First things first, the help description in developer site was incomplete and has already been updated.
With VW2021 we changed how we save Lighting Device Parameters, so that they can be multicell and/or multi accessory. To do that we introduced two new constants in our code - one for 'set all' cells or accessories when the value is set on Lighting Device or specified cell and the value of this constant is -1. Second constant is 'ignore accessories' and its value is -2. It's work only for accessories.
For instance if you want to get Instrument Type of some Lighting Device you need to write:
LDevice_GetParamStr(handle, 0, -2, "Inst Type") // 'Inst Type' is not milticell parameter so we should use indexes from range [0..cell_count - 1]. We should use -2 for accessory index, because we want to get Instrument Type of the Lighting Device, so we ignore accessories
If you want to get Instrument Type of some accessory on your Lighting Device, for instance, on the first cell, 3th accessory, you need to write:
LDevice_GetParamStr(handle, 0, 2, "Inst Type") // the indexes start from 0, on both cells and accessories. The first accessory of every cell is with index 0.
And one last example: If you want to get milticell parameter, such as 'Purpose' and if you want to get it only for second cell(or every cell you want), you need to write:
LDevice_GetParamStr(handle, 1, -2, "Purpose") // 1 is the index of the second cell, and -2 for ignore accessories
'Purpose' also is milti accessory parameter, so you can get purpose of every accessory on your Lighting Device like this:
LDevice_GetParamStr(handle, cellIndex, accessoryIndex, "Purpose")
Notice the constant -1 for cells is not supported for Get methods.
For Set methods is the same, but with one more parameter for every function that is the new value.
If you ask yourself what is the worksheet name of some parameter of the LightingDevice, you may find it in Spotlight Preferences -> Parameters -> Worksheet Name column. If you wonder which parameter is Multi-cell and which is Accessory, you may find this information at the same place, but the last two columns. Notice they aren't editable, so you can't change which parameter is Multi-cell and which is Accessory.