TweetFollow Us on Twitter

Technical Questions
Volume Number:1
Issue Number:11
Column Tag:Ask Prof. Mac

Technical Questions Answered

By Steve Brecher, Software Supply, MacTutor Contributing Editor

[Prof. Mac is dedicated to helping you solve your Macintosh Programming problems. Each month Prof. Mac will research out your problem and print the best possible solution in MacTutor. Don't waste time in frustration! Send your technical questions to Prof. Mac and let him research your problem for you. Write to Prof. Mac, care of this Journal. -Ed.]

Coordinate Systems

Q. Moving a window by using MoveWindow(..., <portRect.left+offset>, <portRect.top+offset>, ...) doesn't work. What do I need to do?

A. The coordinates you pass to MoveWindow must be global coordinates, so transform them with calls to LocalToGlobal first. The distinction between local and global coordinates can be confusing (it was to me, anyway), so let's discuss coordinate systems.

A coordinate system is an abstraction. I visualize it as an infinitely large sheet of graph paper with one intersection of grid lines designated 0,0. By assigning one grid intersection (0,0 or any other ) to a specific bit in memory, we thereby are able to refer to pixels (memory bits) in terms of coordinates rather than in terms of RAM addresses. This is very convenient when thinking about graphics.

The QuickDraw bitmap is what associates a particlar coordinate system (graph paper) with a particular set of memory locations.

Think of the sheet of graph paper thumbtacked to a bit in memory. The thumbtack goes through the graph paper at the intersection designated by the top, left coordinates of the bitmap's bounds rectangle; this can be any intersection at all -- it needn't be 0,0. The tack's point sticks into memory at the location designated by the bitmap's baseAddr.

A point expressed in local coordinates is merely one that has been thus assigned to a pixel as specified by the relevant grafPort's bitmap. Each and every coordinate found in a grafPort (in the sense of a field in a Pascal record) is, by definition, local to that grafPort.

When we wish to compare the locations with respect to memory (screen) of points in two different grafPorts, we must adjust their coordinate systems so that the same intersection on each port's graph paper is assigned ("thumbtacked") to the same pixel. The convention for doing this is to "move" each graph paper so that its 0,0 coordinate is at the lowest-addressed pixel. Note that this method of inter-port comparison works only if both lowest-addressed pixels (baseAddr's) are the same! This implied requirement -- satisfied, of course, if both baseAddr's are equal to screenBase -- is usually taken for granted in IM discussions.

A local coordinate is an expression of vertical and horizontal distance from the 0,0 intersection on the particular piece of graph paper associated with a grafPort. A global coordinate is an expression of vertical and horizontal distance from the baseAddr pixel. If (and only if) two ports have the same baseAddr, then global coordinates from each may be compared and yield a valid graphics relationship.

While the QuickDraw chapter of Inside Macintosh says (of two ports being compared) "using the same bit image (such as the screen)", the rest of IM when using the term "global" takes for granted that the screen is in fact the common bit image for both ports.

When IM says a document being drawn "sticks to the coordinate system," I mentally translate that to "sticks to the graph paper"; similarly, I mentally translate "sticks to the screen" to "sticks to memory."

Of course, the memory locations designated by a bitmap do not have to coincide with the memory from which the screen is displayed. Drawing merely affects the memory designated by the bitmap; if that memory is (all or partially) in the screen buffer, then the screen display will be affected.

QuickDraw Regions Limitation

Q. L. Tannenbaum of Long Beach, CA, submitted some MacFORTH code that illustrates a problem with QuickDraw's handling of complex regions. His program created 17 vertically-oriented rectangles while defining a region. Subsequently FrameRgn didn't seem to work correctly. He wants to know if the problem is in his code or in QuickDraw.

A. By doing some experiments ,and with the help of MacsBug, I analyzed the problem as follows.

There is a problem in QuickDraw's handling of regions containing more than 12 vertical (higher than wide) rectangles. FrameRgn of a region containing more than 12 vertical rectangles will paint them instead of frame them, and rectangles after the 12th (from left to right) will be enlarged horizonally.

If there are more than 24 such Rectangles, FrameRgn will crash with an address error.

The problem seems to be due to the way region information is stored, in conjunction with the fact that some routines (e.g., FrameRgn, possibly as a part of code common to other routines) allocate a fixed amount of space on the stack which is not large enough to accommodate a chunk of information recorded for the region.

For (at least) multiple rectangles, region information is stored in chunks consisting of pairs of arrays of coordinates in the form

  top[i]         left[1] right[1] left[2] right[2] ... left[n] right[n]
  bottom[i]    left[1] right[1] left[2] right[2] ... left[n] right[n] 

where i ranges over 1 to the number of horizontal lines on which the rectangle corners lie, from top to bottom of the grafPort's portrect. Each array is terminated with a $7FFF marker.

