The styles manager in BX allows us to apply pre-set values easily to the resources of any number of widgets. Suppose, for example, we wanted a pushbutton with a label indicating “Dismiss”, a bold font, with a black foreground and a somewhat olive-colored background; we could use the style editor as shown in Figure 6. Saving this style to a DismissButtonStyle, our style hierarchy tree would look like Figure 7. When we create a pushbutton and apply the style, it would look like Figure 8.
In addition to being able to apply styles to multiple widgets at once, styles can easily be made shareable so they are available to other applications being developed.
BX has two modes of looking at widget hierarchies: class and instance. Class mode indicates what the predefined appearance and behavior of a component will be, in effect defining new types. Instance mode tailors them for a particular widget or component, so we can tweak what makes them different from others of the same type.
From the most general class, we can define more specific sub-classes, each time progressively getting more refined or changing and overriding things as we go along.
To save time redesigning our standard layout, we can join a number of logically related widgets together into a single entity by turning it into a class. This makes reuse a snap, since all newly created classes get added to the palette.
To create a class containing one or more widgets, select the highest-level widget to use, then select the “Make Class” menu option. In the previous widget tree containing a form widget with a few buttons and a scrolled list, I performed the “Make Class” operation, and now have a new component called ListProcessor which I can treat as a stand-alone component. It is much more than a simple widget, because we avoid having to delve into the depths of Xlib, Xt and Motif, remaining at a relatively high level without ever giving up control of any of the underlying widgets.
In class mode, we can use the widget class tree to select which resources to expose, giving us a simplified means to control our newly created component without the clutter of having to view every resource of every widget it contains. As a convenience, any resources flagged as “exposed” have set type methods defined, so we don't have to worry about the exact Motif name for widget resources and the functions to set them.
New class methods (functions and procedures) and data can be added easily when we select the class entity in the browser. Our resource editor puts us into class edit mode automatically when we click the “New” button to add data or methods. (See Figures 9 and 10.)
Our resource editor now appears as shown in Figure 11, with the new entry inserted. We can now select the “Edit” button, and if needed, our source code will be generated before whatever source editor is brought up. At this point, we can look at our code with the cursor placed automatically on the line where our function starts.
One thing we notice from the snapshot in Figure 12 are the “user code block” begin and end comments around the user code blocks. Anything between these can be modified by the programmer. BX reserves the right to make changes outside of these user code blocks, but will otherwise not interfere. BX avoids clobbering user-written code by scanning for and skipping over sections that are reserved by the developer. At the beginning of a project, these are empty lines bounded by the comment delimiters. Throughout the BX-generated code, these comment blocks will be found before, during and after any major code operation. This may seem superfluous to the new GUI programmer used to having only callback code stubs generated, but they can be a big help in tweaking final production code for major systems.
Fast/Flexible Linux OS Recovery
On Demand Now
In this live one-hour webinar, learn how to enhance your existing backup strategies for complete disaster recovery preparedness using Storix System Backup Administrator (SBAdmin), a highly flexible full-system recovery solution for UNIX and Linux systems.
Join Linux Journal's Shawn Powers and David Huffman, President/CEO, Storix, Inc.
Free to Linux Journal readers.Register Now!
- Devuan Beta Release
- May 2016 Issue of Linux Journal
- EnterpriseDB's EDB Postgres Advanced Server and EDB Postgres Enterprise Manager
- The US Government and Open-Source Software
- The Humble Hacker?
- BitTorrent Inc.'s Sync
- Open-Source Project Secretly Funded by CIA
- The Death of RoboVM
- New Container Image Standard Promises More Portable Apps
- AdaCore's SPARK Pro
In modern computer systems, privacy and security are mandatory. However, connections from the outside over public networks automatically imply risks. One easily available solution to avoid eavesdroppers’ attempts is SSH. But, its wide adoption during the past 21 years has made it a target for attackers, so hardening your system properly is a must.
Additionally, in highly regulated markets, you must comply with specific operational requirements, proving that you conform to standards and even that you have included new mandatory authentication methods, such as two-factor authentication. In this ebook, I discuss SSH and how to configure and manage it to guarantee that your network is safe, your data is secure and that you comply with relevant regulations.Get the Guide