[Libreoffice-bugs] [Bug 140176] New: UI: Speedup scrolling/paging by aborting redraw

[bugzilla-daemon at bugs.documentfoundation.org]

https://bugs.documentfoundation.org/show_bug.cgi?id=140176

            Bug ID: 140176
           Summary: UI: Speedup scrolling/paging by aborting redraw
           Product: LibreOffice
           Version: Inherited From OOo
          Hardware: All
                OS: All
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: medium
         Component: Calc
          Assignee: libreoffice-bugs at lists.freedesktop.org
          Reporter: ralacroix at hydro.mb.ca

Description:
Borrowing a technique employed by a 1980s vintage text editor in CP/M,
scrolling can be made very fast by aborting a screen redraw when a new
keystroke is detected in the same scrolling/paging direction.

Steps to Reproduce:
1. Load a large spreadsheet.
2. Fill up all your cores and your GPU with heavy processing. A distributed
computing project is a good candidate.
3. Go to the top of the spreadsheet.
4. Hit the page-down key several times quickly.

Actual Results:
Watch how long LO Calc take to reach the desired cell, and how frustrating it
is to recover from hitting page-down too many times after passing that cell.

Expected Results:
It could be blazingly fast.

The spreadsheet currently buffers keystrokes and processes them serially with
drawing, so you must wait for the drawing operation to complete for each
keystroke. This is painfully slow in a large spreadsheet, on a slow CPU (or one
that is fully in use). By looking ahead in the keystroke buffer while rendering
the page, the program can decide to abort the current display update (which is
going to be replaced anyway), then process the next keystroke and recommence
the display update from the new position.


Reproducible: Always


User Profile Reset: No



Additional Info:
Version: 7.0.4.2
Build ID: dcf040e67528d9187c66b2379df5ea4407429775
CPU threads: 12; OS: Linux 4.19; UI render: default; VCL: gtk3
Locale: en-CA (en_CA.utf8); UI: en-US
Calc: threaded

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