PREFAB-ELEMENT(2) PREFAB-ELEMENT(2)
NAME
prefab: Element - menu and display elements for ITV toolkit
SYNOPSIS
include "draw.m";
include "prefab.m";
prefab := load Prefab Prefab->PATH;
# types of Elements
EIcon: con 0;
EText: con 1;
ETitle: con 2;
EHorizontal:con 3;
EVertical: con 4;
ESeparator: con 5;
# first arg to Element.adjust: size of elements
Adjpack: con 10; # leave alone, pack tightly
Adjequal: con 11; # make equal
Adjfill: con 12; # make equal, filling available space
# second arg: position of element within space
Adjleft: con 20;
Adjup: con 20;
Adjcenter: con 21;
Adjright: con 22;
Adjdown: con 22;
Layout: adt
{
font: ref Draw->Font;
color: ref Draw->Image;
text: string;
icon: ref Draw->Image;
mask: ref Draw->Image;
tag: string;
};
Element: adt
{
kind: int;
r: Draw->Rect;
environ:ref Environ;
tag: string;
# different fields defined for different kinds of Elements
kids: cyclic list of ref Element; # children of elists
str: string; # text in an EText element
mask: ref Draw->Image; # part of Eicon, ESeparator
image: ref Draw->Image; # part of Eicon, ESeparator, EText, Etitle
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font: ref Draw->Font; # part of EText, Etitle
icon: fn(env: ref Environ, r: Draw->Rect,
icon, mask: ref Draw->Image):
ref Element;
text: fn(env: ref Environ, text: string,
r: Draw->Rect, kind: int): ref Element;
layout: fn(env: ref Environ, lay: list of Layout,
r: Draw->Rect, kind: int): ref Element;
elist: fn(env: ref Environ, elem: ref Element, kind: int):
ref Element;
separator: fn(env:ref Environ, r: Draw->Rect,
icon, mask: ref Draw->Image): ref Element;
append: fn(elist: self ref Element, elem: ref Element): int;
adjust: fn(elem: self ref Element, equal: int, dir: int);
clip: fn(elem: self ref Element, r: Draw->Rect);
scroll: fn(elem:self ref Element, d: Draw->Point);
translate: fn(elem:self ref Element, d: Draw->Point);
show: fn(elist: self ref Element, elem: ref Element): int;
};
DESCRIPTION
Prefab Elements are the building blocks of the ITV toolkit.
They represent and display text and pictures that can be
grouped in arbitrary two-dimensional menus to be walked by
the infrared remote control. Elements are packaged within
Compounds (see prefab-compound(2)) for display.
environ This specifies the element's environment.
image If the element needs an Image object (see kind
below), this member specifies it.
kind The Prefab module defines six Element varieties,
each labelled by a defined constant in the kind
member.
EIcon
An image.
EHorizontal
A horizontal list of elements.
ESeparator
An Image object, like an EIcon, but intended
to fill space in a list, rather than to serve
as an element of the list. Separators are
ignored when selecting or highlighting list
elements.
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EText
A single line of text. Text for this element
will be drawn with Style.textfont and
Style.textcolor.
ETitle
A single line of text, usually giving the
title of a Compound object. Text for this
element will be drawn with Style.titlefont and
Style.titlecolor.
EVertical
A vertical list of elements.
mask When an element contains an Image object, the
Image.draw function will be used to display it on
the screen. The mask image is used as an argument
to Image.draw; see draw-intro(2) for more informa-
tion.
r All Elements are rectangular, occupying the posi-
tion on the display specified by r.min. The size
of the element also depends on r. During creation,
if the rectangle is degenerate (has zero size), the
element takes its size from the sizes of its compo-
nents: the image size for icons, text width for
strings, etc. Otherwise, the element's size
matches the rectangle.
tag The tag of an element serves two purposes: it
allows an element to be labelled with arbitrary
invisible text, and provides a mechanism to control
which elements of a list may be selected: see the
description of Compound.tagselect in prefab-
compound(2). The tag field of an element may be
modified freely after the element is created.
icon(env, r, icon, mask)
Build one EIcon element to be drawn with the icon
and mask. The rectangle, r, gives the element's
position and size.
text(env, text, r, kind)
Build a textual element or a list of textual ele-
ments. Kind may be EText or ETitle, determining
the style of the drawn text. The resulting Element
object may be a single element or a EVertical list
of the appropriate kind, if the text occupies more
than one line. The text is folded as necessary to
accommodate the available horizontal space; new-
lines in the text cause line breaks. The width of
the text is determined by r, but if r has no width,
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it will be set by the text itself. The height of
the Element is also determined by r; again, if the
height of r is zero, the Element will be made as
tall as necessary (if r is not tall enough, the
rest of the text may be made visible by calls to
Element.scroll). Thus one may choose a specific
size or let the text determine the size by setting
r suitably.
layout(env, lay, r, kind)
Like Element.text, but builds a structure using the
contents of the list lay of Layout structures. The
Layout type allows construction of a more general
form of textual display by providing fine control
over the font and colour in which to display text
and the inclusion of images as textual elements.
