(Though I put the word "flicker" on the subject header, this is not a typical
flicker as you would imagine on a CRT monitor or CRT TV.)
The entire area on the screen below the I-beam mouse pointer often (but not
always) turns black for a fraction of a second, if an I-beam mouse pointer
(instead of an arrow) is present and visible, and if either KWrite, Kate,
Konsole, XTerm or UXTerm is front-most, and if the following action (1) or
state (2) occurs.
(1) pressing a key on a keyboard
(2) the I-beam mouse pointer stays motionlessly on the same line as the
blinking vertical bar caret that indicates the insertion point where the next
character will be written
The I-beam mouse pointer should not be confused with the blinking vertical bar
caret indicating the insertion point where the next character will be written.
The I-beam mouse pointer moves with the mouse, but the blinking insertion bar
The width and height of the affected rectangular area that momentarily turns
black are as follows. Its width is the same as the width of the entire screen.
Its height is the distance between the top of the I-beam and the bottom of the
Let me call this phenomenon "I-beam-related flicker" for both (1) and (2). For
(1) in particular, let me call it "keyboard-led flicker" or "keyboard-triggered
Note that, in general, pressing a key causes the I-beam mouse pointer to
disappear, and it stays invisible until the mouse moves next time. And this
"I-beam-related flicker" occurs only when the I-beam mouse pointer is present
and visible. Therefore, although you will likely see this flicker when you type
the first letter, you will not see the flicker when you type subsequent
letters, unless you keep the mouse moving.
Therefore, to reproduce the problem (1) efficiently, you should keep the mouse
moving as you press keys. For maximum efficiency, press and hold the Space key
or the Enter key (or any letter key) to let it be typed by the automatic
repeat, as you keep the mouse moving. If you do not want to clutter the text
area with letters, then, instead of Space, Enter or any letter key, press a
Shift key repeatedly (not automatically but manually).
For (2), you should keep the mouse motionless while you are waiting for the
momentary black to occur.
For both (1) and (2), remember that the mouse pointer has to be an I-beam. If
the mouse pointer is placed outside the text area, it becomes an arrow, with
which the problem does not occur.
By the way, though I call this phenomenon "flicker", this is not a typical
flicker. A typical flicker such as a flicker of a candle or that of CRT TV or
CRT monitor turns bright and dark repeatedly. On the other hand, this
"I-beam-related flicker" turns black for a fraction of a second and comes back
normal, and it occurs only once but not repeatedly, unless letters are
repeatedly typed with the mouse kept moving.
This problem was introduced with Debian 9.3. I did not notice this problem when
I used Debian 9.2. This problem does not occur if LibreOffice Writer is
Name Version Architecture
kde-plasma-desktop 5:92 amd64
kwrite 4:16.08.3-1 amd64
kate 4:16.08.3-1 amd64
konsole 4:16.12.0-4 amd64
xterm 327-2 amd64
Debian 9.3.0 amd64