TweetFollow Us on Twitter

Apr 95 Tips
Volume Number:11
Issue Number:4
Column Tag:Tips & Tidbits

Tips & Tidbits

By Scott T Boyd, Editor

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

TIP OF THE MONTH

Doing Passwords the Simple Way

A common problem for people writing multi-user software for the Mac is the need to have a username/password dialog which allows the user to type the password without actually printing the real characters. Apple’s inimitable Tim Dierks released a snippet appropriately entitled “Password” which shows how to accomplish this in a variety of ways, most of which involve keeping one buffer which holds what the user actually types and another which contains the ‘display’ text (usually a line of bullets).

The following snippet shows how to accomplish this by replacing the QuickDraw bottlenecks. The beauty of this approach is that there is no messy buffer-update code needed for handling Cut/Copy/Paste, and text selection with the mouse is handled correctly. You may, however, want to prevent people from cutting or copying text to the clipboard, since if that text is pasted into any other TextEdit area it will display the password in normal text.

#ifdef __cplusplus
extern "C" { 
#endif

PasswordDrawProc
        void    PasswordDrawProc (void)
        {
                Ptr textBuff;
                short byteOff;
                short byteCnt, i;

                // load the correct parameters
                asm     {       move.l  A0, textBuff
                                move.w  D0, byteOff
                                move.w  D1, byteCnt
                        }
                for (i = 1; i <= byteCnt; i++)
                  DrawChar ('•');
        }
PasswordMeasureProc 
        void    PasswordMeasureProc (void)
        {
                short   textLen, offset;
                Ptr     textBuffer;
                short   width;
                
                // load the correct parameters
                asm     {       move.w  D0, textLen
                                move.w  D1, offset
                                move.l  A0, textBuffer
                        }
                width = CharWidth('•') * textLen;
                
                // return the width of the text
                asm     {       move.w  width, D1       }
        }

        TEHandle MakePasswordTextBox (void)
        {
                Rect     viewRect, destRect;
                TEHandle textBlock = NULL;
                
                SetRect (&viewRect, 15, 15, 165, 31);
                SetRect (&destRect, 15, 15, 165, 31);
                textBlock = TENew (&destRect, &viewRect);
                
                if (textBlock)
                  {
                   TECustomHook (intDrawHook,
                     (ProcPtr)PasswordDrawProc, textBlock);
                   TECustomHook (intWidthHook, 
                     (ProcPtr)PasswordMeasureProc, textBlock);
                  }
                return textBlock;
        }
#ifdef __cplusplus 
} 
#endif

- Eric Rosé, rose@nomos.com

SyncWait No More!

Sometimes when you’re AppleTalking or modeming and something goes wrong (like you switch the modem off while data is being sent to it), the computer will hang. The mouse will still move, but clicking will have no effect. Here’s the solution: Drop into MacsBug. You should see the routine name “_vSyncWait” plus something as the current location. If you don’t, you probably hit the system while it was doing something else. Hit Command-G to get back out of MacsBug, and try again. After a few tries you should find _vSyncWait.

_vSyncWait is the routine that the system uses to wait for some input from a serial port. If you can read assembly code, you’ll see that it’s pretty simple. Here’s the dump of the significant part:

+0000  4080BB8C   MOVE.W $0010(A0),D0              | 3028 0010      +0004 
 4080BB90   BGT.S  _vSyncWait   ; 4080BB8C   | 6EFA

Register A0 is pointing to a system data structure, in which a word will be cleared when the awaited input arrives. The MOVE.W instruction grabs this word and puts it into register D0. The BGT.S instruction then Branches back to the MOVE.W if the byte it just fetched is Greater Than zero (hence BGT). So it happens that this byte is never going to arrive for whatever reason, but the computer is going to wait for eternity. The secret to fixing this is to use Command-T to go step along until the MOVE.W instruction is displayed as the current instruction. Now use the “sw” command to set “@(a0+10)” to zero: sw @(a0+10) 0

Then hit Command-T twice more. The MOVE.W instruction will take the zero you just set into memory and put it in D0, so the D0 display on the right of the screen should have its right four digits all zeros. Then when you execute the BGT.S instruction, it should not go back to the MOVE.W since zero is not greater than zero.

Hit Command-G to go. If this was the only byte the software was waiting for, then it should continue running, although it may go a little crazy because it’s been suddenly disconnected from whatever peripheral it was talking to. Quit the program, fix your hardware, and try again.

- Macneil Shonle and Dustin Mitchell
MacneilS@aol.com and DustyM2@aol.com

So Easy To Forget These Things

I asked the question recently, “When debugging using Think C, after hitting the programmer’s switch and landing in MacsBug, how do I get back up to Think C’s source level debugger?”

The answer, while less than what I was looking for, was nonetheless useful. Think C’s debugger polls for Option-Command-Shift-Period. Use that instead of the programmer’s switch and you will be able to break into the debugger as long as the program is stuck in your own code, and not in the operating system somewhere.

- Jeffrey A. Lomicka, Marlboro MA, lomickaj@prnsys.enet.dec.com

What’ll They Call The Next One? Post-Modern Memory Manager?

So you’re trying to figure out whether a zone is a Modern Memory Manager zone? Why? Oh, never mind, you’ve certainly got a good reason (you do, don’t you?), so here’s how:

#define IsNewStyleZone(z)        \
              ((z)->heapType & 0x02)

if (IsNewStyleZone(LMGetSysZone()) {
   ...whatever...

