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# Copyright(c) 1986 Association of Universities for Research in Astronomy Inc.
include <mach.h>
include <gset.h>
include <gio.h>
include "glabax.h"
# GLB_DRAWGRID -- Draw a grid across the plotting surface, i.e., draw
# dotted lines between the major tick marks.
procedure glb_drawgrid (gp, ax1, ax2)
pointer gp # graphics descriptor
pointer ax1 # descriptor for first axis
pointer ax2 # descriptor for second axis
int wcs, major_tick
real x, y, tolerance
real x1, y1, x2, y2, sx, sy
int glb_gettick()
errchk glb_gettick, gseti, gsetr, gline, gctran
begin
tolerance = TOL
wcs = GP_WCS(gp)
# Cache the NDC coordinates of the ends of an axis.
call gctran (gp, AX_START(ax1,1), AX_START(ax1,2), x1,y1, wcs, 0)
call gctran (gp, AX_END(ax1,1), AX_END(ax1,2), x2,y2, wcs, 0)
# Set polyline linetype for a dotted line.
call gseti (gp, G_PLTYPE, GL_DOTTED)
call gsetr (gp, G_PLWIDTH, 1.0)
AX_NLEFT(ax1) = -1
while (glb_gettick (gp, ax1, x, y, major_tick) != EOF) {
if (major_tick == NO)
next
# Draw grid line if we are at a major tick, provided the tick
# is not at the end of the axis.
call gctran (gp, x,y, sx,sy, wcs, 0)
if (AX_HORIZONTAL(ax1) == YES) {
if (sx - x1 > tolerance && sx - x2 < tolerance)
call gline (gp, x, AX_END(ax1,2), x, AX_END(ax2,2))
} else {
if (sy - y1 > tolerance && sy - y2 < tolerance)
call gline (gp, AX_END(ax1,1), y, AX_END(ax2,1), y)
}
}
call gseti (gp, G_PLTYPE, GL_SOLID)
end
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