This document discusses graphical user interfaces (GUIs). It covers the basic components of GUIs like windows, menus, icons, pointers, and desktops. It also compares GUIs to command line interfaces and discusses interactive input methods. The document outlines principles for good GUI design such as consistency, feedback, and transparency. It provides examples of GUI programming code and discusses standards for computer graphics software interfaces.

1. UNIT II
Graphical User Interface
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2. Graphical User interface
• Program interface which takes the
advantage of computer graphics to make
program easier
• Text-keyboard oriented interface
• Command line interface
• Non graphical menu based interface
• Graphical user interface
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3. GUI-Introduction
• Elements of GUI- windows, pull down
menu, buttons, scroll bar, iconic images,
wizards, mouse etc.
• A systems GUI with its input devices is
also said as ‘look and feel’
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4. GUI as class widget
• A class widget can create object instances
for any application
• A widget (or control) is a graphical user
component that a computer user interacts
with such as a window,
• Widgets are the virtual buttons which can
be clicked from mouse
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5. GUI basic components
• Pointer- small angled arrow on screen or I
beam in text application
• Pointing device- Mouse or trackball to
select the objects
• Icons-Pictures that represent commands,
files or windows. They can be moved
• Desktop-Area on the display screen where
icons represent real objects on real desk
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6. • Windows-Screen is divided into different
areas, different programs or files can run
in different windows, their size and shape
can be changed.
• Menus-choice to select the commands are
placed on screen in menus
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7. GUIs vs CLIs
• Command line interface is the text only
interface which requires text strings to
cause the computer to take some action.
• CLIs makes all options accessible but
invisible and not easily remembered
• Users with vision or motion disabilities
prefer CLIs over GUIs.
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8. Interactive input methods
• Request mode- program sends the request to
the device and waits for its response.
• Sample mode- program and device work
independently.
When program requires any value it takes the
value from that device as per its status at that
instant. Ex –numeric pad.
 Event mode- device drives the program. Any
action by the mouse is identified and action is
taken.
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9. Design of GUI
To fulfill a given requirement designing an
interface is
• Part discipline (following platform
conventions and good design principle)
• Part science (usability testing)
• Part art (creating screen layouts that are
informative, intuitive and visually pleasing)
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10. • Tax returns can be filed without reading
manuals
• Car can be driven without knowing the
Working of automobile
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11. • Effective GUI requires functionality and
interface
• Functionality is what program actually
does
• Interface is how user interacts with
program
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12. Application development
• Visual basic, Delphi and visual C++ are
the commonly used tools for GUI
application development.
• They simplify the process of writing an
application while creating its visual
interface.
• The factors that work against creating a
successful GUI are: user centered design,
event driven programming
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13. Programming
Event driven Programming
• Tasks are performed in ordered fashion.
The user can enter data only when
directed
User driven programming
• User controls the program execution via
GUI events like entries using keystroke,
mouse click, light pen, voice command
etc.
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14. GUI examples (Dialog box)
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15. Good program vs great program
Early days
• Good program: one that works
• Great program: one that worked with
fewest resources
Today
Good program: one that works and is easy
to learn
Great program: one that works, user friendly
and need not be learnt
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16. Principles for good GUI design
1. User must be able to anticipate a
widget’s behaviour from its visual
properties-
Principle of consistency at widget level.
Widgets are visual controls like menus
checkbox, scroll bars etc.
Delphi software helps in creating widgets
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17. 17

18. Anticipate the behavior
2. User must be able to anticipate the
behavior of program using knowledge
gained from other program-
Principle of consistency at performance
level.
Consistency of cross platform with host
platform
Placement of menus icons and toolbars.
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20. Warnings and error dialog
3. User should view warnings and error dialog so
as to improve the program interface-
Good GUI rarely uses or needs warnings and error
dialogs.
Signal hardware problem like loose connection or
disk failure
Warnings that asks user consent to perform
irreversible or erroneous step.
Design your program for user to enter appropriate
data and disable the dependent steps.
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21. Error window
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22. Warning messages
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23. Feedback
4. Provide adequate user feedback-
Principle of user feedback applies to widgets and
program activity.
Ex. Click a button it suggests it is depressed.
Ex. Appearance of check box suggests that it is
selected.
Ex. User should know that a program is in
progress by hourglass or progress bar
Novice user should tell what steps are already
performed.
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25. Multimedia clips
5. Use sound, colour, animation and
multimedia clips sparingly-
Appropriate for education or entertainment.
Platforms have written convention that
describes the usage.
Include them only if user’s ability is
improved.
Colour and sound should not be the sole
means of communication. 25

26. Customize
6. Help user customize and preserve their
preferred work environment-
Depends whether the program is single user or
multi user.
Issues like size, location of a window.
Video issues like screen size, video resolution,
contrast.
Ex. Full screen interface looks good on 14 inch
VGA display but not in 17 inch display.
User should be permitted to customize and set
defaults 26

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29. Interface
7. Design an interface so that user can
accomplish their task without being aware
of interface-
Principle of transparency
Interface transparency occurs when user’s
attention is drawn away from interface and
directed at the task.
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30. Program window
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31. GUI programming examples
• A program that represents an application of
object windows. It creates a main window with
caption TEST that can be resized, moved,
minimized and closed
#include<ow1applicat.h>
Int OwlMain(int/*argc*/,char*/*argv*/[ ])
{
Return TApplication (“TEST”).Run( );
}
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32. _ X
TEST
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33. GUI programming examples
• Program to display a window with the title TEST;
message HELLO and an OK button
#include<window.h>
Int_stdcall WinMain(HINSTANCE hIstance,
HINSTANCE HPrevInstance, LPSTR)
Lpsz(Cmdline, intnCmdShow)
{
Messagebox (0, “Hello!”, “TEST”, 0);
Return(0);
}
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34. GUI programming examples
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35. Integration of graphics standard
Three essential system interfaces are:
• Application interface
• Device interface
• User interface
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38. Computer Graphics software
• The application programmer interface is
represented by four standard efforts:
1. GKS (Graphics Kernel system)
2. GKS 3D
3. PHIGS (Programmers Hierarchical
Interactive Graphics System)
4. PHIGS +
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39. GKS
• It is an international standard
• Portability of software among different
hardware is possible.
• It has ability to write device independent
graphics program.
• Program can fully exploit all the facilities
offered by the hardware.
• Initially developed for 2D but came up with
3D support as well.
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40. PHIGS
• Extension of GKS.
• Defines a set of functions and data structures
to manipulate 3D objects
• Increased capability of modeling, rendering
and manipulation.
• Provides the programmer with complete
environment containing hierarchical buffers;
• To store scene description
• And to modify interactively
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41. Device interface
• Software concerned with storage and
transmission of data
• Between graphics system and CAD/CAM
are
• IGES,DXF,STEP,PDES etc.
• IGES and DXF are widely used standards
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42. DXF
• Drawing interchange format developed by
AutoCAD developers.
• CAD/CAM software can import or export
this file format.
• DXF file is normally an ASCII readable
text file.
• Easy to read, to understand and to
manually manipulate.
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43. IGES
• Initial Graphics Exchange Specification is
designed to exchange engineering
characteristics.
• Exchange between CAD software, Reverse
Engineering, RP machines, CAM systems
etc.
• Fundamental unit of data in this file is entity.
• Entities can be geometric or non geometric
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44. • Geometric entities represent physical
shapes like points, curves, surfaces, solids
etc.
• Non geometric entities serve to enrich the
model by providing viewing perspective.
• The file format treats the product definition
as a file of entities.
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45. Thank you
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