TweetFollow Us on Twitter

The Perils Of PostScript

The Perils Of PostScript

SCOTT "ZZ" ZIMMERMAN

Letting your application rather than the LaserWriter driver convert QuickDraw commands into PostScript is simple in most cases, yet when you use direct PostScript to print documents, subtle interactions between the QuickDraw and PostScript imaging models can cause problems. This article will help you in two important areas: using a font from PostScript while selecting it using QuickDraw and preserving your PostScript state while using QuickDraw to select fonts.

When selecting a PostScript font from QuickDraw, an application first calls GetFNum (see Inside Macintosh, volume I, page 223 [IM I-223]) to get the Font Family ID for a particular font. It then calls TextFont (IM I-171) to actually select it. The name passed to GetFNum is the name of the font as seen in the Font menu (for example, Helvetica).

In PostScript, fonts are selected by name using the findfont (see PostScript Language Reference Manual, page 156 [PLRM 156]) and setfont (PLRM 215) operators. If the application attempts to select a font named Helvetica®, however, it will find that this font doesn't exist. This is because the LaserWriter performs a special operation on the font called encoding. Font encoding is the process of mapping missing characters into another font.

For example, a character like ø may not exist in the standard Helvetica font. In order to provide that character, the LaserWriter driver will modify the Helvetica font, inserting a reference to the ø character in the Symbol font. Once this is done, the font is no longer standard Helvetica, so it is renamed. The actual name is something like |_____Helvetica, but this naming convention is not standard and could change in the future.

So if you don't know the font's name, how can you select it? Simple, let QuickDraw do it. When you select a font via TextFont and then use it via one of the QuickDraw text drawing routines (such as DrawChar or DrawString [IM I- 172]), the LaserWriter driver handles the complex task of selecting an appropriate font on the PostScript device. This includes downloading and encoding the font if necessary. Using QuickDraw to select the font not only saves you a lot of work, but also improves compatibility. The process of font downloading and character encoding could change in the future, and if your application does it internally, it will have to be revised. If you use QuickDraw to download the font, your application will be immune to changes in the font downloading mechanism.

PICK A FONT, ANY FONT

Now let's look at the code to actually select a font. The following procedure will select a font for any device, QuickDraw or PostScript:
PROCEDURE  SetFont;(fontName: Str255; fontSize: INTEGER;
    fontStyle: Style);
VAR
    theFontID:  INTEGER;
    thePenLoc:  Point;
BEGIN
    GetFNum(fontName, theFontID);   (* Get the font ID. *)
    TextFont(theFontID);    (* Set it *)
    TextSize(fontSize); (* Set the size *)
    TextFace(fontStyle);    (* ...and the style. *)
    GetPen(thePenLoc);  (* Save the current pen position. *)
    DrawChar(' ');  (* Draw a space so the font gets downloaded.*)
    MoveTo(thePenLoc.h, thePenLoc.v);   (* Restore original pen *)
                (* position. *)
END;

There are two important things to note in the SetFont procedure above. First, the procedure uses the GetFNum trap to get the Font ID. This is essential to make sure that you get the correct font. (See Technical Note #191, Font Names for more information.) Second, the SetFont procedure calls DrawChar to draw a space. This is required to force the font selection on PostScript devices, since the TextFont call only changes the txFont field of the GrafPort. By actually using the font (via DrawChar) the LaserWriter driver's StdText GrafProc is called, and selects the font on the printer. Subsequent calls to the PostScript show (PLRM 222) operator will use this font. Since DrawChar will change the pen position, it is saved (via GetPen [IM I-169]) and restored (via MoveTo [IM I-170]).

ON WITH THE SHOW

Now that we have a font selected, we need to actually draw something with it. For now, as an example, let's say that we want to draw some text with the show operator. We'll send our PostScript using the following procedure. Although convenient for sending PostScript in our example, this method is very inefficient and should not be used in an application. Here's the code:
PROCEDURE SendPostScript(theComment: Str255);
    VAR
        PSCommand   : Str255;
        CommandHdl  : Handle;
        CRString    : Str255;
        theError    : OSErr;
    BEGIN
        CRString := ' ';
        CRString[1] := CHR(13);
        PSCommand := theComment;
        PSCommand := CONCAT(PSCommand, CRString);
        theError := PtrToHand(POINTER(ORD(@PSCommand) + 1),
            CommandHdl,LENGTH(PSCommand));
        if theError <> noErr THEN BEGIN
            (* Handle the error! *)
        END;
        PicComment(PostScriptHandle, 
            LENGTH(PSCommand), CommandHdl);
        DisposHandle(CommandHdl);
    END;

The procedure simply takes a string of text, adds a carriage return at the end of it, and converts it into a handle. The handle is then passed to the PostScriptHandle picture comment, which actually sends it to the printer. Since this procedure created the handle, the procedure also disposes of it. Again, this is not how a normal application would do it, but it keeps things nice and localized for this example. So now that we can send PostScript, consider the following:

SetFont('Helvetica', 14, [bold]);
PicComment(PostScriptBegin, 0, NIL);        
        (********************************************)
        (*** QuickDraw representation of graphic. ***)
        (********************************************)
    (* These calls are only executed by QuickDraw *)
    (* (i.e. non-PostScript) devices.   *)
        MoveTo(50, 50);
        DrawString('This is some gray text.');
        PenPat(ltGray);
        MoveTo(100, 100);
        LineTo(300, 300);
        (*********************************************)
        (*** PostScript representation of graphic. ***)
        (*********************************************)
    (* These calls will only be executed by PostScript devices.*)
    SendPostScript('50 50 moveto (This is some gray text.) show');
    SendPostScript('.10 setgray');
    SendPostScript('100 100 moveto 300 300 lineto stroke');
PicComment(PostScriptEnd, 0, NIL);

In this fragment, the call to SetFont sets the PostScript currentfont to be Helvetica. The PostScriptBegin comment is used to suppress QuickDraw calls on PostScript devices, and vice versa. When the LaserWriter sees PostScriptBegin, it ignores all QuickDraw drawing calls, and just executes picture comments. When a PostScriptEnd is received, the LaserWriter will once again interpret QuickDraw calls. The LaserWriter driver will ignore the QuickDraw representation, and begin executing the SendPostScript calls. The first one draws a string of text, the second one changes the default gray level of the printer from 100% black to 10% black using the setgray (PLRM 216) operator, and the third one draws a diagonal line using the new gray level. Note that the QuickDraw representation for a gray level is handled by using PenPat (IM I-170).

SAVE THE POSTSCRIPT STATE

The fragment we just looked at illustrates a good method for sending both QuickDraw and PostScript. It also demonstrates a new problem. When the PostScriptBegin comment is sent, the LaserWriter driver performs a PostScript gsave (PLRM 166) operation. This saves the current graphics state required for QuickDraw printing. The application can then do what it needs to the state without having to worry about side effects on the QuickDraw environment. When the LaserWriter driver receives a PostScriptEnd comment, it performs a grestore (PLRM 165) operation to restore the QuickDraw state. Normally this is exactly what you would want. But there are cases when an application may want to execute some QuickDraw commands without losing the PostScript state is has setup.

For example, the above code fragment set the gray level of the printer to 10%. At the time we did the PostScriptEnd comment, the gray level was restored to 100%. If we then want to change the font size, and redraw the text, we would have to resend the setgray operator. It would look like this:

   (* Change the font size.*)
    SetFont('Helvetica', 24, [bold]);
    PicComment(PostScriptBegin, 0, NIL);        
        (********************************************)
        (*** QuickDraw representation of graphic. ***)
        (********************************************)
        (* These calls are only executed by QuickDraw *)
        (* (i.e. non-PostScript) devices.*)
        (* The QuickDraw state is unaffected, so there's *)
        (* no need to call PenPat again. *)
        MoveTo(250, 50);
        LineTo(750, 50);

        (*********************************************)
        (*** PostScript representation of graphic. ***)
        (*********************************************)
        (* These calls only executed by PostScript devices. *)
        (* Since the PostScript state was cleared, we need *)
        (* to resend the setgray operator. *)
        SendPostScript('.10 setgray');
        SendPostScript('250 50 moveto 750 50 lineto');
    PicComment(PostScriptEnd, 0, NIL);

Although resending the setgray operator isn't difficult, an application may have set a lot more attributes. To avoid the overhead of resending this state, a new comment may be used. This comment is #196--PostScriptBeginNoSave.

