MenuDynamicListItem

MenuDynamicListItem

A menu item with a dynamic list of values.

Anytime the left or right arrow keys are pressed, a callback function will be executed which will determine what the next value to be displayed should be.

You can also select a menu dynamic list item by pressing enter, which will trigger a separate event that you can listen for.

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Example usage

// The title for the menu item.
string title = "Dynamic list item.";

// The initial selected list item text.
string initialSelectedText = "0";

// Create the callback function for when the left/right arrow
// keys are pressed. Returning a new string value which will become the new
// selected text.
string ChangeCallback(MenuDynamicListItem item, bool left)
{
    // Left will be true when the left arrow key was pressed
    // and false if the right arrow key was pressed.
    if (left)
        return (int.Parse(item.CurrentItem) - 1).ToString();

    return (int.Parse(item.CurrentItem) + 1).ToString();
}

// Use the ChangeCallback function from above to create a new callback delegate.
MenuDynamicListItem.ChangeItemCallback callback = new MenuDynamicListItem.ChangeItemCallback(ChangeCallback);

// optional description
string description = "Description for this dynamic item. Pressing left will make the value smaller, pressing right will make the value bigger.";

// Create the dynamic list item using the variables above.
MenuDynamicListItem dynList = new MenuDynamicListItem(title, initialSelectedText, callback, description);

// Add a menu item to a menu:
menu.AddMenuItem(dynList);

A clamped counter

Because the callback decides what the next value is, you can clamp it, step by any amount, or format it however you like.

string VolumeCallback(MenuDynamicListItem item, bool left)
{
    int value = int.Parse(item.CurrentItem.Replace("%", ""));
    value = MathUtil.Clamp(left ? value - 5 : value + 5, 0, 100);
    return $"{value}%";
}

menu.AddMenuItem(new MenuDynamicListItem(
    "Volume",
    "50%",
    new MenuDynamicListItem.ChangeItemCallback(VolumeCallback),
    "Changes in steps of 5%, between 0% and 100%."
));

Reacting to a dynamic list item

// Fires after your callback returned a new value.
menu.OnDynamicListItemCurrentItemChange += (_menu, _item, _oldValue, _newValue) =>
{
    Debug.WriteLine($"'{_item.Text}' went from {_oldValue} to {_newValue}.");
};

// Fires when the user presses select on the item.
menu.OnDynamicListItemSelect += (_menu, _item, _currentItem) =>
{
    Debug.WriteLine($"'{_item.Text}' was pressed while showing {_currentItem}.");
};

Caution

The callback is called directly, without a null check, so Callback must never be null. It also has to return a value for every input — returning null makes the item display N/A.

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Constructors

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MenuDynamicListItem(string text, string initialValue, ChangeItemCallback callback)

Creates a dynamic list item without a description.

Parameters

Parameter	Type	Description
text	string	The text displayed on the left side of the item.
initialValue	string	The value that is displayed before the user changes anything.
callback	ChangeItemCallback	The function that returns the next value.

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MenuDynamicListItem(string text, string initialValue, ChangeItemCallback callback, string description)

Creates a dynamic list item with a description.

Parameters

Parameter	Type	Description
text	string	The text displayed on the left side of the item.
initialValue	string	The value that is displayed before the user changes anything.
callback	ChangeItemCallback	The function that returns the next value.
description	string	The description shown below the menu while this item is selected.

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ChangeItemCallback

public delegate string ChangeItemCallback(MenuDynamicListItem item, bool left);

The callback runs every time the user presses left or right on the item. Whatever string you return becomes the new displayed value.

Parameter	Type	Description
item	MenuDynamicListItem	The item the user is interacting with. Read item.CurrentItem to get the current value.
left	boolean	True when the left control was pressed, false when the right control was pressed.

Return type	Description
string	The new value to display.

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Properties

Note

All standard MenuItem class properties are inherited. The MenuItem properties RightIcon and Label are not available for MenuDynamicListItems.

Property	Type	Default value	Description	Optional
HideArrowsWhenNotSelected	boolean	false	Hides the left & right arrows when the menu list item is not currently highlighted.	Yes
CurrentItem	string	Null	Gets or sets the current text that is being displayed.	No
Callback	ChangeItemCallback	Null	The callback function to trigger when the left or right arrow key was pressed.	No

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Methods

There are no methods for MenuDynamicListItems.