Fix crash when trying to split and float a dock container.

Since splitting a docking container was allowed and successful, the check
to prevent floating it fails to work. This causes a crash because the
workspace of the container cannot be determined as the dockarea is higher
up in the tree than the workspace it belongs to.

This patch extends to sanity check to nested dock containers when trying to
float a container and also disallows manually splitting a docked container
or changing its layout.

fixes #2034

include/con.h

@@ -112,6 +112,12 @@ bool con_is_internal(Con *con);
  */
 bool con_is_floating(Con *con);
 
+/**
+ * Returns true if the container is a docked container.
+ *
+ */
+bool con_is_docked(Con *con);
+
 /**
  * Checks if the given container is either floating or inside some floating
  * container. It returns the FLOATING_CON container.

src/commands.c

@@ -1270,16 +1270,18 @@ void cmd_move_workspace_to_output(I3_CMD, const char *name) {
  *
  */
 void cmd_split(I3_CMD, const char *direction) {
+    HANDLE_EMPTY_MATCH;
+
     owindow *current;
-    /* TODO: use matches */
     LOG("splitting in direction %c\n", direction[0]);
-    if (match_is_empty(current_match))
-        tree_split(focused, (direction[0] == 'v' ? VERT : HORIZ));
-    else {
-        TAILQ_FOREACH(current, &owindows, owindows) {
-            DLOG("matching: %p / %s\n", current->con, current->con->name);
-            tree_split(current->con, (direction[0] == 'v' ? VERT : HORIZ));
+    TAILQ_FOREACH(current, &owindows, owindows) {
+        if (con_is_docked(current->con)) {
+            ELOG("Cannot split a docked container, skipping.\n");
+            continue;
         }
+
+        DLOG("matching: %p / %s\n", current->con, current->con->name);
+        tree_split(current->con, (direction[0] == 'v' ? VERT : HORIZ));
     }
 
     cmd_output->needs_tree_render = true;
@@ -1606,9 +1608,10 @@ void cmd_move_direction(I3_CMD, const char *direction, long move_px) {
  *
  */
 void cmd_layout(I3_CMD, const char *layout_str) {
+    HANDLE_EMPTY_MATCH;
+
     if (strcmp(layout_str, "stacking") == 0)
         layout_str = "stacked";
-    owindow *current;
     layout_t layout;
     /* default is a special case which will be handled in con_set_layout(). */
     if (strcmp(layout_str, "default") == 0)
@@ -1628,14 +1631,15 @@ void cmd_layout(I3_CMD, const char *layout_str) {
 
     DLOG("changing layout to %s (%d)\n", layout_str, layout);
 
-    /* check if the match is empty, not if the result is empty */
-    if (match_is_empty(current_match))
-        con_set_layout(focused, layout);
-    else {
-        TAILQ_FOREACH(current, &owindows, owindows) {
-            DLOG("matching: %p / %s\n", current->con, current->con->name);
-            con_set_layout(current->con, layout);
+    owindow *current;
+    TAILQ_FOREACH(current, &owindows, owindows) {
+        if (con_is_docked(current->con)) {
+            ELOG("cannot change layout of a docked container, skipping it.\n");
+            continue;
         }
+
+        DLOG("matching: %p / %s\n", current->con, current->con->name);
+        con_set_layout(current->con, layout);
     }
 
     cmd_output->needs_tree_render = true;

src/con.c

@@ -447,6 +447,20 @@ bool con_is_floating(Con *con) {
     return (con->floating >= FLOATING_AUTO_ON);
 }
 
+/*
+ * Returns true if the container is a docked container.
+ *
+ */
+bool con_is_docked(Con *con) {
+    if (con->parent == NULL)
+        return false;
+
+    if (con->parent->type == CT_DOCKAREA)
+        return true;
+
+    return con_is_docked(con->parent);
+}
+
 /*
  * Checks if the given container is either floating or inside some floating
  * container. It returns the FLOATING_CON container.

src/floating.c

@@ -108,7 +108,7 @@ void floating_check_size(Con *floating_con) {
 void floating_enable(Con *con, bool automatic) {
     bool set_focus = (con == focused);
 
-    if (con->parent && con->parent->type == CT_DOCKAREA) {
+    if (con_is_docked(con)) {
         LOG("Container is a dock window, not enabling floating mode.\n");
         return;
     }