When PostScriptBeginNoSave is used with PostScriptEnd, the gsave and grestore operations are not performed. This means that the application is completely responsible for the graphics state of the printer. If you are doing all of your imaging via PostScript this is not a problem. If you plan on mixing PostScript and QuickDraw, you must be very careful. Changes to attributes like line width and the transformation matrix will have a significant effect on QuickDraw drawing operations. If the comment is used for the above example, the code will look like this:

   (* Now illustrate the use of the PostScriptBeginNoSave  *)
    (* PicComment. *)
    PicComment(PostScriptBeginNoSave, 0, NIL);
        PenPat(ltGray);
        SendPostScript('.10 setgray');
    PicComment(PostScriptEnd, 0, NIL);
    
    (* At this point, the gray level of the device is 10% black *)
    (* Now draw something using this state. *)
    (* Draw a light gray line using QuickDraw. *)
    MoveTo(50, 400);
    Line(100, 100);
    
    (* At this point, the gray level is still 10%, so we must *)
    (* reset it  to black. *)
    PicComment(PostScriptBeginNoSave, 0, NIL);
        PenPat(black);  (* Reset QuickDraw gray level.  *)
        SendPostScript('1.0 setgray');  (* Reset PostScript gray*)
                                (* level.   *)
    PicComment(PostScriptEnd, 0, NIL);

Note that instead of sending PostScriptBegin as the first operation, we now send PostScriptBeginNoSave. We then change the gray level to light gray in the QuickDraw world, and 10% black for PostScript. Since we used PostScriptBeginNoSave, sending PostScriptEnd does not effect the state of the printer (i.e. the gray level remains at 10%). Now we want to draw something with the new state. We first send the PostScriptBegin comment, which saves the state we set up, as well as disabling the QuickDraw calls on PostScript devices.

We then send a QuickDraw representation of the line, followed by PostScriptEnd. On QuickDraw devices, the line will be drawn using the ltGray pen pattern. On PostScript devices, the line will be drawn using 10% black. After the line has been drawn, we need to reset the state of the device for subsequent drawing operations. This is done by once again sending the PostScriptBeginNoSave comment, followed by the commands to reset the gray level, as well as any other attributes of the printer.

In summary, we have looked at two ways of avoiding the perils of PostScript. The first was how to use a font from PostScript while choosing it using QuickDraw. The supported method for this was demonstrated by the SetFont procedure. The second was how to preserve your PostScript state while still using QuickDraw to select fonts.

Scott "Zz" Zimmerman is a DTS printing guru. (He's particularly impressed with the strictly enforced dress code at Apple.) In his spare time he sails, scuba dives for lobsters, and plays the piano, guitar, and saxophone. His doorway is adorned by a melted gummy rat, a good luck charm from his Intel days. At home, atop his monitor is perched a rare Asian black scorpion (behind glass, we hope). His other cuddly pets include two geckos and an iguana. *

 
AAPL
$96.02
Apple Inc.
-2.13
MSFT
$43.34
Microsoft Corpora
-0.24
GOOG
$573.60
Google Inc.
-13.82

MacTech Search:
Community Search:

