Re: [platform-swt-dev] How does Accessible interface works ?

[Arnaud De Muyser <ademuyser@xxxxxxxxxx>]

Latest news...

setting breakpoint in swt.accessibility.Accessibility.get_accFocus()
method,
it appear that this method is called
only called 3 times.

As I understand the setFocus() method
(on my WinXP):
public void setFocus(int childID) {
         
      checkWidget();
         
      COM.NotifyWinEvent (COM.EVENT_OBJECT_FOCUS,
control.handle, COM.OBJID_CLIENT, childIDToOs(childID));
        }

This is the role of COM on EVENT_OBJECT_FOCUS
to call back get_accFocus() ... I think.
Does it means there can be a (silent)
problem during COM ... ?
(checkWidget() seems to be ok because
I can see none of the potentially raised error).

Continuing to dig...

Arnaud.

Carolyn MacLeod <Carolyn_MacLeod@xxxxxxxxxx>
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06/30/2004 05:06 PM

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Subject	Re: [platform-swt-dev] How does Accessible interface works ?

You're welcome. 

Think of the role as "what you want your custom widget to be like"
instead of "what it looks like" or anything.
So for example, if I was implementing my little test "for real",
I would probably make the red and blue squares behave very much like radio
buttons, including arrows to traverse and space to select, etc.

The subset of the Windows roles that we implemented match similar roles
on the GTK platform, so that's why we only have a subset. You will note
that it is a large and useful/typical subset - there's only a few esoteric
roles left out. But that is not to say that we wouldn't implement them
if there was a really good reason to do so. 

Good luck, 
Carolyn

Arnaud De Muyser <ademuyser@xxxxxxxxxx>
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06/30/2004 10:33 AM

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Subject	Re: [platform-swt-dev] How does Accessible interface works ?

Thanks Carolyn for the snippet, 
You know what ? I'm terribly jealous ... 
because I still don't understand why yours works fine whereas mine stop
to said anything after 3 times ... 
I'll do deep test, kneading your code to be closer to mine, perhaps I'll
learn interesting thing. 

I've put one eye on ROLE listed in microsoft's web page. Why SWT choose
to not implements all thing ? 
this is strange be role I've tested seems to be really important for Screen
reader. for example using a 
Tooltip role means screen reader (at least the one I used), finish to read
completly the text I return in getValue() 
before starting to read another one, whereas radiobutton role you use let
him stop read immediatly when a 
new text is ready. Role are also really important, because screen reader
said the name of role (ie: "Radio button"
for radio button role), and if we want to meet accessibility in the sense
to help people who need it, why do we 
confuse them reading "radio button" whereas there are no radio
button ... I mean they'll think they can use space
bar to select un select as if there are really a radio button ...
Perhaps in your snippet (and in my code), the closer role we can use is
ROLE_SYSTEM_DIAGRAM ... 

Thanks for the example, I'll seek in it, trying to understand what happen
to me. 
Arnaud.

Carolyn MacLeod <Carolyn_MacLeod@xxxxxxxxxx>
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06/29/2004 11:31 PM

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Subject	Re: [platform-swt-dev] How does Accessible interface works ?

Here is a little test snippet that I had lying around. It's a Canvas with
2 colored squares on it. Each of the squares can take focus (I happened
to use the tab key to traverse between them, but arrow keys is fine, too).
For the role, I just randomly called them "radio buttons" because
there's a "selected" one, and an "unselected" one.
What kind of role do you think your widget, or its "children",
should have? There are several roles on Windows that we did not implement
because other platforms did not have those particular accessible roles.
Here's the complete list of Windows roles, FYI. If you think one of them
is important to your application, please open a bugzilla feature request
against SWT and explain why you need that role. 

http://msdn.microsoft.com/library/en-us/msaa/msaaccrf_4nub.asp

For some production-quality examples of custom controls that have implemented
accessibile interfaces, please see CCombo, CLabel, CTabFolder, and StyledText
classes in the package org.eclipse.swt.custom. 

