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Add RFC: Move to MVC
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‎text/0053-move-to-mvc.md‎

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# Summary
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- Apply the MVC pattern
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- Global config, profile and scene collections are represented by their own object
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- Frontend API functions related to config file are replaced
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# Motivation
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The actual code is almost a chimera of software architectural patterns, applying the MVC pattern will allow to untangle the code and make it more clear.
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# Design
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**The naming of new types is not final.**
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Flowchart diagrams will be used as illustration so the following is the key for those:
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- Parallelogram nodes represent concepts/abstraction.
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- Rectangle nodes represent a piece of software (code, classes, API…).
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- If with round edges, a user can see it and/or interract with it.
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<!-- Hexagon nodes represent plugins-->
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This is a diagram representing basic MVC:
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```mermaid
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flowchart LR
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user(["User(s)"])
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model[/OBS Model/]
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view[/OBS View/]
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controller[/OBS Controller/]
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user-- "interact with" -->view
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view-- "user action" -->controller
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controller-- update -->view
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controller-- manipulate -->model
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model-- notify -->controller
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```
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---
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The following is the same diagram but considering splitting the model in three like it is in OBS Studio (global, profile, scene collection):
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```mermaid
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flowchart LR
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user(["User(s)"])
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view[/OBS View/]
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controller[/OBS Controller/]
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globconf[/Global Config/]
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profile[/Profile/]
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scenecol[/Scene Collection/]
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user-- "interact with" -->view
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view-- "user action" -->controller
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controller-- "update" -->view
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controller-- manipulate -->globconf
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controller-- manipulate -->profile
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controller-- manipulate -->scenecol
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scenecol-- notify -->controller
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```
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---
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If those concept are replaced by their matching elements in the actual OBS Studio (without considering the frontend API), it looks like that:
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```mermaid
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flowchart LR
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user(["User(s)"])
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ui("OBS Studio UI")
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globconf["globalConfig (ConfigFile)"]
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subgraph profile [Profile]
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basicconf["basicConfig (ConfigFile)"]
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streamenc["streamEncoder (OBSData)"]
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recordenc["recordEncoder (OBSData)"]
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service["service (OBSService)"]
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end
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user-- "interact with" -->ui
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ui-- "user action" -->ui
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ui-- "update view" -->ui
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ui-- manipulate -->globconf
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ui-- manipulate --> basicconf
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ui-- manipulate --> streamenc
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ui-- manipulate --> recordenc
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ui-- manipulate --> service
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ui-- "manipulate scene collection" -->ui
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ui-- "scene collection notify" -->ui
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```
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"*OBS Studio UI*" combines "*OBS View*", "*OBS Controller*" and "*Scene Collection*" which is a part of the "*OBS Model*".
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Note that ConfigFile is not a good type to represent *globalConfig* and *basicConfig*.
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"*Profile*" is also splitted into three or four parts (*recordEncoder* is unused if the encode is the same as the stream), so this one really need a type to represent it.
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Note: from now, the node "*Profile*" will be used if the diagram is not related to "*Profile*" itself.
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---
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So by applying MVC, "*OBS Studio UI*" should only serve as "*OBS View*":
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```mermaid
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flowchart LR
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user(["User(s)"])
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subgraph view ["OBS View"]
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ui("OBS Studio UI")
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end
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controller[/OBS Controller/]
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globconf["globalConfig (ConfigFile)"]
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profile[/Profile/]
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scenecol[/Scene Collection/]
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user-- "interact with" -->ui
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ui-- "user action" -->controller
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controller-- update -->ui
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controller-- manipulate -->globconf
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controller-- manipulate -->profile
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controller-- manipulate -->scenecol
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scenecol-- notify -->controller
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```
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## "*Scene Collection*" and "*OBS Studio UI*"
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The "*Scene Collection*" contains everything related to scenes, sources (and filters) are tightly connected to them:
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- Transitions
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- Projectors
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- Scaling of the preview
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- Video mix configuration for the virtual camera
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- Settings of some plugins bound to the collection
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Except the last point, everything is stored in parts of the UI. "*Scene Collection*" shall be split from it into a new type/object.
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```mermaid
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flowchart LR
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user(["User(s)"])
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ui("OBS Studio UI")
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globconf["globalConfig (ConfigFile)"]
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profile[/Profile/]
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scenecol["sceneCollection (OBSSceneCollection)"]
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user-- "interact with" -->ui
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ui-- "user action" -->ui
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ui-- "update view" -->ui
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ui-- manipulate -->globconf
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ui-- manipulate --> profile
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ui-- manipulate --> scenecol
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scenecol-- notify -->ui
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```
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The changes around the "*notify*" part are explained later.
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## "*Profile*" and "*Global Config*"
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New types/objects will be created to represent those:
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```mermaid
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flowchart LR
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user(["User(s)"])
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ui("OBS Studio UI")
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globconf["globalConfig (OBSGlobalConfig)"]
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profile["profile (OBSProfile)"]
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scenecol["sceneCollection (OBSSceneCollection)"]
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user-- "interact with" -->ui
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ui-- "user action" -->ui
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ui-- "update view" -->ui
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ui-- manipulate -->globconf
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ui-- manipulate --> profile
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ui-- manipulate --> scenecol
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scenecol-- notify -->ui
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```
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Note: *OBSProfile* also includes encoders and service.
