# Form Widget

    Application Header file	<X11/Xaw/Form.h>

    Class Header file	<X11/Xaw/FormP.h>

    Class		formWidgetClass

    Class Name	Form

    Superclass	Constraint

The Form widget can contain an arbitrary number of children or subwidgets. The Form provides geometry management for its children, which allows individual control of the position of each child. Any combination of children can be added to a Form. The initial positions of the children may be computed relative to the positions of previously created children. When the Form is resized, it computes new positions and sizes for its children. This computation is based upon information provided when a child is added to the Form.

The default width of the Form is the minimum width needed to enclose the children after computing their initial layout, with a margin of `defaultDistance` at the right and bottom edges. If a width and height is assigned to the Form that is too small for the layout, the children will be clipped by the right and bottom edges of the Form.

## Resources

When creating a Form widget instance, the following resources are retrieved from the argument list or from the resource database:

Name | Class | Type | Notes | Default Value
accelerators | Accelerators | AcceleratorTable |  | NULL
ancestorSensitive | AncestorSensitive | Boolean | D | True
background | Background | Pixel |  | XtDefaultBackground
backgroundPixmap | Pixmap | Pixmap |  | XtUnspecifiedPixmap
borderColor | BorderColor | Pixel |  | XtDefaultForeground
borderPixmap | Pixmap | Pixmap |  | XtUnspecifiedPixmap
borderWidth | BorderWidth | Dimension |  | 1
children | ReadOnly | WidgetList | R | NULL
colormap | Colormap | Colormap |  | Parent's Colormap
defaultDistance | Thickness | int |  | 4
depth | Depth | int | C | Parent's Depth
destroyCallback | Callback | XtCallbackList |  | NULL
height | Height | Dimension | A | Enough space to contain all children
mappedWhenManaged | MappedWhenManaged | Boolean |  | True
numChildren | ReadOnly | Cardinal | R | 0
screen | Screen | Screen | R | Parent's Screen
sensitive | Sensitive | Boolean |  | True
translations | Translations | TranslationTable |  | NULL
width | Width | Dimension | A | Enough space to contain all children
x | Position | Position |  | 0
y | Position | Position |  | 0
_

## Constraint Resources

Each child of the Form widget may request special layout resources be applied to it. These constraint resources allow the Form widget's children to specify individual layout requirements.

Name | Class | Type | Notes | Default Value
bottom | Edge | XawEdgeType |  | XawRubber
fromHoriz | Widget | Widget |  | NULL (left edge of Form)
fromVert | Widget | Widget |  | NULL (top edge of Form)
horizDistance | Thickness | int |  | `defaultDistance` resource
left | Edge | XawEdgeType |  | XawRubber
resizable | Boolean | Boolean |  | FALSE
right | Edge | XawEdgeType |  | XawRubber
top | Edge | XawEdgeType |  | XawRubber
vertDistance | Thickness | int |  | `defaultDistance` resource

    bottom
    left
    right
    top            What to do with this edge of the child when
                   the parent is resized.  This resource may be
                   any edgeType.  See Layout Semantics for
                   details.

    fromHoriz
    fromVert       Which widget this child should be placed
                   underneath (or to the right of).  If a value
                   of NULL is specified then this widget will be
                   positioned relative to the edge of the par-
                   ent.

    horizDistance
    vertDistance   The amount of space, in pixels, between this
                   child and its left or upper neighbor.

    resizable      If this resource is False then the parent
                   widget will ignore all geometry request made
                   by this child.  The parent may still resize
                   this child itself, however.

## Layout Semantics

The Form widget uses two different sets of layout semantics. One is used when initially laying out the children. The other is used when the Form is resized.

The first layout method uses the `fromVert` and `fromHoriz` resources to place the children of the Form. A single pass is made through the Form widget's children in the order that they were created. Each child is then placed in the Form widget below or to the right of the widget specified by the `fromVert` and `fromHoriz` resources. The distance the new child is placed from its left or upper neighbor is deter- mined by the `horizDistance` and `vertDistance` resources. This implies some things about how the order of creation affects the possible placement of the children. The Form widget registers a string to widget converter which does not post- pone conversion and does not cache conversion results.

The second layout method is used when the Form is resized. It does not matter what causes this resize, and it is possi- ble for a resize to happen before the widget becomes visible (due to constraints imposed by the parent of the Form). This layout method uses the `bottom`, `top`, `left`, and `right` resources. These resources are used to determine what will happen to each edge of the child when the Form is resized. If a value of `XawChain` <something> is specified, the the edge of the child will remain a fixed distance from the chain edge of the Form. For example if `XawChainLeft` is specified for the `right` resource of a child then the right edge of that child will remain a fixed distance from the left edge of the Form widget. If a value of `XawRubber` is specified, that edge will grow by the same percentage that the Form grew. For instance if the Form grows by 50% the left edge of the child (if specified as `XawRubber` will be 50% farther from the left edge of the Form). One must be very careful when specifying these resources, for when they are specified incorrectly children may overlap or completely occlude other children when the Form widget is resized.

Edge Type | Resource Name | Description
XawChainBottom | ChainBottom | Edge remains a fixed distance from bottom of Form
XawChainLeft | ChainLeft | Edge remains a fixed distance from left of Form
XawChainRight | ChainRight | Edge remains a fixed distance from right of Form
XawChainTop | ChainTop | Edge remains a fixed distance from top of Form
XawRubber | Rubber | Edges will move a proportional distance

### Example

If you wish to force the Form to never resize one or more of its children, then set `left` and `right` to `XawChainLeft` and `top` and `bottom` to `XawChainTop`. This will cause the child to remain a fixed distance from the top and left edges of the Form, and never to resize.

## Convenience Routines

To force or defer a re-layout of the Form, use

      void XawFormDoLayout
      Widget w
      Boolean do_layout

w

- Specifies the Form widget.

do_layout

- Specifies whether the layout of the Form widget is enabled (`True`) or disabled (`False`).

When making several changes to the children of a Form widget after the Form has been realized, it is a good idea to disable relayout until after all changes have been made.