TweetFollow Us on Twitter

Cursor Control 1
Volume Number:6
Issue Number:6
Column Tag:abC

Related Info: TextEdit Quickdraw

Cursor Control

By Bob Gordon, Minneapolis, MN

Note: Source code files accompanying article are located on MacTech CD-ROM or source code disks.

Managing Cursors

I know how to curse

Shakespeare, The Tempest (Act 1, Scene 2)

If you remember from last time, I had introduced the idea of adding some additional data structures at the end of the window record to aid in keeping track of the data that hangs around with a window. At the end of that article I said we would illustrate the use of the added data in managing the cursor. We will cover that, but first I would like to comment on a nice piece of work by John Nairn in the April issue.

John has presented a full-blown Scrolling Manager to handle all the issues involved with creating and maintaining scrolling windows. While there are a number of differences between what he has done and what I am describing in this column, a couple common points are worth mentioning. First, the approach is to isolate the user interface control from the actual application. That is, as much as possible, develop generic code to handle the basic operation of the windows (or menus or dialogs, for that matter). Second, this generic code will probably require some place to keep the information it uses; develop a data structure to hold this, and attach it in some way to the window (or menu or dialog). There is actually a bit more commonality (I have the advantage of being able to see the parts I have written but not yet published), and we will explore one of those in this article.

One point of difference. John uses the window’s refCon to hold his additional data structure. His new data structure includes its own refCon for the window’s contents. I added the data on to the end of the window’s structure itself. I feel this simplifies things somewhat, and at least for now it does not seem to violate any rules. If you liked John’s article as I did, you certainly have my permission to use the technique I’ve outlined in implementing it. While I haven’t met John, I’m reasonably sure he won’t mind.


The cursor attached to the mouse changes its shape as you move the mouse around the screen. In addition, the user can often affect its shape directly by selecting a tool from a toolbox (usually found in graphics or page layout applications). The problem we deal with this month is how to manage the cursor so it is handled as automatically as possible.

The first issue is getting cursors. There are five built in to the Mac: arrow, crosshairs, plus, clock, i-beam. You can also make your own with ResEdit or some other resource tool. Once we have decided the cursors to use (and made their resources), we need to control the appearance on the screen. What I will describe this month is one way to manage the change of cursor shape as the user moves the mouse around the screen. I am not covering the setting of the cursor’s via tool box or menus.

In June I suggested the use of window margins. The window margin is that area between the window’s frame, which is handled by the Macintosh toolbox routines, and the window’s actual contents, which is what your application is about. The objects that might be in a window margin include scroll bars, rulers, and tool boxes. These are such common components of windows that they can be handled by generic code apart from your application. The other property of the window margin is that the cursor typically changes into the arrow as it is moved into the scroll bar, ruler, etc.


Cursorhelp consists of three functions and an include file to aid in the setting and automatic changing of cursors. These functions assume the window structure described in June. The window margins (mtop,mbottom, mright, mleft) are stored with the window. More importantly, the rectangle that surrounds the actual window contents (cursrt) is also stored (I assume rectangular windows). This rectangle is the area in which the cursor is the shape the user selected (i beam, cross, etc.). I put it in the window structure simply to avoid having to calculate it each time. The final piece is the cursor itself (mouser). That is, the cursor’s shape as selected by the user is a property of the window. With a multi-window application the user can have one window editing text, another editing a graphic, and a third editing a spreadsheet (I am not suggesting anyone actually write something like this), and the appropriate cursor will be displayed automatically as the user selects each window. The main loop need know nothing of the cursors.

The main loop does need to set the cursor. There are two places where this can occur: the users specifies a cursor in some way or, the application displays the watch (or other indicator) to indicate the passage of time. The program calls CursorToUse passing the window and the number of the desired cursor.

The program also needs to set the cursor rectangle. This must be done every time the window’s size is changed or the window margins are changed (for example, choosing to show rulers or not).A call to CursorRect() does that. Note that the window margins must have been previously set.

To actually control the cursor, the program calls CursorMaintain() as it runs through the event loop.

