Implement tiling_drag_threshold

Implements `tiling_drag_threshold <threshold>` to prevent accidental
dragging of tiling containers. If a container (and all of its
descendants) are unfocused and the tile bar is pressed, a threshold
will be used before actually starting the drag. Once the threshold has
been exceeded, the cursor will change to the grab icon and the operation
will switch from `OP_MOVE_TILING_THRESHOLD` to `OP_MOVE_TILING`.

1 files changed, 39 insertions, 2 deletions

diff --git a/sway/input/cursor.c b/sway/input/cursor.c
index f8302ddf..516251f7 100644
--- a/sway/input/cursor.c
+++ b/sway/input/cursor.c
@@ -384,6 +384,30 @@ static void handle_move_tiling_motion(struct sway_seat *seat,
         desktop_damage_box(&seat->op_drop_box);
 }
 
+static void handle_move_tiling_threshold_motion(struct sway_seat *seat,
+                struct sway_cursor *cursor) {
+        double cx = seat->cursor->cursor->x;
+        double cy = seat->cursor->cursor->y;
+        double sx = seat->op_ref_lx;
+        double sy = seat->op_ref_ly;
+
+        // Get the scaled threshold for the output. Even if the operation goes
+        // across multiple outputs of varying scales, just use the scale for the
+        // output that the cursor is currently on for simplicity.
+        struct wlr_output *wlr_output = wlr_output_layout_output_at(
+                        root->output_layout, cx, cy);
+        double output_scale = wlr_output ? wlr_output->scale : 1;
+        double threshold = config->tiling_drag_threshold * output_scale;
+        threshold *= threshold;
+
+        // If the threshold has been exceeded, start the actual drag
+        if ((cx - sx) * (cx - sx) + (cy - sy) * (cy - sy) > threshold) {
+                seat->operation = OP_MOVE_TILING;
+                cursor_set_image(cursor, "grab", NULL);
+                handle_move_tiling_motion(seat, cursor);
+        }
+}
+
 static void calculate_floating_constraints(struct sway_container *con,
                 int *min_width, int *max_width, int *min_height, int *max_height) {
         if (config->floating_minimum_width == -1) { // no minimum
@@ -640,6 +664,9 @@ void cursor_send_pointer_motion(struct sway_cursor *cursor,
                 case OP_MOVE_FLOATING:
                         handle_move_floating_motion(seat, cursor);
                         break;
+                case OP_MOVE_TILING_THRESHOLD:
+                        handle_move_tiling_threshold_motion(seat, cursor);
+                        break;
                 case OP_MOVE_TILING:
                         handle_move_tiling_motion(seat, cursor);
                         break;
@@ -984,12 +1011,22 @@ void dispatch_cursor_button(struct sway_cursor *cursor,
         if (config->tiling_drag && (mod_pressed || on_titlebar) &&
                         state == WLR_BUTTON_PRESSED && !is_floating_or_child &&
                         cont && !cont->is_fullscreen) {
-                if (on_titlebar) {
+                struct sway_container *focus = seat_get_focused_container(seat);
+                bool focused = focus == cont || container_has_ancestor(focus, cont);
+                if (on_titlebar && !focused) {
                         node = seat_get_focus_inactive(seat, &cont->node);
                         seat_set_focus(seat, node);
                 }
+
                 seat_pointer_notify_button(seat, time_msec, button, state);
-                seat_begin_move_tiling(seat, cont, button);
+
+                // If moving a previously unfocused container by it's title bar, use a
+                // threshold for the drag.
+                if (!mod_pressed && !focused && config->tiling_drag_threshold > 0) {
+                        seat_begin_move_tiling_threshold(seat, cont, button);
+                } else {
+                        seat_begin_move_tiling(seat, cont, button);
+                }
                 return;
         }