NAME

XwformWidgetClass − the X Widget’s general widget layout manager

SYNOPSIS

#include <X11/StringDefs.h>
#include <X11/Intrinsic.h>
#include <Xw/Xw.h>
#include <Xw/Form.h>

CLASSES

A Form widget is built from Core, Composite, Constraint and XwManager classes

The widget class to use when creating a form is XwformWidgetClass. 

The class name of Form is Form. 

DESCRIPTION

The Form widget is a constraint based manager that provides a layout language used to establish spatial relationships between its children and then manipulates these relationships when the Form is resized, new children are added to the Form, or its children are resized, unmanaged, remanaged or destroyed. 

The following list highlights the types of layout control provided by the form widget. 

Spanning Constraints
A widget can be created with a set of constraints such that it spans the width or height of a form.  This is often used for the layout of scrollbars and titlebars.  Constraints that cause a widget to span both the width and height of a form can also be specified.

Row Constraints
Sets of widgets can be set up as a row so that resizing a form may increase or decrease the spacing between the widgets.  The form may also make the widgets smaller if desired, but it will not allow the widgets to overlap.

Column Constraints
Sets of widgets can be displayed in a single column or in multiple columns. The form may increase or decrease the spacing between widgets or resize the widgets, but it will not allow the widgets to overlap.

Automatic Form Resizing
The form calculates new sizes or positions for its children whenever they change size or position.  The new orm size thus generated is passed as a geometry request to the parent of the form.  The parent can accept the request or modify it and return it as a geometry almost.  When a geometry almost is returned by the parent, the form respecifies the constraints to match the parent’s reply size. 

Optimal Child Sizes and Positions
The Form widget also calculates the sizes and positions of its children to both match the constraints defined and to match either the initial size of the widget or the size given when the widget was modified through XtSetValues.  These values are further constrained to match a given form size only when the form’s size is being explicitly changed through its resize procedure, or its parent returns a geometry almost when the form makes a geometry request.

Managing, Unmanaging and Destroying Children
When a widget within a form is unmanaged or destroyed, it is removed from the constraint processing and the constraints are reprocessed to reposition and/or resize the form and its contents.  Any widgets that referenced it are rereferenced to the widget that it had been referencing.  For the unmanaged case, if the widget is remanaged, the widgets that were previously referencing it are rereferenced to it, thus preserving the original layout.

NEW RESOURCES

The Form does not add any new resources.  All of the functionality for the form is tied to its constraint resources. 

CONSTRAINT RESOURCES

The following resources are attached to every widget inserted into Form.  To specify an of these resources within a .Xdefaults file, drop the XtN from the resource name.  Refer to CONSTRAINT(3X) for a general discussion of constraint resources.   

XtNxRefName XtNyRefName
When a widget is added as a child of the form its position is determined by the widget it references.  The reference widget must be created before the widget which references it is created.  These resources allow the name of the reference widget to be given.  The form converts this name to a widget to use for the referencing.  Any widget that is a direct child of the form or the form widget itself can be used as a reference widget.

XtNxRefWidget XtNyRefWidget
The application can specify the reference widget as either a string representing the name of the widget (as described above) or as the Widget ID value returned from XtCreateWidget.  This resource is the means by which a widget ID is specified.

XtNxOffset XtNyOffset
The location of a widget is determined by the widget it references.  As the default, a widget’s position on the form exactly matches its reference widget’s location. There are two additional pieces of data used to determine the location.  This resource defines an integer value representing the number of pixels to add to the reference widget’s location when calculating the widget’s location.

XtNxAddWidth XtNyAddHeight
This resource indicates whether or not to add the width or height of the reference widget to a widget’s location when determining the widget’s position.

XtNxVaryOffset XtNyVaryOffset
When a form is resized, it processes the constraints contained within its children.  This resource allows the spacing between a widget and the widget it references to vary (either increase or decrease) when a form’s size changes.  For widgets that directly reference the form widget this resource is ignored.  The spacing between a widget and its reference widget can decrease to 0 pixels if the XtNAddWidth resource is FALSE or to 1 pixel if XtNAddWidth is TRUE.

XtNxResizable XtNyResizable
This resource specifies whether the form can resize (shrink) a widget.  When a form’s size becomes smaller the form will resize its children only after all of the inter-widget spacing of widget’s with their VaryOffset resource set to TRUE.  The form keeps track of a widgets initial size or size generated through XtSetValues so that when the form then becomes larger the widget will grow to it original size and no larger.

XtNxAttachRight XtNyAttachBottom
Widgets are normally referenced from "form left" to "form right" or from "form top" to "form bottom."  The attach resources allow this reference to occur on the opposite edge of the form.  These resources, when used in conjunction with the varyOffset resources, allow a widget to float along the right or bottom edge of the form.  This is done by setting both the Attach and VaryOffset resources to TRUE.  A widget can also span the width and height of the form by setting the Attach resource to TRUE and the VaryOffset resource to FALSE.

XtNxAttachOffset XtNyAttachOffset
When a widget is attached to the right or bottom edge of the form (through the above resources), the separation between the widget and the form is defaulted to 0 pixels.  This resource allows that separation to be set to some other value.  Also, for widgets that are not attached to the right or bottom edge of the form, this constraint specifies the minimum spacing between the widget and the form.

INHERITED RESOURCES

The following resources are inherited from the indicated superclasses:  

KEYBOARD TRAVERSAL

If the XtNtraversalOn resource is set to TRUE at either create time or during a call to XtSetValues, the XwManager superclass will automatically augment the manager widget’s translations to support keyboard traversal.  Refer to the XwManager man page for a complete description of these translations. 

EXAMPLES

The following examples list the desired layout of widgets within a form and the constraints needed to achieve the layout. 

TitleBar
Use the following constraints to get a titlebar widget to span the top of a form the following constraints can be used.  For a widget named title the .Xdefaults file will contain. 
 
 

Dynamic Scrolled Window
The above constraints work generally for any widget type that is to span the form and that need to be resized as the form increases or decreases in size.  For example, if the child widget is a scrolled window named sWin that dynamically resizes as the form resizes in both the horizontal and vertical directions the constraints are as follows. 
 
 

Right or Bottom Attached Widgets
For a widget named widget to float along the right or bottom edge of the form as it is resized the constraint set is the same as for the titlebar example with the following changes. 
 
 

ORIGIN

Hewlett-Packard Company. 

SEE ALSO

CORE(3X), COMPOSITE(3X), CONSTRAINT(3X), XWMANAGERCLASS(3X)

September 29, 2021