[dolphin] [Bug 474644] New: Dolphin's hold-click-drag to select performance is very poor

[bugzilla_noreply at kde.org]

https://bugs.kde.org/show_bug.cgi?id=474644

            Bug ID: 474644
           Summary: Dolphin's hold-click-drag to select performance is
                    very poor
    Classification: Applications
           Product: dolphin
           Version: unspecified
          Platform: Archlinux
                OS: Linux
            Status: REPORTED
          Severity: normal
          Priority: NOR
         Component: view-engine: general
          Assignee: dolphin-bugs-null at kde.org
          Reporter: miranda at mirandastreeter.com
                CC: kfm-devel at kde.org
  Target Milestone: ---

SUMMARY
Dolphin uses an extraordinary amount of CPU for the selection rectangle. This
dramatically worsens as resolution increases. As a result, it feels quite
choppy. It's especially noticeable on high refresh monitors. I'm guessing
something accidentally hit O(n^2) instead of O(n).

STEPS TO REPRODUCE
1. Open Dolphin, maximized. On a high res screen if possible, or alternatively
at low display scale factors
2. Watch CPU usage for Dolphin, in my case I just ran htop --pid=$(pgrep
dolphin) --delay=1
3. Click and drag anywhere in the window (and not by scrolling, but by moving
the mouse cursor)

OBSERVED RESULT
Dolphin's CPU usage spikes to the point it maxes out a core and the effect
feels really choppy

EXPECTED RESULT
Select dragging is performant, not choppy, and doesn't max out a core

SOFTWARE/OS VERSIONS
Linux Version: 6.5.3-arch1-1
KDE Plasma Version: 5.27.8
KDE Frameworks Version: 5.110.0
Qt Version: 5.15.10
KWin Backend: Wayland
Mesa 23.1.7 (AMD RX 6600 XT)

ADDITIONAL INFORMATION
Note this is NOT to do with selecting files/folders and moving them. This is
only as you CREATE the selection box.

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