Include Files
/*windowhelp.h */
#include “TextEdit.h”
#include“abc.h”    /* window add-on structure */

#define WindowStruct struct w_struct
 WindowRecord  wr;  /* the original window record */
 uchar  mtop;    /* margin indents */
 uchar  mleft;
 uchar  mbottom;
 uchar  mright;
 Rect   cursrt;    /* used for cursor control */
 char   mouser;  /* mouse pointer id  */
 char   changed; /* if contents were changed */
 long   ckind;   /* kind of contents */
 short  fileref; /* associated file, if any */
 TEHandle curtext; /* handle to current text */

#define Woffset  18
#define SBarWidth 15

/* these definitions allow easy generation of the four square cornered 
titled windows. The basic (simplest) window is the WDOC (NoGrowDocProc). 
To this optionally add WGROW to add a grow box and/or WZOOM to add a 
zoom box.
#define WDOC4
#define WGROW    -4
#define WZOOM    8
#define WVBAR    16
#define WHBAR    32

/* Value placed in windowKind field of WindowRecord by WindowNew if the 
window has a grow box. This is used by routines that redraw the window 
to decide whether to draw the grow box or not 
#define HASGROW  9


/* cursorhelp.h
 * header file for cursorhelp
 #defineARROW  0
 #defineIBEAM  1
 #defineCROSS  2
 #defineWATCH  4
CursorHelp Functions

/* CursorMaintain
 * Adjusts the cursor according to the value
 * set in the window and the rectangle currect.
 * If the mouse is in the rectangle, the cursor 
 * set to the current cursor, otherwise it is
 * set to the arrow.
 * The if statement checks to see if there is a 
 * valid window and if the window belongs to the
 * application. If it does not belong to the application
 * it is a DA. If the DA is controlling the cursor, there
 * will be a conflict as both programs attempt to control
 * it.
 WindowStruct  *ws;
 Point  pt;
 CursHandle curs;
 short  curcursor; /* current cursor */
 if (ws && (((WindowRecord *)ws)->windowKind > 7) )
 curcursor = ws->mouser;  /* cursor kind is stored in the window struct 
 if ((PtInRect(pt, &(ws->cursrt))) && (curcursor))
 curs = (Cursor **)GetCursor(curcursor);     
 else if (curcursor != WATCH)
 if (ws == NIL)

/* CursorRect
 * Uses the portRect of the window passed in
 * to set the current rectangle.  Adjusts the size
 * of the rectangle to account for window margins.
 * By keeping the rectangle around, we eliminate doing
 * this each time through the event loop.
 WindowStruct    *ws;
 ws->cursrt = ((GrafPort *)ws)->portRect;

/* CursorToUse
 * Sets the cursor to be displayed in the
 * rectangle of the current window.
 * Either pass a pointer to the window struct
 * or a NULL pointer. If a NULL pointer is passed,
 * CursorToUse() will use the front window. 
 * Note: At least one window must exist for this
 * to work, but if no windows exist, it
 * will not hurt.
 WindowStruct  *ws;/* window struct to set cursor for */
 short  c;/* cursor code to use */
 if (!ws)
 ws = (WindowStruct *)FrontWindow();
 if (ws)
 ws->mouser = c;

Using CursorMaintain()

The following fragment shows the call to CursorMaintain() in the main event loop.

 char   c;
 short  windowcode;
 WindowStruct  *ws;
 wp = FrontWindow();
 if (wp)
 if (GetNextEvent(everyEvent,&theEvent))

Other Comments

Check John Nairn’s article for other things to do to automate cursor control. You will note he checks for certain keys being pressed to change the cursor to allow window scrolling (e.g. with a hand).

Last Time

I have a minor error in June’s column. I included some space in the window structure to handle window zooming. These are not needed as zooming is fully supported by the Mac Toolbox. I hadn’t used them for anything yet.

Next Time

Next time I am going to show a quick and very dirty way to help deal with menus.

P.S. Comments are welcome. Send your notes to MacTutor, and please include a phone number.


