Theming in Kivy

Adding consistency to Kivy's Python UI tools

Kivy has a wonderful set of built-in widgets that can be extended in numerous ways. They have very useful behaviors, but their look and feel may not integrate well with your App or the platforms you are targeting. Kivy doesn’t support theming out of the box right now, but if you poke around enough, there are a range of options you can use to customize the default look of widgets without having to define your own inherited versions of them.

I’ll first introduce you to Kivy’s image atlases, which are less mysterious than they sound, and are important groundwork for understanding theming in Kivy. Then you’ll learn two different ways to do manual theming in Kivy, with an eye to future automation.

Introducing Atlases

To understand theming, you must first understand atlases. An atlas is essentially a collection of distinct images combined into a single image file for loading efficiency. A JSON file describes the location of the separate images inside that master image file so that Kivy can access them directly. If you’ve ever worked with CSS sprites, you know exactly what I’m talking about. If you haven’t, the following example should explain everything.

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Why Ruby blocks exist, part III

Never forget to clean up again!

Previous posts in this series used Ruby blocks to iterate over the items in a collection. We’re going to wrap up by showing a very different side of blocks – resource allocation and cleanup.

Close the door!

Here we have a Ruby class representing a refrigerator. Prior to accessing a refrigerator object’s contents via its contents method, you have to call its open method to open the door. (Sensible enough.) Read more…

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The book sprint

Not just for code anymore

OpenStack Operations GuideDo you really want a technical book for your project? Does your community need to provide more helpful docs to support even more users? Does your community have a lot of knowledge they need to get out of heads and into bits and bytes? Do you have a good mix of technical experts and technical writers and users who would enjoy each other’s company for a week of hard work?

If the answer is yes, then consider a book sprint. If you’re in the open source world, you may have heard of a code sprint. A book sprint is a similar event, with an intense collaborative authoring session time boxed by a few days or a week. People get together typically in person to author and complete a book in a week.

Generally speaking it’s best if you have an idea of the scope and audience for the book prior to holding the sprint. These discussions can take place on line, such as on a mailing list or in a wiki page or Etherpad. You can also meet with future collaborators regularly, but understand, the first day of your sprint your book will certainly take shape. As book sprinter Adam Hyde says, “While you may not know the exact book you want when you go into the sprint, by the end you will have the book you need.”

For the OpenStack Operations Guide, we held a five-day book sprint in February 2013. OpenStack releases every April and October, and this timing was nearly halfway between two release dates. With Adam as our facilitator, seven authors agreed to work together and we nervously awaited our fate. We asked, “Could we complete a book in a week?”

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5 PaaS anti-patterns

Common behavior to watch out for when transitioning to a PaaS

Getting Started with OpenShiftToday I am going to cover 5 ways developers may be on a Platform as a Service (PaaS) but have not really embraced the new platform effectively. If you have done any of these things below while building your application hosted on a PaaS, like OpenShift, Heroku, or Google App Engine, don’t feel bad:

  • PaaS is a relatively new concept in the development world and I think some of these patterns are only recently coming to light
  • I have seen veteran developers making these mistakes as they move to the new paradigm

One piece of terminology I will use throughout the article is container. When I am using this word I am referring to the piece of the PaaS that hosts the application and does the work. An application can be composed of multiple containers and the PaaS will probably have a method to add your favorite server-side tech to the container. On OpenShift this is called a gear while on Heroku it is called a dyno.

So without further ado, let’s dig in on some of the code smells in the cloud.

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Just fork it

Making forking the norm

Brian Kardell (вкαя∂εℓℓ)tweeted:

Kip Hamptonreplied:

Free and Open Source software licenses make forking legal. Git makes forking easy. GitHub makes it easy to fork sociably. Can we just make this normal?

The most visible recent fork – LibreSSL‘s blunt forking of OpenSSL – was widely reported as conflict. It’s certainly not a polite break, but the OpenSSL’s Apache-style license means it’s legal.

Meanwhile, in a reminder that specifications can fork too, Ian Hickson put his objections to the W3C forking a WHATWG spec on www-archive to make sure his complaints of plagiarism would be part of the permanent record. WHATWG specs are licensed CC0, so once again, it’s legal.

It seems to be a common pattern to want to grant rights, but only want other people to use those rights if they acknowledge our control. (I sometimes have similar tendencies, granted.) We hope that people will contribute to our works while recognizing our power and our ownership over those works. Even the fact that we have to choose licenses at the start of a project gives us a sense of ownership and control, often hiding the (excellent) lack of control that comes once those licenses are applied.

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Wait, where is my variable defined?

Learn JavaScript scope so you always know where your variables are defined

You may have noticed that Head First JavaScript Programming is released! Now that the book is done, we’ve got a few more Head First JavaScript Programming teasers for you. The book is aimed at those of you who are learning JavaScript from the ground up, and our goal with these teasers is to tease out a few characteristics of the language that might surprise you, trip you up, or that you might want to pay special attention to as you learn.

Whether you’re coming to JavaScript from another language, or you’re learning JavaScript as your first language, the way scope works — that is, when and where your variables are defined — might surprise you. Scope in JavaScript isn’t always intuitive, and it’s easy to make some simple mistakes that can cause your code to work in unexpected ways.

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