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[Agnella Datson]

How to set DPI options for Intel Xorg driver in Fedora 27

If you are using an Intel graphics card with the Xorg driver in Fedora 27, you may notice that the UseEdidDpi and DPI options are no longer available in the xorg.conf file. These options were used to override the DPI value reported by the monitor's EDID, which may be incorrect or undesirable for some users.

In this article, we will explain why these options were removed, and how you can still adjust the DPI settings for your display using other methods.

Why were UseEdidDpi and DPI options removed?

The UseEdidDpi and DPI options were removed from the Intel Xorg driver in version 2.99.917-26, which was released in October 2017. The reason for this change was to align with the upstream Xorg server, which deprecated these options in version 1.19. The upstream developers decided that these options were not reliable or consistent across different drivers and hardware, and that they could cause problems with some applications that rely on the EDID DPI value.

The Intel Xorg driver maintainer explained the rationale behind this decision in a mailing list post[^3^]:

"The problem is that there is no single correct answer for what DPI value to use. It depends on the physical size of the monitor, the resolution of the screen, the distance of the user from the screen, and the personal preference of the user. The EDID value is just a hint from the monitor manufacturer, which may or may not be accurate or suitable for your setup. The X server has no way of knowing any of these factors, so it cannot make a good decision for you."

Therefore, the Intel Xorg driver now follows the X server's default behavior, which is to use the EDID DPI value if available, or fallback to a hardcoded value of 96 DPI otherwise.

How to set DPI options for Intel Xorg driver in Fedora 27?

Even though the UseEdidDpi and DPI options are no longer supported by the Intel Xorg driver, there are still ways to adjust the DPI settings for your display in Fedora 27. Here are some possible methods:

• Use GNOME settings: If you are using GNOME as your desktop environment, you can use the Scale slider in the Displays settings to change the scaling factor for your display. This will affect both the size of fonts and UI elements. You can also use the Text Scaling Factor slider in the Universal Access settings to change only the size of fonts.

• Use xrandr: If you prefer a command-line tool, you can use xrandr to change the DPI value reported by your display. For example, if you want to set your DPI to 120, you can run this command: xrandr --dpi 120. This will affect only the size of fonts, not UI elements. You may need to restart your X session or log out and log back in for the changes to take effect.

• Create a xorg.conf file: If none of the above methods work for you, or if you want more fine-grained control over your DPI settings, you can create a custom xorg.conf file and use the DisplaySize option to specify the physical size of your monitor in millimeters. This will allow you to calculate and set your desired DPI value manually. For example, if you have a 24-inch monitor with a resolution of 1920x1080 pixels, and you want to set your DPI to 120, you can use this formula: DPI = (resolution * 25.4) / size. In this case, you would get: DPI = (1920 51082c0ec5