TweetFollow Us on Twitter

Beginning Windows
Volume Number:2
Issue Number:7
Column Tag:ABC's of C

Beginning Windows

By Bob Gordon, Apropos Publication Services, Contributing Editor

Probably the most visible part of the Macintosh user interface is the window. Since we can't build much of an application without showing something on the screen, we will begin to examine how to use the Macintosh Window Manager. At the same time, we'll take a look at the C preprocessor, the if-statement, and review the topics from last month-the Event Manager, structures, and the case statement.

Preprocess Your Code

The C preprocessor provides a variety of useful services. We saw last month how to use the #define to provide a shorthand name by which to refer to a structure. These 'define' statements and other data structures can be stored in a seperate ".h" file and included into our source code at compile time. We can create our own new ".h" file to reduce some of C's more arcane symbols. We will call this file "abc.h".

/* abc.h 
 *
 * Local definitions to improve readability
 *
 */
 
#define True1
#define False  0
#define Nil 0
#define and &&
#define or||
#define not !
#define equals ==
#define notequal !=

extern char *PtoCstr(); /* from stdio.h  */
extern char *CtoPstr();

The first three definitions provide some standard constants. C has no boolean type, but it is a good idea to use labeled constants rather than numbers when doing logic. It makes the code easier to follow. "Nil" is used with pointers. Assign a pointer Nil when you don't want it to point anywhere. C guarantees that a pointer can never point to zero, so this is a safe initialization value.

We then have replacements for the logical operation symbols. Admittedly, these take longer to type, but they are much easier to read (they are especially helpful if you must show your code to someone who doesn't use C), and they are safer. A very popular C bug is to leave one of the equal signs out of the equality operator (see top of next column):

 if (a = b)
    code;

instead of

 if (a == b)
    code;

The first is a perfectly legal C if-statement: it assigns the value of b to a, then if a is non-zero, the code is executed. The second executes the code only if the value of a equals the value of b. The cleverness of this bug is that not only is it legal, but many times it is what you want to do. Using "equals" instead of "==" makes it much less likely to change the meaning of a line by a typo, and it makes it much easier to find.

The last two entries are the Pascal-to-C and C-to-Pascal string conversion utilities. These are normally defined in the stdio.h file, but since we are not including that file, we can put them here. Remember, C and Pascal strings are different, so if we send a string to a Toolbox routine, it must be a Pascal string. These are the functions that Mac C has. Other compilers may have similar functions (Aztec C calls these ctop() and ptoc()) or they will do the conversion automatically. Check your documentation and place the appropriate functions in abc.h so you can use them without repeating the external declarations in every source file.

To use abc.h, just have it as one of the include files at the begining of a source file. All the definitions will then be available. We may add other definitions later.

By the way, the May 1986 Byte has an article called "Easy C" that describes a considerably expanded set of preproccessor definitions. The authors replace many of the standard C terms with new ones in an effort to increase readability and reduce errors.

Fig. 1 Program output, window highlited.

if-then-else

There are several if-statements in the sample program. The if-statement is C's other branching construct. Its general form is:

if (expression)
 statement;

if (expression)
 statement;
else    /* shows optional else clause */
 statement;

If the experession evaluates to a non-zero value, the statement is executed. If the expression evaluates to zero and an else is present, the statement following the else is executed. If no else is present, execution continues after the if.

