Adding Hide/Show functionality of the bottom panel to Lona

It’s Friday, and it’s time for another story about my Open Source journey. I continue working on Lona, and I’ve fixed another bug earlier this week. Let’s take a look at the issue:

Bug 🐞

The interface of Lona is really similar to Xcode’s interface, and it has three panels. One on the right, one on the left, and one in the bottom. The bottom panel contains some utilities such as parameters, logic, examples and details of the component, and for some reasons, the hide/show button in the navbar didn’t do anything. My goal was to implement this functionality.

Fix 🔧

In order to fix this bug, I did the following steps:

  1. In the ComponentEditorViewController, which contains the bottom panel, I wrote a new function that, basically, hides and shows the bottom panel depending on the value passed in the argument:
private func setBottomItemVisibility(to visible: Bool) {
if (visible && bottomItem.isCollapsed) || (!visible && !bottomItem.isCollapsed) {
            bottomItem.animator().isCollapsed = !visible

2. I created a public variable utilitiesViewVisible, which I’m going to use later in the WorkspaceViewController. This variable has a getter that returns the value of bottomItem.isCollapsed, and a setter which uses the function from the first step to update the value of bottomItem.isCollapsed:

public var utilitiesViewVisible: Bool {
get { return bottomItem.isCollapsed }
set { setBottomItemVisibility(to: newValue) }

The reason why I made this variable is that bottomItem is private, and I cannot access it from the WorkspaceViewController.

3. Then, I used a newly created variable in the WorkspaceViewController:

// this variable contains an array of all panels in the app.
// I added a conditional statement inside filter function that
// checks whether the current item is bottom one.
// If it is true, it returns value of
public var activePanes: [WorkspacePane] {
get {
return WorkspacePane.all.filter {
if $0 == .bottom {
return !(componentEditorViewController.utilitiesViewVisible)
else {

Also, I added another conditional statement to the setVisibility function which is called when the hide/show button is clicked:

private func setVisibility(to visible: Bool, for pane: WorkspacePane, animate: Bool) {
if pane == .bottom {
componentEditorViewController.utilitiesViewVisible = visible
else {
guard let item = splitViewItem(for: pane) else { return }
if (visible && item.isCollapsed) || (!visible && !item.isCollapsed) {
if animate {
item.animator().isCollapsed = !visible
} else {
item.isCollapsed = !visible


As you can see in the GIF below, the bottom panel works properly when the hide/show button is clicked.

Here is a link to the pull request:

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