BodyA printer driver in BeOS R5 is an add-on that exports a specific C interface. This add-on is used by the print_server to add a new printer, configure a page, configure the print job, and print the print job on the printer. This article describes how the print_server interfaces with the printer driver.
The print_server is responsible for maintaining common settings. BMessage objects are used to pass settings from the print_server to a printer driver and vice versa.
Body[Obnoxious, snotty narrator begins]
"....When last we left our heroes at Munstris Diveloperz Inc., they were left wondering how applications can be made truly simple. Some software just worked well and other software just seemed bad, but they couldn't figure out why. It seemed like finding a good software tool was no simpler a task than navigating a vast digital jungle with little more than a pocket knife while wishing for a razor-sharp machete.
This document describes the feature of the BeOS kernel to monitor nodes. First, there is an explanation of what kind of functionality we have to reproduce (along with the higher level API), then we will present the implementation in Haiku.
Requirements - Exported Functionality in BeOS From user-level, BeOS exports the following API as found in the storage/NodeMonitor.h header file:
status_t watch_node(const node_ref *node, uint32 flags, BMessenger target);
BodyI'm sorry, this is not about how to lock Haiku developers into basements to ensure they are most productive--it is a well known fact that this is BGA's speciality, anyway ;-) --no, I want to talk a bit about multiple threads and how to prevent them from mangling shared resources due to uncontrolled access.
Before you skip to the next article expecting to be bored to death by repetition of well-stressed basics, give me a chance to explain: Instead of wading through the fundamentals on BLocker or semaphores, I want to discuss a specific locking problem, for which I recently found, as I feel, quite an elegant solution.
BodyAlmost all of my recent coding efforts have gone into work on BMessage. Early on, I decided that wanted to try a more "modern" back-end to BMessage, something that would leverage the power of the STL. The end result is out there enough that I'm not sure I want to use it. At any rate, I'm not going to talk about that right now; maybe in another article, if you're all good.
BodyPart 1 Before the musicians in the audience get too excited, I'm not going to talk about getting together with buddies to crank out some tunes. Nor will the cooks in the audience find instructions on making the perfect fruit preserves. No, when I say Jamming, I refer to the act of using the Jam build tool.
In this first part of my series on the Jam build tool, I'm going to provide a high level overview as well as show the product of some of my recent labors with Jam: the Jamfile-engine.
BodyAll BeOS programs have "resources". Simply put, a resource is data that is bundled with your application's executable. Typical examples are the application's icons and its signature, but you can attach any data you want. Many applications store bitmaps, text, cursors, and even complete user interfaces (dialog boxes, menus, etc.) as resources.
This may sound a lot like attributes; after all, aren't attributes a way to store additional data alongside your files as well?
BodyThis second part of my introduction to MIDI programming on (Open)BeOS is about timing. If you read Part 1 and tried out the demo app, you may have noticed that playback of the notes really lagged behind if you quickly pressed several keys in a row. That is bad, because we want MIDI processing to be as real-time as possible. This article explains where the lag comes from, and shows you how to prevent it.
BodyOr rather, how to use MIDI on the BeOS and, of course, Haiku. MIDI stands for Musical Instrument Digital Interface and is a well-established protocol for controlling musical devices such as keyboards, synthesizers, drum computers, and a whole bunch of other stuff. The protocol is fairly simple and consists of commands such as "play this note" and "now use this instrument". You don't need to be a MIDI expert to write BeOS MIDI apps, but some knowledge of the protocol helps.
Note: this article was written by Daniel Reinhold who unfortunately left the Haiku project and thus doesn't have his own website account.
The OS scheduler is the heart (nearly literally) of any operating system, so it's got to be in good working order. It needs to be fast, efficient, and distribute the computer's resources fairly. But what does that really mean? What makes a good scheduler?
In order to better understand this critical component, I recently wrote a userland prototype that mimics a real scheduler. This is taking advantage of the 'friendly third option' in kernel development. That is, when you want to test (and/or otherwise examine) a piece of kernel level code, you either:
