Refactor tree_next

- Makes `tree_next` not recursive.
- Adds `focus next|prev [sibling]` command. See (1.) and (2.) in
https://github.com/i3/i3/issues/2587#issuecomment-378505551 (Issue also
requests move command, not implemented here).
- Directional focus command now supports command criteria.

Wrapping is not implemented inside a floating container. This was also
true before the refactor so I am not changing it here.

docs/userguide

@@ -2053,6 +2053,12 @@ parent::
 child::
 	The opposite of +focus parent+, sets the focus to the last focused
 	child container.
+next|prev::
+	Automatically sets focus to the adjacent container. If +sibling+ is
+	specified, the command will focus the exact sibling container,
+	including non-leaf containers like split containers. Otherwise, it is
+	an automatic version of +focus left|right|up|down+ in the orientation
+	of the parent container.
 floating::
 	Sets focus to the last focused floating container.
 tiling::
@@ -2068,6 +2074,7 @@ output::
 <criteria> focus
 focus left|right|down|up
 focus parent|child|floating|tiling|mode_toggle
+focus next|prev [sibling]
 focus output left|right|up|down|primary|<output>
 ----------------------------------------------
 

include/commands.h

@@ -182,6 +182,12 @@ void cmd_exec(I3_CMD, const char *nosn, const char *command);
  */
 void cmd_focus_direction(I3_CMD, const char *direction);
 
+/**
+ * Implementation of 'focus next|prev sibling'
+ *
+ */
+void cmd_focus_sibling(I3_CMD, const char *direction);
+
 /**
  * Implementation of 'focus tiling|floating|mode_toggle'.
  *

include/tree.h

@@ -59,11 +59,16 @@ bool level_down(void);
 void tree_render(void);
 
 /**
- * Changes focus in the given way (next/previous) and given orientation
+ * Changes focus in the given direction
- * (horizontal/vertical).
  *
  */
-void tree_next(char way, orientation_t orientation);
+void tree_next(Con *con, direction_t direction);
+
+/**
+ * Get the previous / next sibling
+ *
+ */
+Con *get_tree_next_sibling(Con *con, position_t direction);
 
 /**
  * Closes the given container including all children.

parser-specs/commands.spec

@@ -146,6 +146,8 @@ state WORKSPACE_NUMBER:
 state FOCUS:
   direction = 'left', 'right', 'up', 'down'
       -> call cmd_focus_direction($direction)
+  direction = 'prev', 'next'
+      -> FOCUS_AUTO
   'output'
       -> FOCUS_OUTPUT
   window_mode = 'tiling', 'floating', 'mode_toggle'
@@ -155,6 +157,12 @@ state FOCUS:
   end
       -> call cmd_focus()
 
+state FOCUS_AUTO:
+  'sibling'
+      -> call cmd_focus_sibling($direction)
+  end
+      -> call cmd_focus_direction($direction)
+
 state FOCUS_OUTPUT:
   output = string
       -> call cmd_focus_output($output)

src/click.c

@@ -212,21 +212,13 @@ static int route_click(Con *con, xcb_button_press_event_t *event, const bool mod
          event->detail == XCB_BUTTON_SCROLL_LEFT ||
          event->detail == XCB_BUTTON_SCROLL_RIGHT)) {
         DLOG("Scrolling on a window decoration\n");
-        orientation_t orientation = con_orientation(con->parent);
         /* Use the focused child of the tabbed / stacked container, not the
          * container the user scrolled on. */
-        Con *focused = con->parent;
+        Con *current = TAILQ_FIRST(&(con->parent->focus_head));
-        focused = TAILQ_FIRST(&(focused->focus_head));
+        const position_t direction =
-        con_activate(con_descend_focused(focused));
+            (event->detail == XCB_BUTTON_SCROLL_UP || event->detail == XCB_BUTTON_SCROLL_LEFT) ? BEFORE : AFTER;
-        /* To prevent scrolling from going outside the container (see ticket
+        Con *next = get_tree_next_sibling(current, direction);
-         * #557), we first check if scrolling is possible at all. */
+        con_activate(con_descend_focused(next ? next : current));
-        bool scroll_prev_possible = (TAILQ_PREV(focused, nodes_head, nodes) != NULL);
-        bool scroll_next_possible = (TAILQ_NEXT(focused, nodes) != NULL);
-        if ((event->detail == XCB_BUTTON_SCROLL_UP || event->detail == XCB_BUTTON_SCROLL_LEFT) && scroll_prev_possible) {
-            tree_next('p', orientation);
-        } else if ((event->detail == XCB_BUTTON_SCROLL_DOWN || event->detail == XCB_BUTTON_SCROLL_RIGHT) && scroll_next_possible) {
-            tree_next('n', orientation);
-        }
 
         goto done;
     }

src/commands.c

@@ -1229,23 +1229,62 @@ void cmd_exec(I3_CMD, const char *nosn, const char *command) {
     } while (0)
 
