Editing Eeschema text modifies Primary selection on GTK (lp:#1823500)

[Original report](https://bugs.launchpad.net/bugs/1823500) created by **Johannes (jos+)**
```
Application: kicad
Version: 5.1.0-060a0da~80~ubuntu18.04.1, release build
Libraries:
    wxWidgets 3.0.4
    libcurl/7.58.0 OpenSSL/1.1.0g zlib/1.2.11 libidn2/2.0.4 libpsl/0.19.1
(+libidn2/2.0.4) nghttp2/1.30.0 librtmp/2.3
Platform: Linux 4.15.0-45-generic x86_64, 64 bit, Little endian, wxGTK
Build Info:
    wxWidgets: 3.0.4 (wchar_t,wx containers,compatible with 2.8) GTK+ 3.22
    Boost: 1.65.1
    OpenCASCADE Community Edition: 6.9.1
    Curl: 7.58.0
    Compiler: GCC 7.3.0 with C++ ABI 1011

Build settings:
    USE_WX_GRAPHICS_CONTEXT=OFF
    USE_WX_OVERLAY=ON
    KICAD_SCRIPTING=ON
    KICAD_SCRIPTING_MODULES=ON
    KICAD_SCRIPTING_PYTHON3=ON
    KICAD_SCRIPTING_WXPYTHON=ON
    KICAD_SCRIPTING_WXPYTHON_PHOENIX=ON
    KICAD_SCRIPTING_ACTION_MENU=ON
    BUILD_GITHUB_PLUGIN=ON
    KICAD_USE_OCE=ON
    KICAD_USE_OCC=OFF
    KICAD_SPICE=ON

The copy and paste functionality for texts in version 5.1 is utterly
broken.

Example for instance in Eeschema

Issue an E, V, U while pointing at any symbol. The system immediately high
lights the text which, based on what actually happens, obviously actions a
copy command which in turn supers imposes any previously issued copy
command within the entire OS. May it be an ordinary ctrl+c/ctrl+v, or the
unix/linux build in copy by high light functionality.

Even within Eeschema itself there is no way to copy field texts between
symbols other than the automatically high lighted text in the target field
itself.

Even attempts to copy some text from outside an open symbol dialogue box
(E, V, U) are futile since as soon as the focus returns to the dialogue box
KiCad again will automatically high light the text (and commit its value to
the copy buffer) where ever the cursor left off. Definitely unwanted
behaviour.

This is rather disturbing and extremely annoying to put it mildly.

I reverted back to 5.02 which does the auto high light as well though it is
possible to copy and paste text (e.g. special symbols) into an open
dialogue box from any system clip board source.

The unix/linux paste by middle mouse click does not work anymore in 5.1!

Reverting back and forth between 5.1 and 5.02 shows that his
(mis)-behaviour is consistent.

5.02 limpingly ‘works’ while 5.1 does not.

<---------------------->

A temporary ‘workaround’ as follows.

Did some more testing and the only way to paste text into e.g. E,V,U of any
symbol within Eeschema is:

    issue an E, V, U command over any symbol.
    delete field contents
    only THEN copy/paste from wherever
    insert as per usual ctrl+c, or middle mouse button click

Kind of a pain, but will have to do short of down grading to 5.02

The same behaviour applies to the Edit Symbol Fields dialogue.

Going by the behaviour as such it suggests an issue in relation with GTK.

<------------------->

Further tests in 5.1 Pcbnewl reveals inconsistent behaviour.

An E over any text property like component value, reference still appears
to have the same behaviour as version 5.02. Meaning here it is possible the
paste as usual.

However an E over any component itself does exhibit the same flaw as in
Eeschema, probably due to the same gtk dialogue used.

Apart from the above KiCad is a great tool. Beats eagle any time.

<-------------------->

To drill down on the issue I did a git pull and re-compile on the 5.1
branch. Behaviour is till present.

Hope this helps.

Cheers

Johannes
Jos
```
Original tags: eeschema gtk pcbnew ui

Story points: 6.0