TweetFollow Us on Twitter

About Color Animation
Volume Number:6
Issue Number:5
Column Tag:Pascal Procedures

Related Info: Vert. Retrace Mgr Event Manager Color Quickdraw

Color Animation

By Ajay Nath, Oakland Gardens, NY

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

[Ajay Nath has B.A. degrees in Mathematics and Chemistry from New York University and is currently a third year medical student at the Mount Sinai School of Medicine where he tries to find the time to program and to learn medicine.]

It all started when I started playing with a shareware breakout game. Paul, a friend of mine who saw me playing it, thought it was neat and liked playing it but there were a few problems with the game. It was an old game and didn’t use the larger screen of my Mac IIcx or color and it had other annoying things about it. Well I’ve been much too busy to write a new game for my friend, but I was able to discover a method for doing simple animation that will work well on a Mac II or better machine.

When I first sat down and thought about the problem I thought, well I’ll simply use a vbl task to set a global variable and my program’s main loop will examine that variable and know when to draw. To do this I declared a variable of the following simple type:

{1}

 XVBLRec= RECORD
 xVBLTask : VBLTask;
 xDoTask: INTEGER;
 END;

The first field of the record (xVBLTask) is used in the calls to install and remove the vbl task, the second field xDoTask is an integer which the vbl task I use will set to 1 when it runs. My programs main loop just has to examine the xDoTask field and draw when it is non-zero.

This technique is not very different from the method which involves examining the current value of the Mac global variable TickCount and drawing when it changes, i.e. (in pseudocode):

{2}

 count = TickCount;
 while count = TickCount do nothing;
 { start drawing real fast! }.

On older Macs the TickCount was changed when vbl tasks were run so the above method was really very similar to using a vbl task to set a global variable.

I took a quick look in Inside Mac Vol. V (pp. 566-567) before I started writing my vbl task and found some interesting information there. The new Macs have vertical retrace interrupts which can vary according to their video card and we can create vbl tasks which run at the ‘heart rate’ of the whichever video card we want. Well, the obvious thing to do is to run our vbl task at the rate of the video card of our main screen, and we then should be able to do simple animation easily! The new calls are called SlotVInstall and SlotVRemove and just like the old calls need a pointer to a vbltask record but in addition, need a slot number so they know which slot to attach the vbl task to. All we need to know then is the slot number of the video card which drives our main screen. After a quick five minute search through IM V I found a call, “GetVideoDefault”, which would give me the slot number of the default video card and I was on my way.

I used TML Pascal II to write my main program and used MPW Assembler to write the vbl task. I’ll explain the vbl tasks code first since its so simple (only three lines). When the task runs, register A0 is a ptr to our vbltask record and this allows us to reset our tasks vblcount. Since we defined an integer that comes right after this record in our XVBLRec type (see above), we can change its value to 1 at this point since A0 points to our record. The three lines of the vbl task do the following (in pseudocode):

1) reset the vblcount

2) set the xDoTask variable to 1

3) return (exit) from the vbl task.

All the main program loop has to do is (in pseudocode):

 repeat
 if (xDoTask <> 0) begin
 DrawStuff;
 set xDoTask to 0
 endif
 until done

The following MPW commands will build and run the example program (you may need to change the paths to build it on your hard disk):

# 3

####
Asm vbltask.a
TMLPascal slotvbltaskdemo.p
Link -w -t ‘APPL’ -c ‘????’ 
 slotvbltaskdemo.p.o vbltask.a.o 
 “HD-80:MPW:Libraries:Libraries:”Runtime.o 
 “HD-80:MPW:Libraries:Libraries:”Interface.o 
 “HD-80:MPW:Libraries:TMLPLibraries:”TMLPasLib.o 
 “HD-80:MPW:Libraries:TMLPLibraries:”SANELib.o 
 -o SlotVBLTaskDemo
Rez -append -o SlotVBLTaskDemo slotvbltaskdemo.r
SlotVBLTaskDemo
####

Note that the code does check to make sure that the machine its running on is a Mac II or better before running, since the new calls are not available on lower end machines. On lower machines using regular vbl tasks is probably sufficient to do simple animation. That’s about all the explanation the code needs other than to say that it ‘bounces’ a red string vertically in its draggable window and can run in the background.

