TweetFollow Us on Twitter

Ports
Volume Number:1
Issue Number:4
Column Tag:C Workshop

Ports

By Chris Derossi

When one thinks of the Macintosh, one of the first things to come to mind is the Mac’s frequent use of windows for multiple, independent areas or objects. Usually, one window is related to one task or concept, and tasks that have very different orientations are in separate windows.

There are several benefits for grouping items or tasks into separate windows. The most important is user interfacing. By using windows, the user can conceptually group similar or common things. This makes the use of sotware more intuitive because the user is shielded from modes in the software. In other words, instead of explicitly needing to have the computer switch to a different mode, all that is needed is to begin operations in a different window.

Obviously, the more intuitive for the user that your software is, the better. Indeed, one of the primary concepts of the Macintosh is that of using tools like icons, the mouse, and windows to decrease the need for special knowledge or special education. In this article, we will take a look at the concept behind windows, that of ports. (In a later article, we will examine windows more closely.)

In order to facilitate the creation of independent windows, the implementation of ports or graph ports provides for completely separate drawing envir- onments. That is, each port is an entire drawing environment, and operations with one port are not related to another.

At any given time, after QuickDraw is initialized, a single port is always active, and is considered the current graph port. QuickDraw operations always occur within the current graph port.

With each graph port are associated several characteristics and parameters. These include location of the port’s bit map, size, clipping region, visible region, background color, and several text mode values. The port’s bit map refers to an area of memory where the bit image of any drawing is put. Usually, this coincides with an area of the screen ram, so that drawing is displayed on the screen. However, this is not a requirement. The port’s bit map can be any area of memory on or off the screen. For example, a port may use an off-screen bit map to prepare an image, then move that image into the screen bit map.

The size of the port is determined by an enclosing rectangle. The rectangle encloses part of the bit map and indicates size and position within the bit map. For ports that are visible, the rectangle encloses an area of the screen.

Clipping region and visible region both restrict the available drawing area within a graph port. While the port itself is rectangular, the clipping and visible areas are regions, providing total flexibility with shape and configuration. The visible region acts like a clipping region, but is separate from it mainly for use by the window manager. (When one window overlaps another, the visible region of the bottom window is set to equal the part of the port that still shows.) There are two regions so that the user may have a region for clipping that is unrelated to the the region needed by the window manager for handling overlap.

Each port is its own drawing environment, and as such has its own drawing characteristics such as pen size, pattern, position, etc. Also, each port has its own text drawing characteristics that are used by the font manager. This way, you need only choose which port in which to draw, and the font, style, and text size associated with that port are automatically used.

In addition to having its own locations, size, and modes, each graph port may also have its own coordinate system. That is, regardless of where on the screen the port is displayed, the upper left corner of the port may be any coordinate. Usually, of course, the upper left coordinate is assigned the value 0,0. This is useful because neither the user nor the programmer need be concerned with the actual position of any port; drawing may be made as if the port were the entire universe. (You might begin to see why moving windows around is so easy; the coordinates inside the window remain constant.)

Since the available coordinate plane is much larger than any visible graph port, this feature allows ports to ‘look at’ different areas of the coordinate plane. For example, a program may draw on the entire plane, and different graph ports may be created as neccessary to view separate parts of the entire area. This can be done without the need for conversions either in the drawing or the displaying; QuickDraw handles all conversions.

There are two important programming practices to develop with regards to ports. The first has already been mentioned; it is a good idea to group similar things, and separate dissimilar things. The second idea is that of port independence. Programs should be written to not rely on any port size or location. (When changing the size of a window, for instance, the program should NOT need a certain size window to perform.)

The sample program this month illustrates the second concept, as the first one is much easier to practice. In this program, the user ‘creates’ television sets on which drawing is displayed. While drawing is occurring, the user may create more TVs, or change which one is active. All this is done by clicking the mouse. If the mouse is clicked in a TV, it becomes the active one, if not, a new TV is created.

