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

VirtualBox 5.1.14 - x86 virtualization s...
VirtualBox is a family of powerful x86 virtualization products for enterprise as well as home use. Not only is VirtualBox an extremely feature rich, high performance product for enterprise customers... Read more
FileZilla 3.24.0 - Fast and reliable FTP...
FileZilla (ported from Windows) is a fast and reliable FTP client and server with lots of useful features and an intuitive interface. Version 3.24.0: New The context menu for remote file search... Read more
BusyContacts 1.1.6 - Fast, efficient con...
BusyContacts is a contact manager for OS X that makes creating, finding, and managing contacts faster and more efficient. It brings to contact management the same power, flexibility, and sharing... Read more
BusyCal 3.1.4 - Powerful calendar app wi...
BusyCal is an award-winning desktop calendar that combines personal productivity features for individuals with powerful calendar sharing capabilities for families and workgroups. Its unique features... Read more
Duplicate Annihilator 5.8.3 - Find and d...
Duplicate Annihilator takes on the time-consuming task of comparing the images in your iPhoto library using effective algorithms to make sure that no duplicate escapes. Duplicate Annihilator detects... Read more
MarsEdit 3.7.10 - Quick and convenient b...
MarsEdit is a blog editor for OS X that makes editing your blog like writing email, with spell-checking, drafts, multiple windows, and even AppleScript support. It works with with most blog services... Read more
WALTR 2 2.0.9 - $39.95
WALTR 2 helps you wirelessly drag-and-drop any music, ringtones, videos, PDF, and ePub files onto your iPhone, iPad, or iPod without iTunes. It is the second major version of Softorino's critically-... Read more
Paperless 2.3.9 - $49.95
Paperless is a digital documents manager. Remember when everyone talked about how we would soon be a paperless society? Now it seems like we use paper more than ever. Let's face it - we need and we... Read more
Adobe After Effects CC 2017 14.1 - Creat...
After Effects CC 2017 is available as part of Adobe Creative Cloud for as little as $19.99/month (or $9.99/month if you're a previous After Effects customer). The new, more connected After Effects CC... Read more
Adobe Premiere Pro CC 2017 11.0.2 - Digi...
Premiere Pro CC 2017 is available as part of Adobe Creative Cloud for as little as $19.99/month (or $9.99/month if you're a previous Premiere Pro customer). Adobe Premiere Pro CC 2017 lets you edit... Read more

Super Mario Run dashes onto Android in M...
Super Mario Run was one of the biggest mobile launches in 2016 before it was met with a lukewarm response by many. While the game itself plays a treat, it's pretty hard to swallow the steep price for the full game. With that said, Android users... | Read more »
WarFriends Beginner's Guide: How to...
Chillingo's new game, WarFriends, is finally available world wide, and so far it's a refreshing change from common mobile game trends. The game's a mix of tower defense, third person shooter, and collectible card game. There's a lot to unpack here... | Read more »
Super Gridland (Entertainment)
Super Gridland 1.0 Device: iOS Universal Category: Entertainment Price: $1.99, Version: 1.0 (iTunes) Description: Match. Build. Survive. "exquisitely tuned" - Rock Paper Shotgun No in-app purches, and no ads! | Read more »
Red's Kingdom (Games)
Red's Kingdom 1.0 Device: iOS Universal Category: Games Price: $4.99, Version: 1.0 (iTunes) Description: Mad King Mac has kidnapped your father and stolen your golden nut! Solve puzzles and battle goons as you explore and battle your... | Read more »
Turbo League Guide: How to tame the cont...
| Read more »
Fire Emblem: Heroes coming to Google Pla...
Nintendo gave us our first look at Fire Emblem: Heroes, the upcoming mobile Fire Emblem game the company hinted at last year. Revealed at the Fire Emblem Direct event held today, the game will condense the series' tactical RPG combat into bite-... | Read more »
ReSlice (Music)
ReSlice 1.0 Device: iOS Universal Category: Music Price: $9.99, Version: 1.0 (iTunes) Description: Audio Slice Machine Slice your audio samples with ReSlice and create flexible musical atoms which can be triggered by MIDI notes or... | Read more »
Stickman Surfer rides in with the tide t...
Stickson is back and this time he's taken up yet another extreme sport - surfing. Stickman Surfer is out this Thursday on both iOS and Android, so if you've been following the other Stickman adventures, you might be interested in picking this one... | Read more »
Z-Exemplar (Games)
Z-Exemplar 1.4 Device: iOS Universal Category: Games Price: $3.99, Version: 1.4 (iTunes) Description: | Read more »
5 dastardly difficult roguelikes like th...
Edmund McMillen's popular roguelike creation The Binding of Isaac: Rebirth has finally crawled onto mobile devices. It's a grotesque dual-stick shooter that tosses you into an endless, procedurally generated basement as you, the pitiable Isaac,... | Read more »

