Allow dragging tiled windows with the mouse. (#3085)

Fixes #2643

Inner drop region behaves like move to mark.
The outer region is close to the edge (currently 30px from the edge).
This will place the container as a sibling in the given direction within
the parent container. If the move direction goes against the orientation
of the parent container, tree_move() is called.

Contributors:
Co-authored-by: Orestis Floros <orestisflo@gmail.com>
See #3085
- Inner drop region behaves like move to mark
- Handle workspaces
- Fix crash when target closes
- Initiate tiling drag from titlebar
- Hide indicator until container is dragged outside of original position
- Calculate outer_threshold using percentages instead of fixed pixel
values
- Emit 'move' event properly
- Don't focus previously unfocused containers
- Use tree_split() on different orientation
- Fix redundant split containers
- DT_PARENT
- Readability & optimizations
- Limit parent threshold by render_deco_height()
- Tests
- Fullscreen container handling
- Initiate drag from title bar
- Fix issue of EnterNotify events still triggering after drag_callback
  is called
- Include decorations for drop target calculation

Co-authored-by: Michael Forster <email@michael-forster.de>
See #2178
- Original implementation of tiling drag + indicator window
> A container can be dragged by the title bar to one of the four sides
> of another container. That container will then be split either
> horizontally or vertically.

Co-authored-by: Tony Crisci <tony@dubstepdish.com>
See #2653
- Original implementation of outer/inner drop region indicator:
> There are two drop regions per direction.
>
> The inner region is closer to the center of the window. Dropping on
> this region will split the target container and put the container
> within the split at the given direction beside the target container.
>
> The outer region is close to the edge (currently 30px from the edge).
> This will place the container as a sibling in the given direction within
> the parent container.
>
> Dropping into the outer region moves the con beside the target. If the
> move direction goes against the orientation of the parent container, the
> con moves out of the row.
- Fix crash: Ignore containers without a managed window (eg i3bar)

include/all.h

@@ -58,6 +58,7 @@
 #include "match.h"
 #include "xcursor.h"
 #include "resize.h"
+#include "tiling_drag.h"
 #include "sighandler.h"
 #include "move.h"
 #include "output.h"

include/con.h

@@ -371,6 +371,7 @@ void con_move_to_output(Con *con, Output *output, bool fix_coordinates);
  */
 bool con_move_to_output_name(Con *con, const char *name, bool fix_coordinates);
 
+bool con_move_to_target(Con *con, Con *target);
 /**
  * Moves the given container to the given mark.
  *

include/tiling_drag.h

@@ -0,0 +1,16 @@
+/*
+ * vim:ts=4:sw=4:expandtab
+ *
+ * i3 - an improved dynamic tiling window manager
+ * © 2009 Michael Stapelberg and contributors (see also: LICENSE)
+ *
+ * tiling_drag.h: Reposition tiled windows by dragging.
+ *
+ */
+#pragma once
+
+/**
+ * Initiates a mouse drag operation on a tiled window.
+ *
+ */
+void tiling_drag(Con *con, xcb_button_press_event_t *event);

include/util.h

@@ -183,3 +183,15 @@ position_t position_from_direction(direction_t direction);
  *
  */
 direction_t direction_from_orientation_position(orientation_t orientation, position_t position);
+
+/**
+ * Converts direction to a string representation.
+ *
+ */
+const char *direction_to_string(direction_t direction);
+
+/**
+ * Converts position to a string representation.
+ *
+ */
+const char *position_to_string(position_t position);