▼ |  | Unstable GUI: May Change Without Warning

1 | Notify-boxes
2 | Preferences
3 | Pict Utilities
4 | Slideshow Presentations
5 | Progressive Picts and Slides
6 | Snip Utilities
7 | Scribble Utilities

► | 5 | Progressive Picts and Slides

5.1 | Progressive Picts
5.2 | Progressive Slides

On this page:

5.1`` Progressive Picts
ppict-do
ppict-do*
ppict-do-state
ppict?
ppict-go
ppict-add
ppict-add*
placer?
refpoint-placer?
coord
grid
cascade
tile
at-find-pict
merge-refpoints
5.2`` Progressive Slides
pslide
pslide-base-pict
pslide-default-placer

top ← prev up next →

### 5`` Progressive Picts and Slides

Ryan Culpepper <ryanc@racket-lang.org>

This library is unstable; compatibility will not be maintained. See Unstable: May Change Without Warning for more information.

#### 5.1`` Progressive Picts

(require unstable/gui/ppict) | package: unstable-lib

A progressive pict or “ppict” is a kind of pict that has an associated “pict placer,” which generally represents a position and alignment. New picts can be placed on the progressive pict by calling ppict-add, and the placer can be updated by calling ppict-go. The ppict-do form provides a compact notation for sequences of those two operations.

> syntax (ppict-do base-expr ppict-do-fragment ...)
> syntax (ppict-do* base-expr ppic-do-fragment ...)
> ppict-do-fragment |  | = |  | #:go placer-expr
> |  | | |  | #:set pict-expr
> |  | | |  | #:next
> |  | | |  | #:alt (ppict-do-fragment ...)
> |  | | |  | elem-expr
> > | base-expr |  | : |  | pict?
> > | placer-expr |  | : |  | placer?
> > | pict-expr |  | : |  | pict?
> > | elem-expr |  | : |  | (or/c pict? real? #f)

Builds a pict (and optionally a list of intermediate picts) progressively. The ppict-do form returns only the final pict; any uses of #:next are ignored. The ppict-do* form returns two values: the final pict and a list of all partial picts emitted due to #:next (the final pict is not included).

A #:go fragment changes the current placer. A #:set fragment replaces the current pict state altogether with a new computed pict. A #:next fragment saves a pict including only the contents emitted so far (but whose alignment takes into account picts yet to come). A #:alt fragment saves the current pict state, executes the sub-sequence that follows, saves the result (as if the sub-sequence ended with #:next), then restores the saved pict state before continuing.

The elem-exprs are interpreted by the current placer. A numeric elem-expr usually represents a spacing change, but some placers do not support them. A spacing change only affects added picts up until the next placer is installed; when a new placer is installed, the spacing is reset, usually to 0.

The ppict-do-state form tracks the current state of the pict. It is updated before a #:go or #:set fragment or before a sequence of elem-exprs. It is not updated in the middle of a chain of elem-exprs, however.

Examples:
> > (define base
> (ppict-do (colorize (rectangle 200 200) "gray")
> #:go (coord 1/2 1/2 'cc)
> (colorize (hline 200 1) "gray")
> #:go (coord 1/2 1/2 'cc)
> (colorize (vline 1 200) "gray")))
> > base

The use of ppict-do in the defnition of base above is equivalent to

> (let* ([pp (colorize (rectangle 200 200) "gray")]
> [pp (ppict-go pp (coord 1/2 1/2 'cc))]
> [pp (ppict-add pp (colorize (hline 200 1) "gray"))]
> [pp (ppict-go pp (coord 1/2 1/2 'cc))]
> [pp (ppict-add pp (colorize (vline 1 200) "gray"))])
> pp)

Examples:
> > (define circles-down-1
> (ppict-do base
> #:go (grid 2 2 2 1 'ct)
> 10
> (circle 20)
> (circle 20)
> 30
> (circle 20)))
> > circles-down-1
> > (define circles-down-2
> (ppict-do circles-down-1
> (colorize (circle 20) "red")
> 40
> (colorize (circle 20) "red")))
> > (inset circles-down-2 20) ; draws outside its bounding box
> > (inset (clip circles-down-2) 20)
> > (ppict-do base
> #:go (coord 0 0 'lt)
> (tag-pict (circle 20) 'circA)
> #:go (coord 1 1 'rb)
> (tag-pict (circle 20) 'circB)
> #:set (let ([p ppict-do-state])
> (pin-arrow-line 10 p
> (find-tag p 'circA) rb-find
> (find-tag p 'circB) lt-find)))
> > (let-values ([(final intermediates)
> (ppict-do* base
> #:go (coord 1/4 1/2 'cb)
> (text "shapes:")
> #:go (coord 1/2 1/2 'lb)
> #:alt [(circle 20)]
> #:alt [(rectangle 20 20)]
> (text "and more!"))])
> (append intermediates (list final)))
> '( )

More examples of ppict-do are scattered throughout this section.

