strange color shadow on Text Properties editor

Description

I only experience it on Text Properties editor

I notice if I start typing, when I reach the right side, the shadow will start moving to the right.

Exaggerated contrast:

KiCad Version

Application: Eeschema

Version: (5.99.0-3761-g9e115a548), release build

Libraries:
	wxWidgets 3.0.4
	libcurl/7.68.0 GnuTLS/3.6.13 zlib/1.2.11 brotli/1.0.7 libidn2/2.2.0 libpsl/0.21.0 (+libidn2/2.2.0) libssh/0.9.3/openssl/zlib nghttp2/1.40.0 librtmp/2.3

Platform: Linux 5.4.0-48-generic x86_64, 64 bit, Little endian, wxGTK, cinnamon, x11

Build Info:
	Date: Oct  4 2020 00:55:04
	wxWidgets: 3.0.4 (wchar_t,wx containers,compatible with 2.8) GTK+ 3.24
	Boost: 1.71.0
	OCE: 6.9.1
	Curl: 7.68.0
	Compiler: GCC 9.3.0 with C++ ABI 1013

Build settings:
	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=OFF
	KICAD_USE_OCE=ON
	KICAD_SPICE=OFF