YUI Library Examples: Widget: Creating custom widget classes

Widget: Creating custom widget classes

Creating Custom Widget Classes

The Base class provides a build method which can be used to create custom versions of classes which derive from Base by adding extension classes to them.

Widget currently ships with four such extensions: WidgetPosition, WidgetStack, WidgetPositionExt and WidgetStdMod. These extensions are used to build the basic Overlay widget, but can also be used individually, to create custom versions of the base Widget class.

Widget with WidgetStdMod support

Adding the WidgetStdMod extension to Widget, creates a statically positioned Widget, with support for standard module format sections - header, body and footer, which maybe useful in portal type use cases, where the positioning/stacking capabilities which come bundled with Overlay are not required.

To create a custom class, we use Base.build, which is described in detail on the documention page for Base.

We pass in Widget as the main class we want to add extensions to, and WidgetStdMod as the extension we'd like added to the main class:

var StandardModule = Y.Base.build("standardModule", Y.Widget, [Y.WidgetStdMod]);
 
// Render from Markup
var stdmod = new StandardModule({
    contentBox: "#widget1",
    width:"12em",
    height:"12em"
});
stdmod.render();

var StandardModule = Y.Base.build("standardModule", Y.Widget, [Y.WidgetStdMod]);
 
// Render from Markup
var stdmod = new StandardModule({
    contentBox: "#widget1",
    width:"12em",
    height:"12em"
});
stdmod.render();

Base.build will:

1. Create a new class which extends Widget
2. Aggregate known Base and Widget fields, such as ATTRS and HTML_PARSER from WidgetStdMod on the new class
3. Augment prototype methods from WidgetStdMod onto the new class prototype

The first argument to build is the NAME of the new class we are creating, just like the NAME we define when extending the Widget class directly.

Note that the Widget class is unchanged, allowing you to still create Widget instances without any standard module support, along with StandardModule instances which have standard module support.

Testing It Out

The example attempts to set content on an instance of the newly created StandardModule class, using the setStdModContent method which is added by the extension (which would otherwise not exist on the Widget instance).

var contentInput = Y.one("#content");
var sectionInput = Y.one("#section");
 
// This should work, since the StandardModule widget has settable 
// header/body/footer sections
Y.on("click", function(e) {
 
    var content = contentInput.get("value");
    var section = sectionInput.get("value");
 
    stdmod.setStdModContent(section, content);
 
}, "#setContent");

var contentInput = Y.one("#content");
var sectionInput = Y.one("#section");
 
// This should work, since the StandardModule widget has settable 
// header/body/footer sections
Y.on("click", function(e) {
 
    var content = contentInput.get("value");
    var section = sectionInput.get("value");
 
    stdmod.setStdModContent(section, content);
 
}, "#setContent");

To verify that no unrequested features are added, we also attempt to move the instance using the move method, which is not part of the base Widget class, and would be added by the WidgetPosition extension. This verifies that the other example classes we'll create, which do create new classes which use WidgetPosition, have not modified the base Widget class.

// This shoud fail, since the StandardModule widget is not positionable
Y.on("click", function(e) {
    try {
        stdmod.move([0,0]);
    } catch (e) {
        alert("move() is " + typeof stdmod.move + ", stdmod.hasImpl(Y.WidgetPosition) : "
        + stdmod.hasImpl(Y.WidgetPosition));
    }
}, "#tryMove");

// This shoud fail, since the StandardModule widget is not positionable
Y.on("click", function(e) {
    try {
        stdmod.move([0,0]);
    } catch (e) {
        alert("move() is " + typeof stdmod.move + ", stdmod.hasImpl(Y.WidgetPosition) : "
        + stdmod.hasImpl(Y.WidgetPosition));
    }
}, "#tryMove");

Note that Base.build adds a hasImpl method to the built class, which allows you to query whether or not it has a particular extension applied.

CSS Considerations

We need to define the CSS which goes with this new StandardModule class we have created. The only rule really required out of the box is the rule which handles visibility (yui-standardmodule-hidden). The "standardmodule" used in the class name comes from the NAME property we set up for the new class, and is used to prefix all state related classes added to the widgets bounding box. Since the StandardModule class is not positionable, we use display:none to define the hidden state.

