FyroxEngine/Fyrox · error

Cannot subtract window from split tile

Error message

Cannot subtract window from split tile

What it means

Tile::minus_window can only remove a window from a tile that is a Window or MultiWindow. If the tile is a Split, it holds no direct windows, so removal is undefined and the library panics. The docs state the tile must be empty, a window, or a multiwindow.

Solutions

1. Match the tile and only call minus_window on Window/MultiWindow variants
2. For Split tiles, recurse into children to find the tile containing the window
3. Use TileContentIterator or find the window's containing tile before removal

Example fix

// before
root_tile = root_tile.minus_window(closing_window);

// after
if matches!(root_tile, Tile::Split { .. }) {
    root_tile = remove_window_from_children(root_tile, closing_window);
} else {
    root_tile = root_tile.minus_window(closing_window);
}

if matches!(tile, Tile::Split { .. }) { descend into children to find the window's tile }

fn is_leaf_tile(tile: &Tile) -> bool { matches!(tile, Tile::Empty | Tile::Window { .. } | Tile::MultiWindow { .. }) }

// avoid panic: only call minus_window on Window/MultiWindow variants
if is_leaf_tile(&tile) { tile.minus_window(w) } else { remove_from_children(tile, w) }

When it happens

Trigger: Calling Tile::minus_window on a Tile::Split variant, regardless of whether the window handle exists anywhere in the tree.

Common situations: Closing docked windows by traversing the tile tree from the root without descending into split children first; generic tile-mutation utilities that assume a leaf tile.

Understand the failure class

Background: "Invalid state transition" errors: "status must be X, actually Y", "already rejected/charging/uninstalled", "cannot ... while running" — what they mean when a library rejects your call — this error's family across 31 libraries.

Related errors

• Cannot add window to split tile
• Invalid texture kind.
• Animation pool must be empty on load!
• Cast to failed!
• An object at index must be returned to a pool it was taken…

AI-assisted analysis of FyroxEngine/Fyrox@76c91aad8e (2026-09-10). Data as JSON: /api/errors/a514744522d2fd24. Report an issue: GitHub.

Appendix: source

Thrown at fyrox-ui/src/dock/tile.rs:147

                let current = windows.get(index as usize).copied();
                windows.retain(|h| h != &window);
                match windows.len() {
                    0 => Self::Empty,
                    1 => Self::Window(windows[0]),
                    _ => {
                        let index = if let Some(current) = current {
                            windows
                                .iter()
                                .position(|w| w == &current)
                                .unwrap_or_default() as u32
                        } else {
                            0
                        };
                        Self::MultiWindow { index, windows }
                    }
                }
            }
            _ => panic!("Cannot subtract window from split tile"),
        }
    }
    /// Construct a new tile that makes the given window active.
    /// If this tile is not a multiwindow or this tile does not contain
    /// the given window, return self.
    pub fn with_active(self, window: Handle<Window>) -> Self {
        match self {
            Self::MultiWindow { index, windows } => {
                let index = if let Some(index) = windows.iter().position(|h| h == &window) {
                    index as u32
                } else {
                    index
                };
                Self::MultiWindow { index, windows }
            }
            _ => self,
        }
    }

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