There is a bug which occurs when things are being drawn at the top of the screen and when you use the simple method of ‘erase old stuff then draw new stuff’ as I do in this example. You may see things start to flicker when drawing at the top of the screen. The problem I think is in the way the screen is drawn which is left to right and from top to bottom. I haven’t thought of a solution for this problem yet other than to use a call to CopyBits to blast in whatever your drawing, rather then to use straight QuickDraw calls. If anyone can think of a good explanation of this problem and how to solve it I’d like to hear about it.

Much love and thanks to the boys of ‘9A’ and of course, to K.S.

Listing:  vbltask.a

 INCLUDE‘SysEqu.a’
 EXPORT MyVBLTask

MyVBLTask PROC
;
; On entry A0 is a ptr to our XVBLRec which was defined
; as follows:
;
;XVBLRec= RECORD
;xVBLTask : VBLTask;
;xDoTask: INTEGER;
;END;
;
; We can use MPW RECORDs to define it in assembly as follows:
;
XVBLRec RECORD 0
xVBLTaskDS.BvblPhase+2
xDoTask DS.W1
 ENDR

kVBLCount EQU    1

 WITH XVBLRec
 ; Reset the vblCount
 MOVE.W #kVBLCount,XVBLRec+xVBLTask+vblCount(A0)

 ; Make xDoTask non-zero
 MOVE.W #1,XVBLRec+xDoTask(A0)

 ; Exit Task
 RTS

ENDWITH
ENDP
 END  ; For Assembler
Listing:  slotvbltaskdemo.p

PROGRAM SlotVBLTaskDemo;

USES
 MemTypes, QuickDraw, OSIntf, ToolIntf;

{ Declare our external vbl task }
PROCEDURE MyVBLTask; EXTERNAL;

CONST
 F =  False;
 T =  True;
 kBallSpeed =  4;

TYPE
 XVBLRec= RECORD
 xVBLTask : VBLTask;
 xDoTask: INTEGER;
 END;

VAR
 gDone  : BOOLEAN;
 gVideoInfoRec : DefVideoRec;
 gEvt : EventRecord;
 gFontInfo: FontInfo;
 gBoxDir: INTEGER;
 gBoxRect : Rect;
 gBoxColor: RGBColor;
 gBoxString :  Str255;

 gDragRect,
 gRect  : Rect;
 gMainWindow:  WindowPtr;
 gWRec  : WindowRecord;

 gXVBLRec : XVBLRec;

{ Proc to run if a crash occurs }
PROCEDURE Crash;
BEGIN
 ExitToShell;
END;

{ Proc that does MacInits }
PROCEDURE MacInits;
BEGIN
 MaxApplZone;

 MoreMasters;
 MoreMasters;
 MoreMasters;
 MoreMasters;

 InitGraf (@thePort);
 InitFonts;
 InitWindows;
 InitMenus;
 TEInit;
 InitDialogs (@Crash);
 InitCursor;
END;

{ Proc that sets up our window }
PROCEDURE SetUpWindows;
BEGIN
 gRect := ScreenBits.bounds;
 WITH gRect DO BEGIN
 left := left + 20;
 right := left + 400;
 top := top + 40;
 bottom := bottom - 20;
 END;

 gMainWindow := NewCWindow (@gWRec, gRect,
 ‘SlotVBLTaskDemo - Click in this window to Exit’,
 T, noGrowDocProc, WindowPtr (-1), F, 0);
 SetPort (gMainWindow);
END;

{ Proc that sets up the box for our ball }
PROCEDURE SetUpBox;
VAR
 width  : INTEGER;
BEGIN
 gBoxDir := kBallSpeed;

 gBoxString := ‘I love you Manu’;

 width := StringWidth (gBoxString);

 GetFontInfo (gFontInfo);

 WITH gBoxRect DO BEGIN
 top := 10;
 bottom := top + gFontInfo.ascent + gFontInfo.descent;
 left := ((gRect.right - gRect.left) DIV 2) - (width DIV 2);
 right := left + width;
 END;

 WITH gBoxColor DO BEGIN
 red := -1;
 green := 0;
 blue := 0;
 END;

 RGBForeColor (gBoxColor);
END;

{ Proc that inits our globals }
PROCEDURE GlobalInits;
BEGIN
 SetUpWindows;
 SetUpBox;
 gDragRect := ScreenBits.bounds;
 InsetRect (gDragRect, 4, 4);

 gDone := F;
END;