If-statements may be nested, but the relation of else to if may be ambigous:

 if (expression)
 if (another expression)
 statement;
 else
 statement;

Does the else go with the first if or the second? The layout on the page says it will go with the first, but the compiler will place it with the second as it is closer. Use braces to clear up ambiguities:

 if (expression)
 {
 if (another expression)
 statement;
 }
 else
 statement;

Fig. 2 Mouse click outside the window

Fig. 3. Cmd T changes title name

Structures, Functions, and Pointers

The only other C issue we need to deal with is how to get structures in and out of functions. The original definition of C did not allow functions to receive structures as parameters or return them (the new ANSI standard does allow this, check your compiler). A function could, however, receive or return a pointer to a structure. In C a pointer is simply an address, and you can get the address of a variable with the address operator (the ampersand). In the example, theEvent is an EventRecord structure to get the next event from the Event Manager; the pointer (or address) to the EventRecord is specified as &theEvent:

 GetNextEvent(everyEvent,&theEvent);

This passes the address of theEvent to GetNextEvent, by specifying it as &theEvent. This works well with all C compilers, but it does not work in all cases with Toolbox functions. The problem is that Pascal allows structures (records) to be passed as parameters, as well as by address. On the Mac, only structures of four or fewer bytes are passed as parameters; longer structures are passed by address. There is one structure of four bytes, the Point, which we saw last month. Mac C handles this automatically. They define the Point as one of the argument types that can be passed to Toolbox routines. If you are using Mac C, pass the address of the Point. Aztec C, on the other hand, uses a special function, pass() to pass points, as shown below:

FindWindow(pass(er.where), &whichWindow); /*aztec */

Finally, since structures are often used with pointers, C has a special operator to access a member of a structure given a pointer to the structure. If er is an EventRecord and erp is a pointer to an Event Record, the what field is accessed by:

 er.what/* the what member */
 erp->what/* the what member */
 (*erp).what/* the what member */

The last example shows the indirection operator (the asterisk). It yields the value at the address contained in the variable. The structure pointer operator (->) is much easier to read.

Putting a Window on the Screen

The example program this month puts a window on the screen, changes its title, and responds to certain mouse commands. The program deals with only one window and does not include the change size command as multiple windows and changing the size involves accessing the Memory Manager. We'll add these features after we cover it.

The program consists of five routines:

main()

Does initialization and calls the main event loop routine. InitWindows() must be done if you want to use any of the Window Manager routines. See what happens if you do not InitCursor(). The dragbounds rectangle limits the range of DragWindow(): it ensures the window does not fall off the screen. Note that I used the preprocessor to define Screen. This was done simply to avoid typing QD->screenBits.bounds. If we find we need to use QD->screenBits.bounds a lot, we can add it to abc.h.

dowindow()

The dowindow() routine creates a new window on the desktop. As such, it is primarily a call to the toolbox trap NewWindow(), which returns a window pointer to the newly created window structure.

There are several potential trouble spots in NewWindow(). First, the window record (windowRec) must be static. I made it a global. Notice the use of the string conversion routines. See what happens if you don't convert the string back. The parameter, (WindowPtr)-1, is the behind parameter. We wish to place our new window in front of all other windows. To do this we must set the pointer to -1. The construct (WindowPtr) casts the -1 into the type WindowPtr. I expect there would be a serious problem if you left the (WindowPtr) out. Try it. Parameter conversion in C is called 'casting'. By enclosing a parameter type such as WindowPtr in parenthesis, followed by a variable, that variable, in this case, -1, is converted into the same parameter type, in this case a four byte address. Hence, (WindowPtr)-1 is just a fancy way of defining -1 as a long int. Finally, the last parameter is refCon, a value passed to the Window Manager for the application's own use. I'm just passing a zero because I don't have anything to do with it at this time. refCon, though is a long. Mac C seems to pass this correctly, but other compilers may require the value to be explicitly a long. This is another case where things that look correct will not work correctly. To make a constant explictly a long, place an "L" after it (0L).

eventloop()

This is similar to last month's program. Here the EventRecord is local to eventloop(). I only wanted to check the keyDown and mouseDown events so I could have changed the event mask. You might rewrite it that way. If you are reading along in Using the Macintosh Toolbox in C, you will notice that they have this program as one function. I try to keep things fairly small.

dokey()

Here we respond to all the keyDown events. Most of the toolbox routines are fairly straight forward. Each window function receives a window pointer as a parameter. What we are checking for is our menu of command keys. Assuming we have a window opened, then our dokey() routine defines the command keys we will respond to:

Key Function

cmd m make a window ( call dowindow() )

cmd x kill the window (close it)

cmd s show a hidden window

cmd h hide a shown window

cmd t change the window's title

cmd q quit by returning to the finder

We get the keyboard character by extracting it from the message portion of our event record and masking it with a mask that guarantees we only get command key sequences. Then we extract the ascii value of the key sans command key, and check it against the above table of allowed keystrokes. We check for the m key first so we can make a new window if one does not already exist. After that, our switch construct can list each of our key commands knowing that a valid window is present.

domouse()

domouse handles the mouseDown events. First it must determine where the mouse is. The function FindWindow() does this and returns a window code and a pointer to the relevant window. Note the use of the address operator to pass the Point where member. Most of the window functions here are straight forward. TrackGoAway() retains control as long as the mouse button is down and lights the go-away box if the mouse pointer is in it.

Note that I am always calling DrawGrowIcon() after each Window Manager call. This is not really necessary because we're not doing anything with the grow box. Try taking it out.

Final Notes

We've only touched on part of the Window Manager functions. Some will wait until we've covered memory management, others until we've covered resources. Placing things like window definitions inside resource files helps structure the program and makes the user interface components easier to modify and port to different languages (human, not computer). Since this column is about C, I'm going to avoid using resources so we can use the C functions as much as possible. Also, resources present an extra step in getting a program to run, and while we're learning how to do things, we don't need the extra steps. To learn more about resources, read Joel West's "Resource Roundup" series.

Next month we'll move to menus. Rather than use the program in Using the Macintosh Toolbox with C, I will add menus to this one. Now all we have to do is figure out something interesting to put in our windows. Suggestions are welcome.

/* window manager demonstration 
 * base on program in 
 * Using Macintosh Toolbox with C
 * page 70
 */
 
 /* Here are our include files */
 
 #include "abc.h"/* Our own defines */
 #include "Events.h" /* also includes Macdefs.h */
 #include "Window.h" /* also includes Quickdraw.h, which 
 in turn requires M68KLIB.D  */
 
 /* Here are our defines */
 
 #defineScreen   QD->screenBits.bounds
 #definecharCodeMask 0x000000FF
 
 /* Here are our Global variables */
 
 WindowPtrtheWindow;
 WindowRecord  windowRec;
 Rect   dragbound;
 Rect   limitRect;
 
main()
{
 InitWindows();
 InitCursor();
 FlushEvents(everyEvent);
 
 /* Initialize our global variables */
 
 theWindow = Nil;/*indicates no window */
 SetRect(&dragbound,
 Screen.left + 4,
 Screen.top + 24,
      Screen.right - 4,
 Screen.bottom - 4);
 SetRect(&limitRect,60,40,
 Screen.right - Screen.left - 4,
 Screen.bottom - Screen.top - 24);
 
 dowindow();/* make new window */  
 eventloop();    /* check for events */
}

dowindow()
{
char    *title;  /* first title for window */
Rect    boundsRect;
 
if (not theWindow) /* if no window exists, make one */
 {
 title = "ABC Window";
 SetRect(&boundsRect,50,50,300,150);
 theWindow = NewWindow(windowRec, &boundsRect, CtoPstr(title),True,documentProc, 
(WindowPtr) -1, True, 0);
 DrawGrowIcon(theWindow);
 PtoCstr(title);
 }
}

eventloop()
{
EventRecord theEvent;

while(True)
 if (GetNextEvent(everyEvent,&theEvent))
 switch(theEvent.what)    
 { 
 case keyDown:   
 dokey(&theEvent); /* check key, */
 break;
 case mouseDown:
 domouse(&theEvent); /* mouse down evts */
 break;
 default:
 break;
 }
}

