by Kamran Husain

IN THIS CHAPTER

• What Is the Interviews System?

• How to Get and Install Interviews

• Sample Applications

• idraw

• 
  Changes to Xdefaults

• ibuild

• 
  Code Generation

• Building an Application with ibuild

In this chapter, you will learn about the Interviews C++ class library development system. You will learn about the tools available for Interviews and how to use them to create front-end GUI applications.

Interviews offers a rich set of C++ functionality and tools for building applications. This chapter can't possibly do it justice in the space provided. By reading to the end of the chapter, though, you will get a feel for creating truly object-oriented applications using Interviews.

To get the most out of this chapter, you need some knowledge of how to run the C++ compiler and how to program in object-oriented languages. If you have not already done so, you should install the X window package with at least Motif window manager (mwm) or the OPEN LOOK manager (olwm).

The Interviews subsystem is a windowing system for X Window. Interviews is copyrighted by The Board of Trustees of the Leland Stanford Junior University. Interviews was developed by Mark Linton's group at Stanford.

What makes Interviews an interesting environment is that it provides an object-oriented approach to building user interfaces. All components within Interviews, such as windows, menus, scrollbars, and so on, are objects with inherited behavior. The name Interviews is derived from the package presenting an interactive view of some data. For example, a front end to a database provides an interactive view to the data in the database.

The Interviews kit is distributed in two packages: iv1 and iv2. The first package, iv1, contains the binary and source files for the libraries. The second package includes the man pages and a PostScript reference manual for the Interviews system.

The Interviews package is included on the CD that comes with this book.

$ ls -al /usr/interviews/bin

total 1187

drwxr-xr-x    2 root     root         1024 Nov  5 17:40 .

drwxr-xr-x    6 root     root         1024 Nov  5 17:40 ..

-rwxr-xr-x   1 root     root         9220 Apr 17  1994 alert

-rwxr-xr-x   1 root     root           82 Apr 17  1994 cpu

-rwxr-xr-x   1 root     root        17412 Apr 17  1994 dclock

-rwxr-xr-x   1 root     root       259076 Apr 17  1994 doc

-rwxr-xr-x   1 root     root         1616 Apr 17  1994 ibmkmf

-rwxr-xr-x   1 root     root       689156 Apr 17  1994 ibuild

-rwxr-xr-x   1 root     root        37892 Apr 17  1994 iclass

-rwxr-xr-x   1 root     root        17412 Apr 17  1994 idemo

-rwxr-xr-x   1 root     root       115716 Apr 17  1994 idraw

-rwxr-xr-x   1 root     root         9220 Apr 17  1994 ifc

-rwxr-xr-x   1 root     root          642 Apr 17  1994 ivmkmf

-rwxr-xr-x   1 root     root        13316 Apr 17  1994 logo

-rwxr-xr-x   1 root     root        17412 Apr 17  1994 mailbox

-rwxr-xr-x   1 root     root         1736 Apr 17  1994 remind

Let's start with an application in the Interviews package. Learning this application will familiarize you with Interviews and working with its development tools. (See Figure 33.3.)

The idraw application lets you draw rectangles, polygons, ellipses, and other shapes interactively. Drawings are stored in files that can be printed on a PostScript printer. You can open an existing drawing by typing a filename on the command line when starting up idraw.

You must engage a tool before you can use it. You engage a tool by clicking on its icon, or by typing the character that is below and to the right of its icon. The icon of the drawing tool that's engaged appears in inverted colors. When it is engaged, you use the tool by clicking the left mouse button in the drawing area.

• Scale is used to resize graphics about their centers.

• Stretch lets you stretch graphics vertically or horizontally, while tying down the opposite edge.

• Rotate enables you to rotate graphics about their centers, according to the angle between two radii: the one defined by the original clicking point and the one defined by the current dragging point.

• Alter is used to alter a graphic's structure. See the rest of the descriptions of tools to see how Alter affects each tool individually.

• Magnify is used to magnify a portion of the drawing specified by sweeping out a rectangular area. The idraw application magnifies the area to occupy the entire screen, if possible.

