Hello,
I recently installed Linux Mint 18.1 with the KDE desktop. I generally like KDE but I have an issue that I have so far been unable to resolve. I have posted first on Linux Mints forum and then a couple of other general Linux forums and now since I have been successful at finally getting logged in here on the KDE forum. The problem I am having is that I use my computer a lot for both gaming as well as a HTPC and find myself using my computer a lot from across the room from my sofa on my HDTV and will soon be upgrading to a 4K UHDTV. I have been using Windows 10 Pro after their free upgrade but have recently dumped Windows 10 due to their extreme issues with data mining an Microsoft stealing over 50% of my internet upload band width I have a fast symmetrical connection 75mb/sec down and 75 mb/sec upload. On Windows 10 my hard drive activity light was constantly flickering and when I checked my upload speed was capped at only 20 mb/sec. When I check my internet speed with my mobile devices or when booted into the same PC using a Linux live usb pen drive I would consistently get 85 down and between 85 0 89 up, and when I restored Windows 7 I got 85 and 89 for my speeds. Now that I have reinstalled from a back up Windows 7 Ultimate I plan on using it only when I play my large library of Windows only games and I want to make Linux my main OS. Currently my default resolution is 1920x1080 and on Windows with this resolution set by my Nvidia drivers the desktop is easily scaled so that all of the desktop elements are made larger from the fonts to the windows widgets etc so that they are easily seen from a distance without changing the resolution setting for the display. So far I have been unsuccessful in figuring out if this is possible when using KDE. At the moment the only thing that I have been able to do is to set my resolution to 720P instead of 1080P which is not acceptable. On Windows 10 the desktop is set by default at 150% larger than normal with normal being 100% on Windows 7 it is set by default to the actual default resolution but it too is easily changed in the personalize settings. All you have to do is to right click on the desktop and select personalize settings and then select display and on Windows 7 there are three selections on a page that says "Make Your Screen Easier To Read" there is small, medium(125%) and large(150%). I do not know that actual technical term for it but it is like the whole screen is magnified by a big magnifying glass so that it is 150% bigger. Is there a way to do this easily when using KDE?
Thanks for your time,
Robert

Here are some random ideas and links to get you going. Note that these are often mutually exclusive, or interfer. Experimentation is needed per screen setup and per application.

KDE screen scaling:
This is what Plasma developers suggest to use as a starting point, but I had mixed experiences with that. For example, you need newest unstable Plasma to have support for fractional scaling values.
-> systemsettings5 > Hardware > Display & Monitor > Scale Display

Physical (monitor) DPI:
This may be needed on monitors that do not report the correct values via DDC port.
-> https://wiki.archlinux.org/index.php/xo ... ze_and_DPI

Logical (font) DPI:
If you want 150% scaling, try DPI set to 144 (= 96 * 1.5). As far as I know, this may also be respected by GTK+ applications (see below for Firefox).
-> systemsettings5 > Appearance > Fonts > Force fonts DPI

KDE font sizes or icon sizes:
Here you can fine-tune font and icon sizes, per font type (menus, toolbars etc.) and per icon type. Not all values are respected, because the settings there are somewhat historic. But Plasma 5.10, for example, will respect the Panel icon size again.
-> systemsettings5 > Appearance > Fonts / Icons

xrandr scaling:
This may be needed if you are using multiple screens with different DPI, because X11 officially (= historically) only supports a single DPI value. Using the scaling, you can emulate a higher DPI on a low-DPI screen.
-> xrandr --scale, see https://wiki.archlinux.org/index.php/HiDPI

Qt scaling:
This may be needed to fix certain applications by changing QT_* environment variables. Some examples are Okular and Gwenview.
-> http://doc.qt.io/qt-5/highdpi.html
-> http://blog.qt.io/blog/2016/01/26/high- ... in-qt-5-6/
-> https://bugs.kde.org/show_bug.cgi?id=362856#c24
-> https://bugs.kde.org/show_bug.cgi?id=373178#c5

I don't know about GTK+ scaling, I guess they simply uses the logical DPI, but I had used Firefox with CSS scaling. That was the last GTK+ application I had used, but I am now back to a pure Qt5+KF5 system, using Otter Browser instead of Firefox.

Firefox:
- https://fedoramagazine.org/how-to-get-f ... nd-fedora/

In general, the search keywords to use are HiDPI, 4K, DPI, and "display scaling".