Static Versus Dynamic Layout
As mentioned previously, porting your application to Motif is not an
object-for-object swap. Such swapping concentrates on the static aspects
of your application user interface. Complex applications in particular contain
many objects that manage the application infrastructure and make it work
in dynamic situations. (Dynamic aspects of your application include, but
are not limited to, resizing windows, localization, and font changes.) These
manager widgets that handle the dynamic geometry in
your application are different in the OPEN LOOK and Motif toolkits. Your
application will not display the dynamism you want if you try an object-for-object
swap of manager widgets. Introducing an appropriate design to handle the
dynamic aspects of your application typically increases the complexity of
its architecture.
XView does not provide much variety for dynamic layout. It primarily
fixes objects at (x, y) positions, which can cause difficulties if an application
font is changed or the application is localized. Motif and OLIT provide a
variety of geometry manager widgets; however, they have significant differences.
Table 6-1 OLIT and Motif Geometry Manager Widgets
|
OLIT
|
Motif
|
Comments
|
|
BulletinBoard
|
XmBulletinBoard
|
Basically equivalent; provide static
x,y pixel-based positioning for children
|
|
Caption
|
(none)
|
OLIT Caption widget provides a way
to automatically place a label on one of the four sides of a control widget.
To get this functionality in Motif, create a separate XmRowColumn widget that contains two children: the label and the
control
|
|
ControlArea
|
XmRowColumn
|
Both widgets provide a way to lay
out children in rows and columns.
The OLIT ControlArea widget supports aligning Caption widget children
vertically by colon, which the Motif XmRowColumn widget
does not. [CDE App Builder provides a geometry manager abstraction called a group that enables widgets to be automatically positioned in common
layouts, including being vertically aligned by colon. App Builder generates
all the code to implement this functionality.]
The Motif XmRowColumn widget enforces
certain size policies on children (usually forces children in a particular
row or column to be the same size), but the OLIT ControlArea
widget does not.
|
|
FooterPanel
|
(none)
|
OLIT FooterPanel widget provides a
way to lay out a window with a floating footer child at the bottom.
The Motif XmMainWindow widget can be configured for this
layout by setting the "message area child" to be a widget that
can be used as a footer (such as an XmForm or XmRowColumn widget).
|
|
Form
|
XmForm
|
Both widgets provide a means for attaching
their children relative to each other and relative to the Form
itself, however each takes a different view of these "attachments."
The OLIT Form widget provides attachment
resources for the x and y dimensions, while the Motif XmForm
widget provides separate attachments for all four sides (top, bottom, left,
right). You can convert OLIT Form widget attachments to
equivalent XmForm widget attachments if both attachment
paradigms are well understood.
The Motif XmForm
widget also provides a special type of attachment called "Position."
Children can be attached to dynamic positions in the Form
widget which change as the Form widget's size changes.
This enables children to be configured to always occupy a certain percentage
of the Form widget's real estate.
|
|
RubberTile
|
(none)
|
OLIT RubberTile widget enables children
to be configured to take up a percentage of the RubberTile
widget's height (if vertically oriented) or width (if horizontally oriented).
In Motif you can achieve similar functionality by using the
Position-based attachment resources in the XmForm widget.
|
|
ScrolledWindow
|
XmScrolledWindow
|
Both widgets provide a way to encompass
a child widget into a scrollable view port.
|
|
(none)
|
XmMainWindow
|
Motif XmMainWindow widget provides
a manager that lays out its children into specific areas of the window. These
areas include the menu bar area, command area, work area, and message area.
OLIT has no equivalent widget.
|
|
(none)
|
XmPanedWindow
|
Motif XmPanedWindow widget provides
a way to lay out its children in vertically oriented panes. Each of the panes
has a sash that can vertically resize the pane.
OLIT has no equivalent
widget.
|
