TweetFollow Us on Twitter

December 93 - GRAPHICAL TRUFFLES

GRAPHICAL TRUFFLES

REMEDIES FOR COMMON QUICKDRAW PROBLEMS

JOHN WANG

[IMAGE 095-096_Graphical_Truffl1.GIF]



During the past two years alone, the Developer Support Center has answered more than 1000 QuickDraw-related questions. The answers to most of these questions are now available in Apple's plentiful "one-to-many" sources of support for developers, includingInside Macintosh , Technical Notes, Q&As, sample code, and of coursedevelop. But you might find it helpful to look here first if you're having a QuickDraw problem. The symptoms of some common problems are listed in this column along with Dr. John's suggested remedies.

These are the symptoms that we'll suggest remedies for:

  • CopyBits is too slow.
  • You have a palette created with a tolerance of 0, but the colors in your graphics port don't match the palette.
  • You're using palettes stored in 'pltt' resources and they don't seem to have any effect.
  • Strange colors get drawn when you do a CopyBits between different graphics ports.
  • The pen pattern isn't being used when PaintRect is called with hilite penmode.
  • NewGWorld doesn't return an error and the GWorldPtr it returns is unchanged.
  • QuickDraw routines aren't working on your GWorld.
  • Your complement procedure isn't being called for InvertRect.

THE REMEDIES

CopyBits is too slow.
Remedy:
There's little doubt that CopyBits is a complex piece of code, so there aremany factors that can affect its execution speed. In fact, there's a long Technical Note dedicated to this topic, called "Of Time and Space and _CopyBits" (QuickDraw 21). But here are a couple of quick hints for possible ways to speed up CopyBits:

  • If your source and destination graphics ports have matching color tables, set the ctSeed field in the color tables of the source and destination to be the same. This removes the overhead of comparing the entries in the color tables to determine whether color mapping is necessary.
  • Use GWorlds when copying the entire off-screen buffer to the screen. GWorlds will properly align your pixel data so that CopyBits calls don't require byte and bit shifting. (You must create the GWorld with a depth of 0 and pass the rectangle in global coordinates.)

You have a palette created with a tolerance of 0, but the colors in your graphics port don't match the palette.
Remedy:
The colors in the graphics port may appear to be different, but remember that only the high eight bits of an RGB color component are important. The lower eight bits aren't significant because they're ignored by the hardware. Consequently, for optimization and implementation reasons, NewPalette creates a palette of colors by copying the high byte of each color in the input color table to both the high byte and the low byte of the palette. For example, if the color table has the color ($ff00, $75fe, $0080), the equivalent palette entry would be ($ffff, $7575, $0000).

You're using palettes stored in 'pltt' resources and they don't seem to have any effect.
Remedy:
You're having this problem because GetNewPalette doesn't work as documented inInside MacintoshVolume VI. The description of this routine in Volume VI states that a palette will be loaded and attached to the current window, and if the palette requested isn't available, the default application palette is used instead. The actual implementation of GetNewPalette is much simpler: it only loads the specified 'pltt' resource with GetResource and detaches it with DetachResource to make it a handle; if the specified 'pltt' resource isn't found, GetNewPalette doesn't load the default application palette.

Strange colors get drawn when you do a CopyBits between different graphics ports. Remedy:More than likely, your graphics port and device are incorrectly set. The current port and device must always be set to the destination port and device. So if you're copying from a window to an off-screen GWorld, you must call SetGWorld to set the GWorld as the current port and device. When you do a CopyBits from a GWorld to a window, you must set the port to the window and the graphics device to the MainGDevice. This rule actually applies to all QuickDraw drawing.

The pen pattern isn't being used when PaintRect is called with hilite penmode.
Remedy:
A bug in QuickDraw causes the pen pattern to be ignored when used with hilite penmode in the following calls:

  • FrameRect, PaintRect, and FillRect
  • LineTo (vertical and horizontal lines only)
  • FrameRgn, PaintRgn, and FillRgn (rectangular regions only)
  • FramePoly, PaintPoly, and FillPoly (rectangular polygons only)
A simple workaround for PaintRect is to call PaintRoundRect instead; that is, call

PaintRoundRect(&myRect, 0, 0);

rather than

PaintRect(&myRect);

NewGWorld doesn't return an error and the GWorldPtr it returns is unchanged.
Remedy:
The cause of this problem is typically memory movement. Many object-oriented languages, such as MacApp, store data in handles. If the GWorldPtr pointer variable you pass to NewGWorld is stored in a relocatable block of memory, and if that block moves during execution of NewGWorld, NewGWorld will store the GWorldPtr in the old dereferenced storage location. Instead, pass a local GWorldPtr to NewGWorld and copy the local GWorldPtr to the relocatable memory block afterward.

