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 layout.gadget
  --datasheet--
  ActivateLayoutGadget
  FlushLayoutDomainCache
  LAYOUT_GetClass
  LayoutLimits
  RethinkLayout
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Docs » Autodocs » layout.gadget » --datasheet--

NAME

        layout.gadget-- An automatic GUI layout arrangement gadget.

SUPERCLASS

        gadgetclass

REQUIRES

        bevel.image

DESCRIPTION

        The layout gadget is used to automatically calculate the
positions and sizes of BOOPSI gadgets and images in a resizable
window. Instead of handling the positions of gadgets by hand,
you can just describe your window layout in a hierarchical
fashion, and the layout gadget will do the rest.
The basic method of layout of a group is as follows:
- Calculate the minimum and maximum size of each gadget.
- Calculate the weight totals for the group. Substract the size
of the fixed size (weighted size 0) gadgets from the total
size of the group.
- Distribute the remaining space in the group according to the
relative weighs of the children.
- If extra space remains, distribute it evenly between the
children.
PRIVATE METHODS
LAYOUT_ACTIVATEOBJECT -- Used by ActivateLayoutGadget(), sets
the handleinput path to a gadget somewhere in a layout hierarchy.
LAYOUT_TABCYCLE -- Sets the gadget attributes based on the
gadget in the end of the handleinput path.
LAYOUT_FIRSTCYCLE -- Sets the handleinput path to the first tab
cycle gadget in a layout hierarchy.
LAYOUT_LASTCYCLE -- Sets the handleinput path to the last tab
cycle gadget in a layout hierarchy.
LAYOUT_FLUSHDOMAINS -- Flushes all domain caches below a certain
level.
LAYOUT_FINDKEY -- Find a gadget with a key in the CommKey list.
LAYOUT_FINDACTIVE -- Find the active gadget pointer.
LAYOUT_FINDHELP -- Find the last gadget that returned helphit.

METHODS

        GM_HANDLEINPUT -- Passed to the currently active child
GM_DOMAIN -- Passed to all children
GM_RENDER -- Passed to all children When invoked
by input.device, the stack is first swapped to provide
more workspace.
GM_LAYOUT -- Passed to all children after first setting
their size and position with SetAttrs. When invoked
by input.device, the stack is first swapped to provide
more workspace.
GM_HITTEST -- Passed to the child in whose domain
rectangle the pointer is
GM_HELPTEST -- Passed to the child in whose domain
rectangle the pointer is
GM_GOACTIVE -- Passed to the currently "active" child (one
that returned GM_HITTEST)
GM_GOINACTIVE -- Passed to the currently active child
OM_SET -- Passed to superclass after scanning the
taglist for layout specific tags
OM_UPDATE -- Passed to superclass after scanning the
taglist for layout specific tags
OM_GET -- Passed to superclass for non-layout tags
OM_NEW -- Passed to superclass, then adding all the
children on the taglist to the private list.
OM_DISPOSE -- Passed to all children (thus disposing all
of them), then to superclass.
GM_CLIPRECT -- Passed to all children.
DTM_PROCLAYOUT -- Like GM_LAYOUT, but passes DTM_PROCLAYOUT
forward. Useful if the layout group contains only
datatype objects.
All other methods are passed to the superclass.

