Related Info: Resource Manager Window Manager Picture Utilities

Separating Data from Code

Using those little pockets of data called resources

By Dave Mark, MacTutor Regular Contributing Author

Last month’s column focused on QuickDraw, the Macintosh drawing environment. The TextBoxer program showed you how to use QuickDraw in combination with the Window Manager to draw text and graphics in a window. This month we’ll learn about resources, the Mac’s mechanism for separating data from code.

Resources

Resources are little pockets of data, designed to pull descriptive data out of your program’s source code. For example, a WIND resource describes the size, location, and characteristics of a Macintosh window. In last month’s column, we used the Window Manager call NewWindow() to create a new window:

/* 1 */

WindowPtr window;
Rect    windowRect;
 
SetRect( &windowRect, 20, 40, 260, 74 );

window = NewWindow( nil, &windowRect, "\pBox o’ Text",
 kVisible, documentProc, kMoveToFront,
 kNoGoAway, kNilRefCon );

The parameters passed to NewWindow() completely describe the window. The trouble is, the description is inexorably bound into the source code. To change the size or position of the window, you’ve got to recompile your program. The WIND resource gives you an alternative to this strategy. Here’s how it works...

Basic Resource Strategy

At the heart of any resource strategy is a resource editor. Though there are others, for my money [especially since it is free - Ed.] ResEdit can’t be beat. ResEdit allows you to edit resources using a graphic resource editor designed for that resource type. For example, Figure 1 shows ResEdit’s WIND editing window.

This window gives you all the tools you’ll need to completely describe a window. At the top is a row of icons that let you select the type of window you’d like to create. At bottom-left is a series of fields you can use to describe the size and location of the window. In the center is a miniature version of your screen, showing how your window will look once it’s created.

Figure 1. ResEdit’s WIND editing window.

Once you design your resources, you load them into your program using a set of Toolbox routines designed to work with resources. As an example, the routine GetNewWindow() loads a WIND resource and creates the same kind of WindowRecord as the Window Manager routine NewWindow():

/* 2 */

window = GetNewWindow( kBaseResID, nil, kMoveToFront );

If you use NewWindow() to create a window, the data that describes the window is embedded in the source code in the form of NewWindow() parameters. If you use GetNewWindow(), the data that describes the window resides outside of your program’s code, in the WIND resource. The WIND resource acts as a template for creating a window.

As you spend more time programming the Macintosh, you’ll learn more and more about the enormous potential of resources. For now, we’ll start slowly, introducing a few basic resources in this column, and adding to our list each month.

Resource Management Specifics

Resources are identified by a resource type and a resource ID. The resource type is a four-byte value, typically made up of readable ASCII characters. The resource type defines the data described by the resource. For example, a WIND resource always follows the same format and always describes a Macintosh window. There are lots of different resource types.

A program can contain more than one resource of a given type. The resource ID serves to differentiate one resource of a given type from another. Typically, resource IDs start at 128 and move upwards from there. If your program used three WIND resources, you’d number them 128, 129, and 130.

This month’s sample program, PICTWindow, makes use of two resources, a PICT and a WIND. The PICT resource contains a Macintosh picture. PICTWindow uses the WIND resource to create a new window, loads the PICT resource into memory, then draws the PICT in the window.

Let’s get to work...

Creating the PICTWindow Resources

If you don’t already have a copy of ResEdit, go out and get one. You can download ResEdit from most of the big bulletin boards, and you can purchase ResEdit from APDA.

In my latest APDA catalog, there were three entries for ResEdit version 2.1.1. $29.95 gets you the manual and disk, $14.95 is the manual only, and $15.00 for the disk only. You can reach APDA by phone at (800) 282-2732 in the United States, (800) 637-0029 in Canada, and (408) 562-3910 internationally.

Once you’ve copied your copy of ResEdit to your hard drive, create a folder for all the PICTWindow files inside your development folder. I called my folder (logically enough) PICTWindow.

Next, use your favorite graphics package to create a pleasing picture. Copy the picture, then paste it into the Scrapbook. Feel free to use color, text, and whatever else pleases your eye in your picture. PICTWindow can handle anything you can paste into the Scrapbook.

Now you’re ready to create some resources. Double-click on the ResEdit icon to start-up ResEdit. When the bouncing Jack-in-the-box appears, click the mouse button. You’ll be prompted for a file to open (if your version of ResEdit doesn’t prompt you, it’s OK, just ignore the rest of this paragraph). Click the Cancel button.

We’re going to create a new resource file. Select New... from the File menu. The dialog box shown in Figure 2 will appear, asking you to name the new resource file. Using the standard techniques, navigate over and in to the PICTWindow folder you created earlier. In the text field at the bottom of the dialog box, type the file name PICTWindow.Π.rsrc exactly as it appears in Figure 2. To type the Π character, hold down the option key and press the p key. Be sure to type the name exactly as shown. Don’t add anything. Don’t leave anything out. You’ll see why later in the column.

Figure 2. Naming your new resource file.

Once the name is typed in, click on the New button. ResEdit will create the new resource file and display a window showing the resources in this file. So far, there are none. We’ll fix that right now.

Select Create New Resource from the Resource menu. A scrolling list of resource types will appear (Figure 3). Scroll to the bottom of the list and select WIND (if you prefer, you can type WIND in the text field). Once WIND is selected (or typed) click the OK button. A WIND icon will be added to the PICTWindow.Π.rsrc main window, showing you that a WIND resource exists. A WIND picker window will appear, listing all the WIND resources in this file. Finally, on top of the other two, a WIND editing window will appear, allowing you to edit your new WIND.

Figure 3. Creating a new WIND resource.

