TweetFollow Us on Twitter

Foundation Of Quickdraw
Volume Number:1
Issue Number:2
Column Tag:features of Mac Pascal

QuickDraw Graphics

By Chris Derossi

One of the most valuable features of Mac Pascal is it ability to take advantage of the Macintosh’s powerful ROM capabilities. To do this, Mac Pascal must be able to access the various routines that are contained within the Mac Toolbox. In this month’s column, we will examine the interface between Mac Pascal and the ROM, and the necessary data structures for accessing quickdraw. Finally, a sample program is included which makes use of quickdraw’s graphics routines.

In order to communicate to the Toolbox, several data structures have to be defined. These data structures are all presented in Pascal format because the routines contained in the Mac ROM are constructed for a Pascal environment. Unlike other programming languages, this makes data compatiblitly pretty much straight forward for Mac Pascal users. But before we get into the details, let’s briefly describe some of the theory behind QuickDraw.

FOUNDATION OF QUICKDRAW

QuickDraw graphics exist in cartesian coordinate planes. What this means is that graphics may be present on any portion of a continuous surface. The QuickDraw planes are finite, and extend from values -32768 to 32767 in both the vertical and horizontal directions. The smallest unit of distance that QuickDraw can work with is 1. An area of 1 by 1 is, therefore, a point. The boundary separating two points at sequential locations of the plane is of size zero. This means that two points placed next to each other are continuous, and have no space between them. Keep in mind that these are theoretical concepts, not screen bit-map specifications.

QUICKDRAW DATA STRUCTURES

In Mac Pascal, the data structure ‘Point’ is a record with two components representing the coordinates of the upper left corner of a point. The two fields of Point are Point.h and Point.v which are the horizontal and vertical coordinates respectively. Each value is of type Integer.

The rectangle is a common object found in QuickDraw. Rectangles are frequently used to create windows, define drawing areas, and to provide parameters for manipualting other objects. A rectangle has four parameters. These are: Top, Left, Bottom, and Right. These parameters may be thought of as four integers, or as the two points TopLeft and BottomRight. In actuality, the second method is used, and the type ‘Rect’ is defined as a record with the two fields Rect.TopLeft and Rect.BotRight. Each of the fields is of type point.

Another object defined with points is the line. Although there is no Mac Pascal data type for this object, it can be characterized by two points, for the beginning and ending positions of the line.

The final data type we will examine this month is the pattern. QuickDraw allows regions to be filled with patterns, as is done with the paint bucket in MacPaint. A pattern is a set of sixty-four points either on or off, arranged in an eight by eight square. To fill an area larger than eight by eight, the Macintosh repeats the pattern both vertically and horizontally as many times as neccessary. The upper left corner of the pattern is aligned with the coordinate (0,0), and is independent of the coordinates of the area being filled.

Since a byte is eight bits, and a bit represents one point, patterns can be represented as a series of eight bytes. In Mac Pascal, the type ‘Pattern’ is an array [0..7] of 0..255, which is effectively eight sequential bytes. There are some predefined patterns including White, Black, and Grey.

DRAWING IN QUICKDRAW

The drawing mechanism in QuickDraw is the Pen. The pen has modifyable properties which include location, width, height, and pattern. There are further properties which will be covered in a later column. A pen of width and height of one, and a pattern of black will always draw with one-point wide, black lines.

In addition to the many objects of QuickDraw, many actions are available to be performed on or with them. Most objects may be Framed, Painted, Filled, and Erased. The QuickDraw actions are called QuickDraw verbs, and they are applied to objects. The verb Frame specifies that the outline of the given object should be drawn. The verb Paint means that the object is drawn completely filled. Each of these actions use the pen for drawing, and as such use the current pen pattern. The verb Erase does not use the pen pattern, but instead uses the pattern currently set for the background. Fill allows you to specify a pattern to use, and is therefore a little bit more versatile than Paint.

For example, FrameRect will draw the outline of a rectangle, while PaintRect will draw a solid rectangle. FillRect will draw a solid rectangle in the given pattern. EraseRect clears the given rectangle to the current background pattern.

