Re: Going over bugs before release...

[Dave D. <dde...@es...>]

Ethan Merritt <merritt@u.washington.edu> writes:

> On Monday 23 February 2004 05:48 am, Dave Denholm wrote:
>> > With the patch applied there is no problem with colors, but any
>> > x11 plot containing rotated text is refreshed very much slower.
>> > This is in particular noticeable when you resize the plot window.
>> > But speeding up window resizing is certainly not release-critical,
>> > so we can address it later.
>>
>> what's the change, and why does it cause a slowdown ?
>
> The previous code assumed that text/background pixel area could
> be represented by a 1-bit deep array.  The array was rotated, and
> then the entire rotated array was ORer back onto the original image
> in one (relatively fast) operation.  The problem is that ORing the
> background color is only harmless if it is represented by all zeros.
> If it is anything else then the OR operation perturbs the existing
> colors.
>
> The new code explicitly tests for pixels in the rotated text box that
> are non-background, and substitutes them back into the original
> image one by one.  That is relatively slow.
>


Yes, that's what I feared...

isn't the standard trick here to

first AND with bg = ~0, fg = reqd colour
then   OR with bg =  0, fg = reqd colour


true there may be an intermediate frame with the wrong foreground colour,
but it's usually not noticable.

dd
-- 
Dave Denholm              <dde...@es...>       http://www.esmertec.com