first usable version of kernel and commands

After an year of hard work, this is a first "usable" version of Jehanne.

sys/src/lib/memlayer/lhide.c

@@ -0,0 +1,76 @@
+/*
+ * This file is part of the UCB release of Plan 9. It is subject to the license
+ * terms in the LICENSE file found in the top-level directory of this
+ * distribution and at http://akaros.cs.berkeley.edu/files/Plan9License. No
+ * part of the UCB release of Plan 9, including this file, may be copied,
+ * modified, propagated, or distributed except according to the terms contained
+ * in the LICENSE file.
+ */
+
+#include <u.h>
+#include <libc.h>
+#include <draw.h>
+#include <memdraw.h>
+#include <memlayer.h>
+
+/*
+ * Hide puts that portion of screenr now on the screen into the window's save area.
+ * Expose puts that portion of screenr now in the save area onto the screen.
+ *
+ * Hide and Expose both require that the layer structures in the screen
+ * match the geometry they are being asked to update, that is, they update the
+ * save area (hide) or screen (expose) based on what those structures tell them.
+ * This means they must be called at the correct time during window shuffles.
+ */
+
+static
+void
+lhideop(Memimage *src, Rectangle screenr, Rectangle clipr, void *etc, int insave)
+{
+	Rectangle r;
+	Memlayer *l;
+
+	USED(clipr.min.x);
+	USED(insave);
+	l = etc;
+	if(src != l->save){	/* do nothing if src is already in save area */
+		r = rectsubpt(screenr, l->delta);
+		memdraw(l->save, r, src, screenr.min, nil, screenr.min, S);
+	}
+}
+
+void
+memlhide(Memimage *i, Rectangle screenr)
+{
+	if(i->layer->save == nil)
+		return;
+	if(rectclip(&screenr, i->layer->screen->image->r) == 0)
+		return;
+	_memlayerop(lhideop, i, screenr, screenr, i->layer);
+}
+
+static
+void
+lexposeop(Memimage *dst, Rectangle screenr, Rectangle clipr, void *etc, int insave)
+{
+	Memlayer *l;
+	Rectangle r;
+
+	USED(clipr.min.x);
+	if(insave)	/* if dst is save area, don't bother */
+		return;
+	l = etc;
+	r = rectsubpt(screenr, l->delta);
+	if(l->save)
+		memdraw(dst, screenr, l->save, r.min, nil, r.min, S);
+	else
+		l->refreshfn(dst, r, l->refreshptr);
+}
+
+void
+memlexpose(Memimage *i, Rectangle screenr)
+{
+	if(rectclip(&screenr, i->layer->screen->image->r) == 0)
+		return;
+	_memlayerop(lexposeop, i, screenr, screenr, i->layer);
+}