Further fix of screen capture

[Benglin]

Purpose

NOTE: This was previously reviewed in #6893

Fix user reported issue #6834 where preview bubble goes beyond the edge of captured PNG image. This is mainly because the position of NodeView was replaced by the values of Canvas.LeftProperty and Canvas.TopProperty. These values should be used to compute the final offset (i.e. TranslateTransform) of image content prior to rendering it. The fix is to determine the minimum corner of the entire graph contents, and use it to offset the rendered image contents.

Before this fix:

After this fix:

Declarations

Check these if you believe they are true

• The code base is in a better state after this PR
• Is documented according to the standards
• The level of testing this PR includes is appropriate
• User facing strings, if any, are extracted into *.resx files
• All tests pass using the self-service CI.
• Snapshot of UI changes, if any.

Reviewers

Hi @ke-yu, please help to take a look at this fix, hopefully I have explained it with enough clarity. Thanks!

FYIs

Thanks for reporting this issue, @vykrum!

Hi @riteshchandawar, if this is tested working on the master branch, I will then cross-merge it to release branch. Thanks!