly-smoothed 'smoothed 'unsmoothed)

See style-delta%.

> method (send a-style-delta get-style-off)
> → (or/c 'base 'normal 'italic 'slant)

See style-delta%.

> method (send a-style-delta get-style-on)
> → (or/c 'base 'normal 'italic 'slant)

See style-delta%.

> method (send a-style-delta get-transparent-text-backing-off)
> → boolean?

See style-delta%.

> method (send a-style-delta get-transparent-text-backing-on)
> → boolean?

See style-delta%.

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

See style-delta%.

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

See style-delta%.

> method (send a-style-delta get-weight-off)
> → (or/c 'base 'normal 'bold 'light)

See style-delta%.

> method (send a-style-delta get-weight-on)
> → (or/c 'base 'normal 'bold 'light)

See style-delta%.

> method (send a-style-delta set-alignment-off v) → void?
> v : (or/c 'base 'top 'center 'bottom)

See style-delta%.

> method (send a-style-delta set-alignment-on v) → void?
> v : (or/c 'base 'top 'center 'bottom)

See style-delta%.

> 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

See style-delta%.

> method (send a-style-delta set-size-in-pixels-on v) → void?
> v : any/c

See style-delta%.

> 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)

See style-delta%.

> method (send a-style-delta set-smoothing-on v) → void?
> | v |  | : |  |
> (or/c 'base 'default 'partly-smoothed
> 'smoothed 'unsmoothed)

See style-delta%.

> method (send a-style-delta set-style-off v) → void?
> v : (or/c 'base 'normal 'italic 'slant)

See style-delta%.

> method (send a-style-delta set-style-on v) → void?
> v : (or/c 'base 'normal 'italic 'slant)

See style-delta%.

> method (send a-style-delta set-transparent-text-backing-off v) → void?
> v : any/c

See style-delta%.

> method (send a-style-delta set-transparent-text-backing-on v) → void?
> v : any/c

See style-delta%.

> method (send a-style-delta set-underlined-off v) → void?
> v : any/c

See style-delta%.

> method (send a-style-delta set-underlined-on v) → void?
> v : any/c

See style-delta%.

> method (send a-style-delta set-weight-off v) → void?
> v : (or/c 'base 'normal 'bold 'light)

See style-delta%.

> method (send a-style-delta set-weight-on v) → void?
> v : (or/c 'base 'normal 'bold 'light)

See style-delta%.
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