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obs-studio/docs/sphinx/reference-canvases.rst
2025-04-02 12:39:46 -04:00

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Canvas API Reference (obs_canvas_t)
===================================
Canvases are reference-counted objects that contain scenes and define how those are rendered.
They provide a video object which can be used with encoders or raw outputs.
libobs maintains a main canvas that exists at all times and is used for the default video outputs.
.. type:: obs_canvas_t
A reference-counted canvas.
.. type:: obs_weak_canvas_t
A weak reference to a canvas.
.. code:: cpp
#include <obs.h>
.. _canvas_signal_handler_reference:
Canvas Signals
--------------
The following signals are defined for canvases:
**remove** (ptr canvas)
Called when the :c:func:`obs_canvas_remove()` function is called on the canvas.
**destroy** (ptr canvas)
Called when a canvas is about to be destroyed.
**video_reset** (ptr canvas)
Called when the canvas's video mix has been reset after a call to
:c:func:`obs_reset_video()` or :c:func:`obs_canvas_reset_video()`.
**source_add** (ptr canvas, ptr source)
Called when a source has been added to the canvas.
**source_remove** (ptr canvas, ptr source)
Called when a source has been removed from the canvas.
**rename** (ptr canvas, string new_name, string prev_name)
Called when the canvas has been renamed.
**channel_change** (ptr canvas, int channel, in out ptr source, ptr prev_source)
Called when a channel source has been changed.
Canvas Flags
------------
Canvases can have different behaviors, these can be controlled via the **flags** parameter when creating a canvas.
Flags may be `0` or a bitwise `OR` combination of the following values:
- **MAIN** - Main canvas, cannot be renamed or reset, cannot be set by user
- **ACTIVATE** - Canvas's sources will become active when they are visible
- **MIX_AUDIO** - Audio from channels in this canvas will be mixed into the audio output
- **SCENE_REF** - Canvas will hold references for scene sources
- **EPHEMERAL** - Indicates this canvas is not supposed to be saved
Additionally, the following preset combinations of flags are defined:
- **PROGRAM** which equals `ACTIVATE | MIX_AUDIO | SCENE_REF`
- **PREVIEW** which equals `EPHEMERAL`
- **DEVICE** which equals `ACTIVATE | EPHEMERAL`
General Canvas Functions
------------------------
.. function:: obs_canvas_t *obs_get_main_canvas()
Get a strong reference to the main OBS canvas.
---------------------
.. function:: obs_canvas_t *obs_canvas_create(const char *name, struct obs_video_info *ovi, uint32_t flags)
Creates a new canvas.
:param name: Name, will be deduplicated if necessary
:param ovi: Video configuration to use for this canvas's video output
:param flags: Canvas flags
:return: Canvas object
---------------------
.. function:: obs_canvas_t *obs_canvas_create_private(const char *name, struct obs_video_info *ovi, uint32_t flags)
Creates a new private canvas.
:param name: Name, will **not** be deduplicated
:param ovi: Video configuration to use for this canvas's video output
:param flags: Canvas flags
:return: Canvas object
---------------------
.. function:: void obs_canvas_remove(obs_canvas_t *canvas)
Signal that references to canvas should be released and mark the canvas as removed.
---------------------
.. function:: bool obs_canvas_removed(obs_canvas_t *canvas)
Returns if a canvas is marked as removed (i.e., should no longer be used).
---------------------
.. function:: void obs_canvas_set_name(obs_canvas_t *canvas, const char *name)
Set canvas name
---------------------
.. function:: const char *obs_canvas_get_name(const obs_canvas_t *canvas)
Get canvas name
---------------------
.. function:: const char *obs_canvas_get_uuid(const obs_canvas_t *canvas)
Get canvas UUID
---------------------
.. function:: uint32_t obs_canvas_get_flags(const obs_canvas_t *canvas)
Gets flags set on a canvas
---------------------
Saving/Loading Functions
------------------------
.. function:: obs_data_t *obs_save_canvas(obs_canvas_t *source)
Saves a canvas to settings data
---------------------
.. function:: obs_canvas_t *obs_load_canvas(obs_data_t *data)
Loads a canvas from settings data
---------------------
Reference Counting Functions
----------------------------
.. function:: obs_canvas_t *obs_canvas_get_ref(obs_canvas_t *canvas)
Add strong reference to a canvas
---------------------
.. function:: void obs_canvas_release(obs_canvas_t *canvas)
Release strong reference
---------------------
.. function:: void obs_weak_canvas_addref(obs_weak_canvas_t *weak)
Add weak reference
---------------------
.. function:: void obs_weak_canvas_release(obs_weak_canvas_t *weak)
Release weak reference
---------------------
.. function:: obs_weak_canvas_t *obs_canvas_get_weak_canvas(obs_canvas_t *canvas)
Get weak reference from strong reference
---------------------
.. function:: obs_canvas_t *obs_weak_canvas_get_canvas(obs_weak_canvas_t *weak)
Get strong reference from weak reference
---------------------
Canvas Channel Functions
------------------------
.. function:: void obs_canvas_set_channel(obs_canvas_t *canvas, uint32_t channel, obs_source_t *source)
Sets the source to be used for a canvas channel.
---------------------
.. function:: obs_source_t *obs_canvas_get_channel(obs_canvas_t *canvas, uint32_t channel)
Gets the source currently in use for a canvas channel.
---------------------
Canvas Source List Functions
----------------------------
.. function:: obs_scene_t *obs_canvas_scene_create(obs_canvas_t *canvas, const char *name)
Create scene attached to a canvas.
---------------------
.. function:: void obs_canvas_scene_remove(obs_scene_t *scene)
Remove a scene from a canvas.
---------------------
.. function:: void obs_canvas_move_scene(obs_scene_t *scene, obs_canvas_t *dst)
Move scene to another canvas, detaching it from the previous one and deduplicating the name if needed.
---------------------
.. function:: void obs_canvas_enum_scenes(obs_canvas_t *canvas, bool (*enum_proc)(void *, obs_source_t *), void *param)
Enumerates scenes belonging to a canvas.
Callback function returns true to continue enumeration, or false to end enumeration.
---------------------
.. function:: obs_source_t *obs_canvas_get_source_by_name(const char *name)
Gets a canvas source by its name.
Increments the source reference counter, use
:c:func:`obs_source_release()` to release it when complete.
---------------------
.. function:: obs_scene_t *obs_canvas_get_scene_by_name(const char *name)
Gets a canvas scene by its name.
Increments the source reference counter, use
:c:func:`obs_scene_release()` to release it when complete.
---------------------
Canvas Video Functions
----------------------
.. function:: bool obs_canvas_reset_video(obs_canvas_t *canvas, struct obs_video_info *ovi)
Reset a canvas's video configuration.
Note that the frame rate property is ignored and the global rendering frame rate is used instead.
---------------------
.. function:: bool obs_canvas_has_video(obs_canvas_t *canvas)
Returns true if the canvas video is configured.
---------------------
.. function:: video_t *obs_canvas_get_video(const obs_canvas_t *canvas)
Get canvas video output
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.. function:: bool obs_canvas_get_video_info(const obs_canvas_t *canvas, struct obs_video_info *ovi)
Get canvas video info (if any)
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.. function:: void obs_canvas_render(obs_canvas_t *canvas)
Render the canvas's view. Must be called on the graphics thread.
---------------------