2.4.4

   * Add a new option to hide inactive tabs from top tab bar. This feature works only on Firefox 59 and later, and require new extra permission. Moreover you need to activate the API manually by `extensions.webextensions.tabhide.enabled`, a secret preference of Firefox itself.
   * Track tabs more correctly at cases multiple tabs are opened quickly.
   * Ask how to open the dropped link on a tab, like legacy versions.
   * Staying on a tab while dragging of a link will switch focus to the dragover tab correctly.
   * Shift-drag on a parent tab now allows to drag the tab as an individual tab.
   * Drag and drop operations of tabs between a regular window and a private browsing window are now blocked.
   * "Move to New Window" and similar operation work correctly for tabs in a private browsing window.
   * Treat Ctrl-PageUp and Ctrl-PaegDown as tab switch trigger, same to Ctrl-Tab/Ctrl-Shift-Tab.
   * Activate "Close Tabs to Right" and "Close Other Tabs" context menu items, on pinned tabs (respecting Firefox 59's behavior.)
   * Theme's background color is now applied ASAP.
   * Synchronize title of a group tab with its first child tab, if it has just a default title.
   * Title edit for dummy group tabs now works correctly.
   * Don't focus to the group tab itself after multiple tabs are automatically grouped.
   * New tabs from pinned tabs are placed at correct position as configured.
   * Expand focused tab if it is an orphan but collapsed. This is just a failsafe.
   * Reduce CPU usage from offscreen rendering of tabs' throbber.
   * Add a new configuration to control the position of the scrollbar in the sidebar.
   * Add a secret configuration `moveDroppedTabToNewWindowForUnhandledDragEvent` to deactivate "move tab to new window by drag and drop" behavior.
   * Synchronize some configurations with Firefox Sync.
   * Update `zh_TW` locale (by lycsjm, thanks!)
   * Add `de` locale (by sicherist, thanks!)
   * Accept [`current` and other special values](https://github.com/piroor/treestyletab/wiki/API-for-other-addons#basics-to-specify-tabs) to specify tabs via APIs.
   * Add new APIs to [indent](https://github.com/piroor/treestyletab/wiki/API-for-other-addons#indent-demote-tab), [outdent](https://github.com/piroor/treestyletab/wiki/API-for-other-addons#outdent-promote-tab), [move](https://github.com/piroor/treestyletab/wiki/API-for-other-addons#move-tree-to-different-position), [duplicate](https://github.com/piroor/treestyletab/wiki/API-for-other-addons#duplicate-tab-as-childsibling-tab), [focus](https://github.com/piroor/treestyletab/wiki/API-for-other-addons#focus-to-the-nextprevious-sibling-tab), and [group](https://github.com/piroor/treestyletab/wiki/API-for-other-addons#create-new-group-from-given-tabs) tabs.

2.4.3

Never group single orphan tab (regression on 2.4.2)

2.4.2

   * Keep group tabs open after restart of Firefox and reload/update of TST itself. (regression: group tabs were unexpectedly lost on such cases, at 2.4.x.)
   * Add ability to group new tabs opened from pinned tabs automatically.

2.4.1

   * Fix regressions around SVG icons and throbber's animation on the simulation mode.
   * Don't attach newly opened tab at the end of the tab bar to the previous tab.

2.4.0

   * Optimize tree restoration with cache. If you see broken tree from cache, please deactivate this feature by the checkbox under "Debug mode" in Tree Style Tab's configurations.
   * Use SVG icons for closeboxes, "New Tab" button, and sound playing indicator. However, due to the [Bug 1377302](https://bugzilla.mozilla.org/show_bug.cgi?id=1377302) and [1421329](https://bugzilla.mozilla.org/show_bug.cgi?id=1421329), it is just a simulation and requires more CPU. If you want to reduce CPU usage, you need to activate `svg.context-properties.content.enabled` via `about:config` and deactivate the simulation by the checkbox under "Debug mode" in Tree Style Tab's configurations.
   * Use system color instead Photon color scheme on Linux by default, on Plain, Flat, Vertigo, and Mixed theme.
   * Add new theme "Hight Contrast" based on system color on any platform. (contributed by actionless, thanks!)
   * Remove "Flat" theme. It was quite similar to "Plain".
   * On "Plain" and similar themes, show top border of the tab bar only when there is any pinned tab.
   * Keep tab's "unread" state after reloading of the sidebar.
   * Reduce needless requests for tab icons. (contributed by UENO Katsuhiro, thanks!)
   * Apply extra margin for overlay-scrollbar on macOS only for overflow tab bar.
   * Title editor and checkbox to toggle "temporary" status are avialable on group tabs.
   * Group tab won't be closed automatically if it is not marked as "temporary".
   * Don't detach tab from window if it is dropped onto the bookmarks toolbar.
   * Don't output log for keyboard events.