Each TV, of course, is a graph port. A port is created, and then in that port a television is drawn. Then, the clipping region of that port is restricted to the ‘picture tube’ part of the picture.

Drawing continues, regardless of which port is active, or where it is. The placement of the port, and the selection of the current port is entirely up to the user. Notice, that the main drawing procedure has absolutely no idea which port is active.

In order to avoid running out of memory, the number of possible ports is restricted. You may vary the constant ‘MaxPorts’ as you like. An array is set up called ‘Screens’ which contains pointers to the graph ports. QuickDraw procedures and functions that act upon ports take a pointer to the port as the parameter, not the port itself. The port is left to be dynamically allocated for flexibility. The type ‘GrafPtr’ is the predefined pointer to a graph port.

The variable ScrnCnt keeps track of how many ports we have created. Since we want to draw only on our TV screens, drawing does not occur if the user has not created any ports yet. When the user clicks the mouse, the program checks to see if the position of the mouse is inside any graph port. The point must first be brought to global coordinates, which makes it independent of any port. Then, one by one, the point is referenced to each graph port and checked against that port’s rectangle. If the point is inside the rectangle, that port is selected as the current one.

When the point lies outside all ports, a new port is created. (Unless all possible ports have been created already; then the program terminates.) The port is initialized and its characteristics are set. Then, the TV is drawn in the port, and the clipping region set. The new port is also set as the current port. Notice that the program explicitly sets the port’s origin. Try playing with the origin values.

When the program ends, it closes each port one by one and frees the memory used by the ports. Then, it creates another temporary port that covers the entire screen. (The default values for the size and location of the port coincide with the screen.) This port is then filled with gray to eliminate the other graphics. Finally, this temporary port is also closed and its memory freed.

Although this is a simple example, it demonstrates a very powerful principle; that of independence. The more independent you programs are, the more flexible they are, and the more control the user may have. This avoids placing pointless limitations on your programs and their users. In addition, programming of this nature helps keep programs functional when the environment changes. (Like moving from a Mac to the Lisa with MacWorks, or future, improved machines.)

This concludes our introduction to the basics of QuickDraw. With this foundation, we can move on into the rest of the Macintosh with a strong background. You might want to try and improve on this sample program as an excersize to increase your skill. For example, try to allow the user to select the size as well as the location of the port. Or, try to prevent the ports from overlapping. If you’re really enthusiastic, have all the TV sets going at once, and let the user change ‘channels’ on each of them, causing different graphics to appear on each channel.

In the next issue, we’ll extend the discussion of ports to windows. We’ll find out what the concept of windows adds to the already powerful idea of ports, and find out what features are provided to the user through the use of windows. Ciao.

program Ports_Demo;

{ Ports_Demo - for MacTutor}
{ -- by Chris Derossi}

 uses
  QuickDraw2;  {QuickDraw2 contains the stuff for regions.}

 const
  MaxScreens = 8;

 type
  TVList = array[1..MaxScreens] of GrafPtr;

 var
  Screens : TVList;
  ScrnCnt : INTEGER;
  done : BOOLEAN;

 procedure SetUp;

 begin
  HideAll;
  ScrnCnt := 0;
  done := FALSE;
 end;

 procedure ShutDown;

  var
   TempPort : GrafPtr;

 begin
  while ScrnCnt > 0 do
   begin
    ClosePort(Screens[ScrnCnt]);
    Dispose(Screens[ScrnCnt]);
    ScrnCnt := ScrnCnt - 1;
   end;

{ Create a new port and fill the screen with gray. }
  NEW(TempPort);
  OpenPort(TempPort);
  BackPat(Gray);
  EraseRect(TempPort^.PortRect);
  ClosePort(TempPort);
  Dispose(TempPort);
 end;

 function MakeTV (Left, Top : INTEGER) : GrafPtr;

  var
   TempPtr : GrafPtr;
   WorkRect : Rect;

 begin
{ Create a new port and set its characteristics. }
  NEW(TempPtr);
  OpenPort(TempPtr);
  PortSize(100, 80);
  MovePortTo(Left, Top);
  SetOrigin(0, 0);