Each verb-object combination is a procedure, and takes applicable parameters. The Rect procedures take a rectangle as their only parameter. The FillRect procedure needs a Rect first, and a Pattern second. The rectangle is drawn as a solid with the pattern.

A frequently encountered situation is one where the Macintosh needs to know if a given point is inside a particular rectangle. (i.e. is the mouse’s position inside a certain window?) To satisfy this need, a function titled PtInRect returns a boolean of True if the point is inside the rectangle, and False if not. The parameters of this function are a point first, and then a rectangle.

PROGRAMMING EXAMPLE

Now let us examine the example program that makes use of these data structures, procedures, and functions. The operation of the program is fairly simple and straight forward. The user is presented with a blank background and the mouse pointer. The user forms rectangles by pressing the mouse button when the pointer is at one of the rectangle’s corners, and holds the button down while dragging the mouse to the opposite diagonal corner. In order to provide some feedback about the shape of the rectangle, a ‘rubber banding’ diagonal line follows the mouse until the button is released. When the button is released, the rubber band line is removed, and the rectangle is drawn.

WHERE’S THE MOUSE?

After the rectangle is drawn, the user may place the mouse pointer inside the rectangle, and press the button. As long as the button is held, the Mac continually fills the rectangle with random, changing patterns. Once the mouse button is pressed outside of the rectangle, the pattern is frozen, and a new rectangle is begun. (Please see the sample output in fig. 1.)

The construction of the program is not complex. The variable declarations for the main program consist of three points and one rectangle. The points are used as work variables for reading the mouse location, and the rectangle is the one currently being drawn or filled.

The main program calls two procedures. The first one allows the user to create the rectangle, and provides the rubberbanding effect. The second one creates random patterns and fills the rectangle.

Since the value of a rectangle’s Top must be less than or equal to that of its bottom, two procedures called ‘Min’ and ‘Max’ help keep the points in the right order. The same holds true for the Left and Right values.

The key procedure calls in the Make_Rect procedure are Button, GetMouse, DrawLine, PenPat, FrameRect, and InsetRect. The function Button returns True if the mouse button is pressed, and False if not. GetMouse uses two VAR parameters for obtaining the current horizontal and vertical position of the mouse pointer.

Since we need to draw and erase the rubberbanding line, we use the two pen patterns of Black and White. This has the disadvantage of erasing whatever the line passes over, but you can’t have everything in a simple little program. The procedure PenPat sets the working pen pattern to the passed value.

DrawLine uses two points, this time in the form of four coordinates, to designate the starting and ending points of the line. DrawLine, of course, uses the current pen pattern.

Finally, after the mouse button is released, the rectangle is drawn with FrameRect. This is done with the pen pattern set to black. Since we don’t want to draw over the outline with subsequent FillRect calls, the procedure InsetRect is called to change the coordinates of the rectangle by one on each side, making it slightly smaller.

After the rectangle is drawn, the Fill_Rect procedure is called to fill it in. Note, please, that Fill_Rect is distinct from FillRect. Fill_Rect uses the calls Button, GetMouse, PtInRect, Random, and FillRect to perform its task. Button and GetMouse are used as before. PtInRect determines if the mouse is inside the new rectangle when the button is depressed.

A new pattern is created by calling the function Random eight times within a loop. Random returns a value from -32768 and 32767. Abs and Mod are used to bring the random number in the range 0..255. After the random pattern is created, FillRect is called to draw the pattern into the rectangle.

MODIFYING THE PROGRAM

The program runs forever, and the menu option Halt must be chosen to exit. In order to overcome this, you might want to modify the program to present you with a Black or Grey box (read rectangle) where you’d click the mouse to quit. Where in the program would you draw the rectangle? At what point or points would you have to check to see if it has been clicked? How will you handle rectangles that overlap your ‘exit’ box? These exercises are left to the student!

