If you are in the business of producing statements for your customers, you are likely interested in adding some targeted advertising. Just adding an advertisement to a form is not hard – the hard part is figuring out how to add the advertisement without causing more pages to be added to your printed output. i.e. how do we place ads in the available whitespace.
To see what the end result looks like, open this sample form. On open we have determined that there is enough room for a very large ad, and we place a “flyer” that is 8 inches tall. Try adding more detail rows by pressing the “+” button. This causes the available white space to shrink and forces us to choose smaller advertisement subforms. After adding two rows, the ad shrinks to a 7 inch flyer. This continues until there is no room for any ads. But then after adding one or two more rows we spill over to a new page. Now once again there is room for a large ad on the second page.
Let’s take a closer look at how this form was designed.
Do nothing until layout:ready
Rendering a dynamic form goes through several processing stages:
- Loading content
- Merging data with template (create Form DOM)
- Executing calculations and validations
- Layout (pagination)
There a couple of script events that tell us when some of these processing stages are complete. The form:ready event fires when step 3 is complete. The layout:ready event fires after step 4.
Discovering whitespace is dependent on having a completed layout. Once all our content has been placed on pages we can examine the resulting placements. Consequently, we put the logic for placing our ad in a layout:ready event. But there is a problem: changing the form after layout:ready causes … another layout and another layout:ready event. Unless we are careful, we will cause an infinite loop of constant [re]layout. To guard against this, the form creates a form variable: vEvalTranspromo to indicate that we are ready for evaluation. Once we have placed our ad, we set it to false. Any time we change the structure of the form (add/remove a subform) we set it to true. (Note that normally we would do this on the server with a print form and would not worry about changes to the structure after the initial layout.)
Structuring the form
This example requires placing your ad content in your form at the spot where a page break will occur. At this location we place an ad container subform which is a wrapper that holds a series of [optional] child subforms of varying sizes. These child subforms hold the ad content. Initially there is no content in the ad container, so it has a height of zero and does not impact layout. Our whitespace calculation is based on taking the Y position of the ad container, and subtracting it from the height of the content area.
When we have discovered how much space is available, we create the largest possible child ad subform to fit.
This form looks at only one aspect of the transpromo problem: discovery/usage of whitespace. Another key component is to select ads based on context. If this were a credit card statement, we would select the ads based on the transaction and customer data. This level of logic requires some sort of integration with a rules engine. This could happen as a pre-processing step or as a web-service request during layout.
Until then, enjoy your holidays. ‘Peace on earth, goodwill toward men’.