If you look at the documentation for the GEM AES Scrap Library, two things soon become very obvious.

First, it’s clear that the designers of GEM at Digital Research recognized the need for and utility of a well-designed system clipboard that applications could use to quickly and easily exchange data.

Second, it’s even more clear that within no more than a couple of minutes after sitting down to map out what sort of library functions were needed and what sort of predefined data exchange formats should be used, something distracted them to such a degree that they put down their engineering comp books, got up from their desks, and left the office.

I’m guessing the distraction was lunch time. Maybe the food truck rolled into the parking lot and tooted its horn.

A third thing becomes obvious soon after. After lunch was over, they never came back to finish what they’d started.

Three Functions

The GEM AES scrap library consists of three functions.

You heard me. Three functions.  Here they are:

  • scrp_write allowed an application to specify a directory which would contain file(s) containing the data being placed on the clipboard.
  • scrp_read allowed an application to retrieve the directory containing clipboard files.
  • scrp_clear function deleted all files in the clipboard directory.

Actually, I lied. The scrp_clear function was only on PC, not Atari. I can only imagine that two or three minutes into the five minute task of bringing the PC code over, the guy doing it said, “screw it — nobody’s gonna use this anyway” and went off for a long weekend.

And Yet, Not Very Useful Functions

The first problem with this setup is that it makes individual applications responsible for deciding where the clipboard resides, rather than the system. That’s simply a recipe for disaster, especially on a hard drive where you could easily end up with a separate clipboard folder for each and every application.

The next problem is that it doesn’t provide a definitive way for an application to find out if there is data on the clipboard or not.  It has to read the directory returned by scrp_read to see if there are any files there or not.  That doesn’t sound terrible at first, but there’s no mechanism for an application to be notified when the clipboard status is changed by another application.  So, as a practical matter, an application has to check again every time it loses and then regains focus.  On a hard drive system, with a fixed system-defined directory, this would be moderately painful.  With the possibility of the directory changing every single time you check, it’s much less moderate.  And that’s on a hard drive system.

On a floppy drive system… well, shit, that set of problems deserves its own section of the article.

Not Remotely Practical Without Hard Drive

Another problem can be neatly summed up in three words: floppy disk system.

Well, not so much a problem in its own right as a problem magnifier.  Trying to use this clipboard setup on a floppy disk system basically takes every problem and makes it worse. When the user has to use one disk to boot the system, another to launch an application, and yet another to load documents, there’s a lot of disk swapping going on.  So, let’s make it worse by having the clipboard on floppy disk also.  We could use the document disk for that, or we could use a separate disk just for the clipboard.  Let’s assume that last option.

Now imagine that you need to copy some formatted text from your word processor into your favorite graphics program.  Let’s step through it.

Boot system on one disk.  Switch disks to launch word processor.  Switch disks to load the document you want.  Switch disks again to clipboard floppy.  Copy/cut the text, meaning the word processor writes out one or more files with the currently selected text.  Now, maybe, switch back to the document floppy to save changes to the file.  Exit the word processor.  Switch disks to the graphics program floppy and launch that program.  Switch to the floppy with your graphics files and load your graphics file.  Once that’s loaded, switch disks to the clipboard floppy.

Now, remember what we said earlier about an application having to check the clipboard folder ever time it loses and regains focus?  That didn’t actually happen here.  The application stayed in focus the whole time, but we switched floppy disks.  How is the program supposed to know this so it can, or should, check to see if clipboard data is now available?  Should the program have to monitor floppy drive media change just to use the clipboard? Apparently so, even though that’s just ridiculous.

Anyway, let’s just skip past the details and assume the program has checked again for clipboard files.  Maybe there’s a menu item for “refresh clipboard” or something equally inelegant but functional.  So now the graphics program finds the clipboard data with the text saved earlier by the word processor.

But now there’s a new problem.  The word processor saved out plain ASCII into CLPBOARD.ASC and formatted text into CLPBOARD.WUP, because the word processor is WordUp and WUP is that program’s native file format.  But the graphics program, like every other application in the known universe other than WordUp, has no clue whatsoever how to read a WUP file and extract anything useful from it.

Data Formats

There was no problem with the idea of WordUp saving its own native WUP format to the clipboard.  The problem was that it didn’t also save the information using a more universally recognized file format. There was zero documentation to indicate anything about what kind of data could (or should) be exchanged via this whole process, or what file formats should be used.

I’m not exaggerating. When I say “zero” I mean exactly that.  The official GEM 1.0 documentation says nothing whatsoever about clipboard data formats. I would imagine the guys at DRI assumed GEM metafiles would be used for vector graphics and IMG files for bitmapped graphics, but they didn’t actually put those ideas into the docs.

And what about other data? How should formatted text be transferred? What about a block of cells from a spreadsheet?  How about MIDI sequencer data?

The answer ultimately was, your guess is as good as mine. Is it any wonder that application programmers basically ignored the scrap library?

The real tragedy of this situation is that it’s entirely a documentation problem. There’s got to be probably no more than 8 or 10 basic, simple types of data that would cover probably 95% of all clipboard requirements. If the guys at DRI, or at Atari for that matter, had written a couple of pages of documentation saying “use this format for this kind of data” then maybe applications would have supported the clipboard.

