editor: highlight multiple selections and words on cursor

[azizk]

Hi!

I reworked the paint_selection_find function so that:

• Multiple cursor regions are taken into account.
• data.doc.selection_find is used directly because a FindProgress isn't really necessary for an implicit search like this which is also limited to the visible lines.
• The "active" selection under the cursor isn't filled with a color as it's distracting and makes only sense with a Ctrl+F search.
• The phantom text (to the right) isn't included in the rectangular highlight (also fixed for Ctrl+F).
• Selecting backwards is working (start and end are swapped).
• Renamed variables for readability.

Notes/Issues:

• I'm still learning Rust, so there may be beginner mistakes.
• The code for getting multiple regions and iterating over them seems correct to me, but it doesn't actually highlight all selections. Only those of the first cursor. Not experienced enough to debug this.
• I left the curly braces block in there after removing the if clause, so that the diff remains readable.

[azizk]

I fixed the issue with the highlighting of multiple selection regions. ✌️ (select_word() wasn't given the correct variable)

I also made the change to match whole words if the SelRegion is a caret. If non-empty text is selected, the search is done without checking word boundaries. Maybe we can add an option in the future for enabling or disabling the case sensitivity of the search.

Edit: I just noticed that it already takes the case sensitivity setting from the Ctrl+F search box. 😆
Edit2: It didn't, but I fixed that later on.

[azizk]

More fixes and improvements:

• Completely removed unneeded update_selection_find function.
• Call paint_selection_find after highlight_scope_and_brackets so the highlight rectangle is drawn over the vertical scope lines when overlapping.
  
• No need to call .occurrences().regions_in_range() as the selection_find.update_find() function is already called with the first and last screen line offsets.
• Remember the search strings to search for and the match_whole_words setting for each string.
• Actually take the case_matching setting from the finder box widget.
• No need to for line in &screen_lines.lines since we know the range and can iterate over start_line..=end_line instead.
• Draw the highlight rectangle with rounded corners.
• Refactored code into a more functional style.

[azizk]

TODO: I saw that the view is painted frequently and the search is run each time, so maybe we should cache the selection search results so that redraws are as fast as possible?

[codecov-commenter]

Codecov Report

Merging #2281 (5593960) into master (8ebbbe2) will decrease coverage by 0.01%.
The diff coverage is 0.00%.

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@@            Coverage Diff            @@
##           master   #2281      +/-   ##
=========================================
- Coverage    9.06%   9.06%   -0.01%     
=========================================
  Files         137     137              
  Lines       59462   59468       +6     
=========================================
  Hits         5393    5393              
- Misses      54069   54075       +6     

Impacted Files	Coverage Δ
lapce-core/src/cursor.rs	5.01% <0.00%> (-0.12%)	⬇️
lapce-data/src/document.rs	0.00% <ø> (ø)
lapce-ui/src/editor.rs	0.00% <0.00%> (ø)

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[azizk]

• Moved code for getting the selection ranges to as_selection() in impl Cursor.
• No need to call selection_find.update_find() with include_slop: true. Instead calculate the search range from the longest selected string to search for.

[azizk]

I'm not sure but I think I found a bug in Find::update_find(). When you search for an Umlaut with whole_words = true the app crashes:

selection_find.search_string = Some("ä".to_string());
selection_find.whole_words = true;
selection_find.update_find(buffer.text(), start, end, false);

Snippet from logs:

[2023-03-27][02:26:59][panic][ERROR] thread 'main' panicked at 'byte index 904 is not a char boundary; it is inside 'ä' (bytes 903..905) of `...ä...`[...]': /home/aziz/.cargo/registry/src/github.com-1ecc6299db9ec823/lapce-xi-rope-0.3.1/src/rope.rs:663
   0: <backtrace::capture::Backtrace as core::default::Default>::default
             at /home/aziz/.cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.66/src/capture.rs:410:9

[azizk]

I really had to implement these continuous multi-line highlights:

😁

Cool thing is you'll be able to use the same functions for normal Ctrl+F searches!

I'd love to do one final thing: render the shape with rounded corners. I think it will look more pleasant that way.