> syntax ppict-do-state

Tracks the current state of a ppict-do or ppict-do* form.

> procedure (ppict? x) → boolean?
> x : any/c

Returns #t if x is a progressive pict, #f otherwise.

> procedure (ppict-go p pl) → ppict?
> p : pict?
> pl : placer?

Creates a progressive pict with the given base pict p and the placer pl.

> procedure (ppict-add pp elem ...) → pict?
> pp : ppict?
> elem : (or/c pict? real? #f 'next)
> > procedure
> > (ppict-add* pp elem ...) |  | → |  |
> > pict? |  | (listof pict?)
> pp : ppict?
> elem : (or/c pict? real? #f 'next)

Creates a new pict by adding each elem pict on top of pp according to pp’s placer. The result pict may or may not be a progressive pict, depending on the placer used. The ppict-add function only the final pict; any occurrences of 'next are ignored. The ppict-add* function returns two values: the final pict and a list of all partial picts emitted due to 'next (the final pict is not included).

An elem that is a real number changes the spacing for subsequent additions. A elem that is #f is discarded; it is permitted as a convenience for conditionally including sub-picts. Note that #f is not equivalent to (blank 0), since the latter will cause spacing to be added around it.

> procedure (placer? x) → boolean?
> x : any/c

Returns #t if x is a placer, #f otherwise.

> procedure (refpoint-placer? x) → boolean?
> x : any/c

Returns #t if x is a placer based on a reference point, #f otherwise.

> > procedure
> > (coord |  | rel-x |  |  |  |
> > |  | rel-y |  |  |  |
> > | [ | align |  |  |  |
> > |  | #:abs-x abs-x |  |  |  |
> > |  | #:abs-y abs-y |  |  |  |
> > |  | #:compose composer]) |  | → |  | refpoint-placer?
> rel-x : real?
> rel-y : real?
> align : (or/c 'lt 'ct 'rt 'lc 'cc 'rc 'lb 'cb 'rb) = 'cc
> abs-x : real? = 0
> abs-y : real? = 0
> composer : procedure? = computed from align

Returns a placer that places picts according to rel-x and rel-y, which are interpeted as fractions of the width and height of the base progressive pict. That is, 0, 0 is the top left corner of the base’s bounding box, and 1, 1 is the bottom right. Then abs-x and abs-y offsets are added to get the final reference point.

Additions are aligned according to align, a symbol whose name consists of a horizontal alignment character followed by a vertical alignment character. For example, if align is 'lt, the pict is placed so that its left-top corner is at the reference point; if align is 'rc, the pict is placed so that the center of its bounding box’s right edge coincides with the reference point.

By default, if there are multiple picts to be placed, they are vertically appended, aligned according to the horizontal component of align. For example, if align is 'cc, the default composer is vc-append; for 'lt, the default composer is vl-append. The spacing is initially 0.

Examples:
> > (ppict-do base
> #:go (coord 1/2 1/2 'rb)
> (colorize (circle 20) "red")
> #:go (coord 1/2 1/2 'lt)
> (colorize (circle 20) "darkgreen"))
> > (ppict-do base
> #:go (coord 1 0 'rt #:abs-x -5 #:abs-y 10)
> 50 ; change spacing
> (text "abc")
> (text "12345")
> 0 ; and again
> (text "ok done"))
> > (ppict-do base
> #:go (coord 0 0 'lt #:compose ht-append)
> (circle 10)
> (circle 20)
> (circle 30))

> > procedure
> > (grid |  | cols |  |  |  |
> > |  | rows |  |  |  |
> > |  | col |  |  |  |
> > |  | row |  |  |  |
> > | [ | align |  |  |  |
> > |  | #:abs-x abs-x |  |  |  |
> > |  | #:abs-y abs-y |  |  |  |
> > |  | #:compose composer]) |  | → |  | refpoint-placer?
> cols : exact-positive-integer?
> rows : exact-positive-integer?
> col : exact-integer?
> row : exact-integer?
> align : (or/c 'lt 'ct 'rt 'lc 'cc 'rc 'lb 'cb 'rb) = 'cc
> abs-x : real? = 0
> abs-y : real? = 0
> composer : procedure? = computed from align

Returns a placer that places picts according to a position in a virtual grid. The row and col indexes are numbered starting at 1.

Uses of grid can be translated into uses of coord, but the translation depends on the alignment. For example, (grid 2 2 1 1 'lt) is equivalent to (coord 0 0 'lt), but (grid 2 2 1 1 'rt) is equivalent to (coord 1/2 0 'rt).