As with many other GEM shortcomings, there would be 3rd party attempts to fix the broken situation. The PC version of GEM eventually included some documentation about data formats, but it was way too late, and limited mostly to very obvious things like TXT, IMG, IMG, and CSV.  And for whatever reason this information never really circulated to the Atari side of things at the time.

The Simple Fix, Part 1

Making the clipboard genuinely useful would have been fairly simple, had anybody been paying attention at the time. The first fix would have been to define a reasonable list of standard data exchange formats. and to make sure that list wasn’t completely GEM-centric.   For example, here’s a few just off the top of my head:

  • GEM – GEM metafile vector graphics
  • IMG – Bitmapped graphics
  • ASC or TXT – Plain ASCII text.
  • CSV – Comma separated values, text file containing one or more data records with fields separated by commas.
  • RTF – Rich Text Format formatted text.
  • MID – MIDI Data

Each “standard” format would be assigned a 4-byte value like “_ASC” or “_IMG” that will be used as an identifier.  In most cases the code would correspond roughly to the filename extension commonly used.

Keep in mind that there are some file formats in common use today that weren’t around in 1984. For example, the TIFF format for graphics files was introduced in 1986.  JPEG came out in the early 90’s just barely in time for the creation of the WWW.

The choice of IMG files for bitmapped graphics seems unavoidable, yet there is a critical flaw in that IMG doesn’t allow color palette information to be saved with the bitmap.  DRI seemed to think you’d save out a .GEM metafile defining the palette, but that conflicts with another likely scenario: if your source data is vector graphics, then saving out a rendered bitmap version on the clipboard is entirely reasonable.

This is just a short simple list that serves to illustrate the point.

The Simple Fix, Part 2

After defining the basic data formats, the main thing would be to allow for the clipboard to be either disk or RAM-based.  Most copy/paste operations could be done with a fairly small RAM-based clipboard, but it would have been easily to accommodate disk-based clipboard data when needed.

The existing functions scrp_read and scrp_write are history in this scenario as far as I’m concerned.  In their place, I would have suggested a pair of functions for saving & retrieving RAM-based clipboard data.  Something like this:

int resultcode = scrp_copy( CLIPBOARDDATA *cDataSaved )
 
int resultcode = scrp_paste( CLIPBOARDDATA *cDataRequested )

Yeah, I know. We started with two functions and I’m proposing replacing them with two functions. Kind of ironic, but keep reading and I think you’ll agree I get a lot more mileage out of my two functions than AES got out of the original scrap library functions.

The CLIPBOARDDATA Structure

The CLIPBOARDDATA structure defines the information being saved to the clipboard or retrieved from it. It looks like this:

typedef struct
{
    WORD    formatCount;
    DWORD   *formats;
    UCHAR   **data;
    DWORD   *lengths;
} CLIPBOARDDATA;

The formatCount field indicates specifies the size of the arrays pointed to by the formats, data, and lengths parameters.   When writing data to the clipboard, it specifies how many types of data the application is saving.  When requesting data from the clipboard, it specifies the formats that the application knows how to process.  When the system returns clipboard data to the application, it indicates which formats were actually returned. Note that an application can request one format at a time, or many.

Each of the formats specified should represent the same basic data in different formats. For example, a word processor might save formatted text in its own native file format like WUP, but also using both RTF (Rich Text Format) and plain ASCII TXT.  A graphics application might save vector graphics as EPS and GEM, but also a rendered bitmap version as IMG and TIFF.

The formats parameter is a pointer to an array of 32-bit ASCII format identifier codes (like “_IMG” or “_GEM”)  as mentioned earlier.  Each code represents a single type of data, like ASCII text, IMG bitmap, etc.  The list we defined earlier would form the core of this.

The data parameter is a pointer to an array of UCHAR pointers (WORD aligned), with formatCount elements,  that point to the data.  This field is ignored as input to the scrp_paste function.

Finally, the lengths parameter points to an array, with formatCount elements, where each element specifies the length of the data items pointed to by the data parameter.   This field is ignored as input to the scrp_paste function.

The API Functions

The scrp_copy function would save data, as defined in the CLIPBOARDDATA structure, to the clipboard, in each of the specified formats. Depending on the length of the data, it will be copied from the application space to a buffer allocated and maintained by AES, or saved out as a file to the system clipboard directory.  Or possibly both.

Calling scrp_copy would cause AES to send a message to all open applications indicating that the clipboard had been updated.  (Some later 3rd party revision of GEM added a message named SC_CHANGED for this purpose but it was not part of GEM’s original specification.)

The scrp_paste function would retrieve the current data on the clipboard, if any is available in the requested formats.  On input, the CLIPBOARDDATA structure specifies the data formats the application can accept.  This allows the AES to ignore clipboard formats the program won’t be using.  On output, the structure will be updated to indicate the data formats being returned and the actual data.

The resultcode value returned is 0 for no error,  or various negative values to indicate different errors.

Do We Need More Than That?

We could stop right there and the result would be a billion times more useful than the original scrap library.  There is at least one more function which would be nice to have, though.

  • scrp_bufferinfo – Retrieve information about the RAM-based clipboard data buffer, like maximum size.

Something like this would have been easy to create, fairly compact, and it would have made the GEM clipboard a genuinely useful tool from day one.

Next Time

I think we’ll be headed back to VDI topics for next time around but it’s still up in the air.   Don’t be afraid to comment and let me know what topics you’d like!

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