Created attachment 133346 [details]
patch to render text immediately in textbox

SUMMARY
When Konqueror is used with KHTML engine,
- Text input in textbox is not rendered immediately.
- Pressed button does not get disarmed.
When changing the window focus to other, the text in textbox is rendered and
button get disarmed, triggerring any actions with it.


STEPS TO REPRODUCE
1. Launch Konqueror with KHTML engine. Input methods probably should be off.
2. Browse a page with a text box, such as http://www.google.com/ .
3. Type text into the text box. It isn't visible. Text cursor caret is also missing.
4. Switch focus to another window. The typed text will be rendered.

OBSERVED RESULT
Input text is not visible. It is rendered after window focus change.

EXPECTED RESULT
Input text should be visible immediately.

SOFTWARE/OS VERSIONS
Linux: CentOS 8.2/EPEL 8
KDE Plasma Version: 5.68
KDE Frameworks Version: 5.68
Qt Version: 5.12.5

khtml version: 5.59, 5.60, 5.65, 5.66, 5.68, 5.75

ADDITIONAL INFORMATION

A simple HTML to show the bug:

<FORM>
<INPUT id=1 type="text" size=20 />
<INPUT type="button" value="append x" onclick="getElementById(1).value+='x'" />
</FORM>

When pressing the button, button doesn't get disarmed;
changing the window focus disarms the button and the textbox will have "x" appended.

This is a revised report of
Konqueror KHTML text input not shown, button not disarmed until window focus change
https://bugs.kde.org/show_bug.cgi?id=422950
which the patch didn't update region outside the initial viewport.

Similar bug was reported in year 2017
Konqueror does not display any text typed in text fields/areas nor changes in... 
https://bugs.kde.org/show_bug.cgi?id=380134
KHTML Forms: text not visible, email attachments not sent 
https://bugs.kde.org/show_bug.cgi?id=369682

but was not addressed.