Software Updates via MacUpdate

OmniPlan 2.3.6 - Robust project manageme...
With OmniPlan, you can create logical, manageable project plans with Gantt charts, schedules, summaries, milestones, and critical paths. Break down the tasks needed to make your project a success,... Read more
Command-C 1.1.1 - Clipboard sharing tool...
Command-C is a revolutionary app which makes easy to share your clipboard between iOS and OS X using your local WiFi network, even if the app is not currently opened. Copy anything (text, pictures,... Read more
Knock 1.1.7 - Unlock your Mac by knockin...
Knock is a faster, safer way to sign in. You keep your iPhone with you all the time. Now you can use it as a password. You never have to open the app -- just knock on your phone twice, even when it's... Read more
Mellel 3.3.6 - Powerful word processor w...
Mellel is the leading word processor for OS X and has been widely considered the industry standard since its inception. Mellel focuses on writers and scholars for technical writing and multilingual... Read more
LibreOffice 4.3.0.4 - Free Open Source o...
LibreOffice is an office suite (word processor, spreadsheet, presentations, drawing tool) compatible with other major office suites. The Document Foundation is coordinating development and... Read more
Freeway Pro 7.0 - Drag-and-drop Web desi...
Freeway Pro lets you build websites with speed and precision... without writing a line of code! With it's user-oriented drag-and-drop interface, Freeway Pro helps you piece together the website of... Read more
Drive Genius 3.2.4 - Powerful system uti...
Drive Genius is an OS X utility designed to provide unsurpassed storage management. Featuring an easy-to-use interface, Drive Genius is packed with powerful tools such as a drive optimizer, a... Read more
Vitamin-R 2.15 - Personal productivity t...
Vitamin-R creates the optimal conditions for your brain to work at its best by structuring your work into short bursts of distraction-free, highly focused activity alternating with opportunities for... Read more
Toast Titanium 12.0 - The ultimate media...
Toast Titanium goes way beyond the very basic burning in the Mac OS and iLife software, and sets the standard for burning CDs, DVDs, and now Blu-ray discs on the Mac. Create superior sounding audio... Read more
OS X Yosemite Wallpaper 1.0 - Desktop im...
OS X Yosemite Wallpaper is the gorgeous new background image for Apple's upcoming OS X 10.10 Yosemite. This wallpaper is available for all screen resolutions with a source file that measures 5,418... Read more

Latest Forum Discussions

See All

Puzzle Roo Review
Puzzle Roo Review By Jennifer Allen on July 31st, 2014 Our Rating: :: PUZZLE-BASED TWISTUniversal App - Designed for iPhone and iPad A different take on the usual block dropping puzzle game, Puzzle Roo is quite pleasant.   | Read more »
Super Crossfire Re-Release Super Crossfi...
Super Crossfire Re-Release Super Crossfighter Coming Soon, Other Radiangames Titles Go 50% Off Posted by Ellis Spice on July 31st, 2014 [ | Read more »
Hexiled Review
Hexiled Review By Rob Thomas on July 31st, 2014 Our Rating: :: HEX SELLSUniversal App - Designed for iPhone and iPad In space, no one can hear you… spell? Hexiled is a neat concept for a word scramble puzzle, but it doesn’t go too... | Read more »
Despicable Me: Minion Rush is One Year O...
Despicable Me: Minion Rush is One Year Old, Gets its Biggest Update Yet Posted by Jennifer Allen on July 31st, 2014 [ permalink ] Universal App - Designed for iPhone and iPad | Read more »
Plants vs. Zombies 2 Enters the Second H...
Plants vs. Zombies 2 Enters the Second Half of the Dark Ages Posted by Ellis Spice on July 31st, 2014 [ permalink ] Universal App - Designed for iPhone and iPad | Read more »
Why Does It Spin? (Games)
Why Does It Spin? 1.0 Device: iOS Universal Category: Games Price: $2.99, Version: 1.0 (iTunes) Description: THERE'S ONLY ONE RULE: DON'T TOUCH THE WALLS! Do you think you're able to follow this simple rule even if you would have to... | Read more »
Ice Wings Plus (Games)
Ice Wings Plus 1.0 Device: iOS Universal Category: Games Price: $1.99, Version: 1.0 (iTunes) Description: THE GREAT ENDLESS RUNNER OF COMBAT JETS IS BACK !! With more than 680.000 downloads in the App Store, Ice Wings: Skies of Steel... | Read more »
Murl the Squirrel (Games)
Murl the Squirrel 1.0 Device: iOS Universal Category: Games Price: $.99, Version: 1.0 (iTunes) Description: Meet Murl. He is teased by a group of flying squirrels because he can't fly. Determined to show them he's can fly, he meets... | Read more »
Celleste (Games)
Celleste 0.1 Device: iOS Universal Category: Games Price: $2.99, Version: 0.1 (iTunes) Description: Lots of cute action with amazing 3D graphics and a new type of gameplay! Take control over the forces of the universe to help a group... | Read more »
Super Heavy Sword (Games)
Super Heavy Sword 0.0.1 Device: iOS Universal Category: Games Price: $.99, Version: 0.0.1 (iTunes) Description: Get Ready to Get HEAVY! Monster Robot Studios presents SUPER Heavy Sword! The sequel to the smash hit HEAVY sword which... | Read more »

