Question Gamma color space - unexpected result?

So, I created a simple new project in Unity 2021.3, set up URP, created a plane on a scene and attach a very simple shader to it:

Code (csharp):

1.  
2. v2f vert (appdata v)
3. {
4.     v2f o;
5.     o.vertex = UnityObjectToClipPos(v.vertex);
6.     o.uv = v.uv;
7.     return o;
8. }
9.  
10. fixed4 frag(v2f i) : SV_Target
11. {
12.     float o = i.uv.x;
13.     return fixed4(o.xxx, 1.0);
14.  
15. }
16.  

As you can see I am outputting a linear gradient from the shader (based on a UV coord).

The project uses the Gamma color space and while I am outputting a linear gradient (not gamma-corrected), my expectation was that the resulting color gradient on the screen will not be linear. BUT that's what I get:



... isn't that a linear gradient?! When I am sampling the middle pixel (just below the blue arrow) in Photoshop, I am getting the mid color value exactly:



What would indicate that the gradient is linear indeed.

Is that expected? My understanding was that the output from a shader should always be gamma-corrected when using the Gamma color space in order to look consistent on the screen. Or am I missing something?

An explanation of this unexpected result may be the fact that every time I switch from the Linear space to Gamma space in the project settings I get the following warning:

Requested RenderTexture with sRGB format. sRGB formats are not supported in gamma mode, fallback to a UNorm format. Use a UNorm format instead of sRGB to silence this warning.

UnityEditor.EditorGUI/PopupCallbackInfo:SetEnumValueDelegate (object,string[],int)/ICODE]

 

It looks like the behavior is exactly the same when using the legacy render pipeline so it is not strictly URP-related. May I ask an admin to move the thread into the General Graphics subforum?

 

Looks like an sRGB (gamma) gradient to me.

Image source: https://twitter.com/BartWronsk/status/1453379834579726337/photo/2