dokey(er)
 EventRecord*er;
{
 char   c;/* character from message */
 char   *title2; /* second title for window */
 
 if (not(er->modifiers & cmdKey))  
 return;/* only pay attention to cmd keys */
 /* extract character, lower 8 bits */
 c = er->message & charCodeMask; 
 if (c equals 'q' or c equals 'Q') /* 'q' quits program */
 ExitToShell();  
 
 if (not theWindow)
 {
 if (c equals 'm' or c equals 'M')
 {
 dowindow();
 return;
 }
 else
 {
 SysBeep(1);
 return;
 }
 }
 /* Have a window, so try commands */
 switch (c)
 {
 case 'x':
 case 'X':
 CloseWindow(theWindow);
 theWindow = Nil;
 break;
 case 's':
 case 'S':
 ShowWindow(theWindow);
 DrawGrowIcon(theWindow);
 break;
 case 'h':
 case 'H':
 HideWindow(theWindow);
 break;
 case 't':
 case 'T':
 title2 = "A Different Title";
 SetWTitle(theWindow, CtoPstr(title2));
 PtoCstr(title2);
 break;
 default:
 SysBeep(1);
 break;
 }
}

domouse(er)
 EventRecord*er;
{
 short  windowcode;
 WindowPtrwhichWindow;
 short  ingo;
 long   size;
 
 windowcode = FindWindow(&er->where, &whichWindow);
 switch (windowcode)
 {
 case inDesk:
 if (theWindow notequal 0)
 {
 HiliteWindow(theWindow, False);
 DrawGrowIcon(theWindow);
 }
 else
 ExitToShell();  /* exit if no window */
 break;
 case inMenuBar:
 SysBeep(1);
 break;
 case inSysWindow:
 SysBeep(1);
 break;
 case inContent:
 HiliteWindow(whichWindow,True);
 DrawGrowIcon(theWindow);
 break;
 case inDrag:
 DragWindow(whichWindow, &er->where, &dragbound);
 DrawGrowIcon(theWindow);
 break;
 case inGrow:
 /* not included this month */
 break;
 case inGoAway:
 ingo = TrackGoAway(whichWindow, &er->where);
 if (ingo)
 {
 CloseWindow(whichWindow);
 theWindow = Nil;
 }
 break;
 }
}

Why Did They Do it Dept.?

Here is another little oops for Apple's new Mac Plus. It seems on the old ROMS, if you held down a menu item with the mouse and then did a cmd-shift-3 to take a paint snapshot, when you released the mouse, the menu remained down while the screen was captured in a paint document. This became a great feature because it allowed you to document your menu bar selections. In the new ROMs, this feature no longer works. When you release the mouse, the menu snaps up and then the screen is captured. The result is that there is no way to document your menu bar selections anymore. Boo! MacTutor will pay $250 for the best article that provides a convenient patch for Apple's blunder.

