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.

Cursors

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

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”
 
#ifndef WINDOWHELP_H
#define WINDOWHELP_H
#include“abc.h”    /* window add-on structure */

#define WindowStruct struct w_struct
WindowStruct
 {
 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 */
 };
 
WindowStruct*WindowNew();

#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

#endif

/* cursorhelp.h
 * header file for cursorhelp
 */
 
 #defineARROW  0
 #defineIBEAM  1
 #defineCROSS  2
 #definePLUS3
 #defineWATCH  4
CursorHelp Functions
#include“abc.h”
#include“Quickdraw.h”
#include“windowMgr.h”
#include“windowhelp.h”
#include“cursorhelp.h”

/* 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.
 */
CursorMaintain(ws)
 WindowStruct  *ws;
{
 Point  pt;
 CursHandle curs;
 short  curcursor; /* current cursor */
 
 if (ws && (((WindowRecord *)ws)->windowKind > 7) )
 {
 GetMouse(&pt);
 curcursor = ws->mouser;  /* cursor kind is stored in the window struct 
*/
 if ((PtInRect(pt, &(ws->cursrt))) && (curcursor))
 {
 curs = (Cursor **)GetCursor(curcursor);     
 SetCursor(*curs); 
 }
 else if (curcursor != WATCH)
 {
 InitCursor();
 }
 }
 if (ws == NIL)
 InitCursor();
}

/* 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.
 */
 
CursorRect(ws)
 WindowStruct    *ws;
{
 ws->cursrt = ((GrafPort *)ws)->portRect;
 AdjustRect(&(ws->cursrt),ws->mtop,ws->mleft,ws->mbottom,ws->mright);
}

/* 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.
 */
CursorToUse(ws,c)
 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.

EventLoop()
{
 EventRecordtheEvent;
 char   c;
 short  windowcode;
 WindowPtrwp;
 WindowStruct  *ws;
 
 while(True)
 {
 wp = FrontWindow();
 SystemTask();
 CursorMaintain(wp); 
 if (wp)
 {
 AppTask(wp);
 } 
 if (GetNextEvent(everyEvent,&theEvent))
 switch(theEvent.what)

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

How to manage your time in Bakery Blitz
It can be tricky, especially when you risk burning your kitchen to the ground if you forget a cake in the oven, so make sure to use these time management tricks to keep your bakery running smoothly. Don’t collect the money right away [Read more] | Read more »
Model 15 (Music)
Model 15 1.0 Device: iOS iPhone Category: Music Price: $29.99, Version: 1.0 (iTunes) Description: The Moog Model 15 App is the first Moog modular synthesizer and synthesis educational tool created exclusively for iPad, iPhone and... | Read more »
How to deal with wind in Angry Birds Act...
Angry Birds Action! is a physics-based puzzler in which you're tasked with dragging and launching birds around an obstacle-littered field to achieve a set objective. It's simple enough at first, but when wind gets introduced things can get pretty... | Read more »
How to get three stars in every level of...
Angry Birds Action! is, essentially, a pinball-style take on the pull-and-fling action of the original games. When you first boot it up, you'll likely be wondering exactly what it is you have to do to get a good score. Well, never fear as 148Apps... | Read more »
The beginner's guide to Warbits
Warbits is a turn-based strategy that's clearly inspired by Nintendo's Advance Wars series. Since turn-based strategy games can be kind of tricky to dive into, see below for a few tips to help you in the beginning. Positioning is crucial [Read... | Read more »
How to upgrade your character in Spellsp...
So you’ve mastered the basics of Spellspire. By which I mean you’ve realised it’s all about spelling things in a spire. What next? Well you’re going to need to figure out how to toughen up your character. It’s all well and good being able to spell... | Read more »
5 slither.io mash-ups we'd love to...
If there's one thing that slither.io has proved, it's that the addictive gameplay of Agar.io can be transplanted onto basically anything and it will still be good fun. It wouldn't be surprising if we saw other developers jumping on the bandwagon,... | Read more »
How to navigate the terrain in Sky Charm...
Sky Charms is a whimsical match-'em up adventure that uses creative level design to really ramp up the difficulty. [Read more] | Read more »
Victorious Knight (Games)
Victorious Knight 1.3 Device: iOS Universal Category: Games Price: $1.99, Version: 1.3 (iTunes) Description: New challenges awaits you! Experience fresh RPG experience with a unique combat mechanic, packed with high quality 3D... | Read more »
Agent Gumball - Roguelike Spy Game (Gam...
Agent Gumball - Roguelike Spy Game 1.0 Device: iOS Universal Category: Games Price: $2.99, Version: 1.0 (iTunes) Description: Someone’s been spying on Gumball. What the what?! Two can play at that game! GO UNDERCOVERSneak past enemy... | Read more »

Price Scanner via MacPrices.net

13-inch 2.5GHz MacBook Pro on sale for $999,...
B&H Photo has the 13″ 2.5GHz MacBook Pro on sale for $999 including free shipping plus NY sales tax only. Their price is $100 off MSRP. Read more
Apple refurbished 2015 iMacs available for up...
Apple now has a full line of 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... Read more
Indian Smartphone Market Grows Annually by 12...
India’s smartphone market grew by 12 percent year-over-year, with 24.4 million units shipping in Q1 2016. The top five vendors stayed the same, with Samsung in the lead, followed by Micromax, Intex... Read more
Get Notifications When Your Friend’s Phone Ba...
Calgary, Canada based Stonelight Pictures has announced the release of Battery Share 1.0.1, its new utility for iOS 9 supported devices. The company notes that people are spending more time on their... Read more
11-inch 1.6GHz/128GB MacBook Air on sale for...
Amazon has the current-generation 11″ 1.6GHz/128GB MacBook Air (sku MJVM2LL/A) on sale for $749.99 for a limited time. Their price is $150 off MSRP, and it’s the lowest price available for this model... Read more
Price drops on clearance 2015 13-inch MacBook...
B&H Photo has dropped prices on clearance 2015 13″ MacBook Airs by up to $250. Shipping is free, and B&H charges NY sales tax only: - 13″ 1.6GHz/4GB/128GB MacBook Air (MJVE2LL/A): $799, $200... Read more
Mac minis on sale for up to $100 off MSRP
B&H Photo has Mac minis on sale for up to $100 off MSRP including free shipping plus NY sales tax only: - 1.4GHz Mac mini: $449 $50 off MSRP - 2.6GHz Mac mini: $649 $50 off MSRP - 2.8GHz Mac mini... Read more
13-inch Retina MacBook Pros on sale for up to...
B&H Photo has 13″ Retina MacBook Pros on sale for $130-$200 off MSRP. Shipping is free, and B&H charges NY tax only: - 13″ 2.7GHz/128GB Retina MacBook Pro: $1169 $130 off MSRP - 13″ 2.7GHz/... 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
SanDisk Half-Terabyte SSD Optimized for Every...
SanDisk Corporation has announced the SanDisk Z410 SSD, a cost-competitive, half-terabyte solid state drive (SSD) that enables manufacturers to design for a broad range of desktop PCs and laptops.... Read more

Jobs Board

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
Simply Mac *Apple* Specialist- Service Repa...
Simply Mac is the largest premier retailer of Apple products in the nation. In order to support our growing customer base, we are currently looking for a driven 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 (US) - A...
Job Description:SalesSpecialist - Retail Customer Service and SalesTransform Apple Store visitors into loyal Apple customers. When customers enter the store, 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
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.