Price Scanner via MacPrices.net

Save up to $130 on an iPad mini with Apple re...
The Apple Store has Certified Refurbished 2nd generation iPad minis with Retina Displays available for up to $130 off the cost of new models, starting at $339. Apple’s one-year warranty is included... Read more
iPad Cannibalization Threat “Overblown”
Seeking Alpha’s Kevin Greenhalgh observes that while many commentators think Apple’s forthcoming 5.5-inch panel iPhone 6 will cannibalize iPad sales, in his estimation, these concerns are being... Read more
Primate Labs Releases July 2014 MacBook Pro P...
Primate Labs’ John Poole has posted Geekbench 3 results for most of the new MacBook Pro models that Apple released on Tuesday. Poole observes that overall performance improvements for the new MacBook... Read more
Apple Re-Releases Bugfixed MacBook Air EFI Fi...
Apple has posted a bugfixed version EFI Firmware Update 2.9 a for MacBook Air (Mid 2011) models. The update addresses an issue where systems may take longer to wake from sleep than expected, and... Read more
Save $50 on the 2.5GHz Mac mini, plus free sh...
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
Save up to $140 on an iPad Air with Apple ref...
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
$250 price drop on leftover 15-inch Retina Ma...
B&H Photo has dropped prices on 2013 15″ Retina MacBook Pros by $250 off original MSRP. Shipping is free, and B&H charges NY sales tax only: - 15″ 2.3GHz Retina MacBook Pro: $2249, $250 off... Read more
More iPad Upgrade Musings – The ‘Book Mystiqu...
Much discussed recently, what with Apple reporting iPad sales shrinkage over two consecutive quarters, is that it had apparently been widely assumed that tablet users would follow a two-year hardware... Read more
13-inch 2.5GHz MacBook Pro on sale for $999,...
Best Buy has the 13″ 2.5GHz MacBook Pro available for $999.99 on their online store. Choose free shipping or free instant local store pickup (if available). Their price is $100 off MSRP. Price is... Read more
Save up to $300 on an iMac with Apple refurbi...
The Apple Store has Apple Certified Refurbished iMacs available for up to $300 off the cost of new models. Apple’s one-year warranty is standard, and shipping is free. These are the best prices on... Read more

Jobs Board

Sr. Product Leader, *Apple* Store Apps - Ap...
**Job Summary** Imagine what you could do here. At Apple , great ideas have a way of becoming great products, services, and customer experiences very quickly. Bring Read more
Sr Software Lead Engineer, *Apple* Online S...
Sr Software Lead Engineer, Apple Online Store Publishing Systems Keywords: Company: Apple Job Code: E3PCAK8MgYYkw Location (City or ZIP): Santa Clara Status: Full Read more
Sr Software Lead Engineer, *Apple* Online S...
Sr Software Lead Engineer, Apple Online Store Publishing Systems Keywords: Company: Apple Job Code: E3PCAK8MgYYkw Location (City or ZIP): Santa Clara Status: Full Read more
*Apple* Solutions Consultant (ASC) - Apple (...
**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
Sr. Product Leader, *Apple* Store Apps - Ap...
**Job Summary** Imagine what you could do here. At Apple , great ideas have a way of becoming great products, services, and customer experiences very quickly. Bring Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.