Browse Application

In this example we will create a Web browser. The browser accesses explicitly typed URLs and permits hyperlinking from the display.

Step 1: Create the application

• Create an empty application, switch to Intertask view, and enable the palette.
• Drag a text box task and drop it on the design space. This will be the text box for explicitly typing-in a URL. To put a static heading on this widget: double-click the task, select the "Graphic" dialog, change the caption to "URL:," and enable "Show caption."
• Drag-and-drop a "merge" task. The desired program behavior calls for treating URLs from two sources the same. Merge combines typed URLs with hyperlinks. (Note: the graphic uses name "asynchronous append" instead of "merge.")
• Create an arrow from URL: to merge.
• Drag an "HTTP Access" task and drop it on the design space. Connect the output of merge to the 7 o'clock position of this task (see discussion below about why 7 o'clock).
• Drag a "Textual HTML" task and drop it on the design space. Put a static heading on this widget saying "HTML page:" using the method described above.
• Connect the output of HTML page to the input of asynchronous append. The screen should appear as shown below.

• Switch to edit document view and reposition the widgets for a pleasing layout.
• Press the start button.
• Type-in a URL. Upon defocusing, the application will fetch and display the specified URL.
• Click on a hyperlink. The new URL will supersede the display. The screen should appear as shown below.

Discussion: The HTTP access task can access HTML data or submit forms, depending on its inputs. By convention, NetAlive uses 7 o'clock inputs for "dynamic addresses" like a URL, and the 9 o'clock input for data like "post data." The HTTP access task uses method GET or POST depending on whether a 9 o'clock input is present. NetAlive resolves relative URLs from the context of the last URL accessed (feature not implemented in version 0.0.3). The HTTP access task gets data from a standard HTTP server. (The HTTP access task has additional properties not described here.)

The Textual HTML task displays HTML input in a widget. The widget cannot be changed, but clicking on a hyperlink causes output of the hyperlink's URL. Version 0.0.3 of NetAlive can display HTML only as characters, hence the adjective "textual."

Completing the Application

• A typical Web browser maintains a history of HTML pages for backtracking, etc. The Textual HTML widget maintains such as history, but connection to "forward" and "backward" buttons.