Introduction to X

1
Introduction to X

• Features of X
• Industry standard
• Device Independent
• Motif A high level toolkit
• Programs based on Motif
• Xlib lowest level
• Xt Intrinsics hides details of Xlib
• Motif builds on Xt and provides visual
  components.

2
The Client-Server Model

• The server is a program that controls all I/O.
• Creates and manipulates windows
• produces text and graphics
• handles input
• The client is a program that uses the I/O
  services of a server

3
The Window Hierarchy

• The window tree
• root window entire screen
• every window has a parent window except for the
  root window
• windows can have child windows
• The X coordinate system
• upper left corner is (0, 0)
• x increases to the right and y increases
  downwards

4
Events

• The server communicates with clients by sending
  "events" to the client application
• X programs(client applications) are "event
  driven"
• they wait for an event
• they respond to the event
• then they wait for another event

5
Xt Intrinsics

• Xlib is low level
• Many lines of code required to perform common
  functions
• Xt is a toolkit for building UI toolkits
• defines an object-oriented architecture for UI
  components or "widgets" such as buttons,
  scrollbars and menus
• independent of any particular look or feel

6
Widgets

• A widget is a window a data structure
• Two fundamental types of widgets
• Display widgets for user info/ input
• Container widgets for grouping other widgets
  together on the screen
• It implies a widget hierarchy or a widget tree
• The root of every widget tree is a shell widget

7
Xt Widget Classes

• Core
• Superclass for all other widget classes
• Composite
• contains and manages other child widgets
• Constraint
• subclass of the Composite class
• manage children using constraint information
  (size, position)

8
Xt Widget Class (contd.)

• Shell
• subclass of the composite class
• can have only one child
• three subclasses
• ApplicationShell
• provide the main windowfor an application
• OverrideShell
• no "decorations" and good for popup menus
• TransientShell
• displayed for short time (dialog boxes)

9
Event Dispatching

• Event Handlers
• Actions
• Callbacks
• functions to be called when some widget-specific
  condition occurs which is usually related to an
  event

10
Xt Resources

• Xt resources
• are customizable parameters supported by widgets
• control most aspects of widgets appearance and
  behavior
• it is possible to
• "hard code" resources
• retrieve them from a database allowing them to be
  specified outside the application i.e. user can
  change them without recompiling

11
The Core widget Class

• All widgets inherit the resources, callbacks and
  other behavior from Core
• rarely used directly

12
Core widget class Resources

• XmNx, XmNy
• XmNwidth, XmNheight
• XmNborderWidth
• XmNsensitive
• XmNancestorSensitive
• XmNcolormap
• XmNbackground
• XmNbackgroundPixmap
• XmNborderColor
• XmNborderPixmap
• XmNmappedWhenManaged

13
Primitive Motif Widgets

• XmPrimitive
• subclass of Core
• they do not support children
• also called "display" widget, since they usually
  display information
• Behaviors
• Top and bottom shadows
• Keyboard traversal of windows
• support for highlighting

14
XmPrimitive Class Resources

• XmNforeground
• XmNhighlightOnEnter
• XmNhighlightThickness
• XmNhighlightColor
• XmNshadowThickness
• XmNtopShadowColor, XmNbottomShadowColor
• XmNuserData

15
XmLabel Widget Class

• Provides support for XmPushButton,
  XmToggleButton, XmDrawnButton, XmCascadeButton
• used to display text or pixmap in a window

16
XmLabel Class Resources

• XmNalignment
• XmNlabelType
• XmNmarginHeight, XmNmarginWidth
• XmNmarginLeft, XmNmarginRight, XmNmarginTop,
  XmNmarginBottom
• XmNfontList
• XmNlabelPixmap
• XmNlabelString
• XmNinsensitivePixmap
• XmNrecomputeSize

17
XmPushButton Widget Class

• Very common
• characteristic Motif 3D look
• appear to protrude until pushed in

