4 Animations
The
slideshow/play module
provides tools for generating animations as multiple, automatically
advanced slides.
Many of the tools are based on a function that takes a number between
0.0 and 1.0 inclusive and produces a
pict. The pict produced for the input 0.0 is
the starting image of the animation, and the pict produced for
1.0 is the ending image, while intermediate values produced
intermediate images. For example,
corresponds to an animation that fades in the word “Hello.”
4.1 Generating Animated Slides
Generates steps+1 slides by calling gen on
equally-spaced values from 0.0 (inclusve) to 1.0
(exclusive). Except for the first of the slides, each slide has a
timeout of delay-secs, so that the next slide appears
automatically.
Normally, play is called via play-n, which
effectively calls gen on 1.0 without a timeout to
complete the animation and stop the auto-advance of slides. The
play-n function also manages with multi-step animations.
If skip-first? is #f, then one fewer slide is
generated, because gen is not called on 0.0.
The title, name, and layout arguments are
passed on to slide, at least when title and/or
name are not functions. When title or name
is a function, the function is applied to the value used to produce
the slide content, and the resulting title or name is passed on to
slide.
In condensed mode (i.e., when condense? is #t), any
slide that would be registered with a timeout is instead skipped.
| (play-n | | gen* | | | | | | | [ | #:steps steps | | | | | | | | #:delay delay-secs | | | | | | | | #:skip-first? skip-first? | | | | | | | | #:skip-last? skip-last? | | | | | | | | #:title title | | | | | | | | #:name name | | | | | | | | #:layout layout]) | | → | | void? |
|
| gen* : (() (listof (real-in 0.0 1.0)) . ->* . pict?) |
|
| delay-secs : real? = 0.05 |
| skip-first? : any/c = #f |
| skip-last? : any/c = #f |
|
|
| layout : (or/c 'auto 'center 'top 'tall) = 'auto |
Generates a sequence of slides by calling gen* with, for each
of its arguments, numbers from 0.0 to 1.0. If
gen* accepts n arguments, then result is a sequence of
animations with a pause (i.e., not auto-advanced) between each of
n segments.
If gen* accepts a single argument, then play-n is
like play, except that gen* is also called with
1.0 to generate a slide with no timeout. If gen*
accepts multiple arguments, then slides are generated by calling
gen* with the first argument varying from 0.0 to
1.0 while all other arguments are 0.0. Then, the
first argument is held at 1.0 while the second argument varies
from 0.0 to 1.0, and so on.
For example,
generates an animation to fade in the word “Hello,” and then pauses
for a manual advance, and then fades “Hello” back out.
If skip-first? is #t, then the very first slide of
the sequence is skipped. Similarly, if skip-last? is
#t, then the last slide of the sequence is skipped.
The steps argument controls how many steps happen in each
phase on the animation. If it is a number, then that number is used for
each phase. If it is a pair of two numbers, then the first number is used
for the first phase, and the second number is used for the rest of the
phases. Similarly, if it is (cons num_1 (cons num_2 num_3)),
num_1 and num_2 are used for the first two phases
and num_3 is used for the rest.
The delay-msecs, title,
name, and layout arguments are passed on to
play for each of the n segments of animation.
Accepts slide content similar to
slide with
'next
and
'alts and produces a procedure suitable for use with
play-n. The result is similar to using
slide, but
with fades for
'next and
'alts transitions (to
better fit the style, perhaps, of surrounding animations).