Cursor colors and stipples

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2 total messages Started by Glen Whitney Fri, 23 Aug 1991 20:25

#1768

Author: Glen Whitney
Date: Fri, 23 Aug 1991 20:25

34 lines
2153 bytes

I'm running into what looks like a bug on Epoch 3.2, patch level 1, running on
a Decstation 3100. The problem is with the function "cursor-color". If I say

(cursor-color "Green" (current-screen))

then, sure enough, I get return value t, and the cursor turns green. But if I
then say 

(cursor-color nil (current-screen))

I get the return value #<X-Cardinal 1>, which seems to be black, for example
if I use it as an argument to cursor-color. I had expected that

(cursor-color (cursor-color nil (current-screen)) (current-screen))

would have no effect. Is this fixed in the second patch?


As a separate issue, the documentation on style stipples seems to me unclear.
For example, it says that for background stipples, "the on bits are displayed
in the screen background and the off bits in the text background". It took
me a while to figure out that the "text background" was the style
background color and the "screen background" was the background color in
the absence of
a style. Also, it says that for the text stipple, "on bits are displayed in
the text foreground and the off bits are displayed in the text background",
when what seems to happen is that off bits force display in the background
color, whereas on bits are displayed as they would be without the stipple. In
other words, it seems that the text stipple is pixelwise ANDed with the
displayed characters. Is this the intended behavior?

    Thanks for the help,
	Glen Whitney
        UCLA Math Dept.

Re: Cursor colors and stipples

#1770

Author: Alan M. Carroll
Date: Sat, 24 Aug 1991 15:33

47 lines
3137 bytes

In article <1991Aug23.202507.6527@math.ucla.edu>, gwhitney@deimos.math.ucla.edu (Glen Whitney) writes:
>The problem is with the function "cursor-color". If I say
>Is this fixed in the second patch?

I believe so - it works here. If the patch 2 doesn't fix it, let me
know.

> As a separate issue, the documentation on style stipples seems to me unclear.

Sorry about that. Stipples are a complex issue, made more so by the
fact that you can have 2 stipples "competing" in the same character
space, and we committed to only using X supported stipple operations.

What this means is if there is no style for a group of characters,
they are drawn using XDrawImageString(). However, if a stipple is
present this must be done in two parts, first a XFillRectangle() for
the background, and then XDrawString() to put the characters in. The
background stipple is used for the first operation, and the text
stipple for the second.

> a style. Also, it says that for the text stipple, "on bits are displayed in
> the text foreground and the off bits are displayed in the text background",
> when what seems to happen is that off bits force display in the background
> color, whereas on bits are displayed as they would be without the stipple. In
> other words, it seems that the text stipple is pixelwise ANDed with the
> displayed characters. Is this the intended behavior?

Yes. It seems a little strange at first, but it was originally the
other way round, and we found that this was even more confusing,
because the meaning of bits relative to the text background color
changed depending on whether the stipple was used in the background or
text slot. In practice it required keeping a stipple and it's inverse
around. With this scheme, if you use a stipple for either text or
background, off bits are the text background color, i.e. the
background color that would have been used without a stipple*.

In terms of the ANDing behaviour of a stipple on text, that's what
stipples do. What other behaviour did you expect?

* If there are no colors set in the style, then the screen background
and text background are the same, and this is trivially true. If
there's no style, there's no stipple.

-- 
Alan M. Carroll          <-- Another casualty of applied metaphysics
Epoch Development Team   
Urbana Il.               "I hate shopping with the reality-impaired" - Susan

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