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Views – an XML-based independent GUI system. Judith Bishop University of Pretoria, South Africa Nigel Horspool University of Victoria, Canada http://www.cs.up.ac.za/rotor. Motivation. Forward looking Move to platform independent GUI systems Integration of XML into languages (cf XEN) - PowerPoint PPT Presentation
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2nd Rotor Workshop 2003 1
Views – an XML-based independent GUI system
Judith BishopUniversity of Pretoria, South Africa
Nigel HorspoolUniversity of Victoria, Canada
http://www.cs.up.ac.za/rotor
2nd Rotor Workshop 2003 2
Motivation
Forward looking– Move to platform independent GUI systems– Integration of XML into languages (cf XEN)
Technical– Rotor does not have a GUI capability– Interesting challenges in Reflection, RegEx etc
Educational– Dissatisfaction with method-oriented or drag and drop GUIs– Separation of concerns
2nd Rotor Workshop 2003 3
The reality of a single cross-language, cross-platform GUI interface programming model is in sight, based on an XML description language supported by fast native
runtimes. [Russel Jones, DevX, Nov 2002]
Supporting many GUIs isn't just a simple process of including one set of libraries or another; it's often a frustrating and error-prone exercise in writing GUI-
specific code. [Russel Jones, DevX, Aug 2003]
Where GUIs are going
2nd Rotor Workshop 2003 4
VS.NET
Common Language Runtime
System
System.Data(ADO.NET)
System.Xml
System.Drawing
System.Web(ASP.NET)
System.WinForms
SDK Tools
Rotor CLI Implementation
C#
JScript
Platform Abstraction
System.WinForms
2nd Rotor Workshop 2003 5
GUI building today
GUI BuilderGUI Builder
Add ListenersAdd Listeners
Handlers
widget rendering in the OS
widget rendering in the OS
Visual Studio
C#
Windowswidget calls in a language
Application
2nd Rotor Workshop 2003 6
A GUI using XML
Application
Handlers
widget rendering in the OS
widget rendering in the OS
Control Engine
Add ListenersAdd Listeners
GUI
XML
Spec
GUI
XML
Spec
2nd Rotor Workshop 2003 7
Example in ViewsViews.Form f = new Views.Form(@"<Form> <vertical> <horizontal> <Button Name=Show/> <Button Name=Hide/> </horizontal> <PictureBox Name=pic Image='Jacarandas.jpg' Height=175/> </vertical></Form>" );
string c;for (;;) { c = f.GetControl(); if (c==null) break; PictureBox pb = f["pic"]; switch (c) { case ”Show" : pb.Show(); break; } case ”Hide" : pb.Hide(); break; } }}
No pixel positioning
No generated code
Separation of concerns
XML C#
2nd Rotor Workshop 2003 8
The Views Notationform: <form> controlGroup </form>controlGroup: <vertical> controlList </vertical>
| <horizontal> controlList </horizontal>controlList: { control }
textItemList: { <item> text </item> }control: controlGroup
| <Button/> | <CheckBox/>| <CheckedListBox> textItemList </CheckedListBox>| <DomainUpDown> textItemList </DomainUpDown>| <GroupBox> radioButtonList </GroupBox>| <Label/> | <ListBox/>| <OpenFileDialog/> | <SaveFileDialog/>| <PictureBox/> | <TextBox/>| <ProgressBar/> | <TrackBar/>
radioButtonList: { <RadioButton/> }
2nd Rotor Workshop 2003 9
The Eight Handler methodsForm(string spec,params)
The constructor.
void CloseGUI( )
Terminates the execution thread
string GetControl( )
Waits for the user to perform an action
string GetText(string name)
Returns the value of the Text attribute
int GetValue(string name)
Returns the Value attribute from TrackBar, ProgressBar and CheckBox
int GetValue(string name, int index) Returns the status of CheckBox at position index
void PutText(string name, string s)Displays the string in a TextBox or ListBox control.
void PutValue(string name, int v)Sets an integer value associated with a ProgressBar or CheckBox
Essentially five kinds of methods:
construct
close
getControl
get
put
PLUS … direct access
2nd Rotor Workshop 2003 10
Views1 implementation
RegEx API would be nice for normalising XML– If REs fail to match, hard to create a use friendly error message– did not use the RE package.
XML API produces poor error messages when reading XML– implemented our own lexical analyzer for the XML specifications– preprocess the user’s XML then use the XML package,
Views inverts the interaction logic of controls
– normally events cause invocation of handling routines asynchronously
– our simple interface has the user invoke Views to wait for an event to happen ...
s = form.GetControl();
switch(s) { ...
case "Push Me":
2nd Rotor Workshop 2003 11
Views2 implementation
Views2 is a general-purpose tool for creating sophisticated graph structures whose nodes are arbitrary class instances and where the structure layout is defined by a simple XML notation
Correspondence can be made to work with reflection:Views2.Create( "<TagName A1=V1 A2=V2 A3=V2 .. />" )
so we can introduce new tags without preprogramming Views for all controls
Views2 can handle asynchronous events<Button Name="Show" Click="ButtonClick"/>
c.f. show.Click += new EventHandler(ActionPerformed);
2nd Rotor Workshop 2003 12
Future Work
Completing Views2 and writing it up
Completing the TCL/Tk version and looking at alternative GUI tools
Completing a drag and drop stand-alone tool to emit Views XML
Further investigating the pedagogy
Thinking of asking MS to make Regex available in all operating systems – e.g. “PDA .NET environment we've seen doesn'tinclude the regexp
library, threading, reflection or a full version of collections.”
Long term – XML checking in the language
2nd Rotor Workshop 2003 13
References on www.cs.up.ac.za/rotor
Horspool R N and Bishop J M, Views - and independent GUI development tool for Rotor, 1st Rotor Workshop, Cambridge July 2002.
Bishop J M and Horspool R N, Views - a Vendor Independent Extensible Windowing System, presented at IFIP WG2.4 meeting, Dagstuhl, Germany, November 2002
Bishop J M, Horspool R N and Worrall B G, Experience with integrating Java with C# and .NET, JavaGrande, Seattle, November 2002, and Concurrency and Computation - Practice and Experience, to be published, January 2004
Bishop J M, Tutorial at RISE, University of Linkoping, Sweden, December 2002
Bishop J M and Horspool R N, Views report to Microsoft, January 2003
Bishop J M and Horspool R N, C# - the modular language for the 2000s. Tutorial at JMLC, Klagenfurt, August 2003
Bishop J M and Horspool R N, C# Concisely, Addison Wesley, appear October 2003.
Bishop J M and Horspool, Towards principles of GUI programming using Views, paper submitted to SIGCSE 2004.