Archives for category: Code

Really?

There’s a fresh debate raging in the JavaScript community. The battle lines are drawn between those who like all-in-one solutions for app development, and those who prefer to assemble the pieces themselves. Really, the fight is more between those who make these things, not those who use them.

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Good documentation doesn’t come easy

Documenting source code is rarely something a coder likes to do. I’m just as guilty as anyone else. I know it’s a “good thing”, but my natural inclination is to code first and document later. Sometimes later comes so late that it’s a chore to get it done. I’ve been forcing myself to document as I go, and it usually works out pretty well in the end.

I’m a control freak

What’s made this process easier for me is to completely dump the notion of auto-generated documentation (I’m looking at you, javadoc, jsdoc, yuidoc, ruby-doc and the like). Instead, I favor writing the documentation for a given piece of code with markdown.

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Warning: this is a short-term solution, it may cause interesting results in future versions of the webOS SDK, so use wisely.

One minor frustration I’ve run into with making JavaScript webOS apps (games in particular) is the mousemove events don’t seem to fire very often on custom controls. This is particularly noticeable when users finger-paint on canvas tags or drag elements around. I suspect that this quirk in the webOS webkit was introduced as a performance improvement, but running up against it can be painful.

A fix I’ve discovered is this simple CSS addition to any elements which need higher resolution mouse movement (er, touch movement, whichever):

myelement {
    -webkit-user-drag: element;
}

Just put any valid CSS selector in place of “myelement” above, and you should notice a marked improvement in mouse movement precision for the element(s) in question.

This is not a future-proof solution, because if Palm’s webkit properly supports this CSS property in the future, your users will be dragging a shadowed version of the control around in ways you probably don’t want. Please be sure and test this with new SDK versions and be ready to take it out of your app at some point.

Twelve minutes of Jo, showing the same JavaScript web app code running on webOS, iPhone, iPad, Android, Symbian and… Dashboard widgets? Yup. First in a series of videos, this screencast is a quick intro to the cross-platform capabilities of this JavaScript framework (both for mobile apps with PhoneGap and mobile web apps). Followup videos will cover making your first Jo app, getting it running with PhoneGap, theming it with CSS and other goodies. Enjoy!

You can also read more about this open source project at joapp.com.

The last post revealed how a simple call to PalmSystem from your JavaScript code opens the door for you to take a stock web app with your favorite framework and turn it into a simple webOS app without having the overhead (or the wealth of cool features, in the interest of fairness) of Mojo.

Continuing with my explorations in the webOS 1.4.5 SDK, I’ve picked out a couple of other useful calls to the PalmSystem object. Both can be added to the “hello world” example I started in part one, and they’re really quick.

Free-wheeling orientation

A common requirement for mobile apps is the ability to respond to device orientation. I’m still digging around to see where you can hook into these events, but in the meantime here’s a simple call which is quite useful:

window.PalmSystem.setWindowOrientation('free');

This tells webOS to let your app rotate along with the device orientation, switching from portrait to landscape as necessary. It’s a high-value one-liner call which should serve most orientation needs.

You can also specify a “locked” orientation with different strings in place of “free”. Options are: up (default portrait), down, left and right. So if you have a side-scroller game that would benefit from horizontal presentation, just use:

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One neat discovery I found in the webOS 1.4.5 SDK is that it is possible to have a simple app which doesn’t use Mojo. Why would you want to? Load time! Mojo brings a lot to the table, but if you want to use your own favorite JavaScript framework, much of that ends up being overhead and increases your app’s load time.

Step one: Make a web app and test it in Chrome or Safari.

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01//EN"
"http://www.w3.org/TR/html4/strict.dtd">
<html lang="en">
<head>
    <title>Hello</title>
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
</head>
<body>
    <h1>Hello World!</h1>
</body>
</html>

Save this into a new folder (using a folder name of “hello” in this example) as index.html. This will become your app folder. You can test your app in Chrome or Safari by simply opening this file in your browser. Not terribly impressive, but hey, it’s a start.

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