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

Apple Pro Video Formats 2.0.2 - Updates...
Apple Pro Video Formats brings updates to Apple's professional-level codes for Final Cut Pro X, Motion 5, and Compressor 4. Version 2.0.2: Includes support for the following professional video codecs... Read more
Apple Final Cut Pro X 10.2.2 - 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 4.2.1 - 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
Apple Motion 5.2.2 - 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 10.00b1 - File, p...
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
CrossOver 14.1.6 - Run Windows apps on y...
CrossOver can get your Windows productivity applications and PC games up and running on your Mac quickly and easily. CrossOver runs the Windows software that you need on Mac at home, in the office,... Read more
Printopia 2.1.14 - Share Mac printers wi...
Run Printopia on your Mac to share its printers to any capable iPhone, iPad or iPod Touch. Printopia will also add virtual printers, allowing you to save print-outs to your Mac and send to apps.... Read more
Google Drive 1.24 - File backup and shar...
Google Drive is a place where you can create, share, collaborate, and keep all of your stuff. Whether you're working with a friend on a joint research project, planning a wedding with your fiancé, or... Read more
Chromium 45.0.2454.85 - 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. Version 45.0.2454.85: Note: Does not contain the "... Read more
OmniFocus 2.2.5 - GTD task manager with...
OmniFocus helps you manage your tasks the way that you want, freeing you to focus your attention on the things that matter to you most. Capturing tasks and ideas is always a keyboard shortcut away in... Read more

Spirit Hunter is an Upcoming Collectible...
Boomlagoon, the team behind hybrid CCG/runner Monsu, has announced their newest project: a collectible card game/action RPG named Spirit Hunter. [Read more] | Read more »
Zen Brush 2 (Entertainment)
Zen Brush 2 1.0 Device: iOS Universal Category: Entertainment Price: $2.99, Version: 1.0 (iTunes) Description: Zen Brush 2 is a drawing app focused on the strong yet beautiful feel of the East Asian ink brush. | Read more »
NetNewsWire (News)
NetNewsWire 4.0.0 Device: iOS iPhone Category: News Price: $3.99, Version: 4.0.0 (iTunes) Description: Follow the Web NetNewsWire 4, completely written from the ground up for iPhone. NetNewsWire is the best way to keep up with the... | Read more »
Huzzah! Farming Simulator 16 Supports Cl...
As though it weren't difficult enough to resist the siren call of Farming Simulator 16, now it's been updated with cloud saves - so you can jump between devices without missing any of that precious crop-harvesting time. [Read more] | Read more »
Don't Starve: Pocket Edition Finall...
I've made no effort to hide my enjoyment of Don't Starve: Pocket Edition, but I will admit I was a tiny bit disappointed that it was only available for the iPad. Well nuts to that, because Klei Entertainment has made it universal! [Read more] | Read more »
Goat Simulator Wasn't Enough? Then...
If you just didn't get enough goat in Goat Simulator - or if you've been wanting to play a simulated MMO as a microwave - then you're in luck! Goat Simulator MMO Simulator is out now, and it's a game about simulated goats in simulated MMOs. Plus... | Read more »
You Can Play Madfinger Games' Unkil...
Madfinger Games - probably best known for the Dead Trigger series - has officially launched their newest zombie shooter (that isn't called Dead Trigger), named Unkilled. [Read more] | Read more »
KORG iELECTRIBE for iPhone (Music)
KORG iELECTRIBE for iPhone 1.0.1 Device: iOS iPhone Category: Music Price: $9.99, Version: 1.0.1 (iTunes) Description: ** 50% OFF Special Launch Sale - For a Limited Time **The ELECTRIBE reborn in an even smaller form A full-fledged... | Read more »
Toca Life: City Just Got a Bunch of New...
Toca Life: City is Toca Boca's most popular app (number 1 in 47 different countries, apparently), and it's just had an update that adds a bunch of new content. [Read more] | Read more »
My Country 3D is More About Cities than...
My Country 3D is an upcoming city builder from Game Insight that looks pretty decent - although the name seems a tad out of whack for a city builder. Ah well, it is what it is. [Read more] | Read more »

Price Scanner via MacPrices.net

DEVONthink and Co. 40% Off For Students And E...
Students and teachers are either preparing for the new semester or are already back in school. And the better organized they are the easier it is for them to concentrate on what’s really important:... Read more
Labor Day Weekend Sale: MacBook Air for up to...
Best Buy has MacBook Airs on sale for up to $150 off MSRP on their online store this weekend. Choose free shipping or free local store pickup (if available). Sale prices for online orders only, in-... Read more
BassJump Subwoofer for MacBook Refreshed...
Twelve South has released a software update for BassJump, their portable subwoofer for Macbook. BassJump 3.0 has a radically redesigned interface, and the software refresh makes the BassJump... Read more
Near-Office Input Functionality Virtually Any...
Today Logitech introduced the Logitech K380 Multi-Device Bluetooth Keyboard and the Logitech M535 Bluetooth Mouse, giving users the freedom to work on any device, most anywhere. According to... Read more
College Student Deals: Additional $100 off Ma...
Take an additional $100 off all MacBooks and iMacs at Best Buy Online with their College Students Deals Savings, valid through September 4, 2015. Anyone with a valid .EDU email address can take... Read more
2.8GHz Mac mini available for $988, includes...
Adorama has the 2.8GHz Mac mini available for $988, $11 off MSRP, including a free copy of Apple’s 3-Year AppleCare Protection Plan. Shipping is free, and Adorama charges sales tax in NY & NJ... Read more
Will You Buy An iPad Pro? – The ‘Book Mystiqu...
It looks like we may not have to wait much longer to see what finally materializes as a new, larger-panel iPad (Pro/Plus?) Usually reliable Apple product prognosticator KGI Securities analyst Ming-... Read more
eFileCabinet Announces SMB Document Managemen...
Electronic document management (EDM) eFileCabinet, Inc., a hosted solutions provider for small to medium businesses, has announced that its SecureDrawer and eFileCabinet Online services will be... Read more
WaterField Designs Unveils American-Made, All...
San Francisco’s WaterField Designs today unveiled their all-leather Cozmo 2.0 — an elegant attach laptop bag with carefully-designed features to suit any business environment. The Cozmo 2.0 is... Read more
Apple’s 2015 Back to School promotion: Free B...
Purchase a new Mac or iPad at The Apple Store for Education 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

Jobs Board

*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
Content Partner Engineer - *Apple* TV - App...
**Job Summary** The Apple TV team is looking for an experienced engineer with a passion for delivering first in class home entertainment solutions. The candidate will Read more
*Apple* Desktop Analyst - KDS Staffing (Unit...
…field and consistent professional recruiting achievement. Job Description: Title: Apple Desktop AnalystPosition Type: Full-time PermanentLocation: White Plains, NYHot Read more
*Apple* Retail - Multiple Customer Support P...
Job Description: Customer Support Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the Read more
*Apple* Desktop Analyst - KDS Staffing (Unit...
…field and consistent professional recruiting achievement. Job Description: Title: Apple Desktop AnalystPosition Type: Full-time PermanentLocation: White Plains, NYHot Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.