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Tweak new info in grass7.txt

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AlisterH 2023-07-02 00:09:29 +12:00 committed by Nyall Dawson
parent 830dc772b6
commit 2b9e2b77be
1 changed files with 4 additions and 4 deletions
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python/plugins/grassprovider/grass.txt
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@ -173,17 +173,17 @@ There are 4 different levels where you can add logic:
- Processing the command itself: if you need to chain more than one GRASS command for your algorithm.
- Processing the outputs: if you need to do special things before exporting layers or if you need special export methods.
To add some logic on one (or more) level(s), you have to create a .py file named according to the algorithm name in python/plugins/grassprovider/ext, replacing '.' with '_'.
Then you need to create methods using the respective names:
To add some logic on one or more of these levels you have to create a .py file named according to the algorithm name in python/plugins/grassprovider/ext, replacing '.' with '_'.
Then create methods using the respective names:
- Input parameters: checkParameterValuesBeforeExecuting
- Inputs import: processInputs
- Command: processCommand
- Outputs: processOutputs
If there is a Python file with the algorithm name in the ext directory, methods will be imported from the file and run instead of the common methods (there are "standard" processCommand/processInputs/processOutputs/checkParameterValuesBeforeExecuting methods in the code of the GRASS provider for QGIS Processing, in python/plugins/grassprovider/grass_algorithm.py).
If there is a Python file with the algorithm name in the ext directory, methods will be imported from the file and run instead of the common methods (there are "standard" processCommand/processInputs/processOutputs/checkParameterValuesBeforeExecuting methods in the code of the GRASS provider, in python/plugins/grassprovider/grass_algorithm.py).
If we take the example of v.what.rast, there is an ext file: ext/v_what_rast.py.
In this file there is a processCommand method. It just launches the standard processCommand but with the delOutputs option set to True (we do not want to have standard outputs).
Then there is also a customized processOutputs which exports the input vector as an output for QGIS. We need to do this because v.what.rast modifies values directly in the input vector layer instead of generating a new output, so we have to build this output ourself.
If you want to do special things in the ext mechanism, you will need to read (and understand) the GRASS provider code standard methods in Grass7Algorithm.py.
If you want to do special things in the ext mechanism, you will need to read (and understand) the code for the standard methods in Grass7Algorithm.py.