{ Proc that cleans up before we exit }
PROCEDURE CleanUps;
BEGIN
 CloseWindow (gMainWindow);
END;

{ Func that makes sure we run in the currect environment }
FUNCTION EnvironmentOK : BOOLEAN;
VAR
 err  : OSErr;
 theWorld : SysEnvRec;
BEGIN
 EnvironmentOK := F; { Assume env is bad }

 err := SysEnvirons (curSysEnvVers, theWorld);

 IF (err = noErr) THEN BEGIN
 IF (theWorld.machineType >= envMacII) THEN
 EnvironmentOK := T;
 END; { IF }
END;

{ Func that sets up our vbl task }
FUNCTION VBLTaskSetUp : BOOLEAN;
VAR
 err  : OSErr;
BEGIN
 VBLTaskSetUp := F; { Assume we fail }

 GetVideoDefault (@gVideoInfoRec);

 WITH gXVBLRec DO BEGIN
 xDoTask := 0;

 WITH xVBLTask DO BEGIN
 qType := ORD (vType);
 vblAddr := @MyVBLTask;
 vblCount := 1;
 vblPhase := 0;
 END;

 err := SlotVInstall (@xVBLTask, gVideoInfoRec.sdSlot);
 IF (err = noErr) THEN
 VBLTaskSetUp := T; { We succeeded! }
 END;
END;

{ Proc that removes our vbl task }
PROCEDURE RemoveVBLTask;
VAR
 err  : OSErr;
BEGIN
 err := SlotVRemove (@gXVBLRec.xVBLTask, gVideoInfoRec.sdSlot);
END;

{ Proc that draws our window }
PROCEDURE DrawStuff;
VAR
 oldPort: GrafPtr;
BEGIN
 GetPort (oldPort);
 SetPort (gMainWindow);
 EraseRect (gBoxRect);

 WITH gBoxRect DO BEGIN
 top := top + gBoxDir;
 bottom := bottom + gBoxDir;
 END;

 IF (gBoxRect.bottom >= gWRec.port.portRect.bottom) THEN
 gBoxDir := -kBallSpeed
 ELSE BEGIN
 IF (gBoxRect.top <= gWRec.port.portRect.top) THEN
 gBoxDir := kBallSpeed;
 END;

 MoveTo (gBoxRect.left, gBoxRect.bottom - gFontInfo.descent);
 DrawString (gBoxString);

 SetPort (oldPort);
END;

{ Proc that handles mouse downs }
PROCEDURE DoMouseDown;
VAR
 result : INTEGER;
 whichWindow:  WindowPtr;
BEGIN
 result := FindWindow (gEvt.where, whichWindow);

 CASE result OF
 inContent:
 gDone := T;
 inDrag:
 DragWindow (whichWindow, gEvt.where, gDragRect);
 OTHERWISE
 END;
END;

{ Main }
BEGIN
 MacInits;

 IF (EnvironmentOK) THEN BEGIN
 GlobalInits;

 IF (VBLTaskSetUp) THEN BEGIN

 REPEAT
 IF NOT (WaitNextEvent (mDownMask, gEvt, 0, NIL)) THEN BEGIN
 IF (gXVBLRec.xDoTask <> 0) THEN BEGIN
 DrawStuff;
 gXVBLRec.xDoTask := 0;
 END;
 END
 ELSE
 DoMouseDown;
 UNTIL (gDone);
 RemoveVBLTask;
 END;
 CleanUps;
 END;

 ExitToShell; { Back to the Finder! (or MultiFinder) }
END.
Listing:  slotvbltaskdemo.r

#include “Types.r”
#define kMinSize 25/* application’s minimum size (in K) */
#define kPrefSize50/* application’s preferred size (in K) */

resource ‘SIZE’ (-1) {
 dontSaveScreen,
 acceptSuspendResumeEvents,
 enableOptionSwitch,
 canBackground,  /* we can background  */
 multiFinderAware,
 backgroundAndForeground,
 dontGetFrontClicks,
 ignoreChildDiedEvents,
 not32BitCompatible,
 reserved,
 reserved,
 reserved,
 reserved,
 reserved,
 reserved,
 reserved,
 kPrefSize * 1024,
 kMinSize * 1024 
};

