interactive: set grab parameters at cursor press

Add interactive_set_grab_context() which is called when the mouse button
is first pressed, before interactive_begin(). This fixes two small issues:

- The cursor origin position for interactive move/resize was slightly
  off (depending on mouse resolution), because it was set after the
  mouse had already moved slightly. Now it's exact.

- If app- or keybind-initiated maximize (etc.) happened after the button
  press but before the mouse was moved, then interactive_begin() would
  still start move/resize even though the view might now be far away
  from the cursor. Now interactive_cancel() works as expected, even if
  called before interactive_begin().

Also, make sure to call interactive_cancel() for un-maximize as well.

src/action.c

@@ -1262,6 +1262,14 @@ run_action(struct view *view, struct server *server, struct action *action,
 		break;
 	case ACTION_TYPE_MOVE:
 		if (view) {
+			/*
+			 * If triggered by mousebind, grab context was already
+			 * set by button press handling. For keybind-triggered
+			 * Move, set it now from current cursor position.
+			 */
+			if (view != server->seat.pressed.ctx.view) {
+				interactive_set_grab_context(ctx);
+			}
 			interactive_begin(view, LAB_INPUT_STATE_MOVE,
 				LAB_EDGE_NONE);
 		}
@@ -1285,9 +1293,13 @@ run_action(struct view *view, struct server *server, struct action *action,
 			 */
 			enum lab_edge resize_edges =
 				action_get_int(action, "direction", LAB_EDGE_NONE);
-			if (resize_edges == LAB_EDGE_NONE) {
-				resize_edges = cursor_get_resize_edges(
-					server->seat.cursor, ctx);
+			/*
+			 * If triggered by mousebind, grab context was already
+			 * set by button press handling. For keybind-triggered
+			 * Resize, set it now from current cursor position.
+			 */
+			if (view != server->seat.pressed.ctx.view) {
+				interactive_set_grab_context(ctx);
 			}
 			interactive_begin(view, LAB_INPUT_STATE_RESIZE,
 				resize_edges);