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

NeoFinder 7.4.1 - Catalog your external...
NeoFinder (formerly CDFinder) rapidly organizes your data, either on external or internal disks, or any other volumes. It catalogs and manages all your data, so you stay in control of your data... Read more
Tunnelblick 3.8.0 - GUI for OpenVPN.
Tunnelblick is a free, open source graphic user interface for OpenVPN on OS X. It provides easy control of OpenVPN client and/or server connections. It comes as a ready-to-use application with all... Read more
Tweetbot 3 for Twitter 3.3.1 - Popular T...
Tweetbot is a full-featured OS X Twitter client with a lot of personality. Whether it's the meticulously-crafted interface, sounds and animation, or features like multiple timelines and column views... Read more
Monosnap 3.5.9 - Versatile screenshot ut...
Monosnap lets you capture screenshots, share files, and record video and .gifs. Features Capture Capture full screen, just part of the screen, or a selected window Make your crop area pixel... Read more
Monosnap 3.5.9 - Versatile screenshot ut...
Monosnap lets you capture screenshots, share files, and record video and .gifs. Features Capture Capture full screen, just part of the screen, or a selected window Make your crop area pixel... Read more
Tweetbot 3 for Twitter 3.3.1 - Popular T...
Tweetbot is a full-featured OS X Twitter client with a lot of personality. Whether it's the meticulously-crafted interface, sounds and animation, or features like multiple timelines and column views... Read more
Tunnelblick 3.8.0 - GUI for OpenVPN.
Tunnelblick is a free, open source graphic user interface for OpenVPN on OS X. It provides easy control of OpenVPN client and/or server connections. It comes as a ready-to-use application with all... Read more
Bookends 13.2.5 - Reference management a...
Bookends is a full-featured bibliography/reference and information-management system for students and professionals. Bookends uses the cloud to sync reference libraries on all the Macs you use.... Read more
Quicken 2019 5.11.2 - Complete personal...
Quicken makes managing your money easier than ever. Whether paying bills, upgrading from Windows, enjoying more reliable downloads, or getting expert product help, Quicken's new and improved features... Read more
Bookends 13.2.5 - Reference management a...
Bookends is a full-featured bibliography/reference and information-management system for students and professionals. Bookends uses the cloud to sync reference libraries on all the Macs you use.... Read more

Latest Forum Discussions

See All

Void Tyrant guide - Tips and tricks for...
Void Tyrant continues to get a lot of play in these parts. Probably because the game is just so deep and varied. The next stop on our guide series for Void Tyrant is class-specific guides. First up is the Knight, as it’s the first class anyone has... | Read more »
Summon beasts and battle evil in epic re...
Imagine a tale of conlict between factions of good and evil, where rogueish heroes summon beasts to aid them in them in warfare and courageously battle dragons over fields of scorched earth and brimstone - that's exactly the essence of epic fantasy... | Read more »
Upcoming visual novel Arranged shines a...
If you’re in the market for a new type of visual novel designed to inform and make you think deeply about its subject matter, then Arranged by Kabuk Games could be exactly what you’re looking for. It’s a wholly unique take on marital traditions in... | Read more »
TEPPEN guide - The three best decks in T...
TEPPEN’s unique take on the collectible card game genre is exciting. It’s just over a week old, but that isn’t stopping lots of folks from speculating about the long-term viability of the game, as well as changes and additions that will happen over... | Read more »
Intergalactic puzzler Silly Memory serve...
Recently released matching puzzler Silly Memory is helping its fans with their intergalactic journeys this month with some very special offers on in-app purchases. In case you missed it, Silly Memory is the debut title of French based indie... | Read more »
TEPPEN guide - Tips and tricks for new p...
TEPPEN is a wild game that nobody asked for, but I’m sure glad it exists. Who would’ve thought that a CCG featuring Capcom characters could be so cool and weird? In case you’re not completely sure what TEPPEN is, make sure to check out our review... | Read more »
Dr. Mario World guide - Other games that...
We now live in a post-Dr. Mario World world, and I gotta say, things don’t feel too different. Nintendo continues to squirt out bad games on phones, causing all but the most stalwart fans of mobile games to question why they even bother... | Read more »
Strategy RPG Brown Dust introduces its b...
Epic turn-based RPG Brown Dust is set to turn 500 days old next week, and to celebrate, Neowiz has just unveiled its biggest and most exciting update yet, offering a host of new rewards, increased gacha rates, and a brand new feature that will... | Read more »
Dr. Mario World is yet another disappoin...
As soon as I booted up Dr. Mario World, I knew I wasn’t going to have fun with it. Nintendo’s record on phones thus far has been pretty spotty, with things trending downward as of late. [Read more] | Read more »
Retro Space Shooter P.3 is now available...
Shoot-em-ups tend to be a dime a dozen on the App Store, but every so often you come across one gem that aims to shake up the genre in a unique way. Developer Devjgame’s P.3 is the latest game seeking to do so this, working as a love letter to the... | Read more »