Community Search:
MacTech Search:

Software Updates via MacUpdate

VueScan 9.5.59 - Scanner software with a...
VueScan is a scanning program that works with most high-quality flatbed and film scanners to produce scans that have excellent color fidelity and color balance. VueScan is easy to use, and has... Read more
Skype - Voice-over-internet p...
Skype allows you to talk to friends, family and co-workers across the Internet without the inconvenience of long distance telephone charges. Using peer-to-peer data transmission technology, Skype... Read more
Box Sync 4.0.7724 - Online synchronizati...
Box Sync gives you a hard-drive in the Cloud for online storage. Note: You must first sign up to use Box. What if the files you need are on your laptop -- but you're on the road with your iPhone? No... Read more
Cosmo Run 2.5.1 - Arcade game with ever-...
Cosmo Run is an arcade game with ever-changing aspect of the play-world. Survive long enough and you will meet special alternative paths - both hardcore and rewarding. Are you worthy to command the... Read more
Delicious Library 3.6.1 - Import, browse...
Delicious Library allows you to import, browse, and share all your books, movies, music, and video games with Delicious Library. Run your very own library from your home or office using our... Read more
Cosmo Run 2.5 - Arcade game with ever-ch...
Cosmo Run is an arcade game with ever-changing aspect of the play-world. Survive long enough and you will meet special alternative paths - both hardcore and rewarding. Are you worthy to command the... Read more
TunnelBear 3.0.3 - Subscription-based pr...
TunnelBear is a subscription-based virtual private network (VPN) service and companion app, enabling you to browse the internet privately and securely. Features Browse privately - Secure your data... Read more
ForkLift 3.0 Beta 4 - Powerful file mana...
ForkLift is a powerful file manager and ferociously fast FTP client clothed in a clean and versatile UI that offers the combination of absolute simplicity and raw power expected from a well-executed... Read more
Coda 2.5.18 - One-window Web development...
Coda is a powerful Web editor that puts everything in one place. An editor. Terminal. CSS. Files. With Coda 2, we went beyond expectations. With loads of new, much-requested features, a few surprises... Read more
Coda 2.5.18 - One-window Web development...
Coda is a powerful Web editor that puts everything in one place. An editor. Terminal. CSS. Files. With Coda 2, we went beyond expectations. With loads of new, much-requested features, a few surprises... Read more

Latest Forum Discussions

See All

Arcane Online takes Online RPG’s to anot...
If you think that you need a desktop to enjoy high quality MMO gaming then Arcane Online hopes to prove you emphatically wrong. An epic fantasy Online RPG set in the land of Eldine, Arcane Online offers an abundance of features and content that... | Read more »
It’s time to step up and start your spoo...
So you’ve just downloaded Seekers Notes: Hidden Mystery, and you obviously want to hit the ground running. Well you’re in luck because you just so happen to be reading our very useful guide to playing. First released in July last year, the game has... | Read more »
Diggy’s Adventure launches on Android an...
Diggy’s Adventure is the exciting new mobile app brought to you by Pixel Federation. Transporting you all the way to Egypt, you’ll join Diggy and his mates in their quest to find Diggy’s dear old dad – completing challenges put to you by the gods (... | Read more »
Eggggg - The Platform Puker (Games)
Eggggg - The Platform Puker 1.2 Device: iOS Universal Category: Games Price: $1.99, Version: 1.2 (iTunes) Description: | Read more »
The Bug Butcher (Games)
The Bug Butcher 1.0 Device: iOS Universal Category: Games Price: $3.99, Version: 1.0 (iTunes) Description: The Bug Butcher is an intense action shooter, wrapped in stylistic 2D art, and smeared with humor where timing and fierce... | Read more »
Plants vs. Zombies Heroes and 3 other ul...
| Read more »
3 apps to feed your online shopping addi...
The internet has changed the way we shop, ensuring that we basically have no need to leave our homes to go shopping if we so desire. That process has been streamlined with the sheer variety of apps on the market to make online shopping even more... | Read more »
FabFocus (Photography)
FabFocus 1.0.1 Device: iOS iPhone Category: Photography Price: $1.99, Version: 1.0.1 (iTunes) Description: With only one touch, FabFocus is a simple and powerful tool for instantly turning your portraits into professional-looking... | Read more »
Happy anniversary Game of Dice
It’s been a great year for JoyCity, as its hit game Game of Dice has just celebrated its one year anniversary in spectacular style. First released in October 2015, the game has been an enormous success - ranking in the top five of the highest... | Read more »
RETSNOM 1.0 Device: iOS Universal Category: Games Price: $.99, Version: 1.0 (iTunes) Description: To celebrate the release of the game, 80% off for limited time!** INDIE STREAM FES 2015 Best of Narrative Award **** Famitsu Gold Dendo... | Read more »

