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

Pinegrow 6.23 - Mockup and design web pa...
Pinegrow (was Pinegrow Web Designer) is desktop app that lets you mockup and design webpages faster with multi-page editing, CSS and LESS styling, and smart components for Bootstrap, Foundation,... Read more
WhatsApp 2.2149.4 - Desktop client for W...
WhatsApp is the desktop client for WhatsApp Messenger, a cross-platform mobile messaging app which allows you to exchange messages without having to pay for SMS. WhatsApp Messenger is available for... Read more
Microsoft Remote Desktop 10.7.4 - Connec...
Microsoft Remote Desktop for Mac is an application that allows connecting to virtual apps or another PC remotely. Discover the power of Windows with Remote Desktop designed to help you manage your... Read more
ffWorks 2.6.7 - Convert multimedia files...
ffWorks, focused on simplicity, brings a fresh approach to the use of FFmpeg, allowing you to create ultra-high-quality movies without the need to write a single line of code on the command-line.... Read more
Opera 82.0.4227.58 - High-performance We...
Opera is a fast and secure browser trusted by millions of users. With the intuitive interface, Speed Dial and visual bookmarks for organizing favorite sites, news feature with fresh, relevant content... Read more
Day One 6.15 - Maintain a daily journal.
Day One is an easy, great-looking way to use a journal / diary / text-logging application. Day One is well designed and extremely focused to encourage you to write more through quick Menu Bar entry,... Read more
Default Folder X 5.6.3 - Enhances Open a...
Default Folder X attaches a toolbar to the right side of the Open and Save dialogs in any OS X-native application. The toolbar gives you fast access to various folders and commands. You just click on... Read more
OmniOutliner Pro 5.9.2 - Pro version of...
OmniOutliner Pro is a flexible program for creating, collecting, and organizing information. Give your creativity a kick start by using an application that's actually designed to help you think. It's... Read more
OmniOutliner Essentials 5.9.2 - Organize...
OmniOutliner Essentials (was OmniOutliner) is a flexible program for creating, collecting, and organizing information. Give your creativity a kick start by using an application that's actually... Read more
QuickBooks 19.0.11.984 - Financial manag...
QuickBooks helps you manage your business easily and efficiently. Organize your finances all in one place, track money going in and out of your business, and spot areas where you can save. Built for... Read more

Latest Forum Discussions

See All

The Best Wordle Clone in Town – The Touc...
In this week’s episode of The TouchArcade Show we dig into the drama of the moment which is the cloning and subsequent gloating about the cloning of the lovely little free word game Wordle. This leads into some additional drama about how PUGB Mobile... | Read more »
TouchArcade Game of the Week: ‘Cards Inf...
There’s nothing I love more than a perfect mobile game. What do I mean by that? Well, no game is actually perfect, but there’s something special about a game you know you can just whip out at a moment’s notice and dive into, and you know it will... | Read more »
‘Micro RPG’ Bringing Streamlined RPG Goo...
Originally announced on our forums more than 3 years ago, Micro RPG is an upcoming mobile game from a two-person studio that goes by the name JoliYeti Games and, as the title implies, it looks to offer all the fun of an RPG but in a more condensed... | Read more »
SwitchArcade Round-Up: ‘Kensei: The Seco...
Hello gentle readers, and welcome to the SwitchArcade Round-Up for January 14th, 2022. Yesterday was a big day, but today shows that we’re still warming up the engines for this year. There are a handful of new releases, but nothing nearly as... | Read more »
Mobile MMORPG Shooter ‘Avatar: Reckoning...
Archosaur Games, Tencent, Lightstorm Entertainment, and Disney have just revealed a mobile MMORPG shooter Avatar: Reckoning. Avatar: Reckoning will be published by Level Infinite when it hits iOS and Android. It is an official Avatar game developed... | Read more »
‘Crashlands+’ Is Out Now on Apple Arcade...
The brilliant Crashlands from Butterscotch Shenanigans was confirmed to arrive on Apple Arcade as an App Store Great in the form of Crashlands+ () a little while ago and it has just released worldwide. If it isn’t live yet, it should roll out in... | Read more »
SwitchArcade Round-Up: ‘Eschatos’, ‘To B...
Hello gentle readers, and welcome to the SwitchArcade Round-Up for January 13th, 2022. It’s a Thursday, and we’ve got a pretty hefty bag of new releases to dig into. There are always some fun surprises, and this week that came in the form of SNK Vs... | Read more »
‘Crush the Castle Legacy Collection’ Lau...
Ever since Angry Birds broke into the mainstream and became a household name more than a decade ago, there’s always been a small niche of people on the sidelines who would pipe up to remind everybody that “Crush the Castle did it first!" Indeed, the... | Read more »
Non-Violent Stealth Game ‘El Hijo – A Wi...
Over a year ago, Handy Games brought the non-violent stealth game El Hijo – A Wild West Tale to Switch, PS4, Xbox, PC, and Stadia. El Hijo – A Wild West Tale has been developed by Honig Studios and Quantumfrog. You play as El Hijo, a six year old,... | Read more »
‘ZED BLADE’ from SNK and Hamster Is Out...
After a bit of a break likely due to the holiday season, we’ve gotten a new title in the ACA NeoGeo series on iOS and Android. SNK and Hamster originally brought the series to mobile with Samurai Shodown IV, Alpha Mission II, and Metal Slug 5.... | Read more »