It also allows setting of the tag for each compo-
nent of the resulting element or list of elements.
If the Layout has a non-nil image field, it is
taken as a description of a picture to be incorpo-
rated in the text as an EIcon element (and the text
field is ignored); otherwise the text field speci-
fies the text to be drawn in the indicated font and
color. As with Element.text, Element.layout does
all the geometry management, text line breaking and
folding, etc.
elist(env, elem, kind)
Start a list of Element objects. The kind may be
Prefab->EHorizontal or Prefab->EVertical, specify-
ing the orientation of the list. Elem will be the
first element of the list. It may be nil, which
creates an empty list of the requested orientation.
Subsequent Element.append calls build the list.
separator(env, r, icon, mask)
Build one ESeparator element to be drawn with the
icon and mask. The rectangle, r, gives the
element's position and size.
elist.append(elem)
Append one Element, elem, to an existing list,
elist. The new element will appear after those
already there, either to the right for EHorizontal
or below for EVertical lists.
elem.adjust(spacing, dir)
Format the list so its elements abut. The list-
building functions such as append attempt to build
a sensible geometry. Alternatively, one can build
a list using degenerate geometry and then let
adjust compute the geometry for the whole list.
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For example, one could place all the elements at
(0, 0) and then call adjust to decide where the
elements belong.
Spacing specifies how the elements fit together:
Adjequal
Makes them all equal sized in the dimension of
the list, but only as big as the largest ele-
ment. For example, if the element is a hori-
zontal list, all elements will be as wide as
the widest item. If the list is too big for
the allocated space, only some will be visi-
ble.
Adjfill
Makes them all equal sized in the dimension of
the list, expanding the elements to fit the
space of the list's Element.r. If the list is
too big for the allocated space, only some
will be visible.
Adjpack
Packs elements as tightly as possible, using
the ``natural'' size of each element and set-
ting their rectangles against one another.
Dir controls how each element is placed in its
allotted space:
Adjcenter
Place each element in the middle of its space.
Adjdown
In a vertical list, move each element to the
bottom.
Adjleft
In a horizontal list, move each element to the
left.
Adjright
In a horizontal list, move each element to the
right.
Adjup
In a vertical list, move each element to the
top.
elem.clip(r)
The drawing model for Element objects is that they
occupy some space in the plane, which may be larger
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or smaller than the space occupied by its con-
stituent text, icons, sub-elements, etc. The clip
function sets the rectangle of elem to r, without
changing its internal geometry. Any space made
newly visible by this will be filled in by the
list's Style.elemcolor. For example, if e is an
icon element just large enough to display its
image, e.clip(e.r.inset(-2)) will make a two-
pixel-wide border around the icon when it is drawn.
As another example, lists are scrolled by leaving
their clip rectangle intact while translating the
list elements' coordinates.
elem.scroll(d)
D is a Point, representing a vector; elem is an
Element object to be scrolled. The scroll function
leaves the element's r alone and translates all the
constituent pieces of the list by d, causing a dif-
ferent portion of elem to be visible in its rectan-
gle.
elem.translate(d)
Like elem.scroll(d), but moves r too, thus trans-
lating the entire Element rather than just the vis-
ible part within a fixed rectangle.
elist.show(elem)
Show does nothing if elem is not a list. If it is
a list, the list is scrolled so elem, which must be
a member of the list, is visible through elist.r.
The geometry of elements and the membership of lists may be
modified only through the provided functions; the Limbo-
visible structure is (intended to be) read-only. Tags,
text, and images may be modified freely by the application,
but at the moment there is no way to recalculate the geome-
try if the components of an textual or image icon change
size.
Element objects are never drawn explicitly, nor are they
drawn after any Element operation. They are made visible
only by calls to Compound.draw, described by prefab-
compound(2).
SOURCE
/interp/prefab.c /prefab/*.c
SEE ALSO
prefab-compound(2) prefab-environ(2) prefab-style(2)
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