Section "Monitor"
    Identifier  "HDMI-A-3"
    Option      "Primary" "true"
EndSection

Section "Monitor"
    Identifier  "HDMI-A-4"
    Option      "RightOf" "HDMI-A-3"
EndSection

Section "Monitor"
  Identifier "HDMI-A-3"
  Modeline "1920x1080_60.00"  173.00  1920 2048 2248 2576  1080 1083 1088 1120 -hsync +vsync
  Option "PreferredMode" "1920x1080_60.00"
  Option "LeftOf" "HDMI-A-4"
  Option "DPMS" "true"
EndSection

Section "Monitor"
  Identifier "HDMI-A-4"
  Modeline "1920x1080_60.00"  173.00  1920 2048 2248 2576  1080 1083 1088 1120 -hsync +vsync
  Option "PreferredMode" "1920x1080_60.00"
  Option "RightOf" "HDMI-A-3"
  Option "DPMS" "true"
EndSection

Section "Screen"
  Identifier "Screen0"
  Device "Radeon" # e.g. Radeon, Intel, nvidia
  Monitor "HDMI-A-3"
  DefaultDepth 24
  SubSection "Display"
    Depth 24
    Virtual 3840 2160 # 1920 + 1920 (3840), 1080 + 1080 (2160)
  EndSubSection
EndSection