ATTRIBUTES

      Attributes global to the whole layout group. Pass all of these 
BEFORE adding child objects:
GA_ReadOnly (BOOL)
Disables input to the entire layout group and its chidren.
This tag is NOT propagated to children. The input blocking
occurs within the layout object itself.
Defaults to FALSE
Applicability is (OM_NEW, OM_SET, OM_UPDATE)
GA_Disabled (BOOL)
Disables entire layout group and its chidren. This tag
is propagated all children. When setting/clearing this
tag, take care to re-set/re-clear any children you want
included from this mass disabling ability.
Defaults to FALSE
Applicability is (OM_NEW, OM_SET, OM_UPDATE)
GA_TextAttr (struct TextAttr *)
The font that will be used for the group label.
Defaults to NULL (uses rastport default font).
Applicability is (OM_NEW)
LAYOUT_Orientation (ULONG)
Whether the objects of this group are arranged horizontally or
vertically. Possible values are LORIENT_HORIZONTAL and
LORIENT_VERTICAL.
Defaults to LORIENT_HORIZONTAL.
Applicability is (OM_NEW, OM_SET, OM_UPDATE, OM_GET)
LAYOUT_FixedHoriz (BOOL)
Whether the width of this layout group is fixed to the width
assigned by the window or parent layout group. If set to FALSE,
the gadget will minimize its width to the smallest possible
value. Generally you will have to also set LAYOUT_ShrinkWrap
(below) to TRUE also. It is recommended that this tag is used
only in the top layout group. Using a weighted width of 0 gives
more predictable results elsewhere.
Defaults to TRUE.
Applicability is (OM_NEW, OM_SET, OM_UPDATE, OM_GET)
LAYOUT_FixedVert (BOOL)
Whether the height of this layout group is fixed to the height
assigned by the window or parent layout group. If set to FALSE,
the gadget will minimize its height to the smallest possible
value. Generally you will have to also set LAYOUT_ShrinkWrap
(below) to TRUE also. It is recommended that this tag is used
only in the top layout group. Using a weighted height of 0 gives
more predictable results elsewhere.
Defaults to TRUE.
Applicability is (OM_NEW, OM_SET, OM_UPDATE, OM_GET)
LAYOUT_HorizAlignment (ULONG)
The horizontal alignment of the objects in this layout group.
Possible values are LALIGN_LEFT, LALIGN_RIGHT, and
LALIGN_CENTER.
Defaults to LALIGN_LEFT.
Applicability is (OM_NEW, OM_SET, OM_UPDATE, OM_GET)
LAYOUT_VertAlignment (ULONG)
The vertical alignment of the objects in this layout group.
Possible values are LALIGN_TOP, LALIGN_BOTTOM, and
LALIGN_CENTER.
Defaults to LALIGN_TOP.
Applicability is (OM_NEW, OM_SET, OM_UPDATE, OM_GET)
LAYOUT_ShrinkWrap (BOOL)
If set to TRUE, the layout group will shrink the interspacing
of the child objects to minimum. Normally all extra space (if
the total maximum size of the child objects is less than the
size of the layoutgroup) is evenly distributed between the
gadgets.
Defaults to FALSE.
Applicability is (OM_NEW, OM_SET, OM_UPDATE, OM_GET)
LAYOUT_EvenSize (BOOL)
If TRUE, the layout group will try to reserve enough space to
make the minimum size of each child object equal to the minimum
of the largest child. Using this attribute makes it possible to
have neatly arranged horizontal rows or grids of gadgets. This
can take quite a bit of room, however, depending on the gadgets.
Defaults to FALSE.
Applicability is (OM_NEW, OM_SET, OM_UPDATE)
LAYOUT_SpaceInner (BOOL)
Should layout leave space between objects or not. Set to FALSE
if objects in a group should be put immediately beside each
other.
Defaults to TRUE.
Applicability is (OM_NEW, OM_SET, OM_UPDATE)
LAYOUT_SpaceOuter (BOOL)
Should layout leave space around the group's objects or not.
Set to TRUE if the objects should not be laid out using the
whole group container box (for example if the group has a
bevel around it).
Defaults to FALSE.
Applicability is (OM_NEW, OM_SET, OM_UPDATE)
LAYOUT_InnerSpacing (ULONG)
The minimum space left between objects. The value is in "virtual
pixels", ie absolute pixels assuming bevel is configured for
thin lines. If bevel configuration is something else, the value
will be adjusted accordingly.
Please avoid using this tag, if you do not require absolute
control over the spacing. The LAYOUT_SpaceInner boolean is
provided to tell whether there should be spacing or whether