 /*
- * Implementation of 'focus left|right|up|down'.
+ * Implementation of 'focus left|right|up|down|next|prev'.
  *
  */
-void cmd_focus_direction(I3_CMD, const char *direction) {
+void cmd_focus_direction(I3_CMD, const char *direction_str) {
-    switch (parse_direction(direction)) {
+    HANDLE_EMPTY_MATCH;
-        case D_LEFT:
+    CMD_FOCUS_WARN_CHILDREN;
-            tree_next('p', HORIZ);
+
-            break;
+    direction_t direction;
-        case D_RIGHT:
+    position_t position;
-            tree_next('n', HORIZ);
+    bool auto_direction = true;
-            break;
+    if (strcmp(direction_str, "prev") == 0) {
-        case D_UP:
+        position = BEFORE;
-            tree_next('p', VERT);
+    } else if (strcmp(direction_str, "next") == 0) {
-            break;
+        position = AFTER;
-        case D_DOWN:
+    } else {
-            tree_next('n', VERT);
+        auto_direction = false;
-            break;
+        direction = parse_direction(direction_str);
+    }
+
+    owindow *current;
+    TAILQ_FOREACH(current, &owindows, owindows) {
+        Con *ws = con_get_workspace(current->con);
+        if (!ws || con_is_internal(ws)) {
+            continue;
+        }
+        if (auto_direction) {
+            orientation_t o = con_orientation(current->con->parent);
+            direction = direction_from_orientation_position(o, position);
+        }
+        tree_next(current->con, direction);
+    }
+
+    cmd_output->needs_tree_render = true;
+    // XXX: default reply for now, make this a better reply
+    ysuccess(true);
+}
+
+/*
+ * Implementation of 'focus next|prev sibling'
+ *
+ */
+void cmd_focus_sibling(I3_CMD, const char *direction_str) {
+    HANDLE_EMPTY_MATCH;
+    CMD_FOCUS_WARN_CHILDREN;
+
+    const position_t direction = (STARTS_WITH(direction_str, "prev")) ? BEFORE : AFTER;
+    owindow *current;
+    TAILQ_FOREACH(current, &owindows, owindows) {
+        Con *ws = con_get_workspace(current->con);
+        if (!ws || con_is_internal(ws)) {
+            continue;
+        }
+        Con *next = get_tree_next_sibling(current->con, direction);
+        if (next) {
+            con_activate(next);
+        }
     }
 
     cmd_output->needs_tree_render = true;

src/tree.c

@@ -462,170 +462,162 @@ void tree_render(void) {
     DLOG("-- END RENDERING --\n");
 }
 
+static Con *get_tree_next_workspace(Con *con, direction_t direction) {
+    if (con_get_fullscreen_con(con, CF_GLOBAL)) {
+        DLOG("Cannot change workspace while in global fullscreen mode.\n");
+        return NULL;
+    }
+
+    Output *current_output = get_output_containing(con->rect.x, con->rect.y);
+    if (!current_output) {
+        return NULL;
+    }
+    DLOG("Current output is %s\n", output_primary_name(current_output));
+
+    Output *next_output = get_output_next(direction, current_output, CLOSEST_OUTPUT);
+    if (!next_output) {
+        return NULL;
+    }
+    DLOG("Next output is %s\n", output_primary_name(next_output));
+
+    /* Find visible workspace on next output */
+    Con *workspace = NULL;
+    GREP_FIRST(workspace, output_get_content(next_output->con), workspace_is_visible(child));
+    return workspace;
+}
+
 /*
- * Recursive function to walk the tree until a con can be found to focus.
+ * Returns the next / previous container to focus in the given direction. Does
+ * not modify focus and ensures focus restrictions for fullscreen containers
+ * are respected.
  *
  */
-static bool _tree_next(Con *con, char way, orientation_t orientation, bool wrap) {
+static Con *get_tree_next(Con *con, direction_t direction) {
-    /* When dealing with fullscreen containers, it's necessary to go up to the
+    const bool previous = position_from_direction(direction) == BEFORE;
-     * workspace level, because 'focus $dir' will start at the con's real
+    const orientation_t orientation = orientation_from_direction(direction);
-     * position in the tree, and it may not be possible to get to the edge
-     * normally due to fullscreen focusing restrictions. */
-    if (con->fullscreen_mode == CF_OUTPUT && con->type != CT_WORKSPACE)
-        con = con_get_workspace(con);
 
