Re: [nebula-dev] How to receive ok event only in CDateTime widget?

[Wim Jongman <wim.jongman@xxxxxxxxx>]

Hi Matthias,

Another option is to throttle the selection. Databinding has support for that. Try this snippet:

import org.eclipse.core.databinding.observable.Realm;
import org.eclipse.core.databinding.observable.sideeffect.ISideEffect;
import org.eclipse.core.databinding.observable.sideeffect.ISideEffectFactory;
import org.eclipse.core.databinding.observable.value.IObservableValue;
import org.eclipse.jface.databinding.swt.DisplayRealm;
import org.eclipse.jface.databinding.swt.WidgetSideEffects;
import org.eclipse.jface.databinding.swt.typed.WidgetProperties;
import org.eclipse.jface.layout.GridDataFactory;
import org.eclipse.jface.layout.GridLayoutFactory;
import org.eclipse.swt.SWT;
import org.eclipse.swt.layout.GridData;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Label;
import org.eclipse.swt.widgets.Shell;
import org.eclipse.swt.widgets.Text;

/**
 * This snippet shows how to use the {@link ISideEffect} class together with a
 * delayed IObservable with a {@link Text} widget. If text is entered the side
 * effect is triggered with a delay
 *
 * @since 3.2
 *
 */
public class SnippetSideEffect50_DelayedUpdate {
/**
* @wbp.parser.entryPoint
*/
public static void main(String[] args) {
Display display = new Display();

Realm.runWithDefault(DisplayRealm.getRealm(display), () -> {
// create the Task model object
final Shell shell = new View().createShell();
Display display1 = Display.getCurrent();
while (!shell.isDisposed()) {
if (!display1.readAndDispatch()) {
display1.sleep();
}
}
});
}


static class View {
private Text summaryText;
private Label resultLabel;


public Shell createShell() {
Display display = Display.getDefault();
Shell shell = new Shell(display);
GridLayoutFactory.fillDefaults().applyTo(shell);
GridDataFactory gridDataFactory = GridDataFactory.fillDefaults().grab(true, false);

Label label = new Label(shell, SWT.NONE);
label.setLayoutData(
new GridData(SWT.BEGINNING, SWT.CENTER, false, false));
label.setText("Wait for it....");

resultLabel = new Label(shell, SWT.NONE);
resultLabel.setText("");
gridDataFactory.applyTo(resultLabel);

// create a Text widget, which will be bound to the Task summary
summaryText = new Text(shell, SWT.BORDER);
gridDataFactory.applyTo(summaryText);


bindData();

// Open and return the Shell
shell.pack();
shell.open();

return shell;
}

private void bindData() {

ISideEffectFactory sideEffectFactory = WidgetSideEffects.createFactory(summaryText);

// create the observables, which should be bound by the SideEffect
IObservableValue<String> textModifyObservable = WidgetProperties.text(SWT.Modify).observeDelayed(1000,
summaryText);

sideEffectFactory.create(textModifyObservable::getValue, e -> {
resultLabel.setText(summaryText.getText());
});
}
}

}

On Mon, Mar 15, 2021 at 12:17 PM Matthias Paul Scholz <matthias.paul.scholz@xxxxxxxxx> wrote:

Hi Wim,

I'm aware that the concept of an edit transction makes sense for the graphical mode only where the user has some sort of "edit session".
But at least in that case I think there should be such a concept and the API should provide  a possibility to hook into it.

By the way, I wonder whether both a programmer and the user actually expects that  the value of the widget gets changed already before she presses Enter or clicks the green hook.

Best,
  MP

Am Mo., 15. März 2021 um 11:28 Uhr schrieb Wim Jongman <wim.jongman@xxxxxxxxx>:

Hi Matthias,

It depends on how you use the widget. CDateTime has many faces. When using the widget in its simplest form, there is no concept of Enter or OK. So it means that databinding has to be different based on the style of the widget.

Cheers,

Wim

On Mon, Mar 15, 2021 at 10:08 AM Matthias Paul Scholz <matthias.paul.scholz@xxxxxxxxx> wrote:

Hi all,

For some years we have used the CDateTime widget in our RCP application which works quite good. :)

However, we ran in some troubles lately: to get notion about changes the user made in the widget,  we use the databinding proposed by Henno Vermeulen (see https://www.eclipse.org/forums/index.php/t/172877) that binds our application to a selection event in the widget.

There's an issue with that approach, however: it seems that such a selection event is triggered always on each selection inside of the widget. For instance, when the user cycles through the months in the calendar drop down or selects another day, each time a separate selection event is fired. 

This is inconvenient for us, since we need an event only when the user explicitely commits her changes by selecting the ok button (or pressing enter).

This has become crucial for us lately since we have a new use case now where a change in the widget triggers an expensive backend operation - and it is a no go when this happens each time the user changes the month in the calendar drop down ...

Is there a possibility to listen for or to bind to ok/enter events on the CDateTime widget only?

Thanks,
  MP

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