Price Scanner via MacPrices.net

Apple’s $1489 clearance price on refurbished...
Apple has Certified Refurbished 2018 13″ 2.3GHz 4-Core Touch Bar MacBook Pros available starting at $1489. Apple’s one-year warranty is included, shipping is free, and each MacBook has a new outer... Read more
New 2019 13″ 2.4GHz 4-Core MacBook Pros on sa...
Apple resellers B&H Photo and Amazon are offering the new 2019 13″ 2.4GHz 4-Core Touch Bar MacBook Pros for $150 off Apple’s MSRP. These are the same MacBook Pros sold by Apple in its retail and... Read more
B&H drops prices another $50 on clearance...
B&H Photo has dropped prices on clearance 2018 13″ MacBook Airs by a further $50 with models now available for $250 off Apple’s original MSRP. Overnight shipping, or expedited shipping, is free... Read more
Find the best sales & lowest prices on Ap...
Our Apple award-winning price trackers are the best place to look for the best sales and lowest prices on Apple gear. Scan our price trackers for the latest information on sales, bundles, and... Read more
Apple has clearance 2018 13″ MacBook Airs now...
Apple has Certified Refurbished 2018 13″ MacBook Airs available starting at only $849. Each MacBook features a new outer case, comes with a standard Apple one-year warranty, and is shipped free. The... Read more
Save $400 on the 8-Core iMac Pro today at Ama...
Amazon has the base 8-core iMac Pro on sale today for $4599 including free shipping. Their price is $400 off Apple’s MSRP, and it’s the currently lowest price available for an iMac Pro. For the... Read more
Flash sale! New 11″ 1TB WiFi iPad Pros for th...
Amazon has the 11″ 1TB WiFi iPad Pro on sale today for only $1199.99 including free shipping. Their price is $350 off Apple’s MSRP for this model, and it’s the lowest price ever for a 1TB 11″ iPad... Read more
Weekend Deal: 2018 13″ MacBook Airs starting...
B&H Photo has clearance 2018 13″ MacBook Airs available starting at only $999 with all models now available for $200 off Apple’s original MSRP. Overnight shipping, or expedited shipping, is free... Read more
Apple has clearance 10.5″ iPad Pros available...
Apple has Certified Refurbished 2017 10.5″ iPad Pros available starting at $469. An Apple one-year warranty is included with each iPad, outer shells are new, and shipping is free: – 64GB 10″ iPad Pro... Read more
Apple restocks refurbished iPad mini 4 models...
Apple has restocked Certified Refurbished 32GB iPad mini 4 WiFi models for $229 shipped. That’s $70 off original MSRP for the iPad mini 4. Space Gray, Silver, and Gold colors are available. Read more

Jobs Board

Best Buy *Apple* Computing Master - Best Bu...
**711495BR** **Job Title:** Best Buy Apple Computing Master **Job Category:** Store Associates **Location Number:** 000882-Waterfront-Store **Job Description:** The Read more
Best Buy *Apple* Computing Master - Best Bu...
**711597BR** **Job Title:** Best Buy Apple Computing Master **Job Category:** Sales **Location Number:** 000873-Colma CA-Store **Job Description:** **What does a Read more
Best Buy *Apple* Computing Master - Best Bu...
**711346BR** **Job Title:** Best Buy Apple Computing Master **Job Category:** Store Associates **Location Number:** 001095-Chesterfield-Store **Job Description:** Read more
Best Buy *Apple* Computing Master - Best Bu...
**704899BR** **Job Title:** Best Buy Apple Computing Master **Job Category:** Sales **Location Number:** 000135-Pleasant Hill-Store **Job Description:** **What does Read more
Best Buy *Apple* Computing Master - Best Bu...
**707083BR** **Job Title:** Best Buy Apple Computing Master **Job Category:** Sales **Location Number:** 000045-Rockford-Store **Job Description:** **What does a Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.