Change layer duplication so the duplicate is placed above the original (#1124)

Previously, the duplicated layer would be placed at the top of the stack. It is now inserted one layer above the original.

---------

Co-authored-by: Ollie Dolan <olliedolan10@gmail.com>
Co-authored-by: Keavon Chambers <keavon@keavon.com>

document-legacy/src/document.rs

@@ -718,7 +718,11 @@ impl Document {
 				let layer = self.layer(&path)?.clone();
 				let (folder_path, _) = split_path(path.as_slice()).unwrap_or((&[], 0));
 				let folder = self.folder_mut(folder_path)?;
-				if let Some(new_layer_id) = folder.add_layer(layer, None, -1) {
+
+				let selected_id = path.last().copied().unwrap_or_default();
+				let insert_index = folder.layer_ids.iter().position(|&id| id == selected_id).unwrap_or(0) as isize + 1;
+
+				if let Some(new_layer_id) = folder.add_layer(layer, None, insert_index) {
 					let new_path = [folder_path, &[new_layer_id]].concat();
 					self.mark_as_dirty(folder_path)?;
 					Some(

document-legacy/src/layers/folder_layer.rs

@@ -70,11 +70,14 @@ impl FolderLayer {
 	pub fn add_layer(&mut self, layer: Layer, id: Option<LayerId>, insert_index: isize) -> Option<LayerId> {
 		let mut insert_index = insert_index as i128;
 
+		// Bounds check for the insert index
 		if insert_index < 0 {
 			insert_index = self.layers.len() as i128 + insert_index + 1;
 		}
+		if insert_index > self.layers.len() as i128 || insert_index < 0 {
+			return None;
+		}
 
-		if insert_index <= self.layers.len() as i128 && insert_index >= 0 {
 		if let Some(id) = id {
 			self.next_assignment_id = id;
 		}
@@ -92,9 +95,6 @@ impl FolderLayer {
 		}
 
 		Some(id)
-		} else {
-			None
-		}
 	}
 
 	/// Remove a layer with a given ID from the folder.