[9front] [PATCH] plot: fix disc and circle operations

[an2qzavok <an2qzavok@gmail.com>]

Discs and circles were drawn on screen directly and later erased by
offscreen buffer.
This change puts them in line with other operations, which draw to
offscreen first and to screen when necessary

diff dfee08d50df674cd76f74320bc9c8bc6a4a95f1e uncommitted
--- a/sys/src/cmd/plot/libplot/circ.c
+++ b/sys/src/cmd/plot/libplot/circ.c
@@ -8,5 +8,5 @@
         rad=SCR(-r);
     else
         rad=SCR(r);
-    ellipse(screen, p, rad, rad, 0, getcolor(e1->foregr), ZP);
+    m_circ(p, rad, e1->foregr);
 }
--- a/sys/src/cmd/plot/libplot/disk.c
+++ b/sys/src/cmd/plot/libplot/disk.c
@@ -8,5 +8,5 @@
         rad=SCR(-r);
     else
         rad=SCR(r);
-    fillellipse(screen, p, rad, rad, getcolor(e1->foregr), ZP);
+    m_disc(p, rad, e1->foregr);
 }
--- a/sys/src/cmd/plot/libplot/machdep.c
+++ b/sys/src/cmd/plot/libplot/machdep.c
@@ -34,6 +34,29 @@
     if(offscreen != screen && !buffer)
         draw(screen, xlr(Rect(x0, y0, x1+1, y1+1)), getcolor(c), nil, ZP);
 }
+
+/*
+ * Draw circle at point p with radius rad in color c
+ */
+void
+m_circ(Point p, int rad, int c)
+{
+    ellipse(offscreen, p, rad, rad, 0, getcolor(c), ZP);
+    if (offscreen != screen && !buffer)
+        ellipse(screen, p, rad, rad, 0, getcolor(c), ZP);
+}
+
+/*
+ * Draw disc (filled circle) at point p with radius rad in color c
+ */
+void
+m_disc(Point p, int rad, int c)
+{
+    fillellipse(offscreen, p, rad, rad, getcolor(c), ZP);
+    if (offscreen != screen && !buffer)
+        fillellipse(screen, p, rad, rad, getcolor(c), ZP);
+}
+
 /*
  * Draw text between pointers p and q with first character centered at x, y.
  * Use color c.  Centered if cen is non-zero, right-justified if
right is non-zero.
--- a/sys/src/cmd/plot/libplot/mplot.h
+++ b/sys/src/cmd/plot/libplot/mplot.h
@@ -36,6 +36,8 @@
  */
 #include "../plot.h"
 void m_clrwin(int, int, int, int, int);
+void m_circ(Point, int, int);
+void m_disc(Point, int, int);
 void m_finish(void);
 void m_initialize(char *);
 int m_text(int, int, char *, char *, int, int, int);