Fix the zoom in DocViewer

[s_mccracken]

There is a problem with the zoom in DocViewer. As one zooms in the DocViewer scrolls up the document. For example:

• I start on page 7 of the document fully zoomed out
• I zoom in one step and now I am on page 6
• I zoom in another step and now I am on page 5
• Another step and I am looking at the bottom of page 4 and the top of page 5
• Another step and now I can only see the bottom of page 4
• Another step and I can see only the top of page 4
• Another step and I see only the bottom of page 3

As one zooms out this is reversed.

After contacting Canvas support I have been told that this is the intended behaviour. Two people at Canvas support have told me the same thing: the focal point of the zoom is the top left corner (the top left corner of what I am not sure). 

The following video explanation of one of the Canvas support engineers shows exactly what the problem is: VIDEO. (I am perplexed that the engineer giving the explanation seems to think the behaviour of the zoom tool she is demonstrating is reasonable.)

The sensible behaviour would be for the focal point of the zoom to be the top left corner of the currently visible part of the document. This is how most (if not all) PDF viewers' zooms work. It keeps the topmost and leftmost part of the visible page in the top left corner of the window when zooming in and out. I have been told I have to make a feature suggestion to fix the buggy/nonsensical behaviour of the zoom, so this is what I am doing:

My feature suggestion is:

Fix the zoom in DocViewer so it behaves like those in most PDF viewers (e.g. Adobe Acrobat Reader DC, SumatraPDF).

[Renee_Carney]

 @s_mccracken ‌

Thank you so much for this submission.  It was so kind of the lady in support to provide you with a video, and I'm sure others will find it helpful in understanding how it currently works.

I can appreciate this suggestion.  I know that I have worked with other systems and editors that track differently than I might expect them to when i zoom in and out.  We look forward to hearing what others think!

[mbizer]

Another problem with zoom is that although the document size will change, the size of the comment boxes does not. When zooming, the size of the comment boxes should change as well.

[cholling]

I liked the video as well as it helped me to understand how the zoom functions. That said, I think the way that zoom functions is not the most logical way and it causes me to ponder why developers thought this was the best method. I would like to hear the WHY behind this functionality as it currently stands.