“Easy” GUI Toolkits
Peter Centgraf
05-830 Advanced UI Software
Fall 2004
Introduction to the Problem(s)
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How do we define “Easy”?
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Low developer learning curve?
Maps well to some metaphor?
Low working memory load?
Low configuration/setup overhead?
No code?
Usable by ... non-developers? ... children?
Types of “Easy” UI Development
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Visual Prototyping
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Used in early design iteration
Simulates, rather than implements
Limited interactivity and computation
Sometimes bridged into RAD systems
Types of “Easy” UI Development
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Rapid Application Development
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Buzzword Alert!
Design priority on high turnaround rather than
unique and complex applications.
"Real" development => complete applications
Often focused on corporate IT/database apps
Types of “Easy” UI Development
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End User Programming
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"The document is the program“
Simple interactive documents and tools
Excel spreadsheets are EUP
... but so are Access forms!
... and Flash animations!
... and Alice 3D worlds!
Are these problems distinct?
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Yes … No … Sometimes
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Different domains, similar issues
Complexity/power tradeoffs at different scales
Remember this? <http://www-2.cs.cmu.edu/~NatProg/projectoverview.html>
Everybody Wants to Rule the World
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Many systems address these problems
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(Developers love to write developer tools!)
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Common design themes are often repeated
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The remainder of this talk will discuss:
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The most common approaches
(Many) systems that exemplify them
1…2…3… “Easy”
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1. Edit Visually
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2. Simplify the Model
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3. Use a High-Level Language
1. Edit Visually
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We’ve seen this all before…
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See Lecture 9 for more details
Editing graphical layouts with a graphical tool
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It just makes sense
It provides great productivity improvements
It has been reimplemented ad nauseum
1. Edit Visually
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Some are stand-alone tools
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Glade
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UI Builder for GTK+ Toolkit
Code generators for many languages
Dynamic interface from XML description
http://glade.gnome.org/
wxGlade
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UI Builder for wxWidgets Toolkit
Popular among Python developers
http://wxglade.sourceforge.net/
1. Edit Visually: Glade
1. Edit Visually: wxGlade
1. Edit Visually
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Some have additional development features
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Mac OS X Interface Builder
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Apple Cocoa or Carbon Toolkits
Tied to AppleScript or Objective-C code objects
Visual elements described in “nib” resource file
Component interactions via generated code
Some auto-generation of database access forms
“Test Mode” preview from user’s perspective
1. Edit Visually: Interface Builder
1. Edit Visually
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Some are part of complete IDEs
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Eclipse Visual Editor Project
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Sponsored by IBM
Supports Swing and SWT
Bi-directional code and visual editing
http://www.eclipse.org/vep/
NetBeans IDE
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Sponsored by Sun
Supports Swing, JSP, mobile Java
http://www.netbeans.org
1. Edit Visually: Eclipse Visual Editor
1. Edit Visually: NetBeans IDE
1. Edit Visually
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And many more…
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Visual Basic
Visual Studio .NET
Java Studio Creator
Borland Delphi, Kylix, JBuilder
IntelliJ IDEA
Need I go on?
2. Simplify the Model
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“Model” here refers to the program structure
A broad class of solutions
Move toward lower complexity and power
2. Simplify the Model
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Work with primarily static forms
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Match program to capabilities of visual designer
Dynamic elements limited to widget contents
Visual Basic is most prominent example
Sufficient for a wide variety of business apps
Most successful implementations allow extension
via languages with more dynamic capabilities
2. Simplify the Model: Visual Basic
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Visual Basic <= 6
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Second-highest google hit rate of all languages
according to http://www.dedasys.com/articles/language_popularity.html
Visual “forms” and pure-code “modules”
Uses event-based language to script widgets
Extensive library of COM/ActiveX components
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Common dialog types (OK-Cancel, Yes-No, etc.)
Web browser
Database-backed table and tree controls
2. Simplify the Model
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Layout containers
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Adds automatic continuous resizing to forms
A simple but important upgrade
More gracefully supports dynamic components
Also used in more complex toolkits, e.g. Swing
2. Simplify the Model: Tk
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Tk
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Created by John Ousterhout, 1988
Intended to be paired with his TCL script
Three simple layout managers
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Pack – places widgets in a vertical or horizontal group
Grid – aligns widgets in columns and rows
Place – manual absolute positioning
Nested “frames” with different layout managers
Complex layouts possible with simple combination
2. Simplify the Model: Tk
2. Simplify the Model: WindowsForms
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.NET Windows.Forms
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Used with Visual Basic.NET, C#, etc.
