Apple II
Technical Notes
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                                                  Developer Technical Support

Apple IIgs
#92:    Twisted Tales of TextEdit

Revised by:     C.K. Haun <TR>                                  November 1990
Written by:     C.K. Haun <TR> and Dave Lyons                  September 1990

This Technical Note discusses some undocumented features and some bugs in the
TextEdit tool set through System Software 5.0.3.
Changes since September 1990:  Added definition of onlyGetSelection bit, and
incorporated the section on the TextEdit dirty flag from Apple IIgs Technical
Note #81, Extended Control Ecstasy.
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TEInsert

Using the TEInsert call on an invisible TextEdit record causes the screen to
scroll, exactly as if the TextEdit record were visible.

If you use LETextBox2 style text as input for a TEInsert call, any style change
information contained at the end of the LETextBox2 text is ignored.  To ensure
that the style change is not ignored, append an additional character at the end
of the block, then delete (with TESetSelect and TEDelete) the extra character
after the TEInsert call.

TEGetText

The documentation for TEGetText says that a dataFormat value of $4 returns the
text as "Formatted for input to LineEdit LETextBox2".  This is not a reliable
return method-this call may or may not succeed.  Greater chance for success
occurs with less than 4,000 characters in the TextEdit record.

TEGetText also supports getting just the text of the current selection range.
Adding $0020 (onlyGetSelection) to the number passed in bufferDescriptor
returns the text of the current selection.  This technique does not work with
data format LETextBox2, but does work with all other formats.  Also, there is
no corresponding bit for the associated style record, so you cannot get the
style for just the current selection this way, if you request style information
you get a styleRef for the entire TextEdit record.

TEClick

Using TEClick or TestControl on an inactive record currently causes that record
to activate.

TERuler

Pixel tabbing values must all be greater than zero or TextEdit loops infinitely
on a tab.

TEGetRuler & TESetRuler

TERuler, for the default ruler or any ruler that uses a tabType value of $1
returns a ruler four bytes longer than described in the documentation.  The
extra four bytes are all $FF, and they are the terminator characters for
tabType $2 rulers.  Expand your buffers by four bytes to prevent overwriting
any data.  TextEdit also expects the additional information on a TESetRuler
call, so you should pad your ruler with four $FF bytes if you are using a type
$1 ruler.

TESetText

Passing a zero-length class one input string (a word length string with the
word set to zero) to TESetText causes TextEdit to crash.

TEPaintText

TEPaintText currently prints colored text in only four colors.

It's Not Dirty, It's Text

There has been some confusion about determining if a TextEdit record has been
changed.  The documentation has been a little vague, and the process itself has
mislead some people.  Here is The Truth:  there is a TextEdit dirty flag, and
you can use it and rely on it to tell you when a TextEdit record has changed.

The TextEdit dirty flag is bit 6 (fRecordDirty in the E16.TextEdit interface
file) of the ctlFlag byte.  This has caused some confusion because the ctlFlag
byte is at offset $12 in the control definition template, and it is at offset
$10 in the TextEdit or Control record.  Just remember that it is not in the
same place in the record as it is in the template.

If it is set, then the TextEdit or Control record has been changed since the
last time the dirty bit was cleared.  The dirty bit is clear initially when you
create the TextEdit or Control record.  Anytime after that, if the user enters
text into the TextEdit record, TextEdit sets the dirty flag.  It is up to your
application to clear the dirty flag; TextEdit has no way of knowing when you've
saved or cleared data.

Further Reference
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  o  Apple IIgs Toolbox Reference, Volume 3