objects should be immediately connected to each other.
Defaults to INTERSPACING.
Applicability is (OM_NEW, OM_SET, OM_UPDATE)
LAYOUT_TopSpacing
LAYOUT_BottomSpacing
LAYOUT_LeftSpacing
LAYOUT_RightSpacing (ULONG)
The minimum space left to the top, bottom, left and right of
the group, respectively. This value is in "virtual pixels", see
LAYOUT_Spacing above.
Please avoid using this tag, if you do not require absolute
control over the spacing. The LAYOUT_SpaceOuter boolean is
provided to tell whether there should be spacing or whether
objects should be immediately connected to each other.
If you use one of these tags to override a LAYOUT_SpaceOuter,
pass this tag AFTER the LAYOUT_SpaceOuter tag.
Defaults to 0.
Applicability is (OM_NEW, OM_SET, OM_UPDATE)
LAYOUT_BevelStyle (ULONG)
The style of the bevel drawn around the group. This value is
passed to bevel.image.
Defaults to BVS_NONE.
Applicability is (OM_NEW, OM_SET, OM_UPDATE)
LAYOUT_BevelState (ULONG)
The state of the bevel drawn around the group. Used to
DrawImageState() the bevel.image.
Defaults to IDS_NORMAL.
Applicability is (OM_NEW, OM_SET, OM_UPDATE)
LAYOUT_Label (STRPTR)
The label drawn in the group bevel. This value is passed to
bevel.image. Note that if LAYOUT_BevelStyle is set to BVS_NONE,
no bevel will be rendered, and thus this label will not be used
either.
No default (bevel.image default used)
Applicability is (OM_NEW, OM_SET, OM_UPDATE, OM_GET)
LAYOUT_LabelImage (Object *)
The BOOPSI image to use as the group bevel label. Passed to
bevel.image.
See LAYOUT_Label.
Applicability is (OM_NEW, OM_SET, OM_UPDATE, OM_GET)
LAYOUT_LabelPlace (ULONG)
The position of the label (See LAYOUT_Label).
Applicability is (OM_NEW, OM_SET, OM_UPDATE, OM_GET)
LAYOUT_RemoveChild (Object *)
Pointer to an object you wish to remove from the layout
hierarchy. The object will be disposed of, so after using this
tag, the pointer will be invalid.
Applicability is (OM_SET)
LAYOUT_AddChild (Object *)
Pointer to an object you wish to add to the list of gadgets for
this layout hierarchy level.
Applicability is (OM_NEW)
LAYOUT_AddImage (Object *)
Same as LAYOUT_AddChild, but will mark the object as an
imageclass subclass (meaning that IM_DRAW will be used instead
of GM_RENDER to display it, and that none of the gadgetclass
methods apply to it).
Applicability is (OM_NEW)
LAYOUT_ModifyChild (Object *)
Inform layout gadget that the following child specific tags in
the taglist apply to the specified object. LAYOUT_AddChild will
do this automatically for new objects.
Applicability is (OM_SET)
LAYOUT_RelVerify (BOOL)
When a gadget returns a code that normally makes Intuition send
an IDCMP_GADGETUP message to the application, layout.gadget
will send a notification message (OM_NOTIFY, IDCMP_IDCMPUPDATE)
with the essential information of the gadgetup message. This is
because in certain situations the IDCMP_GADGETUP message can
not be sent (in particular, when tab cycling between gadgets).
The notification will consist of GA_ID set to the ID of the
gadget in question, this LAYOUT_RelVerify tag set to TRUE, and
the LAYOUT_RelCode tag (below) set to the gadget's return code
(IntuiMessage.Code field of the IDCMP_GADGETUP).
Applicability is (OM_NOTIFY)
LAYOUT_RelCode (UWORD)
A copy of the IntuiMessage.Code field of the IDCMP_GADGETUP in
question, sent via OM_NOTIFY (ie. received as OM_UPDATE or
IDCMP_IDCMPUPDATE).
Applicability is (OM_NOTIFY)
LAYOUT_TabVerify (BOOL)
If the gadget release was triggered by tab cycling, this
attribute will be TRUE in the release verify IDCMPUPDATE. This
lets you distinguish, for example, between pressing tab and
enter in a string gadget.
Applicability is (OM_NOTIFY)
LAYOUT_RelAddress (struct Gadget *)
Address of the gadget that sent the gadgetup is provided in the
gadgetup notification using this tag.
Applicability is (OM_NOTIFY)
LAYOUT_HelpHit (UWORD)
When a gadget returns a hit for helptest, the return code, along
with GA_ID, is notified using this tag.
Applicability is (OM_NOTIFY)
LAYOUT_Parent (Object *)
Set automatically by layout.gadget for all child objects, this
attribute points to the parent layout object. If NULL, the
layout object is the window's topmost layout.
