895 export base pair lines

[rayzhuca]

Added export SVG support for base pair lines.

Changes

• Removed the old method of creating a separate method to filter selected base pairs as suggested.
• Modified _base_pairs(bool allow_mismatches) to _base_pairs(bool allow_mismatches, BuiltSet<Strand> selected_strands). Now base_pairs is this._base_pairs(false, strands.toBuiltSet()) and selected_base_pairs(BuiltSet<Strand> selected_strands) just calls _base_pairs directly.
• For each base pair, I added an id base_pair-{helix-id}-{offset} so we can identify the base pairs that is in selected_base_pairs.
• Created a new method List<Element> get_selected_base_pairs(Store<AppState> store) that mirrors the behavior of List<Element> get_selected_strands(Store<AppState> store) so that it adds the base pair HTML elements into the exported SVG.

[dave-doty]

I don't know why, but it's not working for me when copying a PNG image. I create this design:

Then select and copy image:

But when I paste into Powerpoint, no base pair lines:

It does work if I Export an SVG file:

Open the SVG file in Inkscape:

I suspect it would help to refactor the code exporting selected strands to SVG and to PNG to share more code, so that if one gets fixed so does the other.

[rayzhuca]

It should work now. It was a quick fix. In export_svg_middleware, there is an if statement. One branch is for ExportSvg and another is CopySelectedStandsToClipboardImage. I just had to call get_selected_base_pairs in both branches.

[rayzhuca]

The new commit renamed get_selected_strands and get_selected_base_pairs to get_svg_elements_of_strands and get_svg_elements_of_base_pairs as well as changes to function arguments. I also removed the long one-line and refactored two pieces of repeated of code into one function called get_selected_svg_elements.

[dave-doty]

I don't know why I didn't approve this last month. I'll approve it for now since it seems to look okay, hopefully there's not something I missed that needs to be done still.