{ Clear the port to white and draw our ‘television’ }
  BackPat(White);
  EraseRect(TempPtr^.PortRect);
  FrameRect(TempPtr^.PortRect);
  MoveTo(80, 0);
  LineTo(80, 80);
  SetRect(WorkRect, 85, 10, 95, 20);
  FrameOval(WorkRect);
  SetRect(WorkRect, 85, 30, 95, 40);
  FrameOval(WorkRect);

{ Restrict the clipping region to the TV ‘screen’ }
  WorkRect := TempPtr^.PortRect;
  WorkRect.right := WorkRect.Right - 20;
  InsetRect(WorkRect, 1, 1);
  ClipRect(WorkRect);
  MakeTV := TempPtr;
 end;

 procedure SetTV;

{ If the mouse is in one of our ports, select that port. If all}
{possible ports are created and the mouse is not in any port,}
{then we’re done. Otherwise, create a new port.}

  var
   MousePt, Pnt1 : Point;
   I, X, Y : INTEGER;
   TempPtr : GrafPtr;

 begin
  TempPtr := nil;
  GetMouse(X, Y); { Current port’s local coordinates }
  repeat { nothing }
  until not Button;

{ Convert to a point, the to global coordinates }
  MousePt.h := X;
  MousePt.v := Y;
  LocalToGlobal(MousePt);
  Pnt1 := MousePt;

{ Scan the existing ports. }
  if ScrnCnt > 0 then { we have some ports to scan }
   for I := 1 to ScrnCnt do
    begin
    SetPort(Screens[I]);
    MousePt := Pnt1;
    GlobalToLocal(MousePt);
    if PtInRect(MousePt, Screens[I]^.PortRect) then
    TempPtr := Screens[I];
    end; { for loop }

  if TempPtr <> nil then { the mouse is in a port; set it }
   SetPort(TempPtr)
  else if ScrnCnt = MaxScreens then { all ports used }
   done := TRUE
  else
   begin
    ScrnCnt := ScrnCnt + 1;
    Screens[ScrnCnt] := MakeTV(Pnt1.h, Pnt1.v);
   end;
 end;

 procedure MainLoop;

  var
   Figure : INTEGER;
   WorkRect : Rect;

 begin
  if Button then
   SetTV;

  if ScrnCnt > 0 then { do some drawing }
   begin
    if random mod 100 < 5 then { Clear the ‘screen’ }
    begin
    SetRect(WorkRect, 0, 0, 90, 90);
    EraseRect(WorkRect);
    end;

{ Create a random rectangle for drawing }
    WorkRect.top := random mod 80;
    WorkRect.left := random mod 80;
    WorkRect.right := WorkRect.left + (random mod 60);
    WorkRect.bottom := WorkRect.top + (random mod 60);
    Figure := random mod 6;
    case Figure of
    0 : 
    FrameRect(WorkRect);
    1 : 
    FrameRoundRect(WorkRect, 18, 18);
    2 : 
    FrameOval(WorkRect);
    3 : 
    PaintRect(WorkRect);
    4 : 
    PaintRoundRect(WorkRect, 18, 18);
    5 : 
    PaintOval(WorkRect);
    end;
   end;
 end;

begin   { Ports_Demo }
 SetUp;
 while not done do
  MainLoop;
 ShutDown;
end.

