A screen is a graphical user interface that extends Screen, allowing the user to interact and fulfill some functionalities. One example of a screen is a custom config screen of your mod. Screens only exist in the client, so if you are using split sources, make sure to place it in your `client` source set.

You may use mixins to add into an existing screen a button that goes to your screen. But in many cases, we can implement the ModMenuApi of Mod Menu mod, and make it possible to access the screen via the config button in the Mod Menu screen. This article does document how to implement ModMenuApi.

A screen should have several “widgets”, which refer to elements in the screen. We add widgets in the init method.

public class TutorialScreen extends Screen {
  protected TutorialScreen() {
    // The parameter is the title of the screen,
    // which will be narrated when you enter the screen.
    super(Component.literal("My tutorial screen"));
  }
 
 
  public Button button1;
  public Button button2;
 
  @Override
  protected void init() {
    button1 = ButtonWidget.builder(Component.literal("Button 1"), button -> {
      System.out.println("You clicked button1!");
    })
        .bounds(width / 2 - 205, 20, 200, 20)
        .tooltip(Tooltip.create(Component.literal("Tooltip of button1")))
        .build();
    button2 = ButtonWidget.builder(Text.literal("Button 2"), button -> {
      System.out.println("You clicked button2!");
    })
        .bounds(width / 2 + 5, 20, 200, 20)
        .tooltip(Tooltip.create(Component.literal("Tooltip of button2")))
        .build();
 
    addRenderableWidget(button1);
    addRenderableWidget(button2);
  }
}

The init method is called then:

• The screen is created.
• The screen is resized. Before invoking this, all existing elements are removed.

You must use add the elements to the screen via using addRenderableOnly, addWidget or addRenderableWidget. The difference is:

• addRenderableOnly: The element will be rendered, but you cannot select it, either by using mouse or keyboard.
• addWidget: You can select and interact it, but it will not be rendered.
• addRenderableWidget: The element will be both rendered and interactable, which is the most common case.

