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This page is about some core classes of a Modular GUI.


This is the core of each GUI on the client side. It keeps track of all panels. This is where the GuiContext is stored.

Useful methods are:

  • getOwner() returns the owner of the screen (usually a mod id)
  • getName() returns the name of the main panel
  • getContext() returns the GuiContext
  • getWindowManager() returns the WindowManager
  • getSyncManager() returns the GuiSyncManager
  • isClientOnly() returns if the screen is only open on client side
  • registerGuiActionListener() register an interaction listener
  • registerFrameUpdateListener() registers a listener which is called approximately 60 times per second
  • getCurrentTheme() returns the active theme for the screen
  • useTheme() tries to set the new theme (does nothing if theme is overridden by resource packs)


This class keeps track of the current GUI state. For example pressed buttons and keys, focused widgets dragging widgets, mouse position, JEI settings, themes and most importantly viewports and transformations.

Useful methods are:

  • isAbove() returns if the mouse is above a widget
  • all methods related to hovering
  • all methods related to focusing
  • hasDraggable() if the mouse is currently dragging an IDraggable (not including item stacks)
  • isMouseItemEmpty() if the mouse is currently not dragging an ItemStack
  • getMouseX() and getMouseY() returns the current mouse position with the current transformations applied to it. That means it is relative to the current widgets position
  • getMouseAbsX() and getMouseAbsY() returns the true (absolute) mouse position
  • unTransformMouseX() and unTransformMouseY() is like getMouseX() and getMouseY(), but the transformations are inverted
  • getMouseButton() returns the last pressed mouse button
  • getMouseWheel() returns the last scroll wheel use
  • getKeyCode() returns the last typed key code
  • getTypedChar() returns the last typed character
  • getPartialTicks() returns the partial ticks for the current frame
  • getTheme() returns the current active theme
  • getJeiSettings() returns the current modifiable JEI settings


This is the root of each widget tree. Panels are also widgets.


A widget is an element in the widget tree. It has a size and position and it can be rendered on screen.

This class has a lot of useful methods, too many to list them all. But you can take a look yourself. I did my best to structure it and make it clean.


Keeps track of all panels and the main panels. Handles opening and closing panels


Manages sync values. This is the only class (with ModularContainer) that exists on client and server side.


This is the minecraft GuiContainer class which wraps the ModularScreen. This is an internal class.


This is the minecraft Container class. This is an internal class.

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