Asciimatics

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- Added FileBrowser, DatePicker and TimePicker widgets.

- Made `screen` a mandatory positional parameter to all Effects in the process.
- NOTE: Any custom Effects you have created will now need to pass the screen down to the parent
class.

- Added `fill_polygon()` to Screen and Canvas.
- Added the Kaleidoscope and RotatedDuplicate renderers.
- Created Maps demo - which renders vector tiles and satellite images from Mapbox.
- Added optional `is_modal` parameter to Frame constructor.
- Added `on_blur` and `on_focus` parameters to all interactive Widgets.
- Added `colour` property to Cogs Effect.
- Added `title` property to Frame.
- Added `text` property to Label.
- Added `hide_char` parameter to Text constructor to hide any entered text - e.g. for passwords.
- Added optional `height` parameter to Label constructor.
- Allowed programs to set "default" values for Widgets - which means you need to reset each field
in a Frame explicitly rather than relying on reset to blank out uninitialized fields.
- Fixed up signal handling to re-instate old handlers on Screen.close().
- Fixed missing on_select handler for ListBox.

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- Added MultiColumnListBox for displaying tabular data in widgets.
- Improved efficiency of screen refresh on curses systems.
- Improved start-up time by avoiding use of deepcopy()
- Added unicode characters to ColourFileImage to increase rendering resolution.
- Added support for validated free-form text to Text widgets.
- Added force_update() to allow background refresh of the Screen.
- Added custom_colour property to widgets.
- Added support for DELETE key to text widgets.
- Fixed ZeroDivisionError in Frames.
- Fixed issues with double-width glyphs as used by CJK languages.
- Tweaked widget navigation using cursor keys to be more like web forms.

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- Added unicode support for input and output.
- Reworked Screen construction.

- Added open() and close() methods to Screen.
- Retired from_windows(), from_curses() and from_blessed() methods.
- Retired Blessed support.

- Added set_scenes() and draw_next_frame() to allow asynchronous frameworks to
use Screen.
- Added Plasma renderer and sample code to use it.
- Added background colour support to ColourImageFile.
- Added support for multi-colour rendering using ${c,a,b} syntax.
- Added highlight() method to Screen and Canvas.
- Added UT framework for testing and CI configurations to run the tests.
- Added shadows to Frames.
- Fixed bug in restoring console colours on Exit for Windows.
- Fixed up logic for handling Ctrl keys and documented OS restrictions.
- Fixed refresh timer in play() when handling intensive computational load.
- Added repeat flag to play() to allow termination of the animation instead of
infinite looping.
- Improved CPU usage for Widgets-based UIs.
- General docs and test tidy up.

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- Added `widgets` sub-package, providing a Frame effect for encapsulating a User
Interface, a Layout to organise the content and the following widgets:

- Button
- CheckBox
- Divider
- Label
- ListBox
- RadioButtons
- Text
- TextBox

- Added PopUpDialog for simple alerting in a UI.
- Added `attr` option to Print Effect.
- Added `keys` option to BarChart Renderer.

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- Created the ParticleEffect and associated classes.
- Implemented the StarFirework, RingFirework, SerpentFirework, PalmFirework,
Explosion, DropScreen, ShootScreen and Rain effects.
- Added background colour options to BarChart renderer.
- Added set_title() method to set title for window that owns the Screen.

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- Fix for Python 3 support on Linux variants.