Price Scanner via MacPrices.net

Twelve South Releases RelaxedLeather Cases fo...
Inspired by the laid-back luxury of burnished leather boots and crafted in rich tones of taupe, herb and marsala, RelaxedLeather cases deliver smart, easy protection for the iPhone 7. Each genuine... Read more
Week’s Best Deal: New 2016 13-inch 2.0GHz Mac...
Amazon has the new 2016 13″ 2.0GHz non-Touch Bar MacBook Pros on sale for a limited time for $225 off MSRP including free shipping: - 13″ 2.0GHz MacBook Pro, Space Gray (MLL42LL/A): $1274.99 $225 off... Read more
Back in stock: Apple refurbished Mac minis fr...
Apple has Certified Refurbished Mac minis available starting at $419. Apple’s one-year warranty is included with each mini, and shipping is free: - 1.4GHz Mac mini: $419 $80 off MSRP - 2.6GHz Mac... Read more
Apple Ranked ‘Most Intimate Brand’
The top ranked ‘”intimate” brands continued to outperform the S&P and Fortune 500 indices in revenue and profit over the past 10 years, according to MBLM’s Brand Intimacy 2017 Report, the largest... Read more
B-Eng introduces SSD Health Check for Mac OS
Fehraltorf, Switzerland based independant Swiss company- B-Eng has announced the release and immediate availability of SSD Health Check 1.0, the company’s new hard drive utility for Mac OS X. As the... Read more
Apple’s Education discount saves up to $300 o...
Purchase a new Mac or iPad using Apple’s Education Store and take up to $300 off MSRP. All teachers, students, and staff of any educational institution qualify for the discount. Shipping is free: -... Read more
4-core 3.7GHz Mac Pro on sale for $2290, save...
Guitar Center has the 3.7GHz 4-core Mac Pro (MD253LL/A) on sale for $2289.97 including free shipping or free local store pickup (if available). Their price is a $710 savings over standard MSRP for... Read more
128GB Apple iPad Air 2, refurbished, availabl...
Apple has Certified Refurbished 128GB iPad Air 2s WiFis available for $419 including free shipping. That’s an $80 savings over standard MSRP for this model. A standard Apple one-year warranty is... Read more
13-inch 2.7GHz Retina MacBook Pro on sale for...
B&H Photo has the 2015 13″ 2.7GHz/128GB Retina Apple MacBook Pro on sale for $100 off MSRP. Shipping is free, and B&H charges NY tax only: - 13″ 2.7GHz/128GB Retina MacBook Pro (MF839LL/A): $... Read more
Laptop Market – Flight To Quality? – The ‘Boo...
Preliminary quarterly PC shipments data released by Gartner Inc. last week reveal an interesting disparity between sales performance of major name PC vendors as opposed to that of less well-known... Read more

Jobs Board

*Apple* & PC Desktop Support Technician...
Apple & PC Desktop Support Technician job in Manhattan, NY Introduction: We have immediate job openings for several Desktop Support Technicians with one of our most Read more
Senior Workstation Administrator - *Apple*...
…with extraordinary HR. QualificationsJOB SUMMARY/OVERVIEWThe Senior Workstation Administrator - Apple supports the mission of TriNet by providing advanced level Read more
Intermediate *Apple* macOS Systems Integrat...
**Position Summary:** SC3 is actively seeking an Intermediate Apple macOS systems integration administrator that will be responsible for providing Apple Mac Read more
*Apple* & PC Desktop Support Technician...
Apple & PC Desktop Support Technician job in Los Angeles, CA Introduction: We have immediate job openings for several Desktop Support Technicians with one of our Read more
*Apple* Retail - Multiple Positions - Apple,...
SalesSpecialist - Retail Customer Service and SalesTransform 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.