v0.73.0

This is a rather large release. Lots of fixes and enhancements, including optimizations to the DataTable.

There's also a rather nifty addition to the `ProgressBar` widget. Checkout the gradient:

https://github.com/user-attachments/assets/adee9cf8-ace6-4ca0-b9fe-13861a9c0bcf

We've also polished the API docs, which should hopefully make them easier to navigate...

https://textual.textualize.io/api/app/

## [0.73.0] - 2024-07-18

### Added

- Added `TextArea.line_number_start` reactive attribute https://github.com/Textualize/textual/pull/4471
- Added `TextArea.matching_bracket_location` property https://github.com/Textualize/textual/pull/4764
- Added `DOMNode.mutate_reactive` https://github.com/Textualize/textual/pull/4731
- Added "quality" parameter to `textual.color.Gradient` https://github.com/Textualize/textual/pull/4739
- Added `textual.color.Gradient.get_rich_color` https://github.com/Textualize/textual/pull/4739
- `Widget.remove_children` now accepts an iterable if widgets in addition to a selector https://github.com/Textualize/textual/issues/4735
- Raise `ValueError` with improved error message when number of cells inserted using `DataTable.add_row` doesn't match the number of columns in the table https://github.com/Textualize/textual/pull/4742
- Add `Tree.move_cursor` to programmatically move the cursor without selecting the node https://github.com/Textualize/textual/pull/4753
- Added `Footer` component style handling of padding for the key/description https://github.com/Textualize/textual/pull/4651
- `StringKey` is now exported from `data_table` https://github.com/Textualize/textual/pull/4760
- `TreeNode.add` and `TreeNode.add_leaf` now accepts `before` and `after` arguments to position a new node https://github.com/Textualize/textual/pull/4772
- Added a `gradient` parameter to the `ProgressBar` widget https://github.com/Textualize/textual/pull/4774

### Fixed

- Fixed issue with `Tabs` where disabled tabs could still be activated by clicking the underline https://github.com/Textualize/textual/issues/4701
- Fixed scroll_visible with margin https://github.com/Textualize/textual/pull/4719
- Fixed programmatically disabling button stuck in hover state https://github.com/Textualize/textual/pull/4724
- Fixed `DataTable` poor performance on startup and focus change when rows contain multi-line content https://github.com/Textualize/textual/pull/4748
- Fixed `Tree` and `DirectoryTree` horizontal scrolling off-by-2 https://github.com/Textualize/textual/pull/4744
- Fixed text-opacity in component styles https://github.com/Textualize/textual/pull/4747
- Ensure `Tree.select_node` sends `NodeSelected` message https://github.com/Textualize/textual/pull/4753
- Fixed message handlers not working when message types are assigned as the value of class vars https://github.com/Textualize/textual/pull/3940
- Fixed `CommandPalette` not focusing the input when opened when `App.AUTO_FOCUS` doesn't match the input https://github.com/Textualize/textual/pull/4763
- `SelectionList.SelectionToggled` will now be sent for each option when a bulk toggle is performed (e.g. `toggle_all`). Previously no messages were sent at all. https://github.com/Textualize/textual/pull/4759
- Fixed focus styles not being updated on blur https://github.com/Textualize/textual/pull/4771

### Changed

- "Discover" hits in the command palette are no longer sorted alphabetically https://github.com/Textualize/textual/pull/4720
- `TreeNodeSelected` messages are now posted before `TreeNodeExpanded` messages
when an expandable node is selected https://github.com/Textualize/textual/pull/4753
- `Markdown.LinkClicked.href` is now automatically unquoted https://github.com/Textualize/textual/pull/4749
- The mouse cursor hover effect of `Tree` and `DirectoryTree` will no longer linger after the mouse leaves the widget https://github.com/Textualize/textual/pull/4766