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A Rive .riv file is a binary container of artboards, animations, state machines, view models, and assets. The C++ API gives you read-only access to that container (File, Artboard) and mutable instances you can advance and draw (ArtboardInstance, StateMachineInstance).

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Importing a File

#include "rive/file.hpp"

ImportResult result;
rcp<File> file = File::import(
    Span<const uint8_t>{bytes.data(), bytes.size()},
    factory,        // a Factory* — usually your RenderContext
    &result,        // optional
    assetLoader);   // optional rcp<FileAssetLoader>

switch (result) {
    case ImportResult::success:           break;
    case ImportResult::unsupportedVersion: /* runtime is older than file */ break;
    case ImportResult::malformed:          /* bad bytes */                  break;
}
File is reference-counted (rcp<File>). It owns the parsed object graph and the assets imported in-band. Keep it alive for as long as any artboard instance derived from it is alive.
The Factory* you pass in is responsible for constructing every RenderPath, RenderPaint, RenderImage, font, and audio source the file produces. When using Rive’s GPU renderer, this is your RenderContext. When using a custom renderer, it is your Factory implementation.

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Determinism

File::deterministicMode = true;
A static flag that forces a fixed RNG seed and timestamp-driven scrolling for all subsequent loads. Useful for golden-image tests and frame-by-frame captures.

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Querying Artboards

size_t count = file->artboardCount();
std::string name = file->artboardNameAt(0);

Artboard* byName = file->artboard("Hero");          // by name
Artboard* byIndex = file->artboard(size_t{0});      // by index
Artboard* first = file->artboard();                 // file's first artboard
Artboard* returned by these accessors is read-only metadata — do not advance or draw it. To play an artboard, create an instance.

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Instancing

// Most common: copy of the file's default artboard.
std::unique_ptr<ArtboardInstance> ab = file->artboardDefault();

// Or by name / index:
auto namedAb = file->artboardNamed("Hero");
auto indexedAb = file->artboardAt(2);
Each call returns a fresh, independent copy. You can have many instances of the same artboard playing at once — each with its own state machine, its own data bindings, and its own layout. 
size_t   anims  = ab->animationCount();
size_t   states = ab->stateMachineCount();
std::string animName = ab->animationNameAt(0);
std::string smName   = ab->stateMachineNameAt(0);

// Designer-marked default state machine, if any.
int defaultIdx = ab->defaultStateMachineIndex();   // -1 if none

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Creating a State Machine

StateMachineInstance is the unit of playback in C++ — what you advance each frame, draw, and forward pointer events to. 
#include "rive/animation/state_machine_instance.hpp"

std::unique_ptr<StateMachineInstance> sm = ab->defaultStateMachine();
if (!sm && ab->stateMachineCount() > 0) {
    sm = ab->stateMachineAt(0);
}

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Sizing & Layout

Artboards have an intrinsic size set in the editor, plus an optional layout mode (Yoga-driven). For non-layout fits the artboard stays at its intrinsic size; for Fit::layout you drive width and height yourself: 
#include "rive/layout.hpp"

if (fit == Fit::layout) {
    ab->width(static_cast<float>(windowWidth));
    ab->height(static_cast<float>(windowHeight));
} else {
    ab->resetSize();   // back to intrinsic
}

// Re-evaluate layout before the next draw.
sm->advanceAndApply(0.f);
Artboard::bounds() returns the current ‘rect’ — feed it to computeAlignment to map artboard-space into your viewport.

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File Lifetime

Reference-counted ownership keeps lifetimes simple: 
rcp<File> file = File::import(...);
auto ab = file->artboardDefault();   // unique_ptr<ArtboardInstance>
auto sm = ab->defaultStateMachine(); // unique_ptr<StateMachineInstance>

// Tear down in reverse order:
sm.reset();
ab.reset();
file = nullptr;     // last rcp drops the File
Always destroy Rive objects before tearing down your RenderContext — they hold references to GPU resources owned by the context.