Implement floating_modifier and mouse operations for floating views

This implements the following:

* `floating_modifier` configuration directive
* Drag a floating window by its title bar
* Hold mod + drag a floating window from anywhere
* Resize a floating view by dragging the border
* Resize a floating view by holding mod and right clicking anywhere on
the view
* Resize a floating view and keep aspect ratio by holding shift while
resizing using either method
* Mouse cursor turns into resize when hovering floating border or corner

include/sway/commands.h

@@ -106,7 +106,7 @@ sway_cmd cmd_exit;
 sway_cmd cmd_floating;
 sway_cmd cmd_floating_maximum_size;
 sway_cmd cmd_floating_minimum_size;
-sway_cmd cmd_floating_mod;
+sway_cmd cmd_floating_modifier;
 sway_cmd cmd_floating_scroll;
 sway_cmd cmd_focus;
 sway_cmd cmd_focus_follows_mouse;

include/sway/input/seat.h

@@ -34,6 +34,8 @@ struct sway_drag_icon {
 	struct wl_listener destroy;
 };
 
+enum resize_edge;
+
 struct sway_seat {
 	struct wlr_seat *wlr_seat;
 	struct sway_cursor *cursor;
@@ -52,6 +54,20 @@ struct sway_seat {
 	int32_t touch_id;
 	double touch_x, touch_y;
 
+	// Operations (drag and resize)
+	enum {
+		OP_NONE,
+		OP_DRAG,
+		OP_RESIZE,
+	} operation;
+	struct sway_container *op_container;
+	enum resize_edge op_resize_edge;
+	uint32_t op_button;
+	bool op_resize_preserve_ratio;
+	double op_ref_lx, op_ref_ly;         // cursor's x/y at start of op
+	double op_ref_width, op_ref_height;  // container's size at start of op
+	double op_ref_con_lx, op_ref_con_ly; // container's x/y at start of op
+
 	struct wl_listener focus_destroy;
 	struct wl_listener new_container;
 	struct wl_listener new_drag_icon;

include/sway/tree/container.h

@@ -304,6 +304,12 @@ bool container_is_floating(struct sway_container *container);
  */
 void container_get_box(struct sway_container *container, struct wlr_box *box);
 
+/**
+ * Move a floating container by the specified amount.
+ */
+void container_floating_translate(struct sway_container *con,
+		double x_amount, double y_amount);
+
 /**
  * Move a floating container to a new layout-local position.
  */
@@ -318,4 +324,10 @@ void container_set_dirty(struct sway_container *container);
 
 bool container_has_urgent_child(struct sway_container *container);
 
+/**
+ * If the container is involved in a drag or resize operation via a mouse, this
+ * ends the operation.
+ */
+void container_end_mouse_operation(struct sway_container *container);
+
 #endif

include/sway/tree/layout.h

@@ -14,10 +14,11 @@ enum movement_direction {
 };
 
 enum resize_edge {
-	RESIZE_EDGE_LEFT,
-	RESIZE_EDGE_RIGHT,
-	RESIZE_EDGE_TOP,
-	RESIZE_EDGE_BOTTOM,
+	RESIZE_EDGE_NONE   = 0,
+	RESIZE_EDGE_LEFT   = 1,
+	RESIZE_EDGE_RIGHT  = 2,
+	RESIZE_EDGE_TOP    = 4,
+	RESIZE_EDGE_BOTTOM = 8,
 };
 
 struct sway_container;