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

NeoOffice 2014.7 - Mac-tailored, OpenOff...
NeoOffice is a complete office suite for OS X. With NeoOffice, users can view, edit, and save OpenOffice documents, PDF files, and most Microsoft Word, Excel, and PowerPoint documents. NeoOffice 3.x... Read more
DesktopLyrics 2.6.6 - Displays current i...
DesktopLyrics is an application that displays the lyrics of the song currently playing in "iTunes" right on your desktop. The lyrics for the song have to be set in iTunes; DesktopLyrics does nothing... Read more
Ember 1.8.3 - Versatile digital scrapboo...
Ember (formerly LittleSnapper) is your digital scrapbook of things that inspire you: websites, photos, apps or other things. Just drag in images that you want to keep, organize them into relevant... Read more
Apple iTunes 12.1 - Manage your music, m...
Apple iTunes lets you organize and play digital music and video on your computer. It can automatically download new music, app, and book purchases across all your devices and computers. And it's a... Read more
LibreOffice 4.4.3 - Free, open-source of...
LibreOffice is an office suite (word processor, spreadsheet, presentations, drawing tool) compatible with other major office suites. The Document Foundation is coordinating development and... Read more
FoldersSynchronizer 4.2.1 - Synchronize...
FoldersSynchronizer is a popular and useful utility that synchronizes and backs-up files, folders, disks and boot disks. On each session you can apply special options like Timers, Multiple Folders,... Read more
Simon 4.0.2 - Monitor changes and crashe...
Simon monitors websites and alerts you of crashes and changes. Select pages to monitor, choose your alert options, and customize your settings. Simon does the rest. Keep a watchful eye on your... Read more
Cocktail 8.1.2 - General maintenance and...
Cocktail is a general purpose utility for OS X that lets you clean, repair and optimize your Mac. It is a powerful digital toolset that helps hundreds of thousands of Mac users around the world get... Read more
Cyberduck 4.6.4 - FTP and SFTP browser....
Cyberduck is a robust FTP/FTP-TLS/SFTP browser for the Mac whose lack of visual clutter and cleverly intuitive features make it easy to use. Support for external editors and system technologies such... Read more
Herald 5.0.2 - Notification plugin for M...
Note: Versions 2.1.3 (for OS X 10.7), 3.0.6 (for OS X 10.8), and 4.0.8 (for OS X 10.9) are no longer supported by the developer. Herald is a notification plugin for Mail.app, Apple's Mac OS X email... Read more

Playworld Superheroes Review
Playworld Superheroes Review By Tre Lawrence on January 30th, 2015 Our Rating: :: HERO CRAFTINGUniversal App - Designed for iPhone and iPad It’s all about the imagination, fighting bad creatures — and looking good while doing so.   | Read more »
Join the SpongeBob Bubble Party in this...
Join the SpongeBob Bubble Party in this New Match 3 Bubble Poppin’ Frenzy Posted by Jessica Fisher on January 30th, 2015 [ permalink ] | Read more »
Handpick Review
Handpick Review By Jennifer Allen on January 30th, 2015 Our Rating: :: TANTALIZING SUGGESTIONSiPhone App - Designed for the iPhone, compatible with the iPad Handpick will make you hungry, as well as inspire you to cook something... | Read more »
Storm the Halls of Echo Base in First St...
Storm the Halls of Echo Base in First Star Wars: Galactic Defense Event Posted by Jessica Fisher on January 30th, 2015 [ permalink ] Universal App - Designed for iPhone and iPad | Read more »
Contradiction Review
Contradiction Review By Tre Lawrence on January 30th, 2015 Our Rating: :: SPOT THE LIEiPad Only App - Designed for the iPad Contradiction is a live action point and click adventure that’s pretty engaging.   Developer: Tim Follin... | Read more »
Unlock Sunshine Girl in Ironkill with th...
Unlock Sunshine Girl in Ironkill with this special 148Apps code Posted by Rob Rich on January 29th, 2015 [ permalink ] Robo-fighter Ironkill has been out on iOS a | Read more »
Crossroad Zombies Review
Crossroad Zombies Review By Jordan Minor on January 29th, 2015 Our Rating: :: CROSSWALKING DEADiPad Only App - Designed for the iPad Crossroad Zombies is a rough draft of a cool genre mash-up.   | Read more »
Blood Brothers 2 – Tips, Cheats, and Str...
War is hell: Is it the kind of hell you want to check out? Read our Blood Brothers 2 review to find out! Blood Brothers 2, DeNA’s follow-up to the original Blood Brothers, is an intriguing card collecting / role-playing / strategy hybrid. There’s... | Read more »
Blood Brothers 2 Review
Blood Brothers 2 Review By Nadia Oxford on January 29th, 2015 Our Rating: :: AN AGGRAVATING RELATIVEUniversal App - Designed for iPhone and iPad Blood Brothers 2 is built on a simple, solid foundation, but its free-to-play system... | Read more »
I AM BREAD, the Toast of the Town, is Ro...
Have you ever dreamt of being deliciously gluten-y? Do you feel passionate about Rye and Wheat? The guys at Bossa Studios do and that is why they are bringing I AM BREAD to iOS soon. The loafy app will feature all the new content that is being... | Read more »

