Can anyone tell, why it is so extremely complicated just to change state of the button and update others?
Why this simple thing can be an issue?

There are a few places in the Eclipse code with comments about the state attribute and the IMenuStateIds.STYLE. From what I can tell these are old references. This is how things were done in the older IAction world, but it is no longer applicable in the new, declarative world. For more information see eclipse bug 154130 (esp. the part after hahaha in https://bugs.eclipse.org/bugs/show_bug.cgi?id=154130#c27).

The bottom line seems to be that the command state is not linked (and is not planned to be linked) to the UI widget’s state.

Comment 31 (in the same bug) has a pointer to the real solution. In short, make your Handler implement IElementUpdater and then provide an implementation of updateElement that calls #setChecked on the argument uiElement.

A pretty simple and clean solution. Unfortunately took me a few hours to find, hopefully this note will save other people some time.

Suppose you have 2 editor instances, and each one has a handler for the same command, but the checked state differs in each one. Switching the active editor doesn’t update the check state.

It looks like that updateElement() and refreshElements() do nothing.

package de.ralfebert.rcputil;

import java.util.Map;

import org.eclipse.core.commands.AbstractHandler;
import org.eclipse.core.commands.Command;
import org.eclipse.core.commands.ExecutionEvent;
import org.eclipse.core.commands.ExecutionException;
import org.eclipse.core.commands.State;
import org.eclipse.jface.menus.IMenuStateIds;
import org.eclipse.ui.PlatformUI;
import org.eclipse.ui.commands.ICommandService;
import org.eclipse.ui.commands.IElementUpdater;
import org.eclipse.ui.menus.UIElement;

/**
* Use this handler for style=”toggle” command contributions. You need to
* declare a state like this to use this:
*
*
*
*
*
*
*
* The id=”STYLE” is chosen because of IMenuStateIds.STYLE – maybe this will
* work without any Handler Foo in later Eclipse versions.
*
* @author Ralf Ebert
*/
public abstract class ToggleHandler extends AbstractHandler implements IElementUpdater {

private String commandId;

public final Object execute(ExecutionEvent event) throws ExecutionException {
ICommandService commandService = (ICommandService) PlatformUI.getWorkbench().getService(ICommandService.class);
this.commandId = event.getCommand().getId();

State state = event.getCommand().getState(IMenuStateIds.STYLE);
if (state == null)
throw new ExecutionException(
“You need to declare a ToggleState with id=STYLE for your command to use ToggleHandler!”);
boolean currentState = (Boolean) state.getValue();
boolean newState = !currentState;
state.setValue(newState);
executeToggle(event, newState);
commandService.refreshElements(event.getCommand().getId(), null);

// return value is reserved for future apis
return null;
}

protected abstract void executeToggle(ExecutionEvent event, boolean newState);

public void updateElement(UIElement element, Map parameters) {
if (this.commandId != null) {
ICommandService commandService = (ICommandService) PlatformUI.getWorkbench().getService(
ICommandService.class);
Command command = commandService.getCommand(commandId);
element.setChecked((Boolean) command.getState(IMenuStateIds.STYLE).getValue());
}
}

}

it seems that the ToggleState does NOT track the state of the “of the button in the UI”. At least it is never updated by itself. In your example you set the state yourself by toggling the state in parallel:

state.setValue(!(Boolean) state.getValue());

But this is completely unrelated to the actual “toggle” state of the command, isn’t it?

I found “IMenuStateIds.STYLE”, and according to the javadocs, you should get the widget state by naming the state “STYLE”. But this does not work as described.

Ralf

Good to see that you have also brought that question over to the newsgroup. I have also heard of the “:true” flag on the command id but as for you, that didn’t work for me. As in the newsgroup post, i’ll also link to the relevant bug here.