Price Scanner via MacPrices.net

Get an Apple Watch Series 7 for $50 off MSRP,...
Amazon has Apple Watch Series 7 models on sale for $50 off MSRP including free shipping. Their prices are the lowest available for Apple Watch Series 7 models today: – 41mm Apple Watch Series 7 GPS... Read more
Here are the details of Apple’s 2022 Educatio...
Need a new Apple Mac or iPad for school? Whether you’re a student, teacher, or staff member, you can use your .edu email address when ordering at Apple Education to take up to $400 off the price of a... Read more
Amazon is blowing out 2020 21″ iMacs for only...
Amazon has clearance 2020 21″ iMacs (2.3GHz Dual-Core i5, 8GB RAM, 256GB SSD) on sale right now for $599.99 including free shipping. Original MSRP for this model was $1099. Amazon expects delivery in... Read more
Find the best deal on an Apple MacBook using...
In the market for a new 13″ MacBook Air, 13″ MacBook Pro, 14″ MacBook Pro, or 16″ MacBook Pro with M1, M1 Pro, or M1 Max Apple Silicon? Use our Apple award-winning and exclusive price trackers to... Read more
Red Pocket Mobile is offering the Apple iPhon...
Switch to Red Pocket Mobile and get an Apple iPhone 13 Pro for $50 off MSRP, plus get free 6 months of Unlimited nationwide 5G service with the purchase of any iPhone 13. Red Pocket Mobile is a... Read more
24″ M1 iMacs on sale for $1249, $50 off Apple...
Amazon has base 24″ M1 iMacs (8-Core CPU/7-Core GPU/8GB RAM/256GB SSD) on sale today for $1249 shipped. Their price is $50 off Apple’s MSRP, and it’s the lowest price available for a new 24″ M1 iMac... Read more
Open-Box 16″ M1 Pro MacBook Pros available fo...
QuickShip Electronics has open-box return 16″ M1 Pro MacBook Pros in stock and on sale for $200-$300 off MSRP on their eBay store right now with free express delivery. According to QuickShip, “The... Read more
Stock Alert! Order a new 16″ M1 Pro MacBook P...
New 16″ MacBook Pros with Apple’s M1 Pro and M1 Max CPUs have been very hard to find, largely due to current global supply constraints. However, B&H Photo is reporting stock of Space Gray... Read more
Apple has maxed-out 13″ M1 MacBook Airs (16GB...
Save $250 on maxed-out 13″ M1 MacBook Airs today at Apple (16GB RAM/1TB SSD) with Certified Refurbished models available for $1399 in Space Gray and Gold colors. Regular price for this configuration... Read more
New promo at Xfinity Mobile: $400 off any App...
Xfinity Mobile is offering any new Apple iPhone for $400 off MSRP for new customers. This includes the iPhone 13. Price for the phone, including the discount, is spread monthly over a 24 month term... Read more

Jobs Board

Registered Nurse (RN) Employee Health PSJH -...
…is calling for a Registered Nurse (RN) Employee Health PSJH to our location in Apple Valley, CA.** We are seeking a Registered Nurse (RN) Employee Health PSJH to be Read more
Systems Administrator - Pearson (United State...
…and troubleshoot Windows operating systems (workstation and server), laptop computers, Apple iPads, Chromebooks and printers** + **Administer and troubleshoot all Read more
IT Assistant Level 1- IT Desktop Support Anal...
…providing tier-1 or better IT help desk support in a large Windows and Apple environment * Experience using IT Service Desk Management Software * Knowledge of IT Read more
Human Resources Business Partner PSJH - Provi...
…**is calling a** **Human Resources Business Partner, PSJH** **to our location in Apple Valley, CA.** **Applicants that meet qualifications will receive a text with Read more
Manager Community Health Investment Programs...
…is calling a Manager Community Health Investment Programs PSJH to our location in Apple Valley, CA.** **Qualified candidates will be invited to do a self-paced video Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.