When an object is added to the layout hierarchy, it will
receive this tag in OM_SET. If you so wish, you may use this to
let the gadget talk to its parent layout group.
Any group gadget that should work with layout.gadget must
support this attribute.
Applicability is (OM_SET, OM_GET)
LAYOUT_DeferLayout (BOOL)
By setting this tag to TRUE in your window's top layout, you
can defer the layout and refresh process off the input.device
context to your application. This will make input.device more
responsive, and drop the (possibly quite heavy) process of
recalculating the display to normal application priority
instead of the priority 20
of input.device. Input handling will be retained in input.device
context, to keep the GUI responsive.
If you use this tag, you must listen to LAYOUT_RequestLayout
and LAYOUT_RequestRefresh notifications and process them in
prompt manner, or your GUI will not display properly, if at all.
Applicability is (OM_NEW, OM_SET)
LAYOUT_RequestLayout (Object *)
If the above LAYOUT_DeferLayout tag is set to TRUE, the gadget
will defer GM_LAYOUT methods invoked by input.device and notify
its IC target with this tag. You should be listening to it in
your application IDCMP handler (IDCMP_IDCMPUPDATE) and calling
RethinkLayout with FALSE for refresh flag when receiving one.
Defaults to FALSE.
Applicability is (OM_NOTIFY)
LAYOUT_RequestRefresh (Object *)
If the above LAYOUT_DeferLayout tag is set to TRUE, the gadget
will defer GM_RENDER methods invoked by input.device and notify
its IC target with this tag. You should be listening to it in
your application IDCMP handler (IDCMP_IDCMPUPDATE) and calling
RefreshGList when receiving one.
Defaults to FALSE.
Applicability is (OM_NOTIFY)
LAYOUT_TextPen (WORD)
The pen that will be used for group label text. See bevel.image.
Applicability is (OM_NEW)
LAYOUT_FillPen (WORD)
The pen that will be used for the group fill pattern. See
bevel.image.
Applicability is (OM_NEW)
LAYOUT_FillPattern (UWORD *)
The fill pattern for the group. See bevel.image.
Defaults to none.
Applicability is (OM_NEW)
GA_BackFill (struct Hook *)
A layer backfill hook to use in the group to provide a more
complex background pattern.
Defaults to clear for the main layout, and none for sublayouts.
Applicability is (OM_NEW)
LAYOUT_LabelColumn (ULONG)
The side where the on which side of the gadget the label will
be placed in the group. Valid values are PLACETEXT_LEFT and
PLACETEXT_RIGHT. See CHILD_Label.
Defaults to PLACETEXT_LEFT.
Applicability is (OM_NEW, OM_SET, OM_NOTIFY)
LAYOUT_LabelWidth (ULONG)
The width of the label column in a vertical group. This attribute
may be used to justify several layout groups.
Applicability is (OM_SET, OM_GET)
LAYOUT_AlignLabels (Object *)
A pointer to another layout instance that should have equal
label width with this one. Set to a cycle between all the
groups, these will automatically justify their labels with each
other. This attribute should be set as soon as possible, ie. in
OM_NEW or OM_SET directly afterwards, before the layout size is
calculated.
Applicability is (OM_NEW, OM_SET)
LAYOUT_Inversed (BOOL) (V42.27)
Causes children to be added to the layout group via
AddHead() vs AddTail().
Applicability is (OM_NEW, OM_SET)
LAYOUT_WeightBar (BOOL) (V43.1)
Place a user adjustable weighting bar here (ie; balance group bar).
Bugs: Before 45.9 LAYOUT_WeightBar didn't work correctly when used
in the root layoutgroup because the render request on SELECTUP was
rejected by window.class. Possible workarounds for this bug are:
a) Don't use LAYOUT_DeferLayout
b) set WFLG_NOCAREREFRESH
c) don't add the weightbar to the rootlayout, instead add
a "dummy" group to the rootlayout that contains all the
children and the weightbar.
Applicability is (OM_NEW, OM_SET)
Attributes referring to the "current" child object:
CHILD_MinWidth, CHILD_MinHeight (ULONG)
The minimum width and height of the object, in pixels. Setting
this attribute means that GM_DOMAIN is not respected in that
direction.
Defaults to ~0, which means that the layout gadget will ask the
object, using GM_DOMAIN.
Applicability is (OM_NEW, OM_SET, OM_UPDATE)
CHILD_MaxWidth, CHILD_MaxHeight (ULONG)
As above, for the maximum size.
Applicability is (OM_NEW, OM_SET, OM_UPDATE)
