Re: few remarks

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

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

> On Monday 09 August 2004 11:04 pm, mi...@ph... wrote:
>> Bug:
>> On x11 (well, I haven't look to other terminals), points in the points and
>> linepoints styles are "handicapped" -- look by a screen magnificator (xmag,
>> kmag) to points obtained by:
>> 
>> set size ratio 1
>> plot sin(x)/x w point pt 2
>
> That is one strange bug you have found.  The odd thing is that it seems
> to be a bug in the X server.   I can run the same gnuplot_x11 executable
> on two different machines and get two different results.  My best guess
> at the moment is that the key difference is which version of X11 is
> running, although it is also possible that it is a difference in the video
> driver rather than the version.  The issue is whether the rendering
> engine does, or does not, draw the final pixel in a line segment that is
> at 45 degrees. Changing the drawing style from CapButt to CapRound
> while drawing points fixes this, at least on the machines I have tested.
> I can't think of any bad effects from this so I will make the change.
> I'm sure someone will speak up if it uncovers some complementary
> bug on other X11 display setups.
>


Does gnuplot use zero-width lines for these ?  I have a vague
recollection that if linewidth is set to 0, the X server can use a
device-specific algorithm for drawing the pixels. A linewidth of 1
specifies the exact semantics which must be followed.


Yeah - looks like :

	else if (*buffer == 'P') {
	    /* linux sscanf does not like %1d%4d%4d" with Oxxxxyyyy */
	    /* sscanf(buffer, "P%1d%4d%4d", &point, &x, &y); */
	    point = buffer[1] - '0';
	    sscanf(buffer + 2, "%4d%4d", &x, &y);
	    if (point == 7) {
		/* set point size */
		px = (int) (x * xscale * pointsize);
		py = (int) (y * yscale * pointsize);
	    } else {
		if (type != LineSolid || width != 0) {	/* select solid line */
		    XSetLineAttributes(dpy, gc, 0, LineSolid, CapButt, JoinBevel);
		}


- try setting the linewidth param to 1 in the XSetLineAttributes call.


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