Emulator

What's the problem? Describe what went wrong.

The lens_distortion post-processing effect fails parsing with the following log output:

Failed to parse shader
Shader Info Log:
ERROR: 0:171: 'layer' : undeclared identifier
ERROR: 0:171: '' : compilation terminated
ERROR: 2 compilation errors. No code generated.

What steps will reproduce the problem?

Attempt to use the lens_distortion effect

Is the issue present in the latest development version? For future reference, please also write down the version number of the latest development version.

Yes

a9dc4ac3f0
5.0-11665

Is the issue present in the latest stable version?

Feature is not present in version 5.0

If the issue isn't present in the latest stable version, which is the first broken version?

b44a0980eb
5.0-10943

git bisect result:

b44a0980eb310b221feb84a195db63b89276a053 is the first bad commit
commit b44a0980eb310b221feb84a195db63b89276a053
Author: Stenzek stenzek@gmail.com
Date: Wed Oct 2 11:52:52 2019 +1000

PostProcessing: Use correct layer in quad-buffered modes

Previously, only the left eye was being used.

Source/Core/VideoCommon/PostProcessing.cpp | 23 ++++++++++++++---------
1 file changed, 14 insertions(+), 9 deletions(-)

What are your PC specifications? (CPU, GPU, Operating System, more)

AMD FX(tm)-8120
AMD Radeon RX 590
Linux - Debian sid

Is there anything else that can help developers narrow down the issue?

Changing 'layer' to 'src_layer' on line 56 in Data/Sys/Shaders/lens_distortion.glsl restores functionality.
I don't know if this is technically correct, it was just a test based on the changes in the failing commit.