1 files changed, 61 insertions, 0 deletions
diff --git a/sys/gio/wcstogki.x b/sys/gio/wcstogki.x
new file mode 100644
index 00000000..e0591402
--- /dev/null
+++ b/sys/gio/wcstogki.x
@@ -0,0 +1,61 @@
+# Copyright(c) 1986 Association of Universities for Research in Astronomy Inc.
+
+include	<gki.h>
+include	<gio.h>
+
+# GPL_WCSTOGKI -- Transform world coordinates to GKI coordinates using the
+# cached transformation parameters.  There are three possible types of scaling
+# on either axis, linear, log, and "elog".  The latter is a piecewise log
+# scaling function defined for all X, i.e., for negative as well as positive
+# X (see elogr.x).  If a negative number is transformed with normal log
+# scaling it is treated as an indefinite, i.e., plotted as a gap in the plot.
+
+procedure gpl_wcstogki (gp, wx, wy, mx, my)
+
+pointer	gp			# graphics device descriptor
+real	wx, wy			# world coordinates of point
+real	mx, my			# metacode coordinates of point
+
+real	x, y
+real	elogr()
+include	"gpl.com"
+
+begin
+	# Update cached transformation parameters if device changes, cache
+	# has been invalidated, or the current WCS has been changed.
+
+	if (gp != gp_out || GP_WCS(gp) != wcs)
+	    call gpl_cache (gp)
+	    
+	# Transform the coordinates.
+
+	if (xtran == LINEAR) {
+	    x = wx
+	} else if (xtran == LOG) {
+	    if (wx <= 0) {
+		call gpl_flush()
+		return
+	    } else
+		x = log10 (wx)
+	} else
+	    x = elogr (wx)
+
+	if (ytran == LINEAR) {
+	    y = wy
+	} else if (ytran == LOG) {
+	    if (wy <= 0) {
+		call gpl_flush()
+		return
+	    } else
+		y = log10 (wy)
+	} else
+	    y = elogr (wy)
+
+	# Return real rather than int GKI coordinates to avoid digitization
+	# errors in a sequence of draws relative to the current pen position.
+
+	mx = max (0.0, min (real(GKI_MAXNDC),
+	    ((x - wxorigin) * xscale) + mxorigin))
+	my = max (0.0, min (real(GKI_MAXNDC),
+	    ((y - wyorigin) * yscale) + myorigin))
+end