Application design. how to do it better?

Question

Programming

In general, I make applications for mobile. platform for viewing djvu. But in this case it doesn't matter.
As in other applications, we can view pages, scroll, zoom.
While I'm doing it, I see 2 options for designing the so-called viewport (represents the user's screen).
Everyone has flaws. Therefore, I would like to hear advice, someone's experience is better.
Let's say we have pages placed vertically and a viewport.
1. When zooming, the page sizes are constant, and the viewport itself is reduced.
2. When zooming in, the page sizes increase, while the viewport itself remains unchanged (that is, according to the device screen size).
In the first option - calculation errors + headache with conversions to screen size
In the second, there are rather large errors in the calculation, due to which the picture twitches (therefore, it moves in all directions + - a few pixels). And at each stage of the zoom, you need to go through all the pages and resize - obviously overhead.
In general, I'm interested in how such a thing is implemented correctly, perhaps give a link to some kind of opensource application, where everything is very smooth and beautiful.
To make it more clear what the question is, take a look at the Android VuDroid application.
The 2nd idea is implemented there, due to which the zoom is already incredibly twitching on 500-600 pages.

Answer 1

Use a set of fixed viewport sizes for which implement a set of fixed zooms as in Nokia N900