That’s it for this month. In the next column, we’ll further explore the powerful features of QuickDraw, and find out what makes it so unique and wonderful among graphic tools. We’ll also have another program that utilizes these terrific features. If you like our Pascal column or have programming ideas of your own to contribute, please feel free to write me care of MacTech. Ciao.

program MacTutor_QD_Demo;

{ This program will use the standard features of } {QuickDraw to introduce 
use of QuickDraw data} {structures and routine calls from MacPascal.} 

{ -- By Chris Derossi}

 var
  P1, P2, P3 : Point;
  WorkingRect : Rect;

 function Min (Num1, Num2 : integer) : integer;

{ return the minimum of the two numbers passed.}

 begin
  if Num1 < Num2 then
   Min := Num1
  else
    Min := Num2;
 end;

 function Max (Num1, Num2 : integer) : integer;

{ returns the maximum of two numbers passed.}

 begin
  if Num1 > Num2 then
  Max := Num1
  else
    Max := Num2;
 end;

 procedure Make_Rect (var theRect : Rect);

{ This is the first of the two main procedure. It} 
{allows the user to select diagonal corners of the} 
{rectangle to be drawn, using a ‘rubber band’ line.} 
{When the button is released, the recatangle is} 
{drawn.}

 begin
  repeat
   until Button;  {Wait till the button is pressed}
  GetMouse(P1.h, P1.v); {Where was the mouse?}
  P2 := P1;
  P3 := P1;
  while Button do  {update while button is down.}
   begin
      GetMouse(P3.h, P3.v);
    if (P2.h <> P3.h) or (P2.v <> p3.v) then  
 {the mouse has moved}
    begin
        PenPat(White);
      DrawLine(P1.h, P1.v, P2.h, P2.v);  
 {Erase the old line}
      PenPat(Black);
    DrawLine(P1.h, P1.v, P3.h, P3.v);  
 {Draw the new line}
    P2 := P3;
    end;
   end;

  PenPat(White);  {Erase line for the last time.}
  DrawLine(P1.h, P1.v, P2.h, P2.v);
  PenPat(Black);
  theRect.TopLeft.v := Min(P1.v, P2.v); 
  
{Set the rectangle, making sure}
  theRect.TopLeft.h := Min(P1.h, P2.h);   
{that the top is above the bottom}
  theRect.BotRight.v := Max(P1.v, P2.v); 
{and the left is less than the}
  theRect.BotRight.h := Max(P1.h, P2.h); {right.}

  FrameRect(theRect);   {Draw the rectangle}
  InsetRect(theRect, 1, 1);  
{Shrink it so that the pattern does not draw}
 {over the rectangle frame.}
 end;

 procedure Fill_Rect (theRect : Rect);

  var
   myPat : Pattern;
   Index : Integer;
   Done : Boolean;

 begin
  Done := False;
  while not Done do  
{continue until the mouse is outside of the}
   {new rectangle.}
   begin
    repeat
      until Button;   {Wait for the button}
    GetMouse(P1.h, P1.v);
    if PtInRect(P1, theRect) then  
{is the mouse in the rectangle?}
    begin
    for Index := 0 to 7 do
     myPat[Index] := Abs(Random) mod 256; {make a random pattern}
     FillRect(theRect, myPat);  {Fill the rectangle}
    end
    else
    Done := True;
   end; {While}
 end; {Fill_Rect}


begin  {Main Program}
 while true do
  begin
    Make_Rect(WorkingRect);
    Fill_Rect(WorkingRect);
  end;
end.   {Main}

 
AAPL
$101.04
Apple Inc.
+0.51
MSFT
$45.02
Microsoft Corpora
-0.31
GOOG
$584.26
Google Inc.
-2.60

MacTech Search:
Community Search:

