Re: few remarks

[Daniel J S. <dan...@ie...>]

Dave Denholm wrote:

>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.
>

I printed out the numbers and verified that

plot->lwidth

is 1.  I've concluded, like Ethan, that the behavior of this routine 
doesn't match what the documentation says.  (It's as though there is 
some confusion between CapButt and CapNotLast.)  Also, I think CapRound, 
i.e. the endpoints of the lines are rounded when they get thicker would 
look just as good as not rounding when dealing with symbols.

Dan