Screen Vs. Print Output

[Context: HL Kit … Basic Concepts and Terminology … Manipulation of Visual Elements]

The Kit makes a critical distinction between output to the screen and output to the printer. Similarly, there are completely separate portals for the purpose of screen output versus for printed output. Layouts and templates are classified for screen versus print output based on their contents. Panels and sheets are only allowed to contain layouts that are designed for screen and print output, respectively. This begs the question of why?

The obvious distinction is that portals used on the screen will typically involve some means for the user to modify content, while portals for printed output are for display only. However, there are a number of on-screen portals that are solely for display purposes (i.e. labels, images, and fixed tables). In fact, those on-screen portals are the exact ones that have equivalent versions for printed output, so why couldn't those portals be the only ones allowed for output use? Because there is more going that may not be immediately obvious.

The key reason for the separation is that portals for printed output have some critically different needs from on-screen portals. By keeping the portals distinct from each other, those different needs and behaviors can't be inadvertently confused by authors. And by percolating that distinction up through the entire visual hierarchy, everything is kept clear for authors.

So what are some of these important distinctions? A quick sampling is provided below.

• Portals for output have different style needs from on-screen portals. Whether it be the use of color, special borders, or something, the visual for printed output are significantly different from on-screen display.
• Different portals needs to behave differently within printed output. For example, the titles drawn above major sections of printouts don't work the same and have different needs from the titles drawn above sections on-screen.
• For printed output, it is commonplace to need items of varying height within tables. On the screen, it's more valuable to use fixed height items with mouse-over regions so that everything is kept compact and easily scrolled through for long lists.
• The scaling logic used for images can be different when displaying on a comparatively low-resolution screen versus on a high-resolution printer.

The list goes on, but this should give you a good idea of why the distinction between printed and on-screen output is important.