• Text inserts textual data. Create some text. Left-click to position the first line of text, and then type as much text as you want. The input can be edited using emacs-style keystrokes. You can leave text editing mode by typing ESC or simply clicking somewhere else. The Alter tool lets you edit the text in an existing text graphic.

• Line creates a line. The Shift key constrains the line to lie on either the vertical or the horizontal axis. You may left-click with the Alter tool on either endpoint of a line to move the endpoint to a new location.

• Multiline lets you create a set of connected lines. The Shift key constrains each segment to lie on either the vertical or the horizontal axis. Each left-click starts a new segment (adds a vertex). Each right-click removes the last vertex added. The middle button finalizes the multiline. The Alter tool lets you move, add, and remove vertices from an existing multiline.

• Open Spline creates an open B-spline. The Shift key constrains each control point to lie on either the vertical or the horizontal axis with the preceding point. Each left-click adds a control point. Each right-click removes the last control point added. The middle button finalizes the spline. The Alter tool lets you move, add, and remove control points from an existing open spline.

• Ellipse enables you to create an ellipse. The Shift key constrains the ellipse to the shape of a circle. The Alter tool does not affect ellipses.

• Rectangle enables you to create a rectangle. The Shift key constrains the rectangle to the shape of a square. The Alter tool lets you move the rectangle's corners independently to form a four-sided polygon.

• Polygon enables you to create a polygon. The Shift key constrains each side to lie on either the vertical or the horizontal axis. Each left-click starts a new segment (adds a vertex). Each right-click removes the last vertex added. The middle button finalizes the polygon.

• The Alter tool lets you move, add, and remove vertices from an existing polygon.

• Closed Spline enables you to create a closed B-spline in the same manner that you create an open B-spline.

The pull-down menus File, Edit, Structure, Font, Brush, Pattern, FgColor, BgColor, Align, and View, located above the drawing area, contain commands for editing the drawing and controlling idraw's execution. The File menu contains the following commands to operate on files:

New	Destroys the current drawing and replaces it with an unnamed blank drawing.
Revert	Rereads the current drawing, destroying any unsaved changes.
Open...	Specifies an existing drawing.
Save As	Saves the current drawing in a file with a specific name.
Save	Saves the current drawing in the file from which it came.
Print...	Sends a PostScript version of the drawing to a printer or a file.
Import Graphic...	Can import images from files in the following formats: TIFF; PostScript generated by pgmtops, ppmtops, and idraw; X bitmap format; and Unidraw format.
Quit	Quits idraw.

The Edit menu contains the following commands for editing graphics:

Undo	Successive Undo commands undo previous editing operations.
Redo	Successive Redo commands redo subsequent editing operations up to the first operation undone by Undo. Undone operations that have not been redone are lost as soon as a new operation is performed.
Cut, Copy, Paste	Removes the selected graphics from the drawing and places them in a temporary storage area. Copy keeps the original on the drawing area. Paste puts the contents of the storage area, if any, into the location selected by the mouse.
Duplicate	Duplicates the selected graphics and adds the copies to the drawing.
Delete	Destroys all selected graphics.
Select All	Selects every graphic in the drawing.
Flip Horizontal, Flip Vertical	Flips the selected graphics into their mirror images along the horizontal or vertical axis.
90 degrees Clockwise and CounterCW	Rotate the selected graphics 90 degrees clockwise or counterclockwise.
Precise Move..., Precise Scale..., Precise Rotate...	These buttons let you move, scale, or rotate graphics byexact amounts that you type in a dialog box. You can specify movements in pixels, points, centimeters, or inches. Scalings are specified in terms of magnification factors in the horizontal and vertical dimensions. Rotations are always in degrees.

The Structure menu contains the following commands to modify the structure of the drawing, which is the order in which graphics are drawn:

Group	Collects the selected graphics in a newly created picture. A picture is simply a graphic that contains other graphics. Group enables you to build hierarchies of graphics.
Ungroup	Dissolves any selected pictures.
Bring To Front	Brings the selected graphics to the front of the drawing so that they are drawn on top of (after) other graphics.
Send To Back	Sends the selected graphics to the back of the drawing so that they are drawn behind (before) other graphics.

