Decompose Plug-in manager

[AnitaBats]

1. Details are TBD - needs meeting
2. Decomposition needed

Design attached #999

[gera-gas]

Description of task decomposition.
All estimation times have two borders: this is not 100% precision time frame, this is the approximate time window for solving task.

1. Preferences for the custom plugin search path.
   1.1 Create the preference type, by analogy BoolSettings, but for describing plugins paths that will contain a wxArrayString objects, something like - ArrayStringSettings or using StringSetting for economy time.
   1.2 If we using StringSetting, the path will be separated by ;, and this is a not a problem to parse this by wxTokenizer.
   1.3 Second, need patch PluginManager::FindFilesInPathList() with additional search directories from settings.
   Estimate: 4 - 6 hrs.

2. Check method.
   For each plugin type, needed a static method for validation each plugin instance of each plugin type, something like: VSTEffectsModule::Check() and VSTEffectsModule::DiscoverPluginsAtPath().
   2.1 Get information about Audacity CLI command (2,3 hrs).
   2.2 Run a new Audacity process with check command with output result to STDOUT.
   2.3 Catch and parsing STDOUT after this on success.
   2.4 Create this check method for each plugin type: VST (1 hrs), AU (4,5 hrs), VAMP, LV2, LADSPA (6,8 hrs).
   2.5 Call this methods at startup (for example in PluginManager::Initialize() or CheckForUpdates() for comfortable calling from dialog (when user press on Rescan plugins) and collect failed information (2,3 hrs).
   2.6 Output dialog with incompatible plugins list (3,4 hrs).
   Estimate: 18 - 24 hrs + possible time buffer for loss while switching and testing on all OS. (3,4 hrs).

3. Remake PluginRegistrationDialog dialog.
   3.1 Remake wxListCtrl of PluginRegistrationDialog::mEffects to add "Version", "Type" and "Enabled" collumn (5,8 hrs).
   3.2 Remove extra functionality like: "State" collumn, "New" radio button, buttons "Select All", "Enable", etc (4,6).
   3.3 Add callback on button "Rescan plugins", "Done" (2,3) hrs.
   3.4 Final behavior tests (2,4) hrs.
   Estimate: 13 - 21 hrs.

Total estimate: 35 - 51 hrs.

@crsib @Paul-Licameli could you review, please.

[Paul-Licameli]

This looks like a good decomposition. But I think part 1 might make do simply with existing StringSetting, splitting the string on ; characters.

Questions.

• Do you have at least one example of LADSPA, LV2, Vamp, VST2 plug-ins that you can test with?
• This is still supposing only VST2 support -- not yet VST3. Correct?
• I recall we said the new dialog also needs a "failed" state. Instead of one choice in a drop-down menu as now, perhaps a line of the list control is disabled. Do you account for that?
• If the user interface specification is firm enough, perhaps you can attempt step 3 first, to get early feedback and testing. While you have not yet implemented validation for LADSPA, LV2, and Vamp, you might simply always make them "failed."

The user interface can be sent to review and testing, while you concurrently continue working on the AU, LADSPA, LV2, Vamp cases. And perhaps each of those becomes a separate PR.

[gera-gas]

1 - I can download this plugins or at leat build empty plugins for AU, VST2, LV2 and LADSPA.
2 - yes, correct.
3 - yes, I remember that about "failed" state.
4 - okay
I agree about separate and move UI developing part to first order.

[AnitaBats]

Decomposition is done