Introduce splith/splitv layouts, remove orientation

With this commit, the "default" layout is replaced by the splith and
splitv layouts. splith is equivalent to default with orientation
horizontal and splitv is equivalent to default with orientation
vertical.

The "split h" and "split v" commands continue to work as before, they
split the current container and you will end up in a split container
with layout splith (after "split h") or splitv (after "split v").

To change a splith container into a splitv container, use either "layout
splitv" or "layout toggle split". The latter command is used in the
default config as mod+l (previously "layout default"). In case you have
"layout default" in your config file, it is recommended to just replace
it by "layout toggle split", which will work as "layout default" did
before when pressing it once, but toggle between horizontal/vertical
when pressing it repeatedly.

The rationale behind this commit is that it’s cleaner to have all
parameters that influence how windows are rendered in the layout itself
rather than having a special parameter in combination with only one
layout. This enables us to change existing split containers in all cases
without breaking existing features (see ticket #464). Also, users should
feel more confident about whether they are actually splitting or just
changing an existing split container now.

As a nice side-effect, this commit brings back the "layout toggle"
feature we once had in i3 version 3 (see the userguide).

AFAIK, it is safe to use in-place restart to upgrade into versions
after this commit (switching to an older version will break your layout,
though).

Fixes #464

src/tree.c

@@ -39,6 +39,7 @@ static Con *_create___i3(void) {
     content->type = CT_CON;
     FREE(content->name);
     content->name = sstrdup("content");
+    content->layout = L_SPLITH;
 
     x_set_name(content, "[i3 con] content __i3");
     con_attach(content, __i3, false);
@@ -48,6 +49,7 @@ static Con *_create___i3(void) {
     ws->type = CT_WORKSPACE;
     ws->num = -1;
     ws->name = sstrdup("__i3_scratch");
+    ws->layout = L_SPLITH;
     con_attach(ws, content, false);
     x_set_name(ws, "[i3 con] workspace __i3_scratch");
     ws->fullscreen_mode = CF_OUTPUT;
@@ -112,6 +114,7 @@ void tree_init(xcb_get_geometry_reply_t *geometry) {
     FREE(croot->name);
     croot->name = "root";
     croot->type = CT_ROOT;
+    croot->layout = L_SPLITH;
     croot->rect = (Rect){
         geometry->x,
         geometry->y,
@@ -151,6 +154,7 @@ Con *tree_open_con(Con *con, i3Window *window) {
 
     /* 3. create the container and attach it to its parent */
     Con *new = con_new(con, window);
+    new->layout = L_SPLITH;
 
     /* 4: re-calculate child->percent for each child */
     con_fix_percent(con);
@@ -337,7 +341,7 @@ void tree_split(Con *con, orientation_t orientation) {
     /* for a workspace, we just need to change orientation */
     if (con->type == CT_WORKSPACE) {
         DLOG("Workspace, simply changing orientation to %d\n", orientation);
-        con->orientation = orientation;
+        con->layout = (orientation == HORIZ) ? L_SPLITH : L_SPLITV;
         return;
     }
 
@@ -351,8 +355,9 @@ void tree_split(Con *con, orientation_t orientation) {
      * child (its split functionality is unused so far), we just change the
      * orientation (more intuitive than splitting again) */
     if (con_num_children(parent) == 1 &&
-        parent->layout == L_DEFAULT) {
-        parent->orientation = orientation;
+        (parent->layout == L_SPLITH ||
+         parent->layout == L_SPLITV)) {
+        parent->layout = (orientation == HORIZ) ? L_SPLITH : L_SPLITV;
         DLOG("Just changing orientation of existing container\n");
         return;
     }
@@ -364,7 +369,8 @@ void tree_split(Con *con, orientation_t orientation) {
     TAILQ_REPLACE(&(parent->nodes_head), con, new, nodes);
     TAILQ_REPLACE(&(parent->focus_head), con, new, focused);
     new->parent = parent;
-    new->orientation = orientation;
+    new->layout = (orientation == HORIZ) ? L_SPLITH : L_SPLITV;
+    new->split = true;
 
     /* 3: swap 'percent' (resize factor) */
     new->percent = con->percent;
@@ -594,7 +600,9 @@ void tree_flatten(Con *con) {
     DLOG("Checking if I can flatten con = %p / %s\n", con, con->name);
 
     /* We only consider normal containers without windows */
-    if (con->type != CT_CON || con->window != NULL)
+    if (con->type != CT_CON ||
+        parent->layout == L_OUTPUT || /* con == "content" */
+        con->window != NULL)
         goto recurse;
 
     /* Ensure it got only one child */
@@ -602,12 +610,14 @@ void tree_flatten(Con *con) {
     if (child == NULL || TAILQ_NEXT(child, nodes) != NULL)
         goto recurse;
 
+    DLOG("child = %p, con = %p, parent = %p\n", child, con, parent);
+
     /* The child must have a different orientation than the con but the same as
      * the con’s parent to be redundant */
-    if (con->orientation == NO_ORIENTATION ||
-        child->orientation == NO_ORIENTATION ||
-        con->orientation == child->orientation ||
-        child->orientation != parent->orientation)
+    if (con->split ||
+        child->split ||
+        con_orientation(con) == con_orientation(child) ||
+        con_orientation(child) != con_orientation(parent))
         goto recurse;
 
     DLOG("Alright, I have to flatten this situation now. Stay calm.\n");