The Font menu contains a set of fonts in which to display text. When you set the current font from the menu, you also set the font of all selected graphics to that font. A font indicator in the upper-right corner displays the current font.

The Brush menu contains a set of brushes with which to draw lines. When you set the current brush from the menu, you also set the brush of all selected graphics to that brush. The nonexistent brush draws invisible lines and non-outlined graphics.

The arrowhead brushes add arrowheads to one or both ends of lines, multilines, and open splines. A brush indicator in the upper-left corner displays the current brush.

The Pattern menu contains a set of patterns with which to fill graphics, but not text. Text always appears solid, but you can use a different color than black to get a halftoned shade. When you set the current pattern from the menu, you also set the pattern of all the selected graphics to that pattern. The nonexistent pattern draws unfilled graphics, while the other patterns draw graphics filled with a bitmap or a halftoned shade.

The FgColor and BgColor menus contain a set of colors with which to draw graphics and text. When you set the current foreground or background color from the FgColor or BgColor menu, you also set the foreground or background color of all the selected graphics. The ON bits in the bitmaps for dashed lines and fill patterns appear in the foreground color; the OFF bits appear in the background color.

A black-and-white printer prints a halftoned shade of gray for any color other than black or white. The brush, pattern, and font indicators all reflect the current colors.

The Align menu contains commands to align graphics with other graphics.

The first graphic selected stays fixed, while the other graphics move in the order that they were selected according to the type of alignment chosen. The last Align command, Align to Grid, aligns a key point on each selected graphic to the nearest point on idraw's grid.

The View menu contains the following commands:

New View	Creates a duplicate idraw window containing a second view of the current drawing. The second view may be panned, zoomed, and edited independently of the first. Any number of additional views may be made in this manner. Changes made to a drawing through one view appear synchronously in all other views of the same drawing. You may also view another drawing in any idraw window via the Open command.
Close View	Closes the current idraw window. Closing the last idraw window is equivalent to issuing a Quit command.
Normal Size	Sets the magnification to unity so the drawing appears at actual size. A What You See Is What You Get (WYSIWYG) display.
Reduce to Fit	Reduces the magnification until the drawing fits entirely within the view.
Center Page	Modifies the view over the center of a 8.5- by 11-inch page as it's printed. Other page sizes are not supported to date.
Orientation	Toggles the drawing's orientation. If the editor was showing a portrait view of the drawing, it now shows a landscape view of the drawing, and vice versa.
Grid on/off	Toggles idraw's grid on or off. When the grid is on, idraw draws a grid of equally spaced points behind the drawing.
Grid Spacing	Enables you to change the grid spacing by specifying one or two values in the units desired (pixels, points, centimeters, or inches). If two values are given (separated by a space), the first specifies the horizontal spacing, and the second specifies the vertical spacing. One value specifies equal horizontal and vertical spacing.
Gravity on/off Toggle	Toggles gravity on or off. Gravity constrains tool operation to the grid, whether or not the grid is visible.

You can customize the number of changes that can be undone and the font, brush, pattern, or color menus by setting resources in your Xdefaults database. Each string of the form idraw.resource:definition sets a resource. For example, to customize any of the paint menus, set a resource given by the concatenation of the menu's name and the entry's number (such as idraw.pattern8) for each entry that you want to override. All menus use the number 1 for the first entry.

You must set resources only for the entries that you want to override, not for all of them. If you want to add entries to the menus, simply set resources for them. However, don't skip any numbers after the end of the menu, because the menu ends at the first undefined resource. To shorten a menu instead of extending it, specify a blank string as the resource for the entry following the last item on the menu. The idraw application understands the resources listed in Table 33.1. Table 33.1. The idraw resources.

