i3wm "reorient v|h" command to change orientation of selected container. Don't forget to focus parent before running it.

i3wm-reorient-vh.patch

diff --git a/i3.config b/i3.config
index 1a457fc..bf85f02 100644
--- a/i3.config
+++ b/i3.config
@@ -54,6 +54,13 @@ bindsym Mod1+h split h
 # split in vertical orientation
 bindsym Mod1+v split v
 
+# change to horizontal orientation
+bindsym Mod1+Shift+h reorient h
+
+# change to vertical orientation
+bindsym Mod1+Shift+v reorient v
+
+
 # enter fullscreen mode for the focused container
 bindsym Mod1+f fullscreen
 
diff --git a/include/commands.h b/include/commands.h
index 85057d1..ff483da 100644
--- a/include/commands.h
+++ b/include/commands.h
@@ -145,6 +145,14 @@ void cmd_floating(I3_CMD, char *floating_mode);
  */
 void cmd_move_workspace_to_output(I3_CMD, char *name);
 
+
+/**
+ * Implementation of 'reorient v|h|vertical|horizontal'.
+ *
+ */
+void cmd_reorient(I3_CMD, char *direction);
+
+
 /**
  * Implementation of 'split v|h|vertical|horizontal'.
  *
diff --git a/include/tree.h b/include/tree.h
index b9159e3..8fff5b1 100644
--- a/include/tree.h
+++ b/include/tree.h
@@ -39,6 +39,15 @@ Con *tree_open_con(Con *con, i3Window *window);
 void tree_split(Con *con, orientation_t orientation);
 
 /**
+ * Reorients (horizontally or vertically) the given container by changing
+ * its orientation and forcing a redraw.
+ *
+ */
+void tree_reorient(Con *con, orientation_t orientation);
+
+
+
+/**
  * Moves focus one level up.
  *
  */
diff --git a/parser-specs/commands.spec b/parser-specs/commands.spec
index 684fd23..d8913c2 100644
--- a/parser-specs/commands.spec
+++ b/parser-specs/commands.spec
@@ -28,6 +28,7 @@ state INITIAL:
   'open' -> call cmd_open()
   'fullscreen' -> FULLSCREEN
   'split' -> SPLIT
+  'reorient' -> REORIENT
   'floating' -> FLOATING
   'mark' -> MARK
   'resize' -> RESIZE
@@ -133,6 +134,11 @@ state SPLIT:
   direction = 'v', 'h', 'vertical', 'horizontal'
       -> call cmd_split($direction)
 
+# split v|h|vertical|horizontal
+state REORIENT:
+  direction = 'v', 'h', 'vertical', 'horizontal'
+      -> call cmd_reorient($direction)
+
 # floating enable|disable|toggle
 state FLOATING:
   floating = 'enable', 'disable', 'toggle'
diff --git a/src/commands.c b/src/commands.c
index 1e1ee0f..6f8e4a9 100644
--- a/src/commands.c
+++ b/src/commands.c
@@ -1084,6 +1084,19 @@ void cmd_split(I3_CMD, char *direction) {
     ysuccess(true);
 }
 
+/**
+ * Implementation of 'reorient v|h|vertical|horizontal'
+ */
+void cmd_reorient(I3_CMD, char *direction) {
+    /* TODO: use matches */
+    LOG("splitting in direction %c\n", direction[0]);
+    tree_reorient(focused, (direction[0] == 'v' ? VERT : HORIZ));
+
+    cmd_output->needs_tree_render = true;
+    // XXX: default reply for now, make this a better reply
+    ysuccess(true);
+}
+
 /*
  * Implementaiton of 'kill [window|client]'.
  *
diff --git a/src/tree.c b/src/tree.c
index f29369c..327603e 100644
--- a/src/tree.c
+++ b/src/tree.c
@@ -328,6 +328,24 @@ void tree_close_con(kill_window_t kill_window) {
     tree_close(focused, kill_window, false, false);
 }
 
+
+/*
+ * Changes the orientation (split and navigation of the given container)
+ * container which contains the old one and the future ones.
+ *
+ */
+
+void tree_reorient(Con *con, orientation_t orientation) {
+    /* Just change the orientation */
+    DLOG("Changing orientation to %d\n", orientation);
+    con->orientation = orientation;
+
+    /* Force re-rendering. TODO: verify if this is needed or not. */
+    FREE(con->deco_render_params);
+
+
+}
+
 /*
  * Splits (horizontally or vertically) the given container by creating a new
  * container which contains the old one and the future ones.

Looks like it was implemented with split h|v.