Adds dynamic layout via “dock” and “anchor”
“Docked” widgets snap to edge of frame
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When edge moves, widget resizes
“Anchored” widgets are fixed relative to edge
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When edge moves, widget moved an equal distance
2. Simplify the Model: WindowsForms
2. Simplify the Model: WindowsForms
2. Simplify the Model
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Stack of Cards Metaphor
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Pioneered by Apple HyperCard
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Emphasis on data navigation and persistence
“Stack” can take different forms
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… SuperCard, MetaCard, PythonCard, Dreamcard
Each card has a different layout, different functionality
Each card has the same layout, different data
Easily navigate forward/back or follow links
Persist all data in widgets with a single command
2. Simplify the Model: Revolution
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Runtime Revolution
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Cross-platform development environment
“Professional” version of Dreamcard
Combines stack metaphor with dynamic OO scripting
2. Simplify the Model
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Use High-Level Components
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Provide complex functionality in discrete units
Isolate intensely graphical or interactive code
Embed major portions of other applications
Best used in combination with:
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Visual Layout
Event-based Languages
Object-Oriented Languages
2. Simplify the Model: Mozilla Control
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Provides a full web
rendering component
Similar to MS Internet
Explorer control
Exposes events and
methods
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Respond to user action
Manipulate HTML DOM
2. Simplify the Model: PDFKit
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Provides a full PDF
rendering view
Exposes document
structure via methods
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Table of Contents
Bookmarks
PDFView no-code
viewer w/ printing, etc.
Separate projects for:
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Mac OS X 10.4
GNUstep
2. Simplify the Model
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Address a highly-specific domain
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Limit the scope of the toolkit
Support a particular niche
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Database editing forms
2D animations for children
2. Simplify the Model: Access Forms
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MS Access
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Visual form builder tool
Similar to VB layout tool
No scripting required
Widgets populated from
a database or query
2. Simplify the Model: HANDS
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HANDS
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Programming for children
Cards represent data
Scripts animate objects
Language innovations
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Aggregate operators
Tabular queries
Quick Break – 5 Minutes
3. Use a High-Level Language
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Simplified languages for simplified toolkits
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Reduce complexity
Increase code readability
Code in terms of user mental model
Encourage “fast and loose” development
Provide a structured, graphical code editor
3. Use a High-Level Language
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Wrapper libraries
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Expose a friendlier API to an existing toolkit
Hide some features, automate others
EasyGTK
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Dramatically reduces initialization code
Provides sane defaults for complex components
Simple “Hello World” from 30 lines to < 10
3. Use a High-Level Language: EasyGTK
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#include "easygtk.h"
GtkWidget *win, *box, *text, *button;
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void main(int argc, char *argv[])
{
gtk_init(&argc, &argv);
win e_window_create("Hello World", 400, 200, 100, 100, exit);
box e_box_create(win, E_VERTICAL, 2);
text e_text_create(box, FALSE, "Hello World!", E_NO_FUNC);
button e_button_create(box, "Close", exit);
gtk_main();
}
3. Use a High-Level Language
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“English-like” syntax
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Intends to emulate natural language
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No special symbols
Optional articles, prepositions – “a”, “the”, “of”, “to”
Enhances readability
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Statements are imperative verb clauses
Most code has direct spoken equivalent
3. Use a High-Level Language:AppleScript
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AppleScript
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Designed by Apple as end user scripting language
Send messages via “tell” block
Respond to events via “on” block
Handle errors with “try … on error” blocks
on clicked theObject
tell window of the object
try
set theRate to the contents of text field "rate" as number
set theAmount to contents of text field "amount" as a number
set the contents of text field "total" to 0
3. Use a High-Level Language: Transcript
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Native language of Runtime Revolution
Provides high-level facilities
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Events
Aggregate operators
Regular expression matching
if workQueue is not empty then
send "doWork" to me in .0001 seconds
put the result into gWorkMessage
else
close file gLogFile
enable group "optionalControlGroup"
end if
3. Use a High-Level Language
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Event-based languages
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Almost all languages support this style
Some make events and handlers first-class
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VB – Event handlers are primary code entry points
AppleScript – “on” and “tell” blocks
Transcript – “send” command
EasyGTK – callback functions
SUIT – “Interest procedures”
Maps to stimulus-response mental model
3. Use a High-Level Language
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Dynamic typing and conversion
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Common among scripting languages
Automatically converts data types when needed
Encourages focus on action rather than data
Examples:
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VB “Variant” type
All AppleScript variables
Global variables
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All AppleScript variables
Tk components in TCL container heirarchy
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.window.frame.button.label = “Click Me!”
3. Use a High-Level Language
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Structured, graphical code editors
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Replace code with graphical blocks and menus
Syntax errors are impossible!
Can reduce semantic errors via static analysis
Visibility of options is extremely high
Slows down fast typists
3. Use a High-Level Language: Alice
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Alice
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Interactive 3D programming
Targeted to beginning programmers (early teens)
Supports:
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Events
Concurrency
Functional abstraction
Visual, guided debugging
3. Use a High-Level Language: Alice
3. Use a High-Level Language:
AgentSheets
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AgentSheets
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Sets of dynamic, interacting agents
Combines spreadsheet metaphor and productions
Spreadsheet organizes agents
Productions provide behavior
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Similar to events, provides explicit stimulus-response
Block editor for productions
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Less rigid than Alice
Allows typing of expressions and values
3. Use a High-Level Language:
AgentSheets
Conclusions
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“Easy” is not a simple thing
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Tradeoffs between power and simplicity
Different target audiences with different skills
Common issues and related solutions
Multiple Approaches
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Simplify the framework’s capabilities
Simplify the development language
Many ways to do both