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

FotoMagico 5.6.12 - Powerful slideshow c...
FotoMagico lets you create professional slideshows from your photos and music with just a few, simple mouse clicks. It sports a very clean and intuitive yet powerful user interface. High image... Read more
OmniGraffle Pro 7.12.1 - 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
beaTunes 5.2.1 - Organize your music col...
beaTunes is a full-featured music player and organizational tool for music collections. How well organized is your music library? Are your artists always spelled the same way? Any R.E.M. vs REM?... Read more
HandBrake 1.3.0 - Versatile video encode...
HandBrake is a tool for converting video from nearly any format to a selection of modern, widely supported codecs. Features Supported Sources VIDEO_TS folder, DVD image or real DVD (unencrypted... Read more
Macs Fan Control 1.5.1.6 - 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
TunnelBear 3.9.3 - Subscription-based pr...
TunnelBear is a subscription-based virtual private network (VPN) service and companion app, enabling you to browse the internet privately and securely. Features Browse privately - Secure your data... Read more
calibre 4.3.0 - Complete e-book library...
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
Lyn 1.13 - Lightweight image browser and...
Lyn is a fast, lightweight image browser and viewer designed for photographers, graphic artists, and Web designers. Featuring an extremely versatile and aesthetically pleasing interface, it delivers... Read more
Visual Studio Code 1.40.0 - Cross-platfo...
Visual Studio Code provides developers with a new choice of developer tool that combines the simplicity and streamlined experience of a code editor with the best of what developers need for their... Read more
OmniGraffle 7.12.1 - Create diagrams, fl...
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

Latest Forum Discussions

See All

The House of Da Vinci 2 gets a new gamep...
The House of Da Vinci launched all the way back in 2017. Now, developer Blue Brain Games is gearing up to deliver a second dose of The Room-inspired puzzling. Some fresh details have now emerged, alongside the game's first official trailer. [Read... | Read more »
Shoot 'em up action awaits in Battl...
BattleBrew Productions has just introduced another entry into its award winning, barrelpunk inspired, BattleSky Brigade series. Whilst its previous title BattleSky Brigade TapTap provided fans with idle town building gameplay, this time the... | Read more »
Arcade classic R-Type Dimensions EX blas...
If you're a long time fan of shmups and have been looking for something to play lately, Tozai Games may have just released an ideal game for you on iOS. R-Type Dimensions EX brings the first R-Type and its sequel to iOS devices. [Read more] | Read more »
Intense VR first-person shooter Colonicl...
Our latest VR obsession is Colonicle, an intense VR FPS, recently released on Oculus and Google Play, courtesy of From Fake Eyes and Goboogie Games. It's a pulse-pounding multiplayer shooter which should appeal to genre fanatics and newcomers alike... | Read more »
PUBG Mobile's incoming update bring...
PUGB Mobile's newest Royale Pass season they're calling Fury of the Wasteland arrives tomorrow and with it comes a fair chunk of new content to the game. We'll be seeing a new map, weapon and even a companion system. [Read more] | Read more »
PSA: Download Bastion for free, but wait...
There hasn’t been much news from Supergiant Games on mobile lately regarding new games, but there’s something going on with their first game. Bastion released on the App Store in 2012, and back then it was published by Warner Bros. This Warner... | Read more »
Apple Arcade: Ranked - 51+ [Updated 11.5...
This is Part 2 of our Apple Arcade Ranking list. To see part 1, go here. 51. Patterned [Read more] | Read more »
NABOKI is a blissful puzzler from acclai...
Acclaimed developer Rainbow Train's latest game, NABOKI, is set to launch for iOS, Android, and Steam on November 13th. It's a blissful puzzler all about taking levels apart in interesting, inventive ways. [Read more] | Read more »
A Case of Distrust is a narrative-driven...
A Case of Distrust a narrative-focused mystery game that's set in the roaring 20s. In it, you play as a detective with one of the most private eye sounding names ever – Phyllis Cadence Malone. You'll follow her journey in San Francisco as she... | Read more »
Brown Dust’s October update offers playe...
October is turning out to be a productive month for the Neowiz team, and a fantastic month to be a Brown Dust player. First, there was a crossover event with the popular manga That Time I Got Reincarnated as a Slime. Then, there was the addition of... | Read more »