CHILD_NominalSize (BOOL)
If this attribute is TRUE, layout will use GDOMAIN_NOMINAL
instead of GDOMAIN_MINIMUM when requesting the minimum size of
the gadget. This is useful when the minimum size of a gadget
looks unattractive, but the gadget will return a more attractive
size with GDOMAIN_NOMINAL.
Defaults to FALSE.
Applicability is (OM_NEW, OM_SET, OM_UPDATE)
CHILD_WeightedWidth (ULONG)
The relative width of the child object. See the DESCRIPTION
above for the layout method. If set to 0, the child will always
be rendered in the minimum size (specified by either GM_DOMAIN
or CHILD_MinWidth). Use CHILD_MinWidth and a weighted with of 0
instead of CHILD_MinWidth and CHILD_MaxWidth. The latter method
will also work, but will slow down the layout. As a special
rule, many BOOPSI images using bitmap data can not be resized
from the initial size. Fix their size by setting MinWidth and
MinHeight, and the weight to 0.
Defaults to 100.
Applicability is (OM_NEW, OM_SET, OM_UPDATE)
CHILD_WeightedHeight (ULONG)
The relative height of the child object. See CHILD_WeightedWidth.
Applicability is (OM_NEW, OM_SET, OM_UPDATE)
CHILD_WeightMinimum (BOOL)
Setting this tag to TRUE will make the layout group set the
weighted width and height to the minimum values set with
CHILD_MinWidth and CHILD_MinHeight or returned by GM_DOMAIN. This
allows creating layout groups where the relative size of the
objects always remains the same. Be warned that if the object
does not support GM_DOMAIN and minimum size is not set manually,
the weight will be set to 2 (the default minimum size of an
object). Normally you would want to set this tag for every
resizable object in a layout group.
Defaults to FALSE.
Applicability is (OM_NEW)
CHILD_ReplaceObject
CHILD_ReplaceImage (Object *)
Replace the current child object with the one specified. The
current object will be disposed of. See LAYOUT_AddChild,
LAYOUT_AddImage, LAYOUT_RemoveChild, LAYOUT_ModifyChild.
Applicability is (OM_SET)
CHILD_CacheDomain (BOOL)
To speed up resizing, layout gadget will normally cache the
first values returned by GM_DOMAIN and use that cache for
subsequent relayouts, instead of calling GM_DOMAIN again.
Normally this will have the same results all the time. If you
have a custom gadget that might return varying values between
calls to GM_DOMAIN (ie the minimum or maximum size of it could
vary during runtime), set this tag to FALSE for that object and
all its parent groups. Note that since layout groups are aware
of their parent layouts, they can disable caching in the
hierarchy above them automatically, if you SetAttr this
attribute _AFTER_ creating the whole layout hierarchy.
Defaults to TRUE.
Applicability is (OM_NEW, OM_SET) (OM_SET preferred)
CHILD_Label (Object *)
The imageclass object, preferably label.image, to use as the
object's label. These labels are supported only left or right
aligned groups, and will be placed in the left or right of the
gadget even in horizontal groups. All the labels will take the
space of the widest label. Label-less objects will be laid out
in full width; if you want to leave the label column empty, use
the special value LCLABEL_NOLABEL. Every object in a group gets
the same amount of space reserved for a label, whether they have
a label or not. This also (or in particular) applies to
horizontal groups; usually the correct effect is reached by
putting the label on the group itself instead of one of the
objects in it. See LAYOUT_LabelColumn.
Defaults to NULL.
Applicability is (OM_NEW, OM_SET)
CHILD_NoDispose (BOOL)
By setting this attribute, you inform the layout object that
this child object should not be automatically disposed when
the layout object itself is disposed. This attribute allows
sharing objects between layouts.
Default is FALSE.
Applicability is (OM_NEW, OM_SET)
CHILD_ScaledWidth (UWORD) (V42.27)
Scales the child minimum domain size to a larger value;
minwidth = minwidth + ((minsize * scalewidth)/100)
Default is 0.
Applicability is (OM_NEW, OM_SET)
CHILD_ScaledHeight (UWORD) (V42.27)
Scales the child minimum domain size to a larger value;
minheight = minheight + ((minsize * scaleheight)/100)
Default is 0.
Applicability is (OM_NEW, OM_SET)

