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

PDFKey Pro 4.3 - Edit and print password...
PDFKey Pro can unlock PDF documents protected for printing and copying when you've forgotten your password. It can now also protect your PDF files with a password to prevent unauthorized access and/... Read more
Kodi 15.0.beta1 - Powerful media center...
Kodi (was XBMC) is an award-winning free and open-source (GPL) software media player and entertainment hub that can be installed on Linux, OS X, Windows, iOS, and Android, featuring a 10-foot user... Read more
DiskCatalogMaker 6.4.12 - Catalog your d...
DiskCatalogMaker is a simple disk management tool which catalogs disks. Simple, light-weight, and fast. Finder-like intuitive look and feel. Super-fast search algorithm. Can compress catalog data... Read more
Macs Fan Control 1.3.0.0 - Monitor and c...
Macs Fan Control allows you to monitor and control almost any aspect of your computer's fans, with support for controlling fan speed, temperature sensors pane, menu-bar icon, and autostart with... Read more
Lyn 1.5.11 - Lightweight image browser a...
Lyn is a lightweight and fast image browser and viewer designed for photographers, graphic artists and Web designers. Featuring an extremely versatile and aesthetically pleasing interface, it... Read more
NeoOffice 2014.11 - Mac-tailored, OpenOf...
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
LaunchBar 6.4 - Powerful file/URL/email...
LaunchBar is an award-winning productivity utility that offers an amazingly intuitive and efficient way to search and access any kind of information stored on your computer or on the Web. It provides... Read more
Remotix 3.1.4 - Access all your computer...
Remotix is a fast and powerful application to easily access multiple Macs (and PCs) from your own Mac. Features Complete Apple Screen Sharing support - including Mac OS X login, clipboard... 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
VOX 2.5.1 - Music player that supports m...
VOX is a beautiful music player that supports many filetypes. The beauty is in its simplicity, yet behind the minimal exterior lies a powerful music player with a ton of features and support for all... Read more

This Week at 148Apps: May 18-22, 2015
May Days at 148Apps How do you know what apps are worth your time and money? Just look to the review team at 148Apps. We sort through the chaos and find the apps you're looking for. The ones we love become Editor’s Choice, standing out above the... | Read more »
Biz Builder Delux (Games)
Biz Builder Delux 1.0.0 Device: iOS Universal Category: Games Price: $4.99, Version: 1.0.0 (iTunes) Description: Ah, there's nothing like the rhythmic bustle of a burgeoning business burg... especially when you're the one building it... | Read more »
Auroch Digital is Bringing Back Games Wo...
| Read more »
Blades of Brim is a New Endless Runner f...
SYBO Games, the minds behind the ever-popular Subway Surfers, have announced their latest project: Blades of Brim. [Read more] | Read more »
Carbo - Handwriting in the Digital Age...
Carbo - Handwriting in the Digital Age 1.0 Device: iOS Universal Category: Productivity Price: $3.99, Version: 1.0 (iTunes) Description: | Read more »
Draggy Dead (Games)
Draggy Dead 1.1 Device: iOS Universal Category: Games Price: $.99, Version: 1.1 (iTunes) Description: Ditch your dead end job and take up a rewarding career in Grave Robbing today!Guide the recently deceased to a fun filled life of... | Read more »
Bad Dinos (Games)
Bad Dinos 1.0.0 Device: iOS Universal Category: Games Price: $2.99, Version: 1.0.0 (iTunes) Description: | Read more »
The Apple Watch isn't Great as a Fi...
| Read more »
Show the World What You See With Stre.am...
Live broadcasting is getting popular on mobile devices, which is why you can now get Stre.am, by Infinite Takes. [Read more] | Read more »
PhotoTime's 2.1 Update Adds Apple W...
The latest PhotoTime update is adding even more functionality to the handy photo organizing app. Yep, including Apple Watch support. [Read more] | Read more »

Price Scanner via MacPrices.net

12-inch MacBook stock status for Monday, May...
The new 12″ Retina MacBooks are still on backorder at The Apple Store with a 3-5 week waiting period. However, a few models are in stock today at Apple resellers. Stock is limited, so act now if you’... Read more
New 27-inch 3.3GHz 5K iMac in stock with free...
Adorama has the new 27″ 3.3GHz 5K iMac in stock today for $1999 including free shipping plus NY & NJ sales tax only. Adorama will include a free copy of Apple’s 3-year AppleCare Protection Plan. Read more
Memorial Day Weekend Sale: New 27-inch 3.3GHz...
Best Buy has the new 27″ 3.3GHz 5K iMac on sale for $1899.99 this weekend. Choose free shipping or free local store pickup (if available). Sale price for online orders only, in-store prices may vary... Read more
OtterBox Maximizes Portability, Productivity...
From the kitchen recipe book to the boarsroom presentation, the OtterBox Agility Tablet System turns tablets into one of the most versatile pieces of handheld technology available. Available now, the... Read more
Launch of New Car App Gallery and Open Develo...
Automatic, a company on a mission to bring the power of the Internet into every car, has announced the launch of the Automatic App Gallery, an app store for nearly every car or truck on the road... Read more
Memorial Day Weekend Sale: 13-inch 1.6GHz Mac...
Best Buy has the new 13″ 1.6GHz/128GB MacBook Air on sale for $849 on their online store this weekend. Choose free shipping or free local store pickup (if available). Sale price for online orders... Read more
Memorial Day Weekend Sale: 27-inch 3.5GHz 5K...
Best Buy has the 27″ 3.5GHz 5K iMac on sale for $2099.99 this weekend. Choose free shipping or free local store pickup (if available). Sale price for online orders only, in-store prices may vary.... Read more
Sale! 16GB iPad mini 3 for $349, save $50
B&H Photo has the 16GB iPad mini 3 WiFi on sale for $349 including free shipping plus NY sales tax only. Their price is $50 off MSRP, and it’s the lowest price available for this model. Read more
Price drop on 2014 15-inch Retina MacBook Pro...
B&H Photo has dropped prices on 2014 15″ Retina MacBook Pros by $200. Shipping is free, and B&H charges NY sales tax only: - 15″ 2.2GHz Retina MacBook Pro: $1799.99 save $200 - 15″ 2.5GHz... Read more
With a Mission to Make Mobile Free, Scratch W...
Scratch Wireless, claiming to be the world’s first truly free mobile service, has announced the availability of a new Scratch-enabled Android smartphone, the Coolpad Arise. The smartphone is equipped... Read more

Jobs Board

Payments Counsel, *Apple* Pay (mobile payme...
**Job Summary** Apple is looking for an atto ey to join Apple 's Legal Department to support Apple Pay. **Key Qualifications** 7+ years of relevant experience Read more
Touch Hardware Design and Integration Enginee...
…Summary** Design, develop, and launch next-generation Touch solutions in the new Apple Watch product category. The Touch team develops cutting-edge Touch solutions and 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* TV Live Streaming Frameworks Test En...
**Job Summary** Work and contribute towards the engineering of Apple 's state-of-the-art products involving video, audio, and graphics in Interactive Media Group (IMG) at 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
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.