Building Layouts - Unity 3D UI Essentials - page 55

The Canvas Renderer
In order for a GameObject to render visuals on to a Canvas , a GameObject has to have
a CanvasRenderer component attached to it. By default, all built-in UI controls will
add this component and you cannot remove it unless you remove the UI control first.
If you build your own UI components that render to the Canvas , don't forget to add
a [RequiresComponent] for the CanvasRenderer if you want it displayed.
If you build your own UI controls based on one of the existing ones,
the CanvasRenderer will be added automatically by default. Isn't
inheritance brilliant (sometimes)!
If you build your own UI components that render to the
Canvas , don't forget to add a [RequiresComponent] for the
CanvasRenderer if you want it displayed.
Canvas Groups
The Canvas Group component is a simple little component that can change the
behavior of a Canvas in very subtle ways; put simply, it will group child components
together and allow you to group alter certain properties, namely:
• The Alpha value (to allow group fading), which fades all UI components
that are the children of this group.
• Whether or not a set of child controls receives events or they are blocked
(Interactable).
• Whether or not the group Blocks Raycasts to the scene behind the canvas.
• Should the group ignore settings from parent Canvas Groups (if you have
nested groups) allowing you to override settings by checking the Ignore
Parent Groups property.
It's all very simple as you can see here on the component itself, which has been
added to an empty GameObject: