Traitsui

codebase. This release includes updating the WxPython backend to support
WxPython 4, an effort led by Rob McMullen's first cut at support, with
help from a number of other people, particularly Per Brodtkorb. It also
updates the code to use new features of Traits 6, and just like Traits 6,
this release drops support for Python 2.

In addition to the modernization, this code fixes many bugs and adds some
useful new features, including:

- a DatetimeEditor to go with the new Datetime trait in Traits 6
- an API to add placeholder text to a TextEditor
- support for the LEDEditor in Qt

Finally, the documentation has been improved, adding sections about some
of the internals of the TraitsUI mechanisms. Additionally, the Examples,
Demos and Tutorials have been improved and cleaned-up, including fixing and
unifying the demo viewer codebase.

Thanks to Per Brodtkorb, Christian Brodbeck, Kit Choi, Mark Dickinson, Matt
Hancock, Sandhya Govindaraju, Midhun Madhusoodanan, Rob McMullen, Shoeb
Mohammed, Eric Olsen, Roberto Preste, reckoner, Jonathan Rocher, Scott
Talbert, Corran Webster.

Enhancements
~~~~~~~~~~~~
* Documentation improvements (720, 724, 723, 778)
* WxPython 4 compatibility and support (708, 736, 762, 772, 775, 776)
* Traits 6 compatibility and enhancements (689, 690, 693, 695, 713, 727, 770)
* Style improvements (648, 771)
* Add placeholder text option for TextEditor (735)
* Examples clean-up and unification (697, 702, 703, 705, 711, 712, 777)
* Add a DatetimeEditor (719, 730)
* Refactor and clean-up of base Editor class (685, 686, 688)
* Remove use of Category classes from TraitsUI (654)
* Add LEDEditor for Qt (635)
* Add 'docs' command to etstool.py (624)
* Add TabularAdapter to traitsui.api (627)
* Enhancements to CI and testing (683, 714, 740)

Fixes
~~~~~
* Documentation fixes (546, 766)
* Fix cgi.escape for Python 3.8 (780)
* Log exceptions in table sorting (751)
* Use TupleEditor for traits derived from BaseTuple (747)
* Fixes for Undo/Redo (733)
* Add explicit redraw for TableEditor selection (721)
* Fixes for Qt5 support (709)
* Fix bugs in color functions (707, 744)
* Fix importing of ProgressColumn and EditColumn (691)
* Set initial focus item correctly in Qt (602)
* Fix text elision test on some platforms (644)
* Fix a bug with TableEditor column clicking (669)
* Fix typo in progress column exception (662)

-------------

A bugfix release that fixes a number of issues discovered since the

-------------

A bugfix release that fixes a number of issues discovered since the

-------------

A bugfix release to correct some critical issues with the TreeEditor.

Fixes
~~~~~
* Fix TreeNodeObject listener cache (558).
* Fix tree node insertion (561).

-------------

This is an incremental release without many new features, but with
significant improvements in the code base and numerous small bugfixes.
Probably the most significant change, but one not obvious to most users
is that we have moved away from using 2to3 for Python 3 support to using
a single codebase with the six library to patch over the differences.
This significantly enhances maintainability and development speed, and
gives a better path forward for future Python versions.

Additionally, this release introduces experimental support for PySide2
(also known as "Qt for Python"). Pyside2 was enabled as a potential
backend in 6.0.0 but there was no testing being performed. As of this
release PySide2 is now tested as part of the CI system with tests passing
on Linux and OS X using the 5.11 release. There are currently issues with
the 5.12 release which have yet to be fully investigated.

The one significant new feature that has been added to this release is the
ability to completely replace the rendering of TreeEditorNodes with custom
rendering code on Qt (due to the limitations of the Wx tree control, this
is unlikely to be extended to Wx). An example showing the drawing of
sparkline plots in TreeEditor cells has been added to the code demos.

There has been a long-standing issue with the way that the Qt TableEditor
handled selections, and this release fixes this, matching the behaviour of
the Wx backend and the documentation. It is possible that this may break
code that was written expecting the buggy behaviour.

Finally, there are a large number of minor bug fixes

Thanks to:

Martin Bergtholdt, Stefano Borini, Alex Chabot, Kit Choi, Mark Dickinson,
Kevin Duff, Matthew Evans, Matt Hancock, Robert Kern, Fede Miorelli,
Rahul Poruri, Jenni Portman, Prabhu Ramachandran, ransonr, Jonathan Rocher,
Roger Serwy, Ajeet Vivekanandan, Corran Webster, John Wiggins.

Enhancemenrs
~~~~~~~~~~~~
* Switch to using six instead of 2to3 (482, 484, 486, 498, 531).
* Experimental Pyside2 support (451, 500, 504).
* Allow arbitrary rendering of tree nodes in Qt backend (499, 502, 527).
* Use tooltip metadata on a trait instead of desc, if available (473).
* Enable scroll to column for TabularEditor (547)
* Add demo for tabular editor with context menu (460).
* Allow the use of extended trait names in TreeNodes where possible (500, 528).
* Allow drag move and drag copy modes on Qt TabularEditor (363).

Fixes
~~~~~
* Fixes to README (478).
* Documentation fixes (471, 508).
* Fixes to setup.py (549).
* Fix an attribute error on Qt TextRangeEditor (540).
* Use SimpleEditor for Qt TextEditor's "text" style (535).
* Fix handling of Range traits with a mix of constant and named bounds (533).
* Fix display selection on Wx backend (534).
* Fixes for Qt TableEditor selections (275).
* Fix deprecation warnings for inspect.getargspec (530).
* Fixes to etstool (526).
* Fix TreeEditor unhashable type errors (525).
* Fix crash when TabularEditor has no columns (521).
* Clone editor factories so they don't share traits (519).
* Avoid creation of dummy traits by springy items (515).
* Fix drag and drop crash in Python 3 (516).
* Fix Undo/Redo for readonly items and error handling (510).
* Fix source parsing in demo app (501).
* Fix signature of close() method of Qt modal dialog (506).
* Fix incorrect code in Wx ColorEditor (479).
* Fix incorrect code in Wx ProgressEditor (513).
* Remove uses of deprecated HasTraits.set() calls (457).
* Fix rendering of CheckboxColumn on OS X and Qt (456).

-------------

This release introduces preliminary support for Qt5 via PyQt5, thanks to the
work of Gregor Thalhammer which got the ball rolling. Qt5 support is
not yet robustly tested in deployed applications, so there may yet be bugs to
find. As part of this effort all occurences of old-style signals and slots
have been removed; and this has greatly improved stability under Qt.

This release also features a great deal of work at the API level to disentangle
the two-way dependencies between Pyface and TraitsUI. This has involved moving
a number of sub-packages between the two libraries, most notably the zipped
image resource support and a number of trait definitions. We have endeavored
to keep backwards compatibility via stub modules in the original locations,
but we can't guarantee that there will be no issues with third party code
caused by the change in locations. We haven't been able to remove all
dependencies, but as of this release on the dock and workbench submodules have
required dependencies on TraitsUI.

As part of the latter work, support for TraitsUI Themes have been removed. This
was a feature that was only available under WxPython, was slow, was never used
in production code, and was not supported for over a decade. Some of the
codebase remains as it is still used by the Pyface Dock infrastructure and
several editors, but ther long-term intention is to remove this completely.

Another long-desired feature was the ability to write toolkit backends for
Pyface and TraitsUI that are not part of the main codebase. This is now
possible by contributing new toolkit backends to the "traitsui.toolkit"
pkg_resources entry point in a setup.py. This work was accompanied by an
overhaul of the toolkit discovery and loading infrastructure; in particular
Pyface and TraitsUI now share the same code for performing these searches
and loading the backends.

The entire TraitsUI codebase has been run through the AutoPEP8, assisted with
some customized fixups and occasional drive-by cleanups of code, which means
that the codebase is generally easier to read and follows modern Python
conventions.

Finally, the testing infrastructure has been overhauled to provide a one-stop
location to run tests in self-contained environments using Enthought's EDM
package management tool. Tests can be run from any python environment with the
"edm" command available and the "click" library installed with the "etstool.py"
script at the top level of the repository. In particular::

python etstool.py test_all

will run all relevant tests for all available toolkits in all supported
python versions. The TravisCI and Appveyor continuous integration tools have
been updated to make use of these facilities as well.

Thanks to Martin Bergtholdt, Alex Chabot, Kit Choi, Mark Dickinson, Robin Dunn,
Pradyun Gedam, Robert Kern, Marika Murphy, Pankaj Pandey, Steve Peak,
Prabhu Ramachandran, Jonathan Rocher, John Thacker, Gregor Thalhammer,
Senganal Thirunavukkarasu, John Tyree, Ioannis Tziakos, Alona Varshal,
Corran Webster, John Wiggins

Enhancements
~~~~~~~~~~~~
* Support for Qt5 (347, 352, 350, 433)
* Remove TraitsUI Themes (342)
* Improve Toolkit selection and handling (425, 429)
* API Documentation (438)
* Adapter documentation (340)
* Support multi-selection in DataFrameEditor (413)
* DataFrameEditor demo (444)
* Common BasePanel class for toolkits (392)
* Labels honor enable_when values (401)
* Better error messages when toolkit doesn't implement methods (391)
* Improve TraitsUI Action handling (384)
* ListEditor UI improvements (338, 396, 395)
* Remove old style signals and slots for Qt backend (330, 346, 347, 403)
* Expose a "refresh" trait for the DataFrameEditor (288)
* Use Enthought Deployment Manager to automate CI and testing (321, 357)
* Continuous integration on OS X (322)
* Reduce circular dependencies of Pyface on TraitsUI (304)
* PEP8-compliant formatting of source (290)
* Add progress bar column for TableEditor (287)
* Add codecov coverage reports (285, 328)

Fixes
~~~~~
* Fix some issues for newer WxPython (418)
* Fix Wx simple FileEditor (426)
* Fixes for DataFrameEditor (415)
* Fixes for preferences state saving under Qt (410, 447)
* Fix panel state after setting preferences (253)
* Fix TableEditor ColorColumn (399)
* Prevent loopback from slider in Qt RangeEditor (400)
* Fix Action buttons under Qt (393, 394)
* Fix ValueEditor icons (386)
* Fix bug in update_object (379)
* Avoid reading Event trait values in sync_value (375)
* Fix raise_to_debug calls (362, 372)
* Fix errors during garbage collection (359)
* Remove unused argument in wx.hook_events (360)
* Fix button label updates (358)
* Fix TreeEditor label updates (335)
* Proper InstanceEditor dialog lifecycle (332)
* Don't explicitly destroy child widgets under Qt (283)
* Test fixes and improvements (329, 369, 371, 327)
* Fixes for demos and examples (320, 445)
* Fix CheckListEditor string comparison (318)
* Remove some spurious print statements (305)
* Documentation fixes (301, 326, 380, 438, 443)
* Fixes for Python 3 compatibility (295, 300, 165, 311, 410)
* Fix error with Qt table model mimetype (296)
* Fixes for continuous integration (299, 345, 365, 397, 420, 427)
* Fix offset issue when dragging from Qt TreeEditor (293)
* Fix Wx kill-focus event issues (291)
* Fix readthedocs build (281)