history	Sets the maximum number of changes that can be undone (20 by default).
initialfont	Specifies the font that is active on startup. Supply a number that identifies the font by its position in the Font menu, starting from 1 for the first entry.
font	Defines a custom font to use for an entry in the Font menu. Give three strings, separated by whitespace. The first string defines the font's name; the second string defines the corresponding print font; and the third string defines the print size. For example, idraw.font3:8x13bold Courier-Bold 13 defines the third font entry.
initialbrush	Specifies the brush that is active on startup. Give a number that identifies the brush by its position in the Brush menu, starting from 1 for the first entry. Define a custom brush to use for an entry in the Brush menu. The definition requires two numbers: a 16-bit hexadecimal number to define the brush's line style (each 1 bit draws a dash and each 0 bit produces a gap) and a decimal integer to define the brush's width in pixels. For example, idraw.brush2:ffff 1 defines a single pixel-wide solid line. If the definition specifies only the string none, it defines the nonexistent brush.
initialpattern	Specifies the pattern that is active on startup. Give a number that identifies the pattern by its position in the Pattern menu, starting from 1 for the first entry.
pattern	Defines a custom pattern to use for an entry in the Pattern menu. You can specify the pattern from a 16x16 bitmap, an 8x8 bitmap, a 4x4 bitmap, a grayscale number, or the string none. You specify the 16x16 bitmap with sixteen 16-bit hexadecimal numbers, the 8x8 bitmap with eight 8-bit hexadecimal numbers, the 4x4 bitmap with a single 16-bit hexadecimal number, and the grayscale number with a single floating-point number. The floating-point number must contain a period to distinguish itself from the single hexadecimal number, and it must lie between 0.0 and 1.0, with 0.0 corresponding to a solid pattern and 1.0 to a clear pattern. On the printer, the bitmap patterns appear as bitmaps, the grayscale patterns appear as halftoned shades, and the none patterns never obscure any underlying graphics. For example, idraw.pattern8:8421 defines a diagonally hatched pattern.
initialfgcolor	Specify the foreground color that is active on startup. Give a number that identifies the color by its position in the FgColor menu, starting from 1 for the first entry, fgcolor. Define a custom color to use for an entry in the FgColor menu. Give a string defining the name of the color, and (optionally) three decimal numbers between 0 and 65,535 following the name to define the red, green, and blue components of the color's intensity. The intensities override the name; that is, idraw looks up the name in a window system database of common colors only if you omit the intensities.
initialbgcolor	Specifies the background color that is active on startup. Give a number that identifies the color by its position in the BgColor menu, starting from 1 for the first entry.
bgcolor	Defines a custom color to use for the entry in the BgColor menu. The same rules apply to background colors as to foreground colors.

The ibuild package is an editor that enables you to graphically create a user interface for an Interviews application. The ibuild application can save your work as an external file, or as actual C++ code that, when compiled, generates the same user interface that you would create with ibuild. You restore a previously saved interface by typing ibuild and the interface filename on the command line. (See Figure 33.4.)

Now, you can create the application sample1-exe with the following command:

$ make -f sample1-make sample1

This make command spews a lot of messages from the GNU g++ compiler. You should not see any error messages if you have edited your sample1-make file as described earlier. After you have created the application, you can execute this application with this command:

$ sample1

The result of this application is shown in Figure 33.5.

The last order of business for your sample application is to add code to take actions when a button is pressed. This step enables you to attach your own code to your newly created application. A GUI by itself really does not serve any purpose, does it? The code that takes action is called an Interactor.

The final step is to create the classes that wrap the core around another class. Remember that we created a MonoScreen class as the topmost class for this application. Using the Examine tool, get the info on the Mono_* class for this application. When you get the dialog box for this application, change the Class Name to something else, like Sample1. Click OK to save.

Now, generate the code for this application. You see the following four files listed:

iview/Sample1-core.c

iview/Sample1-core.h

iview/Sample1.c

iview/Sample1.h

Do not edit the *-core files. Edit the Sample1.c and Sample1.h files to create your own functions. The Sample1.h file looks like the one shown in Listing 33.2. The Sample1.c file is shown in Listing 33.3.

#ifndef Sample1_h

#define Sample1_h

#include "Sample1-core.h"

class Sample1 : public Sample1_core {

public:

    Sample1(const char*);

    virtual void entered();

};

#endif