Good luck, 
Carolyn 

Here's the snippet: 


import org.eclipse.swt.*;
import org.eclipse.swt.graphics.*;
import org.eclipse.swt.widgets.*;
import org.eclipse.swt.events.*;
import org.eclipse.swt.accessibility.*;

public class
AccessibleShapes { 
      static
Display display; 
      static
Shell parentShell; 
      static
Shell shell; 
      static
Canvas canvas; 
      static
Accessible accessible; 
      static
int
focusShape = -1; 
      static
final
Rectangle blueBounds = new
Rectangle(20, 20, 100, 100); 
      static
final
Rectangle redBounds = new
Rectangle(140, 20, 100, 100); 
      static
boolean
dialog = false;
// true for dialog,
false for plain shell 
      
      public
static
void
main(String[] args) { 
              display = new
Display(); 
              if
(dialog) { 
                    
 parentShell = new
Shell(display); 
                    
 shell = new
Shell(parentShell); 
              } else
{ 
                    
 shell = new
Shell(display); 
              }
              shell.setText(dialog ?
"Dialog"
: "Shell");
              canvas = new
Canvas(shell, SWT.NONE); 
              canvas.setSize(260, 140);
              accessible = canvas.getAccessible();

              canvas.addPaintListener(new
PaintListener() { 
                    
 public
void
paintControl(PaintEvent e) { 
                    
         GC gc = e.gc; 
                    
         gc.setBackground(display.getSystemColor(SWT.COLOR_BLUE));
                    
         gc.fillRectangle(blueBounds);
                    
         if
(focusShape == 0) gc.drawFocus(blueBounds.x, blueBounds.y, blueBounds.width,
blueBounds.height); 

                    
         gc.setBackground(display.getSystemColor(SWT.COLOR_RED));
                    
         gc.fillRectangle(redBounds);
                    
         if
(focusShape == 1) gc.drawFocus(redBounds.x, redBounds.y, redBounds.width,
redBounds.height); 
                    
 } 
              });
              
              canvas.addMouseListener(new
MouseAdapter() { 
                    
 public
void
mouseDown(MouseEvent e) { 
                    
         if
(blueBounds.contains(e.x, e.y)) { 
                    
                 setFocus(0);
                    
         } else
if
(redBounds.contains(e.x, e.y)) { 
                    
                 setFocus(1);
                    
         } else
{ 
                    
                 setFocus(-1);
                    
         } 
                    
 } 
              });
              
              canvas.addFocusListener(new
FocusListener() { 
                    
 public
void
focusGained(FocusEvent e) { 
                    
         if
(focusShape == -1) { 
                    
                 accessible.setFocus(ACC.CHILDID_SELF);
                    
         } else
{ 
                    
                 accessible.setFocus(focusShape);
                    
         } 
                    
 } 
                    
 public
void
focusLost(FocusEvent e) { 
                    
 } 
              });
              
              canvas.addTraverseListener(new
TraverseListener() { 
                    
 public
void
keyTraversed(TraverseEvent e) { 
                    
         switch
(e.detail) { 
                    
                 case
SWT.TRAVERSE_TAB_NEXT: 
                    
                 case
SWT.TRAVERSE_TAB_PREVIOUS: 
                    
                     
   if
(focusShape == 0) setFocus(1); 
                    
                     
   else
setFocus(0); 
                    
                     
   e.doit = true;
                    
                     
   break;
                    
         } 
                    
 } 
              });

              accessible.addAccessibleListener(new
AccessibleAdapter() { 
                    
 public
void
getName(AccessibleEvent e) { 
                    
         switch
(e.childID) { 
                    
                 case
ACC.CHILDID_SELF: e.result = "Canvas";
break;
                    
                 case
0: e.result = "Blue";
break;
                    
                 case
1: e.result = "Red";
break;
                    
         } 
                    
 } 
              });
              accessible.addAccessibleControlListener(new
AccessibleControlAdapter() { 
                    
 public
void
getChildCount(AccessibleControlEvent e) { 
                    
         e.detail = 2; 
                    
 } 
                    
 public
void
getChildren(AccessibleControlEvent e) { 
                    
         e.children = new
Integer[] {new
Integer(0), new
Integer(1)}; 
                    
 } 
                    
 public
void
getChildAtPoint(AccessibleControlEvent e) { 
                    
         Point pt = canvas.toControl(e.x, e.y);
                    
         if
(blueBounds.contains(pt)) e.childID = 0; 
                    
         else
if
(redBounds.contains(pt)) e.childID = 1; 
                    
         else
e.childID = ACC.CHILDID_SELF; 
                    