By default, your new WIND resource is given the resource ID 128. That’s convenient, since that’s the number we wanted it to have. Use the settings shown in Figure 4 to modify your WIND resource. Click the second icon from the left (at the top of the window) and type in the four numbers shown in the lower left corner.

Figure 4. The WIND editing window from WIND 128.

Next, select Set 'WIND' Characteristics... from the WIND menu that appeared along with the WIND editor. Type in an appropriate window title (don’t change any of the other fields) and click the OK button. Congratulations! You’ve just created your first Macintosh resource. Close the WIND editing window and the WIND picker window, leaving the main window for the resource file. A WIND icon should appear in this window.

Let’s add the second resource needed by our program, the PICT resource. Go to the Scrapbook and Copy the picture you pasted in there earlier (if you prefer, Copy one of the pictures that come with the Scrapbook - Don’t copy plain text. Plain text won’t do what we want).

Once your picture is copied, bring the PICTWindow.Π.rsrc window back to the front and select Paste from ResEdit’s Edit menu. A new resource will be created and a PICT icon will appear in the main window verifying this fact. The PICT resource will automatically be given the resource ID 128. Now would be an excellent time to select Save from the File menu. You are done creating resources.

Quit ResEdit by selecting Quit from the File menu.

Creating the PICTWindow Project

Startup THINK C and create a new project in the PICTWindow folder. Name the new project PICTWindow.Π (be sure to spell it exactly this way). When you run a project, THINK C automatically tacks on the five characters “.rsrc” to the end of the project name and looks for a resource file with that name. If a resource file with that name is found, the resources in that file are automatically made available to your program. PICTWindow.Π is the name of your project file and PICTWindow.Π.rsrc is the name of your resource file.

Once the project is created, go into the Mac Libraries folder and add MacTraps to the project. Next, select New from the File menu to create a new source code file. Type in this source code:

/* 3 */

#define kBaseResID 128
#define kMoveToFront (WindowPtr)-1L


/***************/
/*  Functions  */
/***************/

void  ToolBoxInit( void );
void  WindowInit( void );
void  DrawMyPicture( void );


/****************** main ***************************/

void  main( void )
{
 ToolBoxInit();
 WindowInit();
 
 DrawMyPicture();
 
 while ( !Button() ) ;
}


/****************** ToolBoxInit *********************/

void  ToolBoxInit( void )
{
 InitGraf( &thePort );
 InitFonts();
 InitWindows();
 InitMenus();
 TEInit();
 InitDialogs( nil );
 InitCursor();
}


/****************** WindowInit ***********************/

void  WindowInit( void )
{
 WindowPtrwindow;
 
 window = GetNewWindow( kBaseResID, nil, kMoveToFront );
 
 if ( window == nil )
 {
 SysBeep( 10 );  /*  Couldn't load the WIND resource!!!  */
 ExitToShell();
 }
 
 ShowWindow( window );
 SetPort( window );
}


/****************** DrawMyPicture ********************/

void  DrawMyPicture( void )
{
 Rect   pictureRect;
 PicHandlepicture;
 
 picture = GetPicture( kBaseResID );
 
 if ( picture == nil )
 {
 SysBeep( 10 );  /*  Couldn't load the PICT resource!!!  */
 ExitToShell();
 }
 
 pictureRect = (**picture).picFrame;
 
 OffsetRect( &pictureRect, - pictureRect.left,
 - pictureRect.top );
 
 DrawPicture( picture, &pictureRect );
 
 FrameRect( &pictureRect );
}

Once your source code is typed in, select Save from the File menu. Save the file under the name “PICTWindow.c”. Next, add the source file to the project by select Add (not Add...) from the Source menu. Your project window should look like the one shown in Figure 5.

Figure 5. The project window for PICTWindow.Π.

Running the Program

Now you’re ready to run your program. Select Run from the Project menu. If you encounter any errors, check your source code for typos and make sure your project window has the two files shown in Figure 5. Once your program runs, you should see a window similar to the one shown in Figure 6.

Notice that the picture is drawn in the upper left corner of the window. The upper left corner of the picture is at (0,0) in the window’s local coordinate system.

Figure 6. The PICTWindow window!

Key Lines of Code

Most of the program should make sense to you if you read through last month’s TextBoxer example. Rather than repeat last weeks explanations, I’d like to point out three key segments of code. The first is the code that loads the WIND resource and creates a new window:

/* 4 */

 window = GetNewWindow( kBaseResID, nil, kMoveToFront );

As mentioned earlier, this line of code accomplishes the same thing as NewWindow(), except that GetNewWindow() gets its information from the WIND resource, instead of its parameter list. GetNewWindow() is described in Volume I of Inside Macintosh, on page 283.

The second key line of code is the line that loads the PICT resource:

/* 5 */

 picture = GetPicture( kBaseResID );

This line of code loads the PICT resource with an ID matching kBaseResID. Match this line of code up with the following:

/* 6 */

 DrawPicture( picture, &pictureRect );

and you can really see the power of resources. Two lines of code and you’ve drawn a complex graphic in a window!!! By the way, GetPicture() is on page 475 of Volume I of Inside Macintosh and DrawPicture() is on page 190 of Volume I.

Till Next Month

Take some time to play around with ResEdit. Use ResEdit to modify your WIND resource, changing the type of window (click on the icons on the top row of the WIND editor) and the window’s location. Notice that the picture is drawn in the upper left of the window, no matter where the window is drawn on the screen. Look up OffsetRect() in Inside Macintosh and try to figure out why the picture is drawn where it is.

Finally, try to write a routine that centers the picture in the window. For a little help with this last exercise, you can check out the ShowPICT program in Volume I of the Mac Primer.

Sorry to cut this column short, but the next time I speak with you all, I should be a proud new poppa! Stay tuned...