Open Source DOM Component

Corner Pocket

Website popup menu

by Read Write Tools Jan 7, 2020

Abstract
The rwt-corner-pocket DOM component is a popup menu using both text and icons. It is suitable for targeting a small list of external websites.

Motivation

A website's main menu guides the visitor to internal documents, but occasionally there may be a desire to guide visitors to a short list of external websites that are somehow related.

The rwt-corner-pocket DOM component is normally kept hidden until needed, when it slides into the viewport from any one of its four corners. Visibility of the menu is under control of a separate button that triggers the component's toggleMenu method or its event interface.

The component has these features:

The position of the menu is relative to any one of the four viewport corners.
The menu has a title bar running vertically along its left edge.
Each menu item has both text and icon.
The menu item corresponding to the current page is highlighted when the page is loaded.
The menu has an event interface for showing/hiding itself.
The menu emits a custom event to close sibling menus and dialog boxes.
Menu items may be kept separate from the DOM component, allowing the webmaster to change its contents in a single centralized place. Alternatively, menu items may be slotted directly between the component's opening and closing tags.
A keyboard listener is provided to allow a shortcut key to expand/collapse the menu.

In the wild

To see an example of this component in use, visit the BLUEPHRASE website and press F9 "Find It Here". To understand what's going on under the hood, use the browser's inspector to view the HTML source code and network activity, and follow along as you read this documentation.

Prerequisites

The rwt-corner-pocket DOM component works in any browser that supports modern W3C standards. Templates are written using BLUEPHRASE notation, which can be compiled into HTML using the free Read Write View desktop app. It has no other prerequisites. Distribution and installation are done with either NPM or via Github.

Download

Download using NPM

OPTION 1: Familiar with Node.js and the package.json file?
Great. Install the component with this command:

npm install rwt-corner-pocket

OPTION 2: No prior experience using NPM?
Just follow these general steps:

Install Node.js/NPM on your development computer.
Create a package.json file in the root of your web project using the command:

npm init

Download and install the DOM component using the command:

npm install rwt-corner-pocket

Important note: This DOM component uses Node.js and NPM and package.json as a convenient distribution and installation mechanism. The DOM component itself does not need them.

Download using Github

If you prefer using Github directly, simply follow these steps:

Create a node_modules directory in the root of your web project.
Clone the rwt-corner-pocket DOM component into it using the command:

git clone https://github.com/readwritetools/rwt-corner-pocket.git

Using the DOM component

After installation, you need to add four things to your HTML page to make use of it.

Add a script tag to load the component's rwt-corner-pocket.js file:

<script src='/node_modules/rwt-corner-pocket/rwt-corner-pocket.js' type=module></script>

Add the component tag somewhere on the page.

For scripting purposes, apply an id attribute.
Apply a sourceref attribute with a reference to an HTML file containing the menu's hyperlinks.
Apply a titlebar attribute with the text that should appear along the left edge of the popup panel.
Apply a corner attribute with one of these values

top-left
top-right
bottom-left
bottom-right

Optionally, apply a shortcut attribute with something like F3, F4, etc. for hotkey access.
For WAI-ARIA accessibility apply a role=navigation attribute.
For simple menus, the sourceref may be omitted and the menu hyperlinks may be slotted into the DOM component. Simply place the hyperlinks directly between the <rwt-corner-pocket> and </rwt-corner-pocket> tags.
Here's an example HTML tag where the menu items are in a separate file:

<rwt-corner-pocket id=corner-pocket sourceref='/menu.html' corner='bottom-left' titlebar='Find It Here' shortcut=F3 role=navigation></rwt-corner-pocket>

Add a button for the visitor to click to show the dialog:

<a id=corner-pocket-button title='Find It Here (F3)'>✚</a>

Add a listener to respond to the click event:

<script type=module>
    document.getElementById('corner-pocket-button').addEventListener('click', (e) => {
        document.getElementById('corner-pocket').toggleDialog(e);
    });
</script>

Menu template

The content and format of the each menu item should follow this pattern, which uses an anchor <a> that encloses a paragraph <p> and an image <img>.

<a sourceref='https://example.com' tabindex=301 title='Example website'>
    <p>Example Website</p>
    <img src='/img/example-logo.png' />
</a>

Self identification

The menu item corresponding to the current page can be highlighted when it identifies itself to the menu. This is accomplished by adding a meta tag to the page where the content attribute specifies the URL of the menuitem to highlight, like this:

<meta name='corner-pocket:this-url' content='https://example.com' />

Customization

Menu items and sidebar sizing

The images that you provide should be square. They will be resized using the value you specify with the CSS --icon-size variable.

The height of each menuitem is specified with the --item-height variable. You must also specify how many menu items there are, using the --num-items variable. The overall height of the menu will be calculated by multiplying these two values. Vertical scroll bars are only shown when there are more items than specified here.

The overall width of the popup panel is specified with the --width variable. The width of the sidebar title is specified with --sidebar-width, and the remainder is allocated to the menuitem's text and icon.

The position of the panel's offset from the chosen corner is set with the --top, --left, --bottom, and --right variables. (Only the two variables corresponding to the chosen corner are needed.)

rwt-corner-pocket {
    --icon-size: 2rem;
    --item-height: 4rem;
    --num-items: 7;
    --sidebar-width: 2rem;
    --width: 20rem;
    --bottom: 30px;
    --left: 30px;
    --z-index: 1;
}

Menu color scheme

The default color palette for the menu uses a dark mode theme. You can use CSS to override the variables' defaults:

rwt-corner-pocket {
    --color: var(--white);
    --accent-color1: var(--yellow);
    --accent-color2: var(--gray);
    --background: var(--nav-black);
    --accent-background1: var(--light-black);
    --accent-background2: var(--medium-black);
    --accent-background3: var(--pure-black);
}

Life-cycle events

The component issues life-cycle events.

component-loaded: Sent when the component is fully loaded and ready to be used. As a convenience you can use the waitOnLoading() method which returns a promise that resolves when the component-loaded event is received. Call this asynchronously with await.

Event controllers

The menu can be controlled with its event interface.

toggle-corner-pocket: The component listens on DOM document for toggle-corner-pocket messages. Upon receipt it will expand or collapse the menu.
keydown: The component listens on DOM document for keydown messages. If the user presses the configured shortcut key (F9, F10, etc) it will collapse/expand the menu. The Esc key collapses the menu.
collapse-popup: The component listens on DOM document for collapse-popup messages, which are sent by sibling menus or dialog boxes. Upon receipt it will collapse itself.
click: The component listens on DOM document for click messages. When the user clicks anywhere outside the menu, it collapses itself.
The rwt-corner-pocket DOM component is licensed under the MIT License.