Volume 7A: XView Programming Manual

defines attributes that give hints to the window manager to provide such features as title bar

information, resize corners, and so on. If a non-OPEN LOOK window manager is used, there

is no guarantee that these attributes will have any effect.

Pop-up frames are typically used to perform one or more transient functions. They are not

intended to stay up after the set of functions has been completed, although they might remain

up if the user or the application so chooses. This functionality can be handled by a pushpin at

the upper-left corner of the frame. There are different kinds of pop-up frames:

Command Frames give operands and set parameters needed for a command. This is

implemented as a subframe that contains a default panel.

Help Frames display help text for the object under the pointer. This is implemented

as a text subwindow within a subframe.

Notices are special pop-up windows that are used to confirm requests, to dis-

play messages and conditions that must be brought to the user’s atten-

tion and handled immediately. These require immediate attention and

can suspend the application by disallowing the focus from leaving the

Notice.

Figure 2-4 shows a sample unpinned command frame from the OPEN LOOK GUI Specifica-

tion Guide.

Figure 2-4. Sample unpinned command frame

The user may select the option, and the frame will be dismissed (be undisplayed). The push-

pin at the upper-left corner is out of its hole. If the pushpin were in, the command frame

would remain visible even after the user selects an action to take. Figure 2-5 shows a sample

pinned help frame from the OPEN LOOK GUI Specification Guide.

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The XView Programmer’s Model 27

Figure 2-5. Sample help window

Figure 2-6 shows a sample notice from the OPEN LOOK GUI Specification Guide.

Figure 2-6. Sample notice

The user can do nothing but choose either Save or Cancel. Choosing either one will cause

the notice to be dismissed immediately.

28 XView Programming Manual

2.4.4 Subwindows

Subwindows differ from frames in several basic ways. They never exist independently; they

are always owned and maintained by a frame or another window, and they may not them-

selves own frames. While frames can be moved freely around the screen, subwindows are

constrained to fit within the borders of the frame to which they belong. Also, in contrast to

frames, subwindows are tiled—they may not overlap each other within their frame. Within

these constraints (which are enforced by a run-time boundary manager), subwindows may be

moved and resized by either a program or a user.

Canvas subwindows and text subwindows are subclassed from the OPENWIN package, a hid-

den class which implements the notion of splittable views described by OPEN LOOK. Figure

2-7 shows an example of one canvas object providing separate views into one graphic image.

Each view into the object has scrollbars attached. The scrollbars provide the ability to scroll

independently from all the other views attached to the subwindow and to split the views

again.

Figure 2-7. A window with multiple views

All the views, however, are still a part of the same OPENWIN object. Using the scrollbars, the

user can split or join different views.

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The XView Programmer’s Model 29

2.4.4.1 Canvas subwindows

The canvas is the most basic type of subwindow. It provides a drawing surface—a place in

which the result of Xlib graphics calls can be displayed. A canvas object can be configured

to permit the application to draw on an area larger than the size of the visible window. The

entire region representing the drawing surface is a window called the paint window. The vis-

ible portion of the paint window is the view window. It is the view window that appears in

the canvas subwindow. In the previous figure, the paint window contains a picture of an

astronaut. Multiple view windows each show a particular region of the paint canvas. The

view windows are independent of each other. See Chapter 5, Canvases and Openwin, for a

full discussion and illustration of the Canvas model.

2.4.4.2 Text subwindows

Another basic window type is a text subwindow. It provides basic text editing capabilities

using the OPEN LOOK text editing model.

2.4.4.3 Panels

A panel (or control area) is an unbordered region of a window where controls such as but-

tons and settings are displayed. The panel also controls the arrangement of its controls in a

horizontal or vertical fashion. The panel shown in Figure 2-8 presents the typical positioning

of the control area—the top of a base frame with a canvas subwindow under it.

Figure 2-8. A control area above a subwindow

The panel shown in Figure 2-9 presents a control area that is to the right of a canvas subwin-

dow.

30 XView Programming Manual

Figure 2-9. A control area to the right of a pane

Control areas within panes usually contain varied combinations of the following controls:

• Buttons

• Check boxes

• Drop Target Items

• Exclusive and nonexclusive choice lists

• Gauges

• Sliders

• Text and numeric fields

A command frame (subframe) contains only a panel and no other subwindows. Figure 2-10

shows a control area in a command frame. It contains text fields, choice lists, and buttons.

See Chapter 7, Panels, for a discussion of panel items and the PANEL package.

2.4.4.4 Menus

Menus are subclassed from the Generic Object. A menu by itself is a windowless object.

Only when the menu is activated by the user is it bound to a window. This implementation

avoids creating multiple X11 windows (one for each menu) since not all the menus will be

displayed at once. XView has three types of menus:

1. Pop-up menus that are displayed when the user presses the menu button in a window.

2. Pullright menus that are displayed as a menu to the right of a menu.

3. Pulldown menus that are displayed below a menu button on a panel.

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