Price Scanner via MacPrices.net

Score a 37% discount on Apple Smart Keyboards...
Amazon has Apple Smart Keyboards for current-generation 10″ iPad Airs and previous-generation 10″ iPad Pros on sale today for $99.99 shipped. That’s a 37% discount over Apple’s regular MSRP of $159... Read more
Apple has refurbished 2019 13″ 1.4GHz MacBook...
Apple has a full line of Certified Refurbished 2019 13″ 1.4GHz 4-Core Touch Bar MacBook Pros available starting at $1099 and up to $230 off MSRP. Apple’s one-year warranty is included, shipping is... Read more
2019 13″ 1.4GHz 4-Core MacBook Pros on sale f...
Amazon has new 2019 13″ 1.4GHz 4-Core Touch Bar MacBook Pros on sale for $150-$200 off Apple’s MSRP. These are the same MacBook Pros sold by Apple in its retail and online stores: – 2019 13″ 1.4GHz/... Read more
11″ 64GB Gray WiFi iPad Pro on sale for $674,...
Amazon has the 11″ 64GB Gray WiFi iPad Pro on sale today for $674 shipped. Their price is $125 off MSRP for this iPad, and it’s the lowest price available for the 64GB model from any Apple reseller. Read more
2019 15″ MacBook Pros available for up to $42...
Apple has a full line of 2019 15″ 6-Core and 8-Core Touch Bar MacBook Pros, Certified Refurbished, available for up to $420 off the cost of new models. Each model features a new outer case, shipping... Read more
2019 15″ MacBook Pros on sale this week for $...
Apple resellers B&H Photo and Amazon are offering the new 2019 15″ MacBook Pros for up to $300 off Apple’s MSRP including free shipping. These are the same MacBook Pros sold by Apple in its... Read more
Sunday Sale: AirPods with Wireless Charging C...
B&H Photo has Apple AirPods with Wireless Charging Case on sale for $159.99 through 11:59pm ET on November 11th. Their price is $40 off Apple’s MSRP, and it’s the lowest price available for these... Read more
Details of Sams Club November 9th one day App...
Through midnight Saturday night (November 9th), Sams Club online has several Apple products on sale as part of their One Day sales event. Choose free shipping or free local store pickup (if available... Read more
Sprint is offering the 64GB Apple iPhone 11 f...
Sprint has the new 64GB iPhone 11 available for $15 per month for new lines. That’s about 50% off their standard monthly lease of $29.17. Over is valid until November 24, 2019. The fine print: “Lease... Read more
New Sprint November iPhone deal: Lease one iP...
Switch to Sprint and purchase an Apple iPhone 11, 11 Pro, or 11 Pro Max, and get a second 64GB iPhone 11 for free. Requires 2 new lines or 1 upgrade-eligible line and 1 new line. Offer is valid from... Read more

Jobs Board

*Apple* Mobility Pro - Best Buy (United Stat...
**746087BR** **Job Title:** Apple Mobility Pro **Job Category:** Store Associates **Store NUmber or Department:** 000319-Harlem & Irving-Store **Job Description:** Read more
Best Buy *Apple* Computing Master - Best Bu...
**743392BR** **Job Title:** Best Buy Apple Computing Master **Job Category:** Store Associates **Store NUmber or Department:** 001171-Southglenn-Store **Job Read more
Best Buy *Apple* Computing Master - Best Bu...
**746015BR** **Job Title:** Best Buy Apple Computing Master **Job Category:** Sales **Store NUmber or Department:** 000372-Federal Way-Store **Job Description:** Read more
*Apple* Mobility Pro - Best Buy (United Stat...
**744658BR** **Job Title:** Apple Mobility Pro **Job Category:** Store Associates **Store NUmber or Department:** 000586-South Hills-Store **Job Description:** At Read more
Best Buy *Apple* Computing Master - Best Bu...
**741552BR** **Job Title:** Best Buy Apple Computing Master **Job Category:** Sales **Store NUmber or Department:** 000277-Metcalf-Store **Job Description:** **What Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.