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.

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

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

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

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

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

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)

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)

Event Dispatching

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

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

The Core widget Class

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

Core widget class Resources

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

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

XmPrimitive Class Resources

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

XmLabel Widget Class

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

XmLabel Class Resources

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

XmPushButton Widget Class

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

XmPushButton Class

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

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

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

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

XmManager Class Resources

• XmNforeground
• XmNshadowThickness
• XmNtopShadowColor, XmNbottomShadowColor
• XmNuserData

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

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

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

XmForm Class Resources

• XmNrubberPositioning
• XmNresizable
• XmNfractionBase

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

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.

Shell Widget Class

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

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