Initial commit

1 files changed, 54 insertions, 0 deletions

diff --git a/sys/gio/glabax/glbgrid.x b/sys/gio/glabax/glbgrid.x
new file mode 100644
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+++ b/sys/gio/glabax/glbgrid.x
@@ -0,0 +1,54 @@
+# 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