java-gnome-developer

[Java-gnome-developer] Enabling and disabling cut/copy/delete actions based on text buffer selection

[Richard S. <ri...@r-...>]

I've been experimenting with the Java-Gnome libraries over the past few
days and made good progress. It has been an enjoyable and remarkably
productive few days, and I am impressed with the results.

I set myself an exercise of creating a simple text editor. It is working
well but I've run into a problem enabling and disabling actions based on
whether there is a selection in the text buffer. I want to disable the
cut/copy/delete menus and corresponding toolbar buttons when there is
nothing selected in the edit pane and enable them when there is a selection.

My solution to checking for a selection isn't very elegant. I have a
pair of event handlers, one for button released and one for key
released, that do exactly the same thing:

@Override
public boolean onButtonReleaseEvent(Widget w, EventButton e) {

	if (JEditMainWindow.getInstance() != null) {

		// Get a reference to the text buffer
		TextBuffer b =
			JEditMainWindow.getInstance()
			.getEditorPane()
			.getSourceView()
			.getBuffer();

		// Use the action group to enable/disable on selection	
		JEditMainWindow.getInstance()
			.getActions()
			.getValidOnSelection()
			.setSensitive(b.getHasSelection());
	}

	return false;

}

It does work, apart from one case. If I make a selection and then click
_inside_ the selection with the mouse, the selection clears but in the
handler above the buffer.getHasSelection() returns true. So my
cut/copy/delete buttons remain enabled until I click again or press a key.

(For clarification, the way I have designed this is that JEditMainWindow
is a singleton and getActions() returns a Map that exposes the actions
and action groups for the application).

Is my approach to this wrong? Is there another event I could use?

-- 
Regards,

Richard

Re: [Java-gnome-developer] Enabling and disabling cut/copy/delete actions based on text buffer selection

[Andrew C. <an...@op...>]

On Tue, 2010-08-03 at 11:32 +0100, Richard Senior wrote:

> public boolean onButtonReleaseEvent(Widget w, EventButton e) {

[snip]

> It does work, apart from one case. If I make a selection and then click
> _inside_ the selection with the mouse, the selection clears but in the
> handler above the buffer.getHasSelection() returns true. So my
> cut/copy/delete buttons remain enabled until I click again or press a key.
> ...
> Is there another event I could use?

I've always used Widget.ButtonPressEvent for this sort of thing; you
want to do your thing before GTK's default handers get to it.

[Widget.ButtonReleaseEvent is when you let go of the mouse, not when you
click it. I imagine you knew that, but you can sometimes fake yourself
our with what the right behaviour to hook into is. Same goes for key
presses; I work with Widget.KeyPressEvent most of the time, only rarely
does one need Widget.KeyReleaseEvent]

Anyway, give it a try and see how you go.

AfC
Sydney