Price Scanner via

15-inch Retina MacBook Pros on sale for $200...
B&H Photo has 15″ Retina Apple MacBook Pros on sale for $200 off MSRP. Shipping is free, and B&H charges NY tax only: - 15″ 2.2GHz Retina MacBook Pro: $1799 $200 off MSRP - 15″ 2.5GHz Retina... Read more
Apple refurbished 2016 13-inch MacBook Airs a...
Apple has Certified Refurbished 2016 13″ MacBook Airs available starting at $849. An Apple one-year warranty is included with each MacBook, and shipping is free: - 2016 13″ 1.6GHz/8GB/128GB MacBook... Read more
Apple refurbished iMacs available for up to $...
Apple has Certified Refurbished 2015 21″ & 27″ iMacs available for up to $350 off MSRP. Apple’s one-year warranty is standard, and shipping is free. The following models are available: - 21″ 3.... Read more
First IBM Watson Education App for iPad Deliv...
IBM has announced the first IBM MobileFirst for iOS education app. The app, IBM Watson Element for Educators, enables a new level of engagement for teachers by providing a holistic view of each... Read more
Apple price trackers, updated continuously
Scan our Apple Price Trackers for the latest information on sales, bundles, and availability on systems from Apple’s authorized internet/catalog resellers. We update the trackers continuously: - 15″... Read more
Apple refurbished Mac minis available startin...
Apple has Certified Refurbished Mac minis available starting at $419. Apple’s one-year warranty is included with each mini, and shipping is free: - 1.4GHz Mac mini: $419 $80 off MSRP - 2.6GHz Mac... Read more
Satellite Internet Advantage Underscored In F...
One reason I’ve been a longtme laptop and iPad aficionado is that I live in a rural area of eastern Nova Scotia where power blackouts are not uncommon any time of the year, especially in the fall... Read more
12-inch Rose Gold Retina MacBook, Apple refur...
Apple has Certified Refurbished 2016 12″ 1.1GHz Rose Gold Retina MacBooks available for $200 off MSRP. Apple will include a standard one-year warranty with each MacBook, and shipping is free: - 12″ 1... Read more
mStand and mStand360 For MacBooks/Macbook Air...
California based Rain Design Inc. has announced that their mStand and mStand360 are now available in three Apple matching colors: Silver, Gold and Space Gray. Created for Apple MacBooks/Macbook Air... Read more
1.4GHz Mac mini on sale for $449, save $50
Adorama has the 1.4GHz Mac mini on sale for $50 off MSRP including free shipping plus NY & NJ sales tax only: - 1.4GHz Mac mini (Apple sku# MGEM2LL/A): $449 $50 off MSRP To purchase a mini at... Read more

Jobs Board

*Apple* Retail - Multiple Positions- Mishawa...
Job Description: Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
*Apple* Retail - Multiple Positions- Greenwi...
Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, you're also the Read more
SW Engineer *Apple* TV - Apple Inc. (United...
The Apple TV team is looking for excellent software engineers with experience in hardware, media management, media playback, content delivery and a passion for Read more
Restaurant Manager (Neighborhood Captain) - A...
…in every aspect of daily operation. WHY YOU'LL LIKE IT: You'll be the Big Apple . You'll solve problems. You'll get to show your ability to handle the stress and Read more
*Apple* Retail - Multiple Positions - Apple,...
Job Description: Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.