- Dave Falkenburg, Apple

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

The best scanner app on mobile
People always say that the best camera is the one you have with you. Well, the same is true with scanners, and your phone can be a pretty great tool for scanning receipts and other documents while you're on the go. [Read more] | Read more »
MARVEL Avengers Academy guide - How to g...
MARVEL Avengers Academy lets you build your own superhero school and fill it with heroes from the Marvel universe. It can be a little slow going to get your school's attendance up though, so we've gathered together somesome tips to help you do this... | Read more »
Shadow Blade: Reload guide - How to hack...
Shadow Blade: Reload is the kind of action-platformer that would have happily sucked up hours of your time on a console a few years back.Now, you can take it with you wherever you go, and its mobile conversion is not too shabby at all. To help you... | Read more »
Tomb of the Mask guide - How to increase...
Tomb of the Mask is a great endless arcade game from Happymagenta in which quick reflexes and a persistent attitude can go a long way toward earning a top score. Check out these tips to see if you can give yourself an edge on the leaderboards. [... | Read more »
Smooth Operator! (Games)
Smooth Operator! 1.0 Device: iOS Universal Category: Games Price: $2.99, Version: 1.0 (iTunes) Description: Smooth Operator is a weird, weird two-player kissing game. Squeeze in for 2 player fun on a single iPad, creating awkward... | Read more »
Sinless: Remastered (Games)
Sinless: Remastered 1.0 Device: iOS Universal Category: Games Price: $1.99, Version: 1.0 (iTunes) Description: | Read more »
_PRISM Guide - How to solve those puzzle...
_PRISM is a rather delightful puzzle game that’s been tailor made for touch screens. While part of the fun is figuring things out as you go along, we thought we’d offer you a helping hand at getting in the right mindset. Don’t worry about messing... | Read more »
Fractal Space (Games)
Fractal Space 1.3.1 Device: iOS Universal Category: Games Price: $.99, Version: 1.3.1 (iTunes) Description: Live the memorable experience of Fractal Space, a unique first person adventure & puzzle game by Haze Games! Will you... | Read more »
Set off on an adventure through the Cand...
Like match three puzzlers? If so, Jelly Blast, the innovative iOS and Android game which launched last year, is worth a look. Jelly Blast sees you head off on an epic adventure through the Candy Kingdom with your friends Lily, Mr. Hare, and Mr.... | Read more »
Ellipsis - Touch. Explore. Survive. (...
Ellipsis - Touch. Explore. Survive. 1.0 Device: iOS Universal Category: Games Price: $2.99, Version: 1.0 (iTunes) Description: | Read more »

Price Scanner via MacPrices.net

Sale! 27-inch 3.2GHz 5K iMac for $1799, save...
B&H Photo has the 27″ 3.2GHz/1TB Fusion 5K iMac (MK472LL/A) on sale for $1799.99 including free shipping plus NY tax only. Their price is $200 off MSRP, and it’s the lowest price available for... Read more
cb Hardcase – Handmade and Premium Protective...
Baden-Baden, Germany based company cb innovations has introduced the new cb Hardcase for iPhone. Featuring fine Italian Premium leather that makes for a unique look and feel, the cb Hardcase... Read more
Free Quartz News Aggregation App Puts News Yo...
Quartz have released their new iPhone app. via the Apple App Store. The app, exclusive to iPhone (also compatible with iPad and iPod touch.), provides a whole new way to experience Quartz, which set... Read more
Apple Watch on sale for $100 off MSRP, free s...
B&H Photo has the Apple Watch on sale for $100 off MSRP. Shipping is free, and B&H charges NY sales tax only: - Apple Watch Sport: $100 off - Apple Watch: $100 off Read more
Sale! B&H Photo offers 12-inch Retina Mac...
B&H Photo has 12″ Retina MacBooks on sale for $300 off MSRP for a limited time. Shipping is free, and B&H charges NY tax only: - 12″ 1.1GHz Gray Retina MacBook: $999 $300 off MSRP - 12″ 1.... Read more
Save up to $470 with previous generation 27-i...
B&H Photo has previous-generation 27″ iMacs available for up to $470 off original MSRP, with prices starting at $1329. Each iMac includes free shipping, and B&H charges NY sales tax only: -... Read more
12-inch 1.1GHz Gray Retina MacBook on sale fo...
Musician’s Friend has the 12″ 1.1GHz Gray Retina MacBook on sale for $1199.99 including free shipping. Their price is $100 off MSRP, and it’s the lowest price available for this model. Read more
11-inch 256GB MacBook Air on sale for $999, $...
B&H Photo has the 11″ 1.6GHz/256GB MacBook Air on sale for $999.99 including free shipping plus NY sales tax only. That’s $100 off MSRP. MacMall has the 11″ 1.6GHz/256GB MacBook Air on sale for $... Read more
Free Reverso Context 3.1 For iOS Offers Conte...
Montreal, Canada based online and mobile translation and dictionary company Reverso has just released its Reverso Context 3.1 mobile app. The app provides its users with contextual translations of... Read more
Free SOSmart Automatic Car Crash Detection Ap...
Santiago, Chile based SOSmart SpA has announced release and immediate availably of SOSmart automatic car crash detection 2.4.8, an update to their app utility developed for iOS and Android devices.... Read more

Jobs Board

*Apple* Solution Specialist - Healthcare - C...
*Job Description* The Apple Solution Specialist - Healthcare proactively drives revenue and profit in the assigned sales segment, Healthcare, specific to Apple . This Read more
Infrastructure Engineer - *Apple* /Mac - Rem...
…part of a team Requires proven problem solving skills Preferred Additional: Apple Certified System Administrator (ACSA) Apple Certified Technical Coordinator (ACTC) 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
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
*Apple* Reporter - Business Insider, Inc. (U...
Business Insider is looking for a reporter to cover Apple , the biggest and arguably most important company in tech. As our primary Apple reporter, you will: * Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.