-    /* Stop recursing at workspaces after attempting to switch to next
+    Con *first_wrap = NULL;
-     * workspace if possible. */
+    while (con->type != CT_WORKSPACE) {
-    if (con->type == CT_WORKSPACE) {
+        if (con->fullscreen_mode == CF_OUTPUT) {
-        if (con_get_fullscreen_con(con, CF_GLOBAL)) {
+            /* We've reached a fullscreen container. Directional focus should
-            DLOG("Cannot change workspace while in global fullscreen mode.\n");
+             * now operate on the workspace level. */
-            return false;
+            con = con_get_workspace(con);
+            break;
+        } else if (con->fullscreen_mode == CF_GLOBAL) {
+            /* Focus changes should happen only inside the children of a global
+             * fullscreen container. */
+            return first_wrap;
         }
-        Output *current_output = get_output_containing(con->rect.x, con->rect.y);
-        Output *next_output;
 
-        if (!current_output)
+        Con *const parent = con->parent;
-            return false;
+        if (con->type == CT_FLOATING_CON) {
-        DLOG("Current output is %s\n", output_primary_name(current_output));
+            if (orientation != HORIZ) {
+                /* up/down does not change floating containers */
+                return NULL;
+            }
 
-        /* Try to find next output */
+            /* left/right focuses the previous/next floating container */
-        direction_t direction;
+            Con *next = previous ? TAILQ_PREV(con, floating_head, floating_windows)
-        if (way == 'n' && orientation == HORIZ)
+                                 : TAILQ_NEXT(con, floating_windows);
-            direction = D_RIGHT;
+            /* If there is no next/previous container, wrap */
-        else if (way == 'p' && orientation == HORIZ)
+            if (!next) {
-            direction = D_LEFT;
+                next = previous ? TAILQ_LAST(&(parent->floating_head), floating_head)
-        else if (way == 'n' && orientation == VERT)
+                                : TAILQ_FIRST(&(parent->floating_head));
-            direction = D_DOWN;
+            }
-        else if (way == 'p' && orientation == VERT)
+            /* Our parent does not list us in floating heads? */
-            direction = D_UP;
+            assert(next);
-        else
-            return false;
 
-        next_output = get_output_next(direction, current_output, CLOSEST_OUTPUT);
+            return next;
-        if (!next_output)
+        }
-            return false;
-        DLOG("Next output is %s\n", output_primary_name(next_output));
 
-        /* Find visible workspace on next output */
+        if (con_num_children(parent) > 1 && con_orientation(parent) == orientation) {
-        Con *workspace = NULL;
+            Con *const next = previous ? TAILQ_PREV(con, nodes_head, nodes)
-        GREP_FIRST(workspace, output_get_content(next_output->con), workspace_is_visible(child));
+                                       : TAILQ_NEXT(con, nodes);
+            if (next && con_fullscreen_permits_focusing(next)) {
+                return next;
+            }
 