Price Scanner via MacPrices.net

Intel Aims to Transform Workplace With 5th-Ge...
Intel Corporation today announced the availability of its 5th generation Intel Core vPro processor family that provides cutting-edge features to enable a new and rapidly shifting workplace. To meet... Read more
iOS App Sharalike Introduces New Instant Smar...
Sharalike slideshow and photo management software for iOS, is making it easier than ever to create shareable meaningful moments with its new instant SmartShow technology. Staying organized is a goal... Read more
Apple Becomes World’s Largest Smartphone Vend...
According to the latest research data from Strategy Analytics, as global smartphone shipments grew 31 percent annually to reach a record 380 million units in the fourth quarter of 2014. Apple became... Read more
Cut the Cord: OtterBox Resurgence Power Case...
Dead batteries and broken phones are two of the biggest issues for smartphone users today. Otterbox addresses both with the new Resurgence Power Case for Apple iPhone 6, promising to make those panic... Read more
13-inch Retina MacBook Pros on sale for up to...
B&H Photo has 13″ Retina MacBook Pros on sale for $200 off MSRP. Shipping is free, and B&H charges NY sales tax only: - 13″ 2.6GHz/128GB Retina MacBook Pro: $1199.99 save $100 - 13″ 2.6GHz/... Read more
15-inch 2.5GHz Retina MacBook Pro on sale for...
 B&H Photo has the 15″ 2.5GHz Retina MacBook Pro on sale for $2319.99 including free shipping plus NY sales tax only. Their price is $180 off MSRP, and it’s the lowest price available for this... Read more
Back in stock: Refurbished iPod nanos for $99...
The Apple Store has Apple Certified Refurbished 16GB iPod nanos available for $99 including free shipping and Apple’s standard one-year warranty. That’s $50 off the cost of new nanos. Most colors are... Read more
Apple lowers price on refurbished 256GB MacBo...
The Apple Store has lowered prices on Apple Certified Refurbished 2014 MacBook Airs with 256GB SSDs, now available for up to $200 off the cost of new models. An Apple one-year warranty is included... Read more
New Good Management Suite Simplifies Enterpri...
Good Technology has announced the availability of the Good Management Suite, a comprehensive cross-platform solution for organizations getting started with mobile business initiatives. Built on the... Read more
15-inch 2.0GHz Retina MacBook Pro (refurbishe...
The Apple Store has Apple Certified Refurbished previous-generation 15″ 2.0GHz Retina MacBook Pros available for $1489 including free shipping plus Apple’s standard one-year warranty. Their price is... Read more

Jobs Board

*Apple* Solutions Consultant- Retail Sales (...
**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
Event Director, *Apple* Retail Marketing -...
…This senior level position is responsible for leading and imagining the Apple Retail Team's global engagement strategy and team. Delivering an overarching brand Read more
At-Home Chat Specialist- *Apple* Online Stor...
**Job Summary** At Apple , we believe in hard work, a fun environment, and the kind of creativity and innovation that only comes about when talented people from diverse Read more
SW QA Engineer - *Apple* TV - Apple (United...
**Job Summary** The Apple TV team is looking for experienced Quality Assurance Engineers with a passion for delivering first in class home entertainment solutions. **Key Read more
*Apple* Retail - Multiple Positions(US) - Ap...
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
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.