How can I have two mirrored displays (laptop screen + TV monitor) with different resolutions?

Question

My output of xrandr is:

Screen 0: minimum 8 x 8, current 1920 x 1080, maximum 32767 x 32767
eDP1 connected 1366x768+0+0 (normal left inverted right x axis y axis) 340mm x 190mm
   1366x768      60.02*+
   1280x720      59.86    60.00    59.74  
   1024x768      60.00  
   1024x576      60.00    59.90    59.82  
   960x540       60.00    59.63    59.82  
   800x600       60.32    56.25  
   864x486       60.00    59.92    59.57  
   640x480       59.94  
   720x405       59.51    60.00    58.99  
   680x384       60.00  
   640x360       59.84    59.32    60.00  
DP1 disconnected (normal left inverted right x axis y axis)
HDMI1 connected primary 1920x1080+0+0 (normal left inverted right x axis y axis) 480mm x 270mm
   1920x1080i    60.00 +  50.00    59.94  
   1920x1200     59.95  
   1920x1080     60.00*   50.00    59.94  
   1680x1050     59.88  
   1280x1024     60.02  
   1440x900      59.90  
   1280x720      60.00    50.00    59.94  
   1024x768      60.00  
   800x600       60.32  
   720x576       50.00  
   720x480       60.00    59.94  
   640x480       60.00    59.94  
   720x400       70.08  
VGA1 disconnected (normal left inverted right x axis y axis)
VIRTUAL1 disconnected (normal left inverted right x axis y axis)

I want to mirror my laptop screen to my TV monitor. But how I have it currently set up, the laptop screen is too zoomed in. That is, I can't see the task bar (panel) or whisker menu because they are off the screen.

I have found many thread of people changing settings with xrandr, but I can't get it to work for me. Most people seem to have issues with panning or overscanning. My issue seems much simpler but I can't fix it.

I simply want both displays to fit the screen. I'm using EndeavourOS, if that's important to know.

Could anyone please suggest how I can fix this?

EDIT: I've just found the scaling options in the display settings GUI. I now have it fit the screen, but the UI is smaller and text is hard to read. I assume there's a way to do this properly.

Answer 1

Mirroring isn't going to work this way.

The OS keeps track of positions of windows or your mouse cursor using coordinates. Top left coordinates are 0:0, screen resolution shows the bottom right coordinates. That's what keeps your mouse from disappearing from view when it hits the edge of the screen - that's the end of the coordinate matrix.

If you put your mouse on the top left corner, both screens will translate that to 0:0. Now move your mouse 100 pixels right and down on the laptop screen - how should that be translated to the larger resolution?

We could translate it directly to 100:100, no problem. Now move your mouse on the bottom right corner of the laptop screen. The coordinates are now 1366:768. On your larger screen that's a bit right and down from the center, and the mouse can't move further as it hit the coordinate max.

Or we could use the larger resolution as the base for translation. Move the mouse to the bottom right corner of the larger screen and it will be in coordinates 1920:1080 - your laptop monitor can't show it.

Consequently mirroring a screen = exact same resolution. If you want both screens to have the max resolution the only option is to extend the desktop so that both screens are used individually.