+            Con *const wrap = previous ? TAILQ_LAST(&(parent->nodes_head), nodes_head)
+                                       : TAILQ_FIRST(&(parent->nodes_head));
+            switch (config.focus_wrapping) {
+                case FOCUS_WRAPPING_OFF:
+                    break;
+                case FOCUS_WRAPPING_ON:
+                    if (!first_wrap && con_fullscreen_permits_focusing(wrap)) {
+                        first_wrap = wrap;
+                    }
+                    break;
+                case FOCUS_WRAPPING_FORCE:
+                    /* 'force' should always return to ensure focus doesn't
+                     * leave the parent. */
+                    if (next) {
+                        return NULL; /* blocked by fullscreen */
+                    }
+                    return con_fullscreen_permits_focusing(wrap) ? wrap : NULL;
+            }
+        }
+
+        con = parent;
+    }
+
+    assert(con->type == CT_WORKSPACE);
+    Con *workspace = get_tree_next_workspace(con, direction);
+    return workspace ? workspace : first_wrap;
+}
+
+/*
+ * Changes focus in the given direction
+ *
+ */
+void tree_next(Con *con, direction_t direction) {
+    Con *next = get_tree_next(con, direction);
+    if (!next) {
+        return;
+    }
+    if (next->type == CT_WORKSPACE) {
         /* Show next workspace and focus appropriate container if possible. */
-        if (!workspace)
-            return false;
-
         /* Use descend_focused first to give higher priority to floating or
          * tiling fullscreen containers. */
-        Con *focus = con_descend_focused(workspace);
+        Con *focus = con_descend_focused(next);
         if (focus->fullscreen_mode == CF_NONE) {
-            Con *focus_tiling = con_descend_tiling_focused(workspace);
+            Con *focus_tiling = con_descend_tiling_focused(next);
             /* If descend_tiling returned a workspace then focus is either a
              * floating container or the same workspace. */
-            if (focus_tiling != workspace) {
+            if (focus_tiling != next) {
                 focus = focus_tiling;
             }
         }
 
-        workspace_show(workspace);
+        workspace_show(next);
         con_activate(focus);
         x_set_warp_to(&(focus->rect));
-        return true;
+        return;
-    }
+    } else if (next->type == CT_FLOATING_CON) {
-
+        /* Raise the floating window on top of other windows preserving relative
-    Con *parent = con->parent;
+         * stack order */
-
+        Con *parent = next->parent;
-    if (con->type == CT_FLOATING_CON) {
-        if (orientation != HORIZ)
-            return false;
-
-        /* left/right focuses the previous/next floating container */
-        Con *next;
-        if (way == 'n')
-            next = TAILQ_NEXT(con, floating_windows);
-        else
-            next = TAILQ_PREV(con, floating_head, floating_windows);
-
-        /* If there is no next/previous container, wrap */
-        if (!next) {
-            if (way == 'n')
-                next = TAILQ_FIRST(&(parent->floating_head));
-            else
-                next = TAILQ_LAST(&(parent->floating_head), floating_head);
-        }
-
-        /* Still no next/previous container? bail out */
-        if (!next)
-            return false;
-
-        /* Raise the floating window on top of other windows preserving
-         * relative stack order */
         while (TAILQ_LAST(&(parent->floating_head), floating_head) != next) {
             Con *last = TAILQ_LAST(&(parent->floating_head), floating_head);
             TAILQ_REMOVE(&(parent->floating_head), last, floating_windows);
             TAILQ_INSERT_HEAD(&(parent->floating_head), last, floating_windows);
         }
-
-        con_activate(con_descend_focused(next));
-        return true;
     }
 
-    /* If the orientation does not match or there is no other con to focus, we
+    workspace_show(con_get_workspace(next));
-     * need to go higher in the hierarchy */
-    if (con_orientation(parent) != orientation ||
-        con_num_children(parent) == 1)
-        return _tree_next(parent, way, orientation, wrap);
-
-    Con *current = TAILQ_FIRST(&(parent->focus_head));
-    /* TODO: when can the following happen (except for floating windows, which
-     * are handled above)? */
-    if (TAILQ_EMPTY(&(parent->nodes_head))) {
-        DLOG("nothing to focus\n");
-        return false;
-    }
-
-    Con *next;
-    if (way == 'n')
-        next = TAILQ_NEXT(current, nodes);
-    else
-        next = TAILQ_PREV(current, nodes_head, nodes);
-
-    if (!next) {
-        if (config.focus_wrapping != FOCUS_WRAPPING_FORCE) {
-            /* If there is no next/previous container, we check if we can focus one
-             * when going higher (without wrapping, though). If so, we are done, if
-             * not, we wrap */
-            if (_tree_next(parent, way, orientation, false))
-                return true;
-
-            if (!wrap)
-                return false;
-        }
-
-        if (way == 'n')
-            next = TAILQ_FIRST(&(parent->nodes_head));
-        else
-            next = TAILQ_LAST(&(parent->nodes_head), nodes_head);
-    }
-
-    /* Don't violate fullscreen focus restrictions. */
-    if (!con_fullscreen_permits_focusing(next))
-        return false;
-
-    /* 3: focus choice comes in here. at the moment we will go down
-     * until we find a window */
-    /* TODO: check for window, atm we only go down as far as possible */
     con_activate(con_descend_focused(next));
-    return true;
 }
 
