GUI和GUILayout是Unity提供的UIKit。在使用GUI的Controls时都要求设置Rect參数。没办法做到自己主动排版，给适配带来难度。而GUILayout的设计就是为了弥补这个缺陷，GUILayout是在GUI的基础之上复合了一套Layout的排版逻辑。

GUI

class in UnityEngine

Description

The GUI class is the interface for Unity‘s GUI with manual positioning.

See Also: GUI tutorial.

Static Variables

backgroundColor	Global tinting color for all background elements rendered by the GUI.
changed	Returns true if any controls changed the value of the input data.
color	Global tinting color for the GUI.
contentColor	Tinting color for all text rendered by the GUI.
depth	The sorting depth of the currently executing GUI behaviour.
enabled	Is the GUI enabled?
matrix	The GUI transform matrix.
skin	The global skin to use.
tooltip	The tooltip of the control the mouse is currently over, or which has keyboard focus. (Read Only).

Static Functions

BeginGroup	Begin a group. Must be matched with a call to EndGroup.
BeginScrollView	Begin a scrolling view inside your GUI.
Box	Make a graphical box.
BringWindowToBack	Bring a specific window to back of the floating windows.
BringWindowToFront	Bring a specific window to front of the floating windows.
Button	Make a single press button. The user clicks them and something happens immediately.
DragWindow	Make a window draggable.
DrawTexture	Draw a texture within a rectangle.
DrawTextureWithTexCoords	Draw a texture within a rectangle with the given texture coordinates. Use this function for clipping or tiling the image within the given rectangle.
EndGroup	End a group.
EndScrollView	Ends a scrollview started with a call to BeginScrollView.
FocusControl	Move keyboard focus to a named control.
FocusWindow	Make a window become the active window.
GetNameOfFocusedControl	Get the name of named control that has focus.
HorizontalScrollbar	Make a horizontal scrollbar. Scrollbars are what you use to scroll through a document. Most likely, you want to use scrollViews instead.
HorizontalSlider	A horizontal slider the user can drag to change a value between a min and a max.
Label	Make a text or texture label on screen.
ModalWindow	Show a Modal Window.
PasswordField	Make a text field where the user can enter a password.
RepeatButton	Make a button that is active as long as the user holds it down.
ScrollTo	Scrolls all enclosing scrollviews so they try to make position visible.
SelectionGrid	Make a grid of buttons.
SetNextControlName	Set the name of the next control.
TextArea	Make a Multi-line text area where the user can edit a string.
TextField	Make a single-line text field where the user can edit a string.
Toggle	Make an on/off toggle button.
Toolbar	Make a toolbar.
UnfocusWindow	Remove focus from all windows.
VerticalScrollbar	Make a vertical scrollbar. Scrollbars are what you use to scroll through a document. Most likely, you want to use scrollViews instead.
VerticalSlider	A vertical slider the user can drag to change a value between a min and a max.
Window	Make a popup window.

Delegates

WindowFunction

Callback to draw GUI within a window (used with GUI.Window).