For horizontally-oriented rectangles, n=1, and each array contains exactly 3 coordinates. For vertically-oriented rectangles, n is equal to the number of rectangles, and each array is therefore potentially large. QuickDraw appears to do a Link A6,#-562, and part of the stack frame thus allocated appears to be filled with a chunk of coordinates via autoincremented A2 as the destination address of a move loop. If the chunk is too large, stack frame underflow will result.

I submitted the above to Apple's Tech Support team, and Ginger Jernigan replied:

"It isn't a bug, it is a limitation in QuickDraw, which will be documented in the final version of Inside Macintosh. Your analysis of the situation was correct. We're working to fix it or at least alleviate the nasty problems that occur (like getting real syserrors from Quickdraw calls)."

Boldly Outlining Buttons

Q. Mike Scanlin asks: how do you get the thick border to outline a button in a dialog box for the button representing the default if the user hits Return (usually either "OK" or "Cancel")?

A. Usually such button highlighting appears in alert boxes. The Dialog Manager automatically highlights either item 1 or item 2 in an alert box. Whether item 1 or item 2 is highlighted depends on the value of a bit in the "stages" word for the current stage of the alert. (See Inside Macintosh, Dialog Manager, pp. 34-36.)

The stages word is located in the ALRT resource, and is divided into four 4-bit parts, each part governing one stage, or consecutive occurrence, of the alert. One bit in each part governs item highlighting; if the bit is clear, item 1 is highlighted, and if it's set, item 2 is highlighted.

Often item 1 is an "OK" button and item 2 is a "Cancel" button, and IM assumes this in its illustration. But in fact the Dialog Manager will highlight item 1 or item 2 regardless of what kind of item it is. This can somethimes be a problem. For example, if you have an alert with only a message (a statText item) and an "OK" button, you don't want any highlighting. But the Dialog Manager will relentlessly highlight either item 1 or item 2; if the statText is item 2 and the appropriate bit in the stages word is set, the text will have an ugly bold round-corner rectangle drawn around it. If the bit is clear, the "OK" button will be highlighted, which would be silly since it's the only enabled item.

The only way to handle such a situation is to add a dummy item to the alert's item list (such as a one-character statText item located outside of the alert's rectangle) and let that dummy item "take" the highlighting. In our example, the dummy item could be item 1, and the bits in the stages word would be clear so that item 1 is highlighted. To see an example of this technique, use ResEdit to examine the Finder's DITL 129 resource.

To highlight a button in a dialog that is not an alert, you can use a userItem. Usually a userItem just draws a non-standard item, such as a picture. In this case, we can employ a userItem to change the appearance of another item -- namely, of our button.

A userItem consists of a procedure, as documented in IM, Dialog Manager, p. 11. We will ignore the itemNo parameter, since the item that the userItem will be operating on is not the userItem itself, but the button we want to outline. The QuickDraw techniques for boldly outlining a button are shown on p. 13 of the Dialog Manager section:

PenSize(3,3);
InsetRect(displayRect,-4,-4);
FrameRoundRect(displayRect,16,16)

--where displayRect is the button's display rectangle; GetDItem can be used to obtain it.

Print Dialogs

Q. Paul Cozza of Long Beach, CA, asks: two undocumented Printing Manager routines -- PRSTLINIT and PRJOBINIT -- were mentioned on p. 32 of the First Draft (6/11/84) of Printing Manager section of Inside Macintosh. Apple promised documentation in a later release of the manual, but the routines have mysteriously disappeared altogether from the latest version (Second Draft, 3/27/85, distributed with the May 1985 Software Supplement). If these routines are now unavailable, what is the way to modify the print style and job dialogs?

A. My guess is that the routines succumbed to the generalization of printing procedures that was necessitated by the advent of the Laserwriter.

In the Imagewriter file (I'll let you know about the Laserwriter as soon as I can afford one!), the style dialog is the DLOG -8192 resource, and the job dialog is DLOG -8191. If you examine DITL (dialog item list) -8192, you'll see only placeholders where the paper sizes appear in the style dialog.

At least with respect to Imagewriter paper sizes, it is possible to make some changes. The PREC 3 resource in the Imagewriter file specifies the names of the papers as they will appear in the style dialog, and the sizes of the paper. The format of the PREC 3 resource is as follows:

n [1-word count] -- number of paper sizes;

n pairs of words -- vertical,horizontal paper size in 120ths of an inch;

n Pascal-format strings -- names of paper sizes;

1 word -- ? (probably flags for Orientation, Pagination, Reduction).