Software Updates via MacUpdate

Tidy Up 3.0.15.0 - Find duplicate files...
Tidy Up is a complete duplicate finder and disk-tidiness utility. With Tidy Up you can search for duplicate files and packages by the owner application, content, type, creator, extension, time... Read more
Parallels Desktop 10.0 - Run Windows app...
Parallels Desktop is simply the world's bestselling, top-rated, and most trusted solution for running Windows applications on your Mac. With Parallels Desktop for Mac, you can seamlessly run both... Read more
Apple Final Cut Pro X 10.1.3 - Professio...
Apple Final Cut Pro X is a professional video editing solution.Completely redesigned from the ground up, Final Cut Pro adds extraordinary speed, quality, and flexibility to every part of the post-... Read more
Apple Compressor 4.1.3 - Adds power and...
Compressor adds power and flexibility to Final Cut Pro X export. Customize output settings, work faster with distributed encoding, and tap into a comprehensive set of delivery features. Powerful... Read more
Chromium 36.0.1985.143 - Fast and stable...
Chromium is an open-source browser project that aims to build a safer, faster, and more stable way for all Internet users to experience the web. FreeSMUG-Free OpenSource Mac User Group build is... Read more
Macgo Blu-ray Player 2.10.6.1691 - Blu-r...
Macgo Mac Blu-ray Player can bring you the most unforgettable Blu-ray experience on your Mac. Overview Macgo Mac Blu-ray Player can satisfy just about every need you could possibly have in a Blu-ray... Read more
Apple Motion 5.1.2 - Create and customiz...
Apple Motion is designed for video editors, Motion 5 lets you customize Final Cut Pro titles, transitions, and effects. Or create your own dazzling animations in 2D or 3D space, with real-time... Read more
A Better Finder Rename 9.39 - 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
PopChar X 6.6 - Floating window shows av...
PopChar X helps you get the most out of your font collection. With its crystal-clear interface, PopChar X provides a frustration-free way to access any font's special characters. Expanded... Read more
MacUpdate Desktop 6.0.2 - Install Mac ap...
MacUpdate Desktop 6 brings seamless 1-click installs and version updates to your Mac. With a free MacUpdate account and MacUpdate Desktop 6, Mac users can now install almost any Mac app on macupdate.... Read more

Latest Forum Discussions

See All

Space Colors – Tips, Tricks, Strategies,...
Hello Cadets: Want to know what we thought about this hectic space combat/roguelike? Check out our Space Colors review! Space Colors is a cool shooter/roguelike from Team Chaos. You travel from planet to planet across a huge galaxy and complete a... | Read more »
Tap Sports Baseball – Tips, Tricks, and...
Tap Sports Baseball is a pretty simple game to learn, but that doesn’t mean it’s an easy game to master, by any means. To start your batting career off well, we thought we’d give you the heads up on some handy tips and tricks. Hey Batter-Batter:... | Read more »
Tap Sports Baseball Review
Tap Sports Baseball Review By Jennifer Allen on August 20th, 2014 Our Rating: :: LET'S PLAY BALLUniversal App - Designed for iPhone and iPad Tap Sports Baseball is briefly fun but lacks some important features.   | Read more »
Frontier Heroes Review
Frontier Heroes Review By Andrew Fisher on August 20th, 2014 Our Rating: :: BLAZES NO TRAILSUniversal App - Designed for iPhone and iPad Despite awesome visuals and great music, Frontier Heroes just doesn’t quite deliver enough fun... | Read more »
Echo Prime is Now on Sale for $0.99
Echo Prime is Now on Sale for $0.99 Posted by Jessica Fisher on August 20th, 2014 [ permalink ] Universal App - Designed for iPhone and iPad | Read more »
Star Realms Review
Star Realms Review By Andrew Fisher on August 20th, 2014 Our Rating: :: A STAR IS BORNUniversal App - Designed for iPhone and iPad Star Realms is an excellent adaptation of an outstanding deck-builder. With great visuals and an... | Read more »
This. Is. SPRINGFIELD! War comes to The...
This. Is. SPRINGFIELD! | Read more »
One Tap RPG Review
One Tap RPG Review By Campbell Bird on August 20th, 2014 Our Rating: :: DUNGEON SLIDERUniversal App - Designed for iPhone and iPad This casual arcade game introduces some very light rpg elements into its fantasy-themed pachinko... | Read more »
Goodbye Paywall – Table Tennis Touch Eli...
Goodbye Paywall – Table Tennis Touch Eliminates In-App Purchases Posted by Jessica Fisher on August 20th, 2014 [ permalink ] | Read more »
Go to Bed – An Interview With Touchfight...
Touchfight Games is an exciting new indie studio that was co-formed between game journalist and author Nathan Meunier, artist Leonard Kenyon, and programmer Jon Kenyon. Their debut game Go To Bed will be released this fall, and with all the... | Read more »

