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Implementation Note

This command aims to be backward compatible with existing implementation of ctrl+backspace a.k.a deleteWorldLeft because existing ctrl+backspace actually is a hungry delete on the same line with some optimizations for source code editing.

In the previous version which supports only a single cursor, the code just invokes deleteWordLeft command to delete the word before the cursor. In order to support multiple cursors, I need to invoke each cursor to deleteWorldLeft, but I can't find any API available so I write a mock implementation of deleteWorldLeft.

Optimisations for source code editing.

As mentioned before, the existing ctrl+backspace is a hungry delete inline with some optimizations. The examples use the following syntax to illustrates the ideas

  • |: the cursor position
  • => : (after pressing ctrl+backspace)
  • Trivial : Trivial deleteWordLeft
  • VSC: Visual Studio Code existing deleteWordLeft
  • Current: Current implementation that is not the same as VSC

World separators

Visual Studio Code a.k.a VSC have configurable world separators (e.g. @ or =), which will be stopped in deleteWorldLeft Example:

  • Trivial: "This is @@myName|" => "This is |"
  • VSC: "This is @@myName|" => "This is @@|"

Delete continuous world separators util non world separator

Example:

  • Trivial: "This is @@|" => "This is @|"
  • VSC: "This is @@|" => "This is |"

Example 2:

  • Trivial: "This is My@@|" => "This is |"
  • VSC: "This is My@@|" => "This is My|"

Example 3: (This feature is not yet implemented)

  • Trivial: "This is My@@==|" => "This is "
  • VSC: "This is My@@==|" => "This is My|"
  • Current: "This is My@@==|" => "This is My@@|" => => "This is My|"

Delete one whitespace with the previous word

If there is ONLY a white space before the cursor, VSC deleteWordLeft will delete the whitespace with the previous word. Example:

  • Trivial: "This is |" => "This is|"
  • VSC: "This is |" => "This |"

Limitation of API

- Only can register the word pattern but it cannot be retrieved

After a few months I found out that the API actually can retrieve the word pattern, I think the current implementation is acceptable and I am lazy to change it, but I am welcome with the pull request.

  • The word range is undefined when the cursor is placed at word separators

Research

https://github.com/microsoft/vscode/blob/dce493cb6e36346ef2714e82c42ce14fc461b15c/src/vs/workbench/api/common/extHostDocumentData.ts#L217

https://github.com/microsoft/vscode/blob/0a435fb5b173b2b793b3c54a5c3dfdf81b7caee5/src/vs/editor/common/cursor/cursorWordOperations.ts#L380

https://github.com/microsoft/vscode/blob/0a435fb5b173b2b793b3c54a5c3dfdf81b7caee5/src/vs/editor/common/core/wordCharacterClassifier.ts#L15