This exercise demonstrates how to use standard X utilities to create icons and generate PostScript screendumps of X applications. It also introduces some Xlib calls (beginning with X rather than Xt) that are frequently needed in applications built on top of the X Toolkit.

You should have read Chapter 11.1 in Nye and O'Reilly, Vol. 4, before starting this exercise.

1. Make a new copy of your dialogs program, naming it bitmaps. Use X's standard bitmap client to create an icon for the application. Use standard naming conventions for this, calling the file bitmaps.xbm.

   Make the icon 32x32 in size (if it doesn't fit well on the screen, just resize the bitmap window). Remember to keep the design fairly simple, since it will be small on the screen. When you are done, save it in a file and exit bitmap. Now, re-enter bitmap, this time specifying the name of your file rather than a size. It should come up in a reduced size that's convenient for making a screendump (if not, just shrink the size of the window manually). Use the techniques you learned in Exercise 1 to print a copy.

2. Now follow Example 11-2 in the text to associate the icon you designed with the bitmaps program. You will need to incorporate the following changes:
   • include the Shell header file

     ---

     [Warning: this must be after the Intrinsics header file, but should be before the Athena header files. Figure out why.]

     ---

   • include your icon file (note that this goes between quotes, not angle brackets)
   • add a variable of type Pixmap for the icon
   • create the pixmap using a call to XCreateBitmapFromData (be careful with spelling when you mimic this)
   • activate the icon with a call to XtVaSetValues that sets the XtNiconPixmap resource
   • change your Makefile so it re-compiles whenever you alter the icon

   What is the name of the resource that specifies an icon, and what widget class is it associated with?

3. Experiment with the other resource settings that influence the main application window. Note that the user has been having to position the main window of the application. The geometry resource can cause the window to appear automatically, at a specified position. (The position is calculated in the same way that it would be if the user specified the -geometry command-line option; see Exercise 1). In this case, the application developer chooses the position in advance and specifies it in the same way that the icon pixmap resource is set.

   What is the resource named constant for this (see Volume 5's description of shells)? What would the resource setting look like to position the window at coordinates 100,100?

   Implement the resource setting needed to position the application window at roughly the center of the screen. It is also possible to bring up a window in "iconic" form to begin with. This may be handy when you want to bring up a main window, plus a couple of other windows that are initially closed. The availability of icons will signal to the user that other windows are available. Use the iconic resource of shells to force your program to begin in closed (iconic) form.

   When both geometry and iconic resources are set, what are the positions of the icon? the window?

4. Another use for icons is to create toolbox-style pushbuttons, where a graphical icon takes the place of any word label. Change the quit button to have a picture instead of the word "quit":
   • create a small icon for the button, storing it in a file with a name that conforms to normal conventions
   • include the file in your application
   • define a second pixmap, and create it the same way you did the application icon
   • in the call to XtVaCreateManagedWidget that builds the button, set the appropriate resource to your new pixmap (use the description of the Command widget class in Vol. 5 to determine which resource is needed)

5. The cursor is another example of icon use in X applications. So far, you have only been using the default cursor, but you can change the cursor in any X window -- or in the case of a widget-based application, you can change the cursor for any widget(s).

   One of X's "fonts" is actually a collection of predefined cursor shapes. Change the cursor for the quit button in bitmaps to a skull-and-crossbones, following this procedure:

   • gain access to the predefined cursor names by include'ing X11/cursorfont.h
   • figure out which of the predefined cursor names refers to the skull-and-crossbones [hint: use the X client for viewing fonts that you learned in Exercise 5, giving it the font name "cursor"]
   • define a cursor variable, declaring it to be of type Cursor
   • in your initialization code, create the cursor of your choice, using a call to the Xlib routine, XCreateFontCursor:

     cursor-variable = XCreateFontCursor 
          (XtDisplay(toplevel), some-cursor-name);
     

     This step creates a server-side resource, but it does not associate the cursor with any window(s).
   • A cursor cannot be assigned until after the widget has been realized. Immediately after realization, add the following call to another Xlib routine, XDefineCursor:

     XdefineCursor (XtDisplay(quit_button), 
           XtWindow(quit_button), cursor-variable);
     

     The named widget - and all its children -- will use the cursor you defined, rather than the default one.

   Run the program, observing when the cursor changes shape.

   How can you make the new cursor apply to all widgets in the whole application?