A number of changes were made to Tcell for version two, and some of these are breaking.
The import path for tcell has changed to github.com/gdamore/tcell/v2 to reflect a new major version.
The type Style has changed to a structure, to allow us to add additional data such as flags for color setting,
more attribute bits, and so forth.
Applications that relied on this being a number will need to be updated to use the accessor methods.
The middle mouse button was reported as button 2 on Linux, but as button 3 on Windows,
and the right mouse button was reported the reverse way.
Tcell now always reports the right mouse button as button 2, and the middle button as button 3.
To help make this clearer, new symbols ButtonPrimary, ButtonSecondary, and
ButtonMiddle are provided.
(Note that which button is right vs. left may be impacted by user preferences.
Usually the left button will be considered the Primary, and the right will be the Secondary.)
Applications may need to adjust their handling of mouse buttons 2 and 3 accordingly.
A number of terminals have been removed.
These are mostly ancient definitions unlikely to be used by anyone, such as adm3a.
Historically terminfo reported function keys with modifiers set as a different function key altogether. For example, Shift-F1 was reported as F13 on XTerm. Tcell now prefers to report these using the base key (such as F1) with modifiers added. This works on XTerm and VTE based emulators, but some emulators may not support this. The new behavior more closely aligns with behavior on Windows platforms.
These features are not breaking, but are introduced in version 2.
For terminals that appear to behave like the venerable XTerm, tcell automatically adds modifier reporting for ALT, CTRL, SHIFT, and META keys when the terminal reports them.
When using a color by its name or palette entry, Tcell now tries to use that palette entry as is; this should avoid some inconsistency and respect terminal themes correctly.
When true fidelity to RGB values is needed, the new TrueColor() API can be used
to create a direct color, which bypasses the palette altogether.
For some terminals, if the Tc or RGB properties are present in terminfo,
Tcell will automatically assume the terminal supports 24-bit color.
A new color value, ColorReset can be used on the foreground or background
to reset the color the default used by the terminal.
Tcell now has improved support for tmux, when the $TERM variable is set to "tmux".
Tcell has support for strikethrough when the terminal supports it, using the new StrikeThrough() API.
Tcell provides the long requested capability to discriminate paste event by using the
bracketed-paste capability present in some terminals. This is automatically available on
terminals that support XTerm style mouse handling, but applications must opt-in to this
by using the new EnablePaste() function. A new EventPaste type of event will be
delivered when starting and finishing a paste operation.