Alternative Architectures for Hybrid Applications

Hybrid applications seem to be gaining traction now. In what follows, I’d like to present thoughts on an alternative to the emerging standard hybrid app architecture.

The conventional hybrid architecture

Conventional hybrid app architecture

In this model, which to the best of my knowledge is used by Electron, NW.js, and others, the user interface is rendered as HTML using whatever HTML, CSS, and front-end JS frameworks you desire. The use of Web technologies for the UI is an explicit goal of this architecture.

The UI is tightly bound in a one-to-one relationship with the app engine.1 The app engine is implemented with a Web back-end technology, typically Node.js. The app engine makes system calls through the engine’s baked-in features or through generic child_process.exec()-like calls. This means custom and platform-specific behaviors that the app may require will need to be implemented as external child_process.exec() callable units.

This architecture does a good job of leveraging Web technologies to create secure conventional desktop apps. In addition, frameworks like Electron and NW.js have matured to the point that developing hybrid apps that use many desktop app conventions is relatively easy.

An alternative hybrid architecture

In what follows, I present what I believe is a more flexible approach to developing hybrid apps—one that requires more carefully considered design but that yields greater flexibility.

Alternative hybrid app architecture

In this model, the tightly bound user↔app engine connection is replaced by a REST API. Thus the app engine becomes a REST server, possibly embellished with some needed superpowers for accessing host resources. When the app interface is API driven, any REST client technology can be used for the interface, including HTML/CSS/JS clients, native mobile clients, terminal clients, etc. In addition, the client need not be local, making remote-controlled apps almost trivial to implement. Adequate measures must be taken to assure secure and authorized communication with the REST server.

The other change in the above model is that the REST server is implemented in C++. When this is the case, interacting with the host system can be done directly using a wide range of C++ libraries written for this purpose. The choice of C++ here is somewhat arbitrary; it can be any language that supports ready-to-roll support for the system manipulations that your app requires.

The two changes outlined above are decoupled—meaning that either can be adopted in the absence of the other.

One downside to using C++ (or Java, or Python…) for the server part of this approach is that the server must be able to run on the host platform. This isn’t a significant issue with desktop deployment: only recompiling the REST server for each target platform will be required. But it does currently present a problem for mobile deployment as few mobile platforms provide native support for C++ and its oft used libraries. If you plan to target mobile apps, implementing a REST server in a more universally supported language will likely be required.

Follow updates on my wiki.


1. I’m using “app engine” generically here, not as a reference to Google’s App Engine.

Concerns about Qt’s increasing commercial focus

Road closed sign

It’s not just me. Phoronix is reporting on growing concerns in the Qt community about the project’s increasing commercial focus and apparent deprecation of its open source core.

I have said many times in these pages and elsewhere that I really like Qt: it’s the right tool for a lot of jobs. But increasingly I’ve been feeling that any contribution I make in educating users about Qt is benefiting a commercial enterprise and not a community tool. So much so that I am re-surveying other open source multi-platform libraries to use as an alternative to Qt.

If the community no longer has meaningful Qt ownership, a lot of users will no longer be interested.

Addressing some FUD on open vs. closed tech

Gate keepers

It’s a little early and so I may regret posting this, but I will do so anyway.

The Verge today is carrying a piece by Walt Mossberg that argues nothing is really open or really closed so, meh, don’t worry about it y’all ok? Because AppleGoogleMicroplex has your back.

His premise is that the debate between open and closed is false because the terminology is fuzzy. I’m pretty sure Walt is smarter than that. His premise is a festering pile of FUD.

For quite some time now, operationally valid and accepted definitions of “open source software” and “free and open source software” have existed. There’s no fuzziness in the terminology—if you understand the terminology. People involved in open source software have different motivations and philosophies for doing what they do, and this have led to different licenses that confer different rights and responsibilities to the licensee. They essentially break down into two camps: restrictive open source, where you must share all of your code modifications and derivations, and permissive open source, where you don’t have to share anything (but you might be required to attribute the original source with a copyright notice or similar). Both permit use in commercial projects.

Supporters of restrictive open source often strive for platforms that are fully open. Many powerful voices in FOSS today advocate for a computing and technological ecology where the user (the owner) has full and complete access to everything the device can do. They advocate that everything the device can do be documented completely in published, independently buildable and vettable source code and that the user (owner) should she wish be able to change any aspect of what the device can do to fit her needs or desires.

In the realm of communication devices, many advocates (myself included) feel that open access to software needs to extend to the radio units, GPS units, etc. And some (myself included) feel that hardware designs should be open source as well.

Thus there is no fuzziness in what people who engage with software development and those involved open source software movements mean by “open”. There is some fuzziness in application because those who advocate for completely open platforms are constrained by the products that are actually available (which are often built by those who use “open” tools only as leverage in their closed operations).

The other source of fuzziness is the straw-man FUD injected into consumers’ minds by articles like Mossberg’s.

“Open” can have several levels of completeness. However, there is nothing open about a house you buy that gives you access to only one or two rooms and lets you decorate them using only pre-approved designs that come out of an approved catalog. Confusing that with anything resembling “open” is the a serious bastardization of the concept.

Keep AVR open

road-closed-sign

About a week ago, I posted on G+ my concerns regarding the impact that Microchip’s purchase of Atmel might have for the Arduino ecosystem. Turns out I’m not alone, judging from the comments in the post from the Arduino folks that followed the same day.

Communities build incredible product loyalty, and open source (in addition to its other benefits) is an incredibly easy way to build community. Here’s hoping that Microchip realizes this and leaves a good formula alone.

More KiCad modules

kicad-appicon-128

I’ve added a bunch of modules to my KiCad library. These have not yet been vetted, so approach with caution. Here’s what’s new or changed:

  • New library mfk-ipc-7351-diode.mod with:
    • mfk-SOD3716X135N (SOD-123 diode)
  • New library mfk-smd-not-ipc.mod with:
    • mfk-fairchild-SOT23 (Fairchild version of SOT-23)
    • mfk-fairchild-SOT23_213 (as above but with “BEC” pinout)
    • mfk-fairchild-SOT233 (Fairchild version of SOT-233)
    • mfk-fairchild-SOT23_2313 (as above but with “BCEC” pinout)
  • Changes to mfk-ipc-7351-transistor.mod:
    • Deleted mfk-IPC7351-trans-SOT65P210X110-6N_10mil
    • Changed silk width in mfk-SOT65P210X110-6N (SOT363) to 10 mil.
  • New part in mfk-vishay.mod:
    • mfk-Vishay-TSOP341xx-alt (alt version of mfk-Vishay-TSOP341xx)
  • New part in mfk-keystone.mod:
    • Added mfk-KEYSTONE-621