root: Try to preserve relative positions of floating containers

This makes the behavior of floating containers more consistent with i3.
The coordinates of the container are scaled when the size of the
workspace it is on changes or when the container is moved
between workspaces on different outputs.

For scratchpad containers, add a new state that preserves the dimensions
of the last output the window appeared on. This is necessary because
after a container is hidden in the scratchpad, we expect it to be in the
same relative position on the output when it reappears. We can't just
use the container's attached workspace because that workspace's
dimensions might have been changed or the workspace as a whole could
have been destroyed.

1 files changed, 22 insertions, 0 deletions

diff --git a/sway/tree/container.c b/sway/tree/container.c
index 8222a506..d2c4ffc4 100644
--- a/sway/tree/container.c
+++ b/sway/tree/container.c
@@ -712,6 +712,21 @@ void floating_calculate_constraints(int *min_width, int *max_width,
 
 }
 
+void floating_fix_coordinates(struct sway_container *con, struct wlr_box *old, struct wlr_box *new) {
+        if (!old->width || !old->height) {
+                // Fall back to centering on the workspace.
+                container_floating_move_to_center(con);
+        } else {
+                int rel_x = con->pending.x - old->x + (con->pending.width / 2);
+                int rel_y = con->pending.y - old->y + (con->pending.height / 2);
+
+                con->pending.x = new->x + (double)(rel_x * new->width) / old->width - (con->pending.width / 2);
+                con->pending.y = new->y + (double)(rel_y * new->height) / old->height - (con->pending.height / 2);
+
+                sway_log(SWAY_DEBUG, "Transformed container %p to coords (%f, %f)", con, con->pending.x, con->pending.y);
+        }
+}
+
 static void floating_natural_resize(struct sway_container *con) {
         int min_width, max_width, min_height, max_height;
         floating_calculate_constraints(&min_width, &max_width,
@@ -1025,6 +1040,13 @@ void container_floating_move_to(struct sway_container *con,
                 workspace_add_floating(new_workspace, con);
                 arrange_workspace(old_workspace);
                 arrange_workspace(new_workspace);
+                // If the moved container was a visible scratchpad container, then
+                // update its transform.
+                if (con->scratchpad) {
+                        struct wlr_box output_box;
+                        output_get_box(new_output, &output_box);
+                        con->transform = output_box;
+                }
                 workspace_detect_urgent(old_workspace);
                 workspace_detect_urgent(new_workspace);
         }