add window deletion code

The bug in exec.c can now be triggered, if a command
outputs after its window was deleted an invalid buffer
pointer is used.

3 files changed, 40 insertions, 16 deletions

diff --git a/exec.c b/exec.c
index 978cf65..70f2d0e 100644
--- a/exec.c
+++ b/exec.c
@@ -36,6 +36,7 @@ static int put(W *, EBuf *, unsigned);
 static int look(W *, EBuf *, unsigned);
 static int run(W *, EBuf *, unsigned);
 static int new(W *, EBuf *, unsigned);
+static int del(W *, EBuf *, unsigned);
 
 static char *errstr;
 static ECmd etab[] = {
@@ -43,6 +44,7 @@ static ECmd etab[] = {
 	{ "Put", put },
 	{ "Look", look },
 	{ "New", new },
+	{ "Del", del },
 	{ 0, run },
 };
 
@@ -320,12 +322,24 @@ look(W *w, EBuf *eb, unsigned p0)
 }
 
 static int
-new(W *w, EBuf *eb, unsigned pos)
+new(W *w, EBuf *eb, unsigned p0)
 {
-	(void)eb; (void)pos;
 	w = win_new(eb_new());
 	if (w)
 		curwin = win_tag_toggle(w);
+	else
+		err(eb, p0, "no more windows");
+	return 0;
+}
+
+static int
+del(W *w, EBuf *eb, unsigned p0)
+{
+	w = win_delete(w);
+	if (w)
+		curwin = w;
+	else
+		err(eb, p0, "last window");
 	return 0;
 }
 
diff --git a/win.c b/win.c
index f5af3ac..5122864 100644
--- a/win.c
+++ b/win.c
@@ -70,14 +70,12 @@ win_new(EBuf *eb)
 	int i, x, size;
 
 	assert(eb);
-
 	for (w1=wins;; w1++) {
 		if (w1 - wins >= MaxWins)
 			return 0;
 		if (!w1->eb)
 			break;
 	}
-
 	for (i=0; (w = screen[i]) && screen[i+1]; i++)
 		;
 	if (!w) {
@@ -89,27 +87,40 @@ win_new(EBuf *eb)
 		x = w->rectx + w->rectw + g->border;
 		i++;
 	}
-
 	w1->eb = eb;
 	move(w1, x, 0, size, fheight);
 	screen[i] = w1;
 	screen[i+1] = 0;
-
 	return w1;
 }
 
 /* win_delete - Delete a window created by win_new.
+ * An adjacent window is returned.
  */
-void
+W *
 win_delete(W *w)
 {
-	assert(w >= wins);
-	assert(w < wins+MaxWins);
-
+	W *w1, *sw;
+	int rx;
+
+	if (!screen[1])
+		return 0;
+	for (sw = screen; *sw != w; sw++)
+		assert(*sw);
+	if (sw == screen) {
+		w1 = sw[1];
+		rx = 0;
+	} else {
+		w1 = sw[-1];
+		rx = w1->rectx;
+	}
+	move(w1, rx, 0, w->rectw+g->border+w1->rectw, fheight);
 	memset(w, 0, sizeof(W));
 	w->eb = 0;
-	// FIXME, create an invariant such that win_new can be simplified
-	// also, do not delete if only one window is left
+	memmove(sw, sw+1, (MaxWins-(sw-screen))*sizeof(W*));
+	if (tag.visible && tag.owner == w)
+		tag.visible = 0;
+	return w1;
 }
 
 /* win_at - Return the buffer offset at the specified location,
@@ -177,9 +188,8 @@ win_move(W *w, int x, int y)
 	}
 	for (i=j=0; screen[i+1]; i++)
 		if (screen[i] == w) {
-			w1 = screen[i+1];
-			screen[i+1] = screen[i];
-			screen[i] = w1;
+			screen[i] = screen[i+1];
+			screen[i+1] = w;
 			j++;
 		}
 	for (; i>0 && x < screen[i-1]->rectx; i--) {
diff --git a/win.h b/win.h
index 47800b2..111d44b 100644
--- a/win.h
+++ b/win.h
@@ -33,7 +33,7 @@ enum CursorLoc { CTop, CMid, CBot };
 
 void win_init(struct gui *g);
 W *win_new(EBuf *eb);
-void win_delete(W *);
+W *win_delete(W *);
 unsigned win_at(W *w, int x, int y);
 W *win_which(int x, int y);
 void win_move(W *, int x, int y);