18
XmPushButton Class

• XmPushButton Class Resources
• XmNarmColor
• XmNarmPixmap
• XmNfillOnArm
• Callbacks
• XmNarmCallback
• XmNactivateCallback
• XmNdisarmCallback

19
XmSeparator Widget Class

• Used to separate areas of a window
• they can have several apperances
• no additional callbacks
• they support several resources
• XmNorientation
• XmHORIZONTAL and XmVERTICAL
• XmNseparatorType
• XmNO_LINE, XmSINGLE_LINE, XmDOUBLE_LINE,
  XmSINGLE_DASHED_LINE, XmDOUBLE_DASHED_LINE,
  XmSHADOW_ETCHED_OUT, XmSHADOW_ETCHED_IN,
  XmSHADOW_ETCHED_OUT_DASH, XmSHADOW_ETCHED_IN_DASH

20
Manager Widgets

• Used to combine child widgets into large
  applications
• They determine positions of the children
• must be subclasses of Xt's Composite class
• the Composite class provides support for handling
  multiple children
• the Constraint class supports position and size
  for each child

21
XmManager Widget Class

• Provides support for all Motif widgets that
  contain or manage other widgets
• inherit behavior from Core, Composite and
  Constraint
• is an abstract class and is never used directly
• adds support for
• top and bottom shadows
• input focus and keyboard navigation

22
XmManager Class Resources

• XmNforeground
• XmNshadowThickness
• XmNtopShadowColor, XmNbottomShadowColor
• XmNuserData

23
XmBulletinBoard Widget Class

• Simple layout strategy
• child is positioned by setting XmNx, XmNy
  resources
• don't usually move or resize children
• provides services and resources for subclasses

24
XmBulletinBoard Class Resources

• XmNshadowType
• XmSHADOW_IN, XmSHADOW_OUT, XmSHADOW_ETCHED_IN,
  XmSHADOW_ETCHED_OUT
• XmNshadowThickness
• XmNallowOverlap
• XmNresizePolicy
• XmRESIZE_NONE, XmRESIZE_ANY, XmRESIZE_GROW
• XmNbuttonFontList
• XmNlabelFontList
• XmNtextFontList
• XmNtextTranslations
• XmNfocusCallback

25
XmForm Widget Class

• Position their children based on values of
  constraint resources with each child
• resources specify child's position
• child can have "attachments" for their top,
  bottom, left, right sides
• supports dynamically resizable layouts
• flexible and widely used, but tricky to use

26
XmForm Class Resources

• XmNrubberPositioning
• XmNresizable
• XmNfractionBase

27
XmForm Class Constraint Resources

• XmNtopAttachment, XmNbottomAttachment,
  XmNleftAttachment, XmNrightAttachment
• XmATTACH_NONE, XmATTACH_FORM, XmATTACH_WIDGET,
  XmATTACH_OPPOSITE_WIDGET, XmATTACH_POSITION,
  XmATTACH_SELF
• XmNtopWidget, XmNbottomWidget, XmNleftWidget,
  XmNrightWidget
• XmNtopPosition, XmNbottomPosition,
  XmNleftPosition, XmNrightPosition
• XmNtopOffset, XmNbottomOffset, XmNleftOffset,
  XmNrightOffset

28
XmForm Attachment Error

• "Circular" attachments
• E.g. Do not attach the right side of widget A to
  the left side of widget B and the right side of
  widget B to the left side of widget A.

29
Shell Widget Class

• Abstract class of Composite
• Only supports one child
• Resources
• XmNallowShellResize
• XmNgeometry
• Callbacks
• XmNpopupCallback, XmNpopdownCallback

30
WmShell Widget Class

• Subclass of Shell class
• additional support for interacting with window
  manager
• Resources
• XmNbaseHeight, XmNbaseWidth
• XmNHeightInc, XmNwidthInc
• XmNinitialState
• XmNtitle
• XmNminWidth,XmNminHeight,XmNmaxWidth,XmNmaxHeight
• XmNiconPixmap
• XmNiconWindow