QuickDraw routines aren't working on your GWorld.
Remedy:
Although some routines in QuickDraw will work when LockPixels isn't called, most routines will have unexpected results. Always call LockPixels if you want to access or draw into your GWorld. To prevent memory fragmentation, the GWorld image should be unlocked when you're not accessing the pixel data so that it can move in memory.

Your complement procedure isn't being called for InvertRect.
Remedy:
Complement procedures are called from InvertColor only. All other Invert calls simply invert bits, as in QuickDraw's original design.

NEED A REAL DOCTOR?
The next time a QuickDraw problem is giving you a headache, look here first for help. Dr. John's list of remedies may provide just what you need to solve your problem. If you don't find a solution here, check as usual in Inside Macintosh and the many other available sources of help.

JOHN WANG (AppleLink WANG.JY) of Apple's Developer Support Center has a new addition to his family, named Pepper. The four-month-old baby girl weighs in at a healthy nine pounds. She has big brown eyes, baby teeth, and a generous amount of hair. She sleeps all day and makes almost no noise at night. And she's nearly toilet trained already! Pepper even gets along well with her older brother Skate; they like to nibble playfully on each other's ears. But when it comes to food, they're fearless; they fight, kick, and howl -- all for just a bone. *

Thanks to Don Moccia and Brigham Stevens for reviewing this column.*

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

calibre 2.17 - Complete e-library manage...
Calibre is a complete e-book library manager. Organize your collection, convert your books to multiple formats, and sync with all of your devices. Let Calibre be your multi-tasking digital librarian... Read more
OmniGraffle Pro 6.1.2 - Create diagrams,...
OmniGraffle Pro helps you draw beautiful diagrams, family trees, flow charts, org charts, layouts, and (mathematically speaking) any other directed or non-directed graphs. We've had people use... Read more
OmniGraffle 6.1.2 - Create diagrams, flo...
OmniGraffle helps you draw beautiful diagrams, family trees, flow charts, org charts, layouts, and (mathematically speaking) any other directed or non-directed graphs. We've had people use Graffle to... Read more
RoboForm 2.0.2 - Password manager; syncs...
RoboForm is a password manager that offers one-click login, mobile syncing, easy form filling, and reliable security. Password Manager. RoboForm remembers your passwords so you don't have to! Just... Read more
Apple MainStage 3.1 - Live performance t...
Love the sound you got on your recording? MainStage 3 makes it easy to bring all the same instruments and effects to the stage. Everything from the Sound Library and Smart Controls you're familiar... Read more
Freeway Pro 7.0.2 - Drag-and-drop Web de...
Freeway Pro lets you build websites with speed and precision... without writing a line of code! With its user-oriented drag-and-drop interface, Freeway Pro helps you piece together the website of... Read more
A Better Finder Rename 9.44 - File, phot...
A Better Finder Rename is the most complete renaming solution available on the market today. That's why, since 1996, tens of thousands of hobbyists, professionals and businesses depend on A Better... Read more
Stacks 2.6.9 - New way to create pages i...
Stacks is a new way to create pages in RapidWeaver. It's a plugin designed to combine drag-and-drop simplicity with the power of fluid layout. Features: Fluid Layout: Stacks lets you build pages... Read more
Sid Meier's Civilization: Beyond Ea...
Sid Meier's Civilization: Beyond Earth is a new science-fiction-themed entry into the award-winning Civilization series. Set in the future, global events have destabilized the world leading to a... Read more
Logic Pro X 10.1 - Music creation and au...
Apple Logic Pro X is the most advanced version of Logic ever. Sophisticated new tools for professional songwriting, editing, and mixing are built around a modern interface that's designed to get... Read more