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Their ConfigFile could be openned only when loading and saving but…
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### "*OBS Frontend API*" and ConfigFile
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"*OBS Frontend API*" provide functions to access *globalConfig* and *basicConfig* (profile) and modify them without restriction ignoring "*OBS Controller*", the program is not even aware is one of its own config happen to be changed.
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```mermaid
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flowchart LR
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plugins{{"Plugin(s)"}}
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ui("OBS Studio UI")
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api["OBS Frontend API"]
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subgraph model [OBS Model]
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globconf["globalConfig (ConfigFile)"]
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subgraph profile [Profile]
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basicconf["basicConfig (ConfigFile)"]
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streamenc["streamEncoder (OBSData)"]
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recordenc["recordEncoder (OBSData)"]
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service["service (OBSService)"]
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end
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scenecol["sceneCollection (OBSSceneCollection)"]
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end
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plugins-- action -->api
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api-- "event callback" -->plugins
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ui-- "frontend events" -->api
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api-- action -->ui
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ui-- "update view" -->ui
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ui-- manipulate -->globconf
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ui-- manipulate --> basicconf
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ui-- manipulate --> streamenc
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ui-- manipulate --> recordenc
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ui-- manipulate --> service
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ui-- manipulate --> scenecol
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plugins-- "manipulate configs" -->api
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api-- manipulate -->globconf
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api-- manipulate --> basicconf
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```
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So `obs_frontend_get_global_config` and `obs_frontend_get_profile_config` will be deprecated.
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Until those are removed, OBSGlobalConfig or OBSProfile will open the ConfigFile and keep it updated. But changing a OBS config from a plugin will have no effect, the stored value will overwrite what the plugin has put.
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To replace those two functions to allow plugins to save their config in the global config or the profile. Functions like the following will be created for `bool`, `double`, `int64_t`, `uint64_t` and `const char *`(string):
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```c
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EXPORT void obs_frontend_set_global_bool_config(const char *section, const char *name, bool value);
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EXPORT bool obs_frontend_get_global_bool_config(const char *section, const char *name);
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```
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```c
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EXPORT void obs_frontend_set_profile_bool_config(const char *section, const char *name, bool value);
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EXPORT bool obs_frontend_get_profile_module_bool_config(const char *section, const char *name);
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```
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If a section owned by OBS is used with a setter, the setter will do nothing.
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Those settings will be stored in OBSGlobalConfig or OBSProfile, and then written in the file while saving.
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To check if functions to get some OBS config is needed, asking third-party plugins developper may be needed.
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Now "*OBS Frontend API*" no longer bypass "*OBS Controller*" to manipulate the global config and the profile:
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```mermaid
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flowchart LR
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plugins{{"Plugin(s)"}}
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ui("OBS Studio UI")
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api["OBS Frontend API"]
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globconf["globalConfig (OBSGlobalConfig)"]
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profile["profile (OBSProfile)"]
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scenecol["sceneCollection (OBSSceneCollection)"]
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plugins-- action -->api
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api-- "event callback" -->plugins
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ui-- "frontend events" -->api
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api-- action -->ui
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ui-- "update view" -->ui
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ui-- manipulate -->globconf
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ui-- manipulate --> profile
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ui-- manipulate --> scenecol
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scenecol-- notify -->ui
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```
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## "*OBS Controller*" and "*OBS Studio UI*"
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"*OBS Studio UI*" act as "*OBS View*" and "*OBS Controller*". "*OBS Controller*" is scattered in various elements of the UI.
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```mermaid
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flowchart LR
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user(["User(s)"])
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ui("OBS Studio UI")
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globconf["globalConfig (OBSGlobalConfig)"]
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profile["profile (OBSProfile)"]
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scenecol["sceneCollection (OBSSceneCollection)"]
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user-- "interact with" -->ui
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ui-- "user action" -->ui
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ui-- "update view" -->ui
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ui-- manipulate -->globconf
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ui-- manipulate --> profile
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ui-- manipulate --> scenecol
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scenecol-- notify -->ui
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```
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---
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*OBS Controller* shall be split from the UI:
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```mermaid
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flowchart LR
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user(["User(s)"])
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control["OBSController"]
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ui("OBS Studio UI")
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globconf["globalConfig (OBSGlobalConfig)"]
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profile["profile (OBSProfile)"]
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scenecol["sceneCollection (OBSSceneCollection)"]
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user-- "interact with" -->ui
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ui-- "user action" -->control
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control-- "update view" -->ui
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control-- manipulate -->globconf
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control-- manipulate --> profile
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control-- manipulate --> scenecol
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scenecol-- notify -->control
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```
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Other windows (e.g. settings) will parented to the main window but will be created from "*OBSController*".
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---
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Note that OBSController will manage all OBSSignal and bound them to a Qt signal/slot meant for the UI, no OBSSignal will be directly bound to an UI element.
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```mermaid
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flowchart LR
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ui("OBS Studio UI")
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control["OBSController"]
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scenecol["OBSSceneCollection"]
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ui-- "1. QSignal to QSlot" -->control
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control-- "4. QSlot from QSignal" -->ui
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control-- "2. manipulate" -->scenecol
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scenecol-- "3. OBSSignal" -->control
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```
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# Additional Information
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The frontend API is the only part of OBS Studio that have access to "*OBS View*" (dock, action…), "*OBS Controller*" and "*OBS Model*" (sources, scenes…).
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The "OBSBasic" naming could retired from while progressing on the application of this RFC.

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