 /*
- * Changes focus in the given way (next/previous) and given orientation
+ * Get the previous / next sibling
- * (horizontal/vertical).
  *
  */
-void tree_next(char way, orientation_t orientation) {
+Con *get_tree_next_sibling(Con *con, position_t direction) {
-    _tree_next(focused, way, orientation,
+    Con *to_focus = (direction == BEFORE ? TAILQ_PREV(con, nodes_head, nodes)
-               config.focus_wrapping != FOCUS_WRAPPING_OFF);
+                                         : TAILQ_NEXT(con, nodes));
+    if (to_focus && con_fullscreen_permits_focusing(to_focus)) {
+        return to_focus;
+    }
+    return NULL;
 }
 
 /*

testcases/t/101-focus.t

@@ -35,9 +35,13 @@ my $bottom = open_window;
 # end sleeping for half a second to make sure i3 reacted
 #
 sub focus_after {
-    my $msg = shift;
+    my ($msg, $win_id) = @_;
 
-    cmd $msg;
+    if (defined($win_id)) {
+        cmd "[id=$win_id] $msg";
+    } else {
+        cmd $msg;
+    }
     return $x->input_focus;
 }
 
@@ -50,6 +54,14 @@ is($focus, $mid->id, "Middle window focused");
 $focus = focus_after('focus up');
 is($focus, $top->id, "Top window focused");
 
+# Same using command criteria
+$focus = focus_after('focus up', $bottom->id);
+is($focus, $mid->id, "Middle window focused");
+
+cmd 'focus down';
+$focus = focus_after('focus up', $mid->id);
+is($focus, $top->id, "Top window focused");
+
 #####################################################################
 # Test focus wrapping
 #####################################################################

testcases/t/307-focus-next-prev.t

@@ -0,0 +1,72 @@
+#!perl
+# vim:ts=4:sw=4:expandtab
+#
+# Please read the following documents before working on tests:
+# • https://build.i3wm.org/docs/testsuite.html
+#   (or docs/testsuite)
+#
+# • https://build.i3wm.org/docs/lib-i3test.html
+#   (alternatively: perldoc ./testcases/lib/i3test.pm)
+#
+# • https://build.i3wm.org/docs/ipc.html
+#   (or docs/ipc)
+#
+# • http://onyxneon.com/books/modern_perl/modern_perl_a4.pdf
+#   (unless you are already familiar with Perl)
+#
+# Test focus next|prev
+# Ticket: #2587
+use i3test;
+
+cmp_tree(
+    msg => "cmd 'prev' selects leaf 1/2",
+    layout_before => 'S[a b] V[c d* T[e f g]]',
+    layout_after => 'S[a b] V[c* d T[e f g]]',
+    cb => sub {
+        cmd 'focus prev';
+    });
+
+cmp_tree(
+    msg => "cmd 'prev' selects leaf 2/2",
+    layout_before => 'S[a b] V[c* d T[e f g]]',
+    layout_after => 'S[a b*] V[c d T[e f g]]',
+    cb => sub {
+        # c* -> V -> b*
+        cmd 'focus parent, focus prev';
+    });
+
+cmp_tree(
+    msg => "cmd 'prev sibling' selects leaf again",
+    layout_before => 'S[a b] V[c d* T[e f g]]',
+    layout_after => 'S[a b] V[c* d T[e f g]]',
+    cb => sub {
+        cmd 'focus prev sibling';
+    });
+
+cmp_tree(
+    msg => "cmd 'next' selects leaf",
+    # Notice that g is the last to open before focus moves to d*
+    layout_before => 'S[a b] V[c d* T[e f g]]',
+    layout_after => 'S[a b] V[c d T[e f g*]]',
+    cb => sub {
+        cmd 'focus next';
+    });
+
+cmp_tree(
+    msg => "cmd 'next sibling' selects parent 1/2",
+    layout_before => 'S[a b] V[c d* T[e f g]]',
+    layout_after => 'S[a b] V[c d T*[e f g]]',
+    cb => sub {
+        cmd 'focus next sibling';
+    });
+
+cmp_tree(
+    msg => "cmd 'next sibling' selects parent 2/2",
+    layout_before => 'S[a b*] V[c d T[e f g]]',
+    layout_after => 'S[a b] V*[c d T[e f g]]',
+    cb => sub {
+        # b* -> S* -> V*
+        cmd 'focus parent, focus next sibling';
+    });
+
+done_testing;