Bug#891933: "I-beam-related flicker" on the screen with KDE Plasma
Package: kde-plasma-desktop
Version: 5:92
(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
or
(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 does not.
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 screen.
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 flicker".
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 front-most.
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
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