Re: gnuplot-beta Digest, Vol 12, Issue 10

[Ethan M. <merritt@u.washington.edu>]

On Monday 04 June 2007 13:14, Ethan Merritt wrote:
> On Sunday 03 June 2007 19:48, m sutton wrote:
> > I would like a couple of my patches to be considered for inclusion into CVS:
> > 
> >  1659135  	  dashed grid for GD term to accept linewidths
> 
> OK, that's better than the earlier version.

On closer inspection, I'm not entirely happy.
This line:

        static int png_linetype_dotted[MAXLINEWIDTH*MAXLINEWIDTH*5];

ties up 0.2 MByte permanently, on the off-chance that we want
to change the grid width.  Yeah I know, virtual memory is cheap these days.
But it's ugly.  Doesn't 200,000,000 bytes of storage to specify
a 2+3 dot pattern seem a little outrageous?

My reading of the libgd docs is that there is no need for static arrays.
I quote:

    As of version 1.1.1, the style array is copied when you set 
    the style, so you need not be concerned with keeping the 
    array around indefinitely. 

Can't you do something like:

        if (lw != last_lw) {
            int i;
            int psize = lw*lw*2;
            int ssize = lw*lw*5;
            int *png_linetype_dotted = gp_alloc( 5*lw*lw*sizeof(int), "dots");

            /* Fill style with with color then transparent.
             * The style is 2 on / 3 off and scales with linewidth.
             */
            for(i = 0;i < psize; i++)
                png_linetype_dotted[i] = png_state.color;
            for (;i < ssize; i++)
                png_linetype_dotted[i] = gdTransparent;
            gdImageSetStyle(png_state.image, png_linetype_dotted, ssize);
            free(png_linetype_dotted);
            last_lw = lw;
        }

This seems to work, but I haven't tested extensively

-- 
Ethan A Merritt