2.3.0

  * Show scrollbar like narrowed by default, on Windows and Linux.
   * Add extra space for overlay-scrollbar on macOS.
   * Don't expand tree when the Shift key is pressed/released while tab switching by Ctrl-Tab/Ctrl-Shift-Tab.
   * Add ability to prevent control for focusing of tabs when the current tab is focused.
   * Discard accidentally restored tab automatically, on Firefox 58 and later.
   * Detect `about:privatebrowsing` as a new blank tab, in the private browsing mode.
   * Always expand tree when a child is manually attached to a parent tab.
   * Open new sibling tab at correct position for root level tab.
   * Place attached tab to natural position more correctly.
   * Detach tab from window more easily by drag and drop to outside of the window. In old versions, it was done if you move the mouse just left or right.
   * Restore selection of the first tab after opened new tabs are automatically grouped.
   * Restore tree structure from sessions more quickly for "Restore Previous Session".
   * Add ability to inherit container (contextual identity) from its parent tab to newly opened child tabs.
   * Add "Default" to the list of selectable containers, when container inheritance is activated.
   * Allow to bookmark all tabs from the fake context menu. (regression)
   * Cleanup tab element for closed tabs correctly. (regression)
   * Calculate size of elements more correctly. (regression)
   * Animation of throbber is now synchronized correctly on Firefox 57. (Many thanks to Lej77!)
   * Recolor "Plain", "Flat", "Vertigo", "Mixed", and the startup page based on the color scheme of Firefox's default Photon theme.
   * Recolor "Plain Dark" based on the color scheme of Firefox's builtin "Dark" theme.
   * Use more larger closebox on macOS.
   * Hide container selector on the new tab button by default.
   * Add "No Decoration" theme as the base for customization.
   * Use white icon for the toolbar button on the "Dark" theme.
   * Disallow zooming of the sidebar contents by default. You can re-activate the old behavior by setting `zoomable` to `true` in the debug mode.
   * Notify both mousedown and mouseup for other addons via API.
   * Handle middle-click on the new tab button correctly even if any other addon listens click events on the tab bar.
   * Add zh_TW locale (by lycsjm, thanks!)

2.2.11

Fix performance regression for many numbers of tabs, on 2.2.10.

2.2.10

   * Some permissions are now optional.
   * Open plain text dropped onto the sidebar as a URI, if it seems to be formed like a host name.
   * Tabs reopened by [Firefox Multi-Account Containers](https://addons.mozilla.org/firefox/addon/multi-account-containers) are treated as replacement of the original tab, if possible.
   * While switching tabs by keyboard shortuts, staying on a collapsed tree expands the tree automatically.
   * Add more descriptions and links from the configurations.
   * Fix wrong tab focus when there are only tow child tabs and the last one is active and closed.
   * [Add ability to deactivate auto-attaching of tabs.](https://github.com/piroor/treestyletab/issues/1544)

2.2.9

   * Don't apply indent for pinned tabs.
   * Don't close initial message tab automatically.

2.2.8

   * Reduce width of elipsis for cropped long title of tabs.
   * Close collapsed tree without expansion animation correctly. (regression)
   * Update internal order of child tabs correctly, when they are just rearranged. (regression)
   * Don't shrink close button for indented tabs, on the "Sidebar" skin.

2.2.7

Apply theme color for each window.

2.2.6

Skip collapsed tabs for focus switching via Ctrl-Tab/Ctrl-Shift-Tab. [But there are some restrictions.](https://github.com/piroor/treestyletab/issues/1531#issuecomment-344487289) (This feature was described at 2.2.4 but didn't work due to missing file.)

2.2.5

Isolate from unimplemented feature on Firefox 57.

2.2.4

   * Inherit theme colros applied by extensions like [VivaldiFox](https://addons.mozilla.org/firefox/addon/vivaldifox/), [Container Theme](https://addons.mozilla.org/firefox/addon/containers-theme/), and others. Due to limitations of WebExtensions APIs, non-extension theme colors won't be applied.
   * Skip collapsed tabs for focus switching via Ctrl-Tab/Ctrl-Shift-Tab. [But there are some restrictions.](https://github.com/piroor/treestyletab/issues/1531#issuecomment-344487289)
   * Collapse other tree when new tree is created. (regression)

2.2.3

Add new APIs to work with other addons, especially Multiple Tab Handler.

2.2.2

Tabs are opened in correct order when new child tab is attached as a top of existing children. (regression)

2.2.1

   * Introduce new option to operate a parent tab just as a solo tab, by operations outside of the sidebar.
   * Fix some odd behaviors around an window separated from another existing window. (regression)

2.2.0

Optimize initialization, retrieving tab relations based on tree, and collapsing/expanding of tree.

2.1.2

   * Keep tabs indented after deep level tab is closed. (regression)
   * Link to instruction to migrate session information.

2.1.1

   * Optimize animation to collapse/expand tree.
   * Collapse other auto-expanded tree when new tree is created. (regression)
   * Dummy group tab now accept tab title specified without`title=`.
   * Import tree from migration data correctly, including their URIs.