Up to six paper sizes can be accommodated by the style dialog box. The distributed Imagewriter file PREC 3 resource contains the specifications of five sizes (US Letter, A4 letter, US Legal, International Fanfold, Computer Paper).

As to other aspects of the dialogs I'm afraid you're on your own; I note the following warning in IM : "Your application should not change the data in the print record -- be sure to use only the standard dialogs for setting this information."

 
AAPL
$118.93
Apple Inc.
-0.07
MSFT
$47.81
Microsoft Corpora
+0.06
GOOG
$541.83
Google Inc.
+1.46

MacTech Search:
Community Search:

Software Updates via MacUpdate

Adobe Photoshop Elements 13.0 - Consumer...
Adobe Photoshop Elements 12--the #1 selling consumer photo editing software--helps you edit pictures with powerful, easy-to-use options and share them via print, the web, Facebook, and more.Version... Read more
Skype 7.2.0.412 - Voice-over-internet ph...
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
HoudahSpot 3.9.6 - Advanced file search...
HoudahSpot is a powerful file search tool built upon MacOS X Spotlight. Spotlight unleashed Create detailed queries to locate the exact file you need Narrow down searches. Zero in on files Save... Read more
RapidWeaver 6.0.3 - Create template-base...
RapidWeaver is a next-generation Web design application to help you easily create professional-looking Web sites in minutes. No knowledge of complex code is required, RapidWeaver will take care of... Read more
iPhoto Library Manager 4.1.10 - Manage m...
iPhoto Library Manager lets you organize your photos into multiple iPhoto libraries. Separate your high school and college photos from your latest summer vacation pictures. Or keep some photo... Read more
iExplorer 3.5.1.9 - View and transfer al...
iExplorer is an iPhone browser for Mac lets you view the files on your iOS device. By using a drag and drop interface, you can quickly copy files and folders between your Mac and your iPhone or... Read more
MacUpdate Desktop 6.0.3 - Discover and i...
MacUpdate Desktop 6 brings seamless 1-click installs and version updates to your Mac. With a free MacUpdate account and MacUpdate Desktop 6, Mac users can now install almost any Mac app on macupdate.... Read more
SteerMouse 4.2.2 - Powerful third-party...
SteerMouse is an advanced driver for USB and Bluetooth mice. It also supports Apple Mighty Mouse very well. SteerMouse can assign various functions to buttons that Apple's software does not allow,... Read more
iMazing 1.1 - Complete iOS device manage...
iMazing (was DiskAid) is the ultimate iOS device manager with capabilities far beyond what iTunes offers. With iMazing and your iOS device (iPhone, iPad, or iPod), you can: Copy music to and from... Read more
PopChar X 7.0 - Floating window shows av...
PopChar X helps you get the most out of your font collection. With its crystal-clear interface, PopChar X provides a frustration-free way to access any font's special characters. Expanded... Read more

Latest Forum Discussions

See All

Castaway Paradise – Tips, Tricks, and St...
Ahoy there, castaways: Were you curious about our own thoughts regarding this pristine shipwreck? Check out our Castaway Paradise review! Castaway Paradise is out for iOS, finally giving mobile gamers the opportunity to enjoy the idyllic lifestyle... | Read more »
7 tips to get ahead of the competition i...
7 tips to get ahead of the competition in Dynasty of Dungeons Posted by Simon Reed on November 28th, 2014 [ permalink ] Playcrab has launched their action-packed new dungeon crawler, Dynasty of Dungeons, today. | Read more »
Monster Strike Review
Monster Strike Review By Campbell Bird on November 28th, 2014 Our Rating: :: BILLIARD STRATEGYUniversal App - Designed for iPhone and iPad Collect monsters and battle by flinging them across the battlefield in this strangely... | Read more »
Proun+ Review
Proun+ Review By Jennifer Allen on November 28th, 2014 Our Rating: :: TWITCHY RACINGUniversal App - Designed for iPhone and iPad Twitchy racing aplenty in Proun+, an enjoyably tricky title.   | Read more »
Lucha Amigos (Games)
Lucha Amigos 1.0 Device: iOS Universal Category: Games Price: $1.99, Version: 1.0 (iTunes) Description: Forget Ninja Turtles, and meet Wrestlers Turtles! Crazier, Spicier and…Bouncier! Sling carapaces of 7 Luchadores to knock all... | Read more »
Record of Agarest War Zero (Games)
Record of Agarest War Zero 1.0 Device: iOS Universal Category: Games Price: $7.99, Version: 1.0 (iTunes) Description: HyperDevbox Holiday Turkey Black Friday Special Pricing! To celebrate the opening of the holiday season HyperDevbox... | Read more »
Raby (Games)
Raby 1.0.3 Device: iOS Universal Category: Games Price: $2.99, Version: 1.0.3 (iTunes) Description: ***WARNING - Raby runs on: iPhone 5, iPhone 5C, iPhone 5S, iPhone 6, iPhone 6 Plus, iPad Mini Retina, iPad Mini 3, iPad 4, iPad Air,... | Read more »
Oddworld: Stranger's Wrath (Games)
Oddworld: Stranger's Wrath 1.0 Device: iOS Universal Category: Games Price: $5.99, Version: 1.0 (iTunes) Description: ** PLEASE NOTE: Oddworld Stranger's Wrath requires at least an iPhone 4S, iPad 2, iPad Mini or iPod Touch 5th gen... | Read more »
Bounce On Back (Games)
Bounce On Back 1.0 Device: iOS Universal Category: Games Price: $2.99, Version: 1.0 (iTunes) Description: | Read more »
Dwelp (Games)
Dwelp 1.0 Device: iOS Universal Category: Games Price: $.99, Version: 1.0 (iTunes) Description: === 50% off for a limited time, to celebrate release === Dwelp is an elegant little puzzler with a brand new game mechanic. To complete a... | Read more »

