thoth@reef.cis.ufl.edu (Gilligan) (01/05/91)
As part of the XPM effort I have been developing a String to Pixmap
converter that is similar to the String to Bitmap converter. In fact
they are so similar I just copied and modified all the relevant bitmap
files to handle pixmaps instead.
This worked fine until I tried to use the code. The converter was
getting replaced by the String to Bitmap converter somewhere in the
program and NOT in my code. I abandoned the effort after a week of
struggle and didn't return to it until just recently.
I went into the source code for the Athena widgets on the hunch that
one of their widgets was mangling the converters. I found the
offender.
Scrollbar. Someone on bad drugs decided that the Scrollbar wanted a
String to Pixmap converter and decided to use the standard
XmuCvtStringToBitmap. Fine, the Scrollbar has code to handle when the
depth of its particular pixmap does not match the window, but NONE of
the rest of the toolkit does (possible overstatement). Almost
anything with scrollbars is a candidate for a BadMatch error. See the
bug report for a good example.
Bitmaps are NOT suitable replacements for Pixmaps in most cases and
the code in Scrollbar.c is quite erroneous in thinking it will serve.
It also ticks me off when my converters get overridden by obviously
incorrect ones:)
Here's a copy of the bug report I'm sending.
X Window System Bug Report
xbugs@expo.lcs.mit.edu
VERSION:
R4
CLIENT MACHINE and OPERATING SYSTEM:
Sun 4/490 running SunOS 4.1.0, and probably just about any other
machine with Athena Widgets.
DISPLAY TYPE:
HP apollo 9000 series 400 and Sun 3/80 color displays, probably
anything with a depth!=1.
WINDOW MANAGER:
not relevant
AREA:
Xaw, Scrollbar.c
SYNOPSIS:
Scrollbar registers a WHOLLY inappropriate converter.
DESCRIPTION:
The Scrollbar widget registers XmuCvtStringToBitmap as a converter
for String to Pixmap. This converter returns a depth 1 pixmap that is
unsuitable for use as the omnipresent backgroundPixmap or anything
else that is XtRPixmap since most of the toolkit code assumes the
depths of the Pixmaps and windows match. A much more suitable choice
would be XmuCvtStringToPixmap (written by me using the XPM2 library.
Can I get it into R5?).
REPEAT BY:
xmh -xrm "*backgroundPixmap: egypt.bg"
where egypt.bg is a standard X bitmap in your bitmapFilePath
SAMPLE FIX:
This is only a start. There is much code in the Scrollbar
widget that this makes obsolete, but the code shouldn't have been
there in the first place.
*** /cis/src/x11r4/mit/lib/Xaw/Scrollbar.c Fri Dec 15 11:37:21 1989
--- Scrollbar.c Mon Dec 31 21:44:20 1990
***************
*** 171,178 ****
XawInitializeWidgetSet();
XtAddConverter( XtRString, XtROrientation, XmuCvtStringToOrientation,
NULL, (Cardinal)0 );
- XtAddConverter( XtRString, XtRPixmap, XmuCvtStringToBitmap,
- screenConvertArg, XtNumber(screenConvertArg));
}
/*
--- 171,176 ----
If you want a copy of the converter (alpha 0.1 release) and a sample
program you have to send me an ORIGINAL (either you drew it, or I
haven't seen it yet) xpm2 format image that is a tesselation suitable
for a background. No two-color images accepted :) Grey-scales are OK.
Company logos are neat.
--
"Until it's on my desk, it's vaporware" (`it' is the NeXT)
"Those who would trade freedom for security soon will have neither" B. Franklin
I deal with Reality as you _don't_ understand it.