 
/* Visibility - How to handle visibility for this new widget */
.yui-standardmodule-hidden {
    display:none;
}

 
/* Visibility - How to handle visibility for this new widget */
.yui-standardmodule-hidden {
    display:none;
}

The other "yui-standardmodule" rules are only used to create the required look/feel for this particular example, and do not impact the StandardModule widget's functionality.

Widget with WidgetPosition and WidgetStack support

As with StandardModule, we use Base.build to create the new Positionable widget class. This time we add WidgetPosition and WidgetStack support to the base Widget class to create a basic XY positionable widget, with shimming and z-index support.

var Positionable = Y.Base.build("positionable", Y.Widget, 
                            [Y.WidgetPosition, Y.WidgetStack]);
 
// Render from markup
var positionable = new Positionable({
    contentBox: "#widget2",
    width:"10em",
    height:"10em",
    zIndex:1
});
positionable.render("#widget2-example");
 
var xy = Y.one("#widget2-example > p").getXY();
 
positionable.move(xy[0], xy[1]);

var Positionable = Y.Base.build("positionable", Y.Widget, 
                            [Y.WidgetPosition, Y.WidgetStack]);
 
// Render from markup
var positionable = new Positionable({
    contentBox: "#widget2",
    width:"10em",
    height:"10em",
    zIndex:1
});
positionable.render("#widget2-example");
 
var xy = Y.one("#widget2-example > p").getXY();
 
positionable.move(xy[0], xy[1]);

We don't add WidgetPositionExt or WidgetStdMod support, so the widget doesn't have extended positioning support (align, center) or standard module support. Hence we position it manually using the move method which the WidgetPosition extension provides.

Testing It Out

We should now be able to invoke the move method on an instance of the newly created Positionable class:

// This should work, since Positionable has basic XY Positioning support
Y.on("click", function(e) {
    var x = parseInt(xInput.get("value"));
    var y = parseInt(yInput.get("value"));
 
    positionable.move(x,y);
 
}, "#move");

// This should work, since Positionable has basic XY Positioning support
Y.on("click", function(e) {
    var x = parseInt(xInput.get("value"));
    var y = parseInt(yInput.get("value"));
 
    positionable.move(x,y);
 
}, "#move");

And, as with the StandardModule class, we should not be allowed to invoke any methods from an extension which we didn't request:

// This should fail, since Positionable does not have Standard Module sections
Y.on("click", function(e) {
    try {
        positionable.setStdModContent("header", "new content");
    } catch (e) {
        alert("setStdModContent() is " + typeof positionable.setStdModContent + 
            ", positionable.hasImpl(Y.WidgetStdMod) : " + positionable.hasImpl(Y.WidgetStdMod));
    }
}, "#tryContent");

// This should fail, since Positionable does not have Standard Module sections
Y.on("click", function(e) {
    try {
        positionable.setStdModContent("header", "new content");
    } catch (e) {
        alert("setStdModContent() is " + typeof positionable.setStdModContent + 
            ", positionable.hasImpl(Y.WidgetStdMod) : " + positionable.hasImpl(Y.WidgetStdMod));
    }
}, "#tryContent");

CSS Considerations

Since now we have a positionable widget, with z-index support, we set the widget to be absolutely positioned by default, and control it's hidden state using visibility as opposed to display

/* Define absolute positioning as the default for positionable widgets */
.yui-positionable {
    position:absolute;
}
 
/* 
   In order to be able to position the widget when hidden, we define hidden
   to use visibility, as opposed to display
*/
.yui-positionable-hidden {
    visibility:hidden;
}

/* Define absolute positioning as the default for positionable widgets */
.yui-positionable {
    position:absolute;
}
 
/* 
   In order to be able to position the widget when hidden, we define hidden
   to use visibility, as opposed to display
*/
.yui-positionable-hidden {
    visibility:hidden;
}

Widget with WidgetPosition, WidgetStack and WidgetPositionExt support

Lastly, we'll attempt to create a new widget class, which, in addition to basic positioning and stacking support, also has extended positioning support, allowing us to align it with other elements on the page.

Again, we use Base.build to create our new Alignable widget class, by combining WidgetPosition, WidgetStack and WidgetPositionExt with the base widget class:

var Alignable = Y.Base.build("alignable", Y.Widget, 
                    [Y.WidgetPosition, Y.WidgetPositionExt, Y.WidgetStack]);
 
var alignable = new Alignable({
    width:"13em",
    align : {
        node: "#widget3-example",
        points: ["cc", "cc"]
    },
    zIndex:1
});
alignable.get("contentBox").set("innerHTML", 
    '<strong>Alignable Widget</strong><div id="alignment"><p>#widget3-example</p> \
    <p>[center, center]</p></div>');
alignable.render("#widget3-example");

var Alignable = Y.Base.build("alignable", Y.Widget, 
                    [Y.WidgetPosition, Y.WidgetPositionExt, Y.WidgetStack]);
 
var alignable = new Alignable({
    width:"13em",
    align : {
        node: "#widget3-example",
        points: ["cc", "cc"]
    },
    zIndex:1
});
alignable.get("contentBox").set("innerHTML", 
    '<strong>Alignable Widget</strong><div id="alignment"><p>#widget3-example</p> \
    <p>[center, center]</p></div>');
alignable.render("#widget3-example");

Testing It Out

We'll attempt to align an instance of the Alignable class, using some of the additional attributes which WidgetPositionExt adds to the base Widget class: align and centered:

// Align left-center egde of widget to 
// right-center edge of the node with id "widget3-example"
alignable.set("align", {node:"#widget3-example", points:["lc", "rc"]});
 
// Align top-right corner of widget to 
// bottom-right corner of the node with id "widget3-example"
alignable.set("align", {node:"#widget3-example", points:["tr", "br"]});
 
// Center the widget in the node with id "widget3-example"
alignable.set("centered", "widget3-example");
 
// Align the right-center edge of the widget to 
// the right center edge of the viewport (since a node is not provided to 'align')
alignable.set("align", {points:["rc", "rc"]});
 
// Center the widget in the viewport (wince a node is not provided to 'centered')
alignable.set("centered", true);
 
// Return the node to it's original alignment 
// (centered in the node with id "widget3-example")
// NOTE: centered is a shortcut for align : { points:["cc", "cc"] }
alignable.set("align", {node:"#widget3-example", points:["cc", "cc"]});

// Align left-center egde of widget to 
// right-center edge of the node with id "widget3-example"
alignable.set("align", {node:"#widget3-example", points:["lc", "rc"]});
 
// Align top-right corner of widget to 
// bottom-right corner of the node with id "widget3-example"
alignable.set("align", {node:"#widget3-example", points:["tr", "br"]});
 
// Center the widget in the node with id "widget3-example"
alignable.set("centered", "widget3-example");
 
// Align the right-center edge of the widget to 
// the right center edge of the viewport (since a node is not provided to 'align')
alignable.set("align", {points:["rc", "rc"]});
 
// Center the widget in the viewport (wince a node is not provided to 'centered')
alignable.set("centered", true);
 
// Return the node to it's original alignment 
// (centered in the node with id "widget3-example")
// NOTE: centered is a shortcut for align : { points:["cc", "cc"] }
alignable.set("align", {node:"#widget3-example", points:["cc", "cc"]});

CSS Considerations

The Alignable widget class, has the same core CSS rules as the Positionable class, to define how it is positioned and how it is hidden:

/* Define absolute positioning as the default for alignable widgets */
.yui-alignable {
    position:absolute;
}
 
/* 
   In order to be able to position the widget when hidden, we define hidden
   to use visibility, as opposed to display
*/
.yui-alignable-hidden {
    visibility:hidden;
}

/* Define absolute positioning as the default for alignable widgets */
.yui-alignable {
    position:absolute;
}
 
/* 
   In order to be able to position the widget when hidden, we define hidden
   to use visibility, as opposed to display
*/
.yui-alignable-hidden {
    visibility:hidden;
}