 } 
                    
 public
void
getFocus(AccessibleControlEvent e) { 
                    
         if
(canvas.isFocusControl()) { 
                    
                 if
(focusShape == -1) e.childID = ACC.CHILDID_SELF; 
                    
                 else
e.childID = focusShape; 
                    
         } else
{ 
                    
                 e.childID
= ACC.CHILDID_NONE; 
                    
         } 
                    
 } 
                    
 public
void
getLocation(AccessibleControlEvent e) { 
                    
         switch
(e.childID) { 
                    
                 case
ACC.CHILDID_SELF: 
                    
                     
   Rectangle bounds = canvas.getBounds();
                    
                     
   e.x = bounds.x; e.y = bounds.y; e.width = bounds.width; e.height
= bounds.height; 
                    
                     
   break;
                    
                 case
0: 
                    
                     
   e.x = blueBounds.x; e.y = blueBounds.y; e.width = blueBounds.width;
e.height = blueBounds.height; 
                    
                     
   break;
                    
                 case
1: 
                    
                     
   e.x = redBounds.x; e.y = redBounds.y; e.width = redBounds.width;
e.height = redBounds.height; 
                    
                     
   break;
                    
         } 
                    
 } 
                    
 public
void
getRole(AccessibleControlEvent e) { 
                    
         switch
(e.childID) { 
                    
                 case
ACC.CHILDID_SELF: e.detail = ACC.ROLE_CLIENT_AREA; break;
                    
                 case
0: e.detail = ACC.ROLE_RADIOBUTTON; break;
                    
                 case
1: e.detail = ACC.ROLE_RADIOBUTTON; break;
                    
         } 
                    
 } 
                    
 public
void
getSelection(AccessibleControlEvent e) { 
                    
         if
(canvas.isFocusControl()) { 
                    
                 if
(focusShape == -1) e.childID = ACC.CHILDID_SELF; 
                    
                 else
e.childID = focusShape; 
                    
         } else
{ 
                    
                 e.childID
= ACC.CHILDID_NONE; 
                    
         } 
                    
 } 
                    
 public
void
getState(AccessibleControlEvent e) { 
                    
         e.detail = ACC.STATE_FOCUSABLE;
                    
         if
(e.childID == ACC.CHILDID_SELF) { 
                    
                 if
(canvas.isFocusControl() && focusShape == -1) e.detail |= ACC.STATE_FOCUSED;
                    
         } else
{ 
                    
                 e.detail
|= ACC.STATE_SELECTABLE; 
                    
                 if
(e.childID == focusShape) e.detail |= ACC.STATE_FOCUSED | ACC.STATE_SELECTED
| ACC.STATE_CHECKED; 
                    
         } 
                    
 } 
                    
 public
void
getValue(AccessibleControlEvent e) { 
                    
         switch
(e.childID) { 
                    
                 case
ACC.CHILDID_SELF: e.result = "none";
break;
                    
                 case
0: e.result = "blue";
break;
                    
                 case
1: e.result = "red";
break;
                    
         } 
                    
 } 
              });

              shell.pack();
              shell.open();
              if
(dialog) { 
                    
 parentShell.pack(); 
                    
 parentShell.open(); 
                    
 shell.setFocus(); 
                    
 shell = parentShell; 
              }
              canvas.setFocus();
              while
(!shell.isDisposed()) { 
                    
 if
(!display.readAndDispatch()) display.sleep(); 
              }
      } 
      
      static
void
setFocus(int
newFocusShape) { 
              focusShape = newFocusShape;
              canvas.redraw();
              if
(focusShape == -1) { 
                    
 accessible.setFocus(ACC.CHILDID_SELF); 
              } else
{ 
                    
 accessible.setFocus(focusShape); 
              }
      } 
}

Arnaud De Muyser <ademuyser@xxxxxxxxxx>
Sent by: platform-swt-dev-admin@xxxxxxxxxxx

06/29/2004 08:29 AM

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Subject	[platform-swt-dev] How does Accessible interface works ?

Hi, 

I'm trying to implement accessibility on a widget I've created (from swt.Canvas).
As I can see in Eclipse 3.0 help system I implement an "org.eclipse.swt.accessibility.AccessibleControlListener"
(see below), 
and I do the following to setup accessible inside my widget: "getAccessible().addAccessibleControlListener(
new MyAccessible() );". 