Price Scanner via MacPrices.net

Up To 75% Off Infovole Text Apps Over Black F...
Infovole’s entire range of apps, including the Textkraft family of word processors for iPads and iPhones, is being offered at 50-75% off over the Black Friday and Cyber Monday weekend. The five-day... Read more
Black Friday: Up to $60 off Mac minis, NY tax...
 B&H Photo has new 2014 Mac minis on sale for up to $60 off MSRP as part of their Black Friday sale. Shipping is free, and B&H charges NY sales tax only: - 1.4GHz Mac mini: $449.99 $50 off... Read more
Black Friday: 27-inch 5K iMac for $2299, save...
 B&H Photo continues to offer Black Friday sale prices on the 27″ 3.5GHz 5K iMac, in stock today and on sale for $2299 including free shipping plus NY sales tax only. Their price is $200 off MSRP... Read more
Karalux Announces 24K Gold-Plated iPhone 6
Karalux, a Vietnam-based jewellery firm, has launched a unique 24 karat gold-plated iPhone 6 version with gold-cast monolithic dragon on its back panel. The real 24 karat gold plated enclosure doesn’... Read more
Black Friday: 13-inch 2.6GHz Retina MacBook P...
 B&H Photo has lowered their price for the 13″ 2.6GHz/128GB Retina MacBook Pro to $1159 for Black Friday. That’s $140 off MSRP, and it’s the lowest price for this model (except for Apple’s $1099... Read more
View all the Black Friday sales on our Mac Pr...
We’ve updated our Mac Price Trackers with the latest information on prices, bundles, and availability on systems from Apple’s authorized internet/catalog resellers. View Black Friday sale prices at a... Read more
Black Friday: 11-inch MacBook Air for $779, s...
 Best Buy has lowered their price for the 2014 11″ 1.4GHz/128GB MacBook Air to $779.99 for Black Friday. That’s $120 off MSRP. Choose free shipping or free local store pickup (if available). Sale... Read more
Apple Store Black Friday sale for 2014: $100...
BLACK FRIDAY The Apple Store has posted their Black Friday deals for 2014. Receive a $100 PRODUCT(RED) branded iTunes gift card with the purchase of select Macs, $50 with iPads, and $25 with iPods,... Read more
Black Friday: 15% off iTunes Gift Cards
Staples is offering 15% off $50 and $100 iTunes Gift Cards on their online store as part of their Black Friday sale. Click here for more information. Shipping is free. Best Buy is offering $100... Read more
BEVL Releases Dock Tailored for iPhone 6 and...
Seattle based BEVL has released their first product: an iPhone dock that is divergent in build quality, rock-solid function and visual simplicity to complement the iPhone. BEVL is now accepting... Read more

Jobs Board

*Apple* Solutions Consultant (ASC) - Apple (...
**Job Summary** The ASC is an Apple employee who serves as an Apple brand ambassador and influencer in a Reseller's store. The ASC's role is to grow Apple Read more
Senior Event Manager, *Apple* Retail Market...
…This senior level position is responsible for leading and imagining the Apple Retail Team's global event strategy. Delivering an overarching brand story; in-store, Read more
*Apple* Retail - Multiple Positions (US) - A...
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
*Apple* Solutions Consultant (ASC) - Apple (...
**Job Summary** The ASC is an Apple employee who serves as an Apple brand ambassador and influencer in a Reseller's store. The ASC's role is to grow Apple Read more
*Apple* Solutions Consultant (ASC) - Apple (...
**Job Summary** The ASC is an Apple employee who serves as an Apple brand ambassador and influencer in a Reseller's store. The ASC's role is to grow Apple Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.