Currently in histogram (accessed by Layers->Histogram... ) radio button Linear/Logarithmic have no effect. Signal about the change is not propagated to the function that handles mode switch.

Change connects radio button signal directly to the handler function. In addition, I removed the complicated logic of following the switch and replaced it with directly reading the radio button state.

1. Open a reasonable image.
2. In menu select Layers->Histogram.
3. Toggle radio buttons Linear/Logarithmic.
4. Observe that histogram changes.