Examples:
> > (define none-for-me-thanks
> (ppict-do base
> #:go (grid 2 2 1 1 'lt)
> (text "You do not like")
> (colorize (text "green eggs and ham?") "darkgreen")))
> > none-for-me-thanks
> > (ppict-do none-for-me-thanks
> #:go (grid 2 2 2 1 'rb)
> (colorize (text "I do not like them,") "red")
> (text "Sam-I-am."))

> procedure (cascade [step-x step-y]) → placer?
> step-x : (or/c real? 'auto) = 'auto
> step-y : (or/c real? 'auto) = 'auto

Returns a placer that places picts by evenly spreading them diagonally across the base pict in “cascade” style. This placer does not support changing the spacing by including a real number within the pict sequence.

When a list picts is to be placed, their bounding boxes are normalized to the maximum width and height of all picts in the list; each pict is centered in its new bounding box. The picts are then cascaded so there is step-x space between each of the picts’ left edges; there is also step-x space between the base pict’s left edge and the first pict’s left edge. Similarly for step-y and the vertical spacing.

If step-x or step-y is 'auto, the spacing between the centers of the picts to be placed is determined automatically so that the inter-pict spacing is the same as the spacing between the last pict and the base.

Examples:
> > (ppict-do base
> #:go (cascade)
> (colorize (filled-rectangle 100 100) "red")
> (colorize (filled-rectangle 100 100) "blue"))
> > (ppict-do base
> #:go (cascade 40 20)
> (colorize (filled-rectangle 100 100) "red")
> (colorize (filled-rectangle 100 100) "blue"))

> procedure (tile cols rows) → placer?
> cols : exact-positive-integer?
> rows : exact-positive-integer?

Returns a placer that places picts by tiling them in a grid cols columns wide and rows rows high.

Example:
> > (ppict-do base
> #:go (tile 2 2)
> (circle 50)
> (rectangle 50 50)
> (jack-o-lantern 50)
> (standard-fish 50 30 #:color "red"))

> > procedure
> > (at-find-pict |  | find-path |  |  |  |
> > | [ | finder |  |  |  |
> > |  | align |  |  |  |
> > |  | #:abs-x abs-x |  |  |  |
> > |  | #:abs-y abs-y |  |  |  |
> > |  | #:compose composer]) |  | → |  | refpoint-placer?
> find-path : (or/c tag-path? pict-path?)
> finder : procedure? = cc-find
> align : (or/c 'lt 'ct 'rt 'lc 'cc 'rc 'lb 'cb 'rb) = 'cc
> abs-x : real? = 0
> abs-y : real? = 0
> composer : procedure? = computed from align

Returns a placer that places picts according to a reference point based on an existing pict within the base.

Example:
> > (ppict-do base
> #:go (cascade)
> (tag-pict (standard-fish 40 20 #:direction 'right #:color "red") 'red-fish)
> (tag-pict (standard-fish 50 30 #:direction 'left #:color "blue") 'blue-fish)
> #:go (at-find-pict 'red-fish rc-find 'lc #:abs-x 10)
> (text "red fish"))

> procedure (merge-refpoints x-placer y-placer) → refpoint-placer?
> x-placer : refpoint-placer?
> y-placer : refpoint-placer?

Returns a placer like x-placer except that the y-coordinate of its reference point is computed by y-placer.

Example:
> > (ppict-do base
> #:go (cascade)
> (tag-pict (standard-fish 40 20 #:direction 'right #:color "red") 'red-fish)
> (tag-pict (standard-fish 50 30 #:direction 'left #:color "blue") 'blue-fish)
> #:go (merge-refpoints (coord 1 0 'rc)
> (at-find-pict 'red-fish))
> (text "red fish"))

#### 5.2`` Progressive Slides

(require unstable/gui/pslide) | package: unstable-lib

> syntax (pslide ppict-do-fragment ...)

Produce slide(s) using progressive picts. See ppict-do for an explanation of ppict-do-fragments.

Note that like slide but unlike ppict-do*, the number of slides produced is one greater than the number of #:next uses; that is, a slide is created for the final pict.

Remember to include gap-size after updating the current placer if you want slide-like spacing.

Example:
> > (pslide #:go (coord 0 0 'lt)
> (t "You do not like")
> (colorize (t "green eggs and ham?") "darkgreen")
> #:next
> #:go (coord 1 1 'rb)
> (colorize (t "I do not like them,") "red")
> (t "Sam-I-am."))

Note that the text is not flush against the sides of the slide, because pslide uses a base pict the size of the client area, excluding the margins.

> parameter (pslide-base-pict) → (-> pict)
> (pslide-base-pict make-base-pict) → void?
> make-base-pict : (-> pict)

Controls the initial pict used by pslide. The default value is

> (lambda () (blank client-w client-h))

> parameter (pslide-default-placer) → placer?
> (pslide-default-placer placer) → void?
> placer : placer?

Controls the initial placer used by pslide. The default value is

> (coord 1/2 1/2 'cc)

top ← prev up next →