In the Button.builder(…).builder(), you can specify the size and position of the button by using size and pos respectively, or directly using bounds. The tooltip specifies the tooltip, which will be rendered and narrated when your mouse hovers on, or use Tab to focus on it. Tooltip.create takes two arguments, the first to be shown, and the second (optional) to be narrated. For versions before 1.19.3, Button.builder(…) does not exist. In that case, please directly invoke the constructor of Button. ==== Can I instantiate widgets in the constructor ==== Some users may instantiate the widgets in the constructor, or the initialization of class. For example, they may write the code like this: <code java> public ButtonWidget button1 = ButtonWidget.builder(…).build(); public ButtonWidget button2 = ButtonWidget.builder(…).build(); @Override protected void init() { addRenderableWidget(button1); addRenderableWidget(button2); } </code> This is also OK. Its advantage is, if the widgets have some several states (such as the current selections of CycleButton, or typed text in the EditBox), they will not be reset when you resize the screen, because they will not be created again. However, when resizing, the width and height of screen are changed, but the positions and sizes of elements will not update. Therefore, in this case, you have to update the sizes or positions in the init method. <code java> @Override protected void init() { button1.setPosition(width / 2 - 205, 20); button2.setPosition(width / 2 + 5, 20); addRenderableWidget(button1); addRenderableWidget(button2) } </code> ==== Notice about the order ==== After adding amounts of elements, all of them can render and be selected. Some people don't care about the order they are added, because all of the widgets are rendered at the sametime. However, if you select widgets by pressing the “Tab” key, you may find they are focused in a messy order. Therefore, please ensure that the widgets are added in a correct order, which the behaviour of “Tab” key depends on. ===== The parent screen ===== I accessed the screen via another screen, such as the Mod Menu screen, but when I press “Esc” to go back, it just jumped to the main screen, not the previous screen, why? This is because you did not specify a parent screen, and the close method just directly jumps to the main screen. Add a parent as a parameter and field, and use it in the close method: <code java> private final Screen parent; protected TutorialScreen(Screen parent) { super(Component.literal(“My tutorial screen”)); this.parent = parent; } @Override public void onClose() { client.setScreen(parent); } </code> ===== Add narrations ===== By default, when narration is enabled, the screen title and information of the element you hover or focus on will be narrated. If the screen requires extra narrations (for example it has some texts rendered but not added as a widget), you can override updateNarrationState or updateNarratedWidget. The methods take a NarrationElementOutput, in which you can use add method to add narration messages. The narration messages are divided into the following parts (NarratedElementType): * Title: The title of the screen, which is defined in the constructor. When you enter the screen, the title will be automatically narrated. * Position: Telling you the position of the widget you are focusing on. In vanilla, it is: “Screen element %s out of %s”. Besides, if in a list widget, the following will also be narrated: “Selected list row %s out of %s”. * Hint: This refers the tooltip of the element you focus on or hovers on. For example, you may remember about the tooltip method when you create the Button in the code above. The tooltip is narrated in this part. * Usage: In vanilla, the usage is: “Use mouse cursor or Tab button to select element”. Besides the narration of the screen, you can also customize the narration of the element, by overriding appendNarrations method of the class of that element. The element is narrated after the narration of the screen. In the method of appending narrations, using narrationBuilder.nest() can append narrations after the current narrations, instead of replacing existing part of the narration. In some cases, you want repetitive narrations, instead of narrating only once. For example, when loading a level, the percentage of loading is narrated repetitively, telling the user the current loading status. You can call notifyListUpdated in the render or tick method. For more details, you may refer to sources of LevelLoadingScreen. ===== Adding text ===== In render method, you can invoke methods like font.draw, drawString or drawCenteredString to render a text on the screen. <code java> For versions 1.20 below @Override public void render(PoseStack matrices, int mouseX, int mouseY, float delta) { super.render(matrices, mouseX, mouseY, delta); drawCenteredString(matrices, textRenderer, Component.literal(“You must see me”), width / 2, height / 2, 0xffffff); } For versions 1.20 and after @Override public void render(GuiGraphics context, int mouseX, int mouseY, float delta) { super.render(context, mouseX, mouseY, delta); context.drawCenteredString(font, Component.literal(“You must see me”), width / 2, height / 2, 0xffffff); } </code> If you're concerned that the text can be pretty long and may exceed the screen limit, you can use MultilineText so it can be wrapped smartly. <code java> final MultiLineLabel multilineText = MultiLineLabel.create(textRenderer, Component.literal(“The text is pretty long ”.repeat(20)), width - 20); For versions 1.20 below multilineText.renderLeftAligned(matrices, 10, height / 2, 16, 0xffffff); For versions 1.20 and after multilineText.renderLeftAligned(context, 10, height / 2, 16, 0xffffff); </code> Another alterative is using StringWidget or MultilineTextWidget. They are by default not selectable or narratable because their active field is false. ===== Scrolling ===== The screen does not support scrolling, but you can add widgets that supports scrolling. AbstractSelectionList is a class for widgets that contains multiple entries and supports scrolling. However, instead of directly extending it, it is more suitable to extend ObjectSelectionList or ContainerObjectSelectionList, which already implemented navigation and narration. The difference is: * ObjectSelectionList refers to a widget in which you can select a row. In widgets that extends the class, you usually select one entry in the list. Some vanilla examples are biome selection screen in the buffet (single biome) world option, and the language selection screen. * ContainerObjectSelectionList refers to a widget where each row has child elements. In widgets that extends this class, you select and interacts the elements in the rows. Like a Screen, the ContainerObjectSelectionList.Entry'' should have zero, one, or more child elements.

After finishing your screen, in order to avoid potential issues, please check:

• whether the screen returns to the last screen (parent screen) when you press “Esc”
• whether these classes exist only on client (which means they will not be loaded in the dedicated server)
• whether elements are focused in the correct order when you press “Tab” to select them
• whether the behaviors are correct when you resize
• whether the narrations are correct when you use “Tab” or mouse cursor to select element while narration enabled