My widget contains inner rectangle which are able to get the "focus"
(only one can have focus at a time), 
user can give the focus from a rectangle to an other using arrows keys.
To implements full accessibility, when user change the focused rectangle,
I must to make the screen reader talking new data from focused rectangle,
to do this I write the following method: 
private void saidFocusedEvent() 
{ 
  this.getAccessible().setFocus( ACC.CHILDID_SELF );//doesn't work:
this.handle ); 
} 

I'm using two different screen reader: 
1/ first is the Microsoft's Narrator: 
     If this screen reader read all tooltips I open from my widget,
it never said things when I call "saidFocusedEvent" method.

2/second is Windows Eyes 4.5 SP3: 
     this one tell more things than Ms'Narrator, all tooltips,
all "text" I draw in my Widget, 
     But it said texts only for  the first 3 call of  "saidFocusedEvent()",
after that all call to "saidFocusedEvent()" are quiet ... to
bad ! 
     (sometimes it continue to read the first texts I've returned
in MyAccessible.getValue() for each "saidFocusedEvent()" call
... to bad too ). 
     (when it's quiet I can see none of the trace output I wrote
in method like if interface's method are never called ...).

Does anyone have experimented this kind of behaviour ?

As I'm not the only one in development team who experiment this kind of
things, 
I want to know where I'm wrong in my source code ?

How can I make my accessible implementation talk data when I want to do
it ? 

Does anyone knows what I must return in Accessible.getRole() method ? None
of the constants defined in ACC class suit me... 
and if I return nothing ... screen reader just said "Custom control"
without said text I return in getValue()... strange ?

Any help is really welcome, thanks a lot ! 

Arnaud. 


PS: AccessibleControlListener implementation: 

private class MyAccessible implements AccessibleControlListener
{ 
 public void getRole(AccessibleControlEvent e)
 { 
     e.detail=ACC.ROLE_TOOLTIP; //KO:_TABLECELL;//_SCROLLBAR;//_TOOLTIP;
//_LABEL; //KO:_CLIENT_AREA; 
System.out.println("[TITBW] Accessible["+this.hashCode()+"].getRole()");
      
 }   
 public void getValue(AccessibleControlEvent e) 
 { 
   e.result =getFocusedRectangleData(); 
System.out.println("[TIBTW] Accessible["+this.hashCode()+"].getValue()
said ?=<"+s+">");      
 } 
 public void getState(AccessibleControlEvent e)
 { 
   e.detail=ACC.STATE_FOCUSED ; 
System.out.println("[TITBW] Accessible["+this.hashCode()+"]
getState()");       
 } 
 public void getFocus( AccessibleControlEvent e)
 { 
System.out.println("[TITBW] Accessible["+this.hashCode()+"]
getFocus()"); 
   e.detail = ACC.CHILDID_SELF; 
 } 
 public void getChildAtPoint(AccessibleControlEvent e) {
System.out.println("[TITBW] Accessible["+this.hashCode()+"]
getChildAtPoint()"); 
 } 
 public void getLocation(AccessibleControlEvent e) {
System.out.println("[TITBW] Accessible["+this.hashCode()+"]
getLocation()"); 
 } 
 public void getChild(AccessibleControlEvent e) {
System.out.println("[TITBW] Accessible["+this.hashCode()+"]
getChild()"); 
 } 
 public void getChildCount(AccessibleControlEvent e) {
System.out.println("[TITBW] Accessible["+this.hashCode()+"]
getChildCount()"); 
 } 
 public void getDefaultAction(AccessibleControlEvent e) {
System.out.println("[TITBW] Accessible["+this.hashCode()+"]
getDefaultAction()"); 
 } 
 public void getSelection(AccessibleControlEvent e) {
System.out.println("[TITBW] Accessible["+this.hashCode()+"]
getSelection()"); 
    e.detail = ACC.CHILDID_SELF; //ThreadInfoByTimeWidget.this.handle;
 } 
 public void getChildren(AccessibleControlEvent e) {
System.out.println("[TITBW] Accessible["+this.hashCode()+"]
getChildren()"); 
 } 
}