Price Scanner via MacPrices.net

Apple now offering certified refurbished 2014...
 The Apple Store is now offering Apple Certified Refurbished 2014 MacBook Airs for up to $180 off the cost of new models. An Apple one-year warranty is included with each MacBook, and shipping is... Read more
Best Buy’s College Student Deals: $100 off Ma...
Take an additional $100 off all MacBooks and iMacs, $50 off iPad Airs and iPad minis, at Best Buy Online with their College Students Deals Savings, valid through September 6th. Anyone with a valid .... Read more
MacBook Airs on sale for $100 off MSRP, free...
B&H Photo has three 2014 MacBook Airs on sale for $100 off MSRP. Shipping is free, and B&H charges NY sales tax only. They also include free copies of Parallels Desktop and LoJack for Laptops... Read more
Razer Taipan Mouse For Gamers And Non-Gamers...
If you’re a serious gamer on either Mac or Windows PCs, a serious gaming mouse is a necessity for first-tier performance. However, even if like me you’re not much of a gamer, there’s still a strong... Read more
15-inch 2.2GHz MacBook Pro on sale for $1899,...
Adorama has the new 15″ 2.2GHz Retina MacBook Pro on sale for $1899 including free shipping plus NY & NJ sales tax only. Their price is $100 off MSRP, and it’s the lowest price available for this... Read more
Mid-Size Tablet Shootout Posted: iPad mini wi...
I ‘m curious about how many iPads Apple is actually selling these days. It’s been widely rumored and anticipated that new models with A8 SoCs, 2 GB of RAM, 8 megapixel cameras, and fingerprint... Read more
The 15 Biggest iPad Air Problems And How To A...
What’s this? Fifteen “biggest” problems with the iPad Air? Does that mean there are a lot of smaller problems as well? Say it isn’t so! My old iPad 2 has manifested no hardware problems in three... Read more
TYLT Syncable-Duo, 2-in-1 USB Cable With Appl...
TYLT has introduced the Syncable-Duo, a universal cable solution for charging and syncing data to smartphones and tablets. The Syncable-Duo eliminates the need for multiple cables by incorporating... Read more
Save up to $140 off MSRP with Apple refurbish...
Apple is offering Certified Refurbished iPad Airs for up to $140 off MSRP. Apple’s one-year warranty is included with each model, and shipping is free. Stock tends to come and go with some of these... Read more
2.5GHz Mac mini on sale for $549, save $50
B&H Photo has the 2.5GHz Mac mini on sale for $549.99 including free shipping. That’s $50 off MSRP, and B&H will also include a free copy of Parallels Desktop software. NY sales tax only. Read more

Jobs Board

Senior Event Manager, *Apple* Retail Market...
…This senior level position is responsible for leading and imagining the Apple Retail Team's global event strategy. Delivering an overarching brand story; in-store, Read more
*Apple* Solutions Consultant - Apple (United...
**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
Position Opening at *Apple* - Apple (United...
**Job Summary** Being a Business Manager at an Apple Store means you're the catalyst for businesses to discover and leverage the power, ease, and flexibility of Apple Read more
Position Opening at *Apple* - Apple (United...
**Job Summary** At the Apple Store, you connect business professionals and entrepreneurs with the tools they need in order to put Apple solutions to work in their Read more
Project Manager / Business Analyst, WW *Appl...
…a senior project manager / business analyst to work within our Worldwide Apple Fulfillment Operations and the Business Process Re-engineering team. This role will work Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.