NOTES

      Setting the attributes via SetGadgetAttrs() (OM_SET) will not
automatically rerender the display! Call RethinkLayout() to
relayout and refresh display after SetGadgetAttrs().
In this document, the terms layout, group, and object are used
intermixed. Most of the time, layout and group are used as
synonyms. Virtually any object referred to could also be a
layout group.
To make defining layout hierarchies easier, the reaction_macros.h
include file defines a set of macros that hide NewObject()
calls. This will clean up the rather large tag lists for the
creation of layout groups. See the ReAction examples for use of
these macros, and layout.gadget in general.
In relation to above, remember that in AmigaOS (as of V40), the
stack size is restricted. During the beta test period, the
average size of a layout group for a whole window seemed to
average at approximately 1 KB. Building as large tag lists as
this on stack is rather slow, as well as easily overflowing the
small default stacks of AmigaOS. For windows with relatively
static layouts that are opened often, consider building tag
lists as static data and passing a pointer to them for
NewObjectA(). If this is too much work, make sure that your
program's stack is large enough to hold the tag list. If it is
too small, you can use the V37 Exec StackSwap() call to replace
it with a larger one, or simply set the global variable long
__stack to a large enough value, if the startup code you link
with provides stack swap support, as for example the c.o of
SAS/C 5.x and above does.
Due to Intuition limitations, IDCMP_GADGETUP messages are not
fully supported. The IAddress will always point to the root
layout object of the window, not the actual gadget the message
originates from. Use GadgetID to distinguish between gadgets.
When using tab cycle, GADGETUP messages will be lost
altogether. However, layout.gadget sends a notification for all
gadgetups, containing the tags GA_ID, LAYOUT_RelVerify and
LAYOUT_RelCode, containing, respectively, the ID, TRUE, and the
IntuiMessage.Code value it returned. Additionally a
LAYOUT_TabVerify tag will be TRUE or FALSE depending on whether
the gadget release was triggered by tab cycle.
Use of models and/or IDCMP_IDCMPUPDATE is encouraged.

SEE ALSO

ReAction example source for usage.

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