Choice Provisions is Set to Launch Destr...
Choice Provisions is Set to Launch Destructamundo on iOS This Month Posted by Tre Lawrence on January 23rd, 2015 [ permalink ] Choice Provisions – home stable to | Read more »
King of Thieves – An Interview With Zept...
Ahead of the release of ZeptoLab’s King of Thieves, we were able to ask ZeptoLab’s co-founder, Semyon Voinov, a few questions about the inspiration behind the game and what that means for the Cut the Rope franchise. | Read more »
Handle Review
Handle Review By Jennifer Allen on January 23rd, 2015 Our Rating: :: SPEEDY ORGANIZINGUniversal App - Designed for iPhone and iPad Handle is a very convenient way of juggling your emails, To Do list, and Calendar all through one... | Read more »
The New Disney Inquizitive App Offers a...
The New Disney Inquizitive App Offers a Place for Fans to Take Disney Quizzes Posted by Tre Lawrence on January 23rd, 2015 [ permalink ] | Read more »
Hands-On With Cut the Rope Developer Zep...
Marking quite a departure from ZeptoLab’s past successes, namely the Cut The Rope series, King of Thieves is shaping up to be quite promising. Due for release in February, we were lucky enough to have some time with a preview build to see exactly... | Read more »
Fast Fishing Review
Fast Fishing Review By Jennifer Allen on January 23rd, 2015 Our Rating: :: LIVES UP TO ITS NAMEUniversal App - Designed for iPhone and iPad Fishing is far from relaxing in Fast Fishing, but it is fun.   | Read more »
The LEGO Movie Video Game is Available N...
The LEGO Movie Video Game is Available Now for iOS Posted by Ellis Spice on January 23rd, 2015 [ permalink ] Universal App - Designed for iPhone and iPad | Read more »
Satellina Review
Satellina Review By Jennifer Allen on January 23rd, 2015 Our Rating: :: TWITCHY BUT TACTICALUniversal App - Designed for iPhone and iPad Satellina requires quick thinking and twitchy fingers, and it’s pretty fun.   | Read more »
Tail Drift, the Crazy 360 Degree Flyer,...
Tail Drift, the Crazy 360 Degree Flyer, Has Gone Free-to-Play in a New Update Posted by Jessica Fisher on January 22nd, 2015 [ permalink ] | Read more »
PureSkate 2 Review
PureSkate 2 Review By Tre Lawrence on January 22nd, 2015 Our Rating: :: ALMOST ALL AIRUniversal App - Designed for iPhone and iPad PureSkate 2 lets one’s fingers do the skateboarding.   | Read more »

Price Scanner via MacPrices.net

iPhone 6 and 6 Plus GIve Apple Half Of US Mob...
Chicago-based Consumer Intelligence Research Partners, LLC (CIRP) have released analysis of the results of its research on mobile phone manufacturers for the calendar quarter that ended December 31,... Read more
Save $100 on MacBook Airs with 256GB of stora...
B&H Photo has 256GB MacBook Airs on sale for $100 off MSRP. Shipping is free, and B&H charges NY sales tax only: - 11″ 1.4GHz/256GB MacBook Air: $999 $100 off MSRP - 13″ 1.4GHz/256GB MacBook... Read more
21-inch 2.7GHz iMac on sale for $1179, save $...
B&H Photo has the 21″ 2.7GHz iMac on sale for $1179 including free shipping plus NY sales tax only. Their price is $120 off MSRP, and it’s the lowest price available for this model from any... Read more
iPhone Usage Rates by State Correlate With Ed...
Chitika Insights notes that despite iPhones being the largest source of smartphone Internet traffic in North America, their latest study finds a relatively high degree of variation of iPhone usage... Read more
ProGearX Extendable Pole “Pov/Selfie Stick” M...
There’s something inescapably narcissistic about the concept of selfies as they’ve developed as a smartphone-driven social (particularly social media) phenomenon that rubs me the wrong way. However,... Read more
iPad Air 2 on sale for up to $100 off MSRP, 2...
 Best Buy has iPad Air 2s on sale for up to $100 off MSRP on their online store for the next two days. Choose free shipping or free local store pickup (if available). Sale prices available for online... Read more
Roundup of Apple refurbished MacBook Pros and...
The Apple Store has Apple Certified Refurbished 2014 MacBook Pros and MacBook Airs available for up to $400 off the cost of new models. An Apple one-year warranty is included with each model, and... Read more
Sale! 13-inch 2.8GHz Retina MacBook Pro for $...
 B&H Photo has the 13″ 2.8GHz Retina MacBook Pro on sale for $1599 including free shipping plus NY sales tax only. Their price is $200 off MSRP, and it’s the lowest price available for this model... Read more
Next OS X/iOS Version Upgrades Should Concent...
On stage at Apple’s World Wide Developers’ Conference in June 2009, Bertrand Serlet, the company’s Senior Vice President of Software Engineering at the time, announced that the forthcoming OS X... Read more
First National Bank to Offer Apple Pay Adds I...
First National Bank will make Apple Pay available to customers beginning in the first quarter of 2015. Apple Pay will enable customers to easily make secure mobile payments with their First National... Read more

Jobs Board

*Apple* Solutions Consultant (ASC)- Retail S...
**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 - Retail Sales...
**Job Summary** As an Apple Solutions Consultant (ASC) you are the link between our customers and our products. Your role is to drive the Apple business in a retail Read more
*Apple* Lead Operator, GSOC - Apple (United...
**Job Summary** Apple is seeking an exceptional, customer service oriented and experienced persons to fulfill the role of Apple Lead Operator (ALO) as part of the Read more
Order Support Supervisor- *Apple* Online Sto...
**Job Summary** The Apple Online Store (AOS) Order Administration team is looking for an Order Support Supervisor to manage and lead a team of Specialists through the Read more
Senior Program Manager, *Apple* Online Supp...
**Job Summary** The Apple Online Support Planning team is looking for an experienced Senior Project Manager to lead key Quality program initiatives across the Online Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.