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1 files changed, 42 insertions, 0 deletions

diff --git a/sys/gio/glabax/glbticlen.x b/sys/gio/glabax/glbticlen.x
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+++ b/sys/gio/glabax/glbticlen.x
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+# Copyright(c) 1986 Association of Universities for Research in Astronomy Inc.
+
+include	<mach.h>
+include	<gio.h>
+include	"glabax.h"
+
+# GLB_TICKLEN -- Compute the length of a tick in world coordinates.  All tick
+# drawing is performed in world coordinates since the ticks show the world
+# coordinate system.  The position of a tick must be computed in world coords
+# when the axis is drawn to reflect log scaling (or any other nonlinear
+# scaling.  Less obviously, the tick offset should be given in world coords
+# so that when the tick is drawn by a GRDRAW the tick will follow a line of
+# constant X or Y in world coordinates, and this line will not necessarily be
+# a line of constant X or Y in NDC coordinates.
+
+real procedure glb_ticklen (gp, ax, ndc_length)
+
+pointer	gp			# graphics descriptor
+pointer	ax			# axis descriptor
+real	ndc_length		# length of tick in NDC units
+
+int	wcs
+real	x, y, wx, wy
+
+begin
+	wcs = GP_WCS(gp)
+	call gctran (gp, AX_TICK1(ax,1), AX_TICK1(ax,2), x, y, wcs, 0)
+
+	if (AX_HORIZONTAL(ax) == YES)
+	    y = y + ndc_length
+	else
+	    x = x + ndc_length
+
+	call gctran (gp, x, y, wx, wy, 0, wcs)
+	if (AX_HORIZONTAL(ax) == YES) {
+	    call pargr (wy - AX_TICK1(ax,2))
+	    return (wy - AX_TICK1(ax,2))
+	} else {
+	    call pargr (wx - AX_TICK1(ax,1))
+	    return (wx - AX_TICK1(ax,1))
+	}
+end