Hi all,
I have a command object which toggles the value of a boolean property
"showLabel".
I also have a qx.ui.menu.CheckBox, which toggles "showLabel" indirectly
by using the command object.
Whenever the property value is changed, whether that's done by the
command object, the checkbox or some external source, I need the
checkbox state to reflect the new value. Obviously, this is easy to do
using data binding. Everything is fine when the property change is
initiated from the command object, or from the outside world.
But trouble arises when the change is initiated from the CheckBox. The
CheckBox automatically changes its checked state whenever its execute
event is fired. However, since the CheckBox uses the command object, the
execute itself changes the value of "showLabel", which (due to the data
binding) changes the checked state of the CheckBox. Chicken or the egg?
Not surprisingly, this results in strange/unwanted behaviour.
To prevent this the unwanted behaviour, I want to suppress the checkbox
behaviour of changing its checked state on execution. This can be done
by removing its internal "execute" listener right after creating the
checkbox:
button.removeListener("execute", button._onExecute, button, false);
This works, but since this makes use of unexposed CheckBox interiors: is
there's a better way of handling it?
Code example below:
********************************************************
qx.Class.define("test.Window", {
extend : qx.ui.window.Window,
construct : function() {
this.base(arguments);
this.setLayout(new qx.ui.layout.Canvas());
this.setWidth(300);
this.setHeight(200);
this._label = new qx.ui.basic.Label("Rightclick or press L to hide
this text.");
this.add(this._label);
this._command = new qx.ui.core.Command("L");
this._command.addListener("execute", this.toggleShowLabel, this);
this.initShowLabel(true);
this.setContextMenu(this._getMenu());
},
properties :
{
showLabel : {
deferredInit: true,
check: "Boolean",
apply: "_applyShowLabel",
event: "showLabelChanged"
}
},
members :
{
_label: null,
_command : null,
_applyShowLabel : function(value, old) {
this._label.setVisibility(value ? "visible" : "excluded");
},
_getMenu : function() {
var menu = new qx.ui.menu.Menu;
var button = new qx.ui.menu.CheckBox("Show label");
//suppress default behaviour of toggling checked value on execute
button.removeListener("execute", button._onExecute, button, false);
button.setCommand(this._command);
this.bind("showLabel", button, "value");
menu.add(button);
return menu;
}
}
});
********************************************************
If you comment out the removeListener line, you will notice that the
checkbox state will not be updated on the first "showLabel" change. All
subsequent showLabel changes will be passed to the checkbox, but its
state will be inverted.
Thanks,
Marc
------------------------------------------------------------------------------
This SF.net email is sponsored by Sprint
What will you do first with EVO, the first 4G phone?
Visit sprint.com/first -- http://p.sf.net/sfu/sprint-com-first
_______________________________________________
qooxdoo-devel mailing list
[email protected]
https://lists.sourceforge.net/lists/listinfo/qooxdoo-devel
