Source/WebCore/Modules/mediastream/CanvasCaptureMediaStreamTrack.cpp

/*
 * Copyright (C) 2017 Apple Inc. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1.  Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
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 *     notice, this list of conditions and the following disclaimer in the
 *     documentation and/or other materials provided with the distribution.
 *
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 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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#include "config.h"
#include "CanvasCaptureMediaStreