c0d3r

The top 2 must have 3rd party components in my list: kbmMW and RTC

Disable the option, then open all the units AFTER (it won't cause issues for the units that were opened already.) or just restart Delphi, load project, you will see.

When the option "Enable Flow Control Highlighting" is turned off, the slow scrolling issues would be happened everywhere not only just bottom white spaces, but EVERYWHERE.

Definitely Delphi IDE issue, I opened Task Manager right beside Delphi, While the scrolling issues were happening, its running 50%-60% CPU, eventually the status changed to 'not responding', Power usage changed to 'Very High', until scrolling was done, then CPU back to normal. Its definitely doing something that I saw once Delphi window Title/Caption Bar turned to White color from the Blue ActiveGradientColor during slowing scroll up/down, while the caption bar turned to white, it displayed like: "<The Project name> - Delphi10.4 - <Unit Name> [ Not Responding]". Btw, I have the startidepage270.bpl disabled, and had a project group opened in IDE, one desktop application and one Windows service project.

No. It didn't either. Whats puzzled me was that the scrolling issues only occurred at end/bottom of each opened unit where you could see empty spaces, if passed the empty spaces, everything works just fine. and also occured when the option "Enable flow control highlighting" was turned off, so I'm still thinking its the Delphi IDE thing. Same video card, same 4K resolution, same VM settings on the same host, Delphi 2007 works very smooth.

Thats interesting. I'm thinking of now it could be my 4 years-old laptop can't handle 4K resolution properly? the laptop LCD screen resolution is 1920x1080p but it does support 4K 60hz, I'm currently connect it to Delll U2720Q as the main monitor.

Yes. that was the reason.

There is no MMX entry in that Registry. but I still got the error each time starting Delphi.

Uninstall MMX Code Explorer, restart Delphi 10.4, got: How to get rid of this.

I think its definitely Delphi IDE issue, you literally have to wait to see the codes scrolling up/down finish then continue coding. Otherwise it works okay. I found so far that can be reproducible: 1. The mouse wheel scrolling issues were only occurred at End/Bottom of every opened unit where you see the empty spaces UNTIL you turn off "Enable Flow Control Highlighting" option, However: 2. Once the option is turned off, then all the units that are opened after are having seriously mouse wheel scrolling lags. 3. When highlight a block of codes, there would be mouse wheel scrolling lags. 4. If an unit has over 10,000+ lines, while you are typing codes, you would literally see the characters being inserted one by one, like typing in one character per second speed. Same VM setting on the same host computer, Delphi 2007 doesn't have any issues at all, but with IDEFixPack (not sure if it could make things differently).

faster system in general, but Delphi IDE is still slow, main tool bar drag& drop lags like hell, mouse wheel scrolling issue still there, I'm not so sure if its due to my older Laptop (4 years old) or not. Since the guest OS is using the host DPI which was set to 125%, and Delphi 10.4 isn't DPI aware, so you would get blurred screens.

I didn't use 3rd party software, just running the guest OS from Hyper-V manager, I guess its the default Windows Remote Desktop??. However, I do see it mentioned that you can't change display settings or DPI from remote access.

Spent some times to convert 2 vmdks to vhdxs, and install Hyper-V. Its a bit faster than VMWare. However, here is the big one I don't like: It automatically scale the virtual machine screen display to match the host DPI, and there is no way you can change it in Guest OS (they are all disabled), I'm always using full screen mode, so its hard to test applications by using different DPIs.

Thank you very much.

OK. will let you know when I have times to try Hyper-V. I can't make smooth Delphi 10.4 IDE on VM. I was starting use Delphi since Turbo Pascal era, can't believe its getting worse after 20 years, tons of bugs.