Hyperlinks are URLs (Internet hyperlinks) that are embedded into objects in a drawing. If an object has a hyperlink, double clicking on the object will launch an Internet browser using the object's URL. If an object does not have a hyperlink, double clicking on it will launch the Fields dialog.
Adding hyperlinks to objects:
1. Open the drawing's table.
2. Create a new field called URL that is of type URL or any text type (fixed or variable length ANSI or Unicode text).
3. For each object that is to have a hyperlink, enter the desired hyperlink into the object's record in the URL column.
When the mouse is double-clicked on an object in a drawing, Manifold goes to the URL field of the table, fetches the hyperlink stored there for that object and launches an Internet browser using that link. If the URL field is empty, or if it is not of database type "URL," Manifold will launch the Fields dialog for the object.
This provides a fast meaning for double clicking on an object in most cases. If the object has a URL an Internet browser is launched. If it does not have a URL, the Fields dialog pops open.
Example
We would like to use the Congress.map example provided on the Manifold CD to look up the web pages of each US congressional representative by double clicking on their district in a map.
Open the Congress Table associated with the Congress drawing. The table has a column called Web page that contains the URL of each congressional representative's web page. This Web page field is an ANSI Text field.
First we will rename the field to URL. Right-click on the Web page column head and choose Rename. Change the name to URL.
Next, we will change the field type to URL. Right click on the column head and choose Change Type. In the Column Type dialog, change the field type to URL. [Manifold has a "URL" database field type]. Press OK. Close the table window.
We can now open the Congress drawing window. Whenever we double-click on a congressional district in the drawing, Manifold will launch a browser window loaded with that representative's web page taken from the URL field. For example, we can double-click on Nevada (which has only one congressman for the entire state outside of Las Vegas).
Like magic, a browser window pops open with Congressman Jim Gibbon's web page in it.
If we wanted to see the fields associated with that district, we could have CTRL-double-clicked onto Nevada.
That will open the Object Fields dialog for that object.
More sophisticated uses
The example above shows URLs in use to open a very simple web page. We can also use URLs that are local references to files on our local hard disk. If such files are image files in a format that can be displayed in browsers (such as .jpg, .png or .gif) we can URLs to show pictures associated with objects.
Because web pages can be very rich and browsers can display all sorts of things automatically, we can use the general mechanism of specifying a hyperlink via a URL to display all sorts of things. For example, we could have a drawing that shows a factory floor plan with locations of different machines. For each machine we could have a URL pointing to a PDF document or other document that provides its user manual. Double clicking on the machine in the drawing will open its manual.
More dynamic information can be achieved by linking a table into the Manifold project from an external database and then forming a relation between the linked table and our drawing's table. If the linked table contains a URL field called "URL" and that column is brought in via a relation it will be used for the hyperlink. We could therefore keep a database of sites, documents, images or other information that dynamically changes so that whenever we double-click onto an object in the drawing the URL field to which the browser jumps will be taken from the external database provider's table.
Tech Tips
Since most drawings in GIS aren't used for Internet hyperlinks the fallback behavior of hyperlinks to launch the Fields dialog is a useful way of preserving double-click functionality for a quick look at object fields. However, in the case of drawings that are used for Internet hyperlinks if a particular object has an empty URL field the Fields dialog will also be launched. That may not be desired. To avoid this situation, create a simple web page that reports something like "This item does not have a web site" and save it on the local disk. In the table window select all records with an empty URL field and fill it with the local path to that web site.
For example, if we created an empty.html web page in the C:\tmp folder we would fill all empty URL fields in the table with C:\tmp\empty.html. When someone clicked on an object that did not have a web site the browser would launch using our empty.html web page.
Whether double-clicking an object launches a new browser window or appears within a previous browser window is set by your browser options. In Microsoft Internet Explorer, see Tools - Internet Options - Advanced and uncheck the Reuse windows for launching shortcuts box if you would like each URL to launch a new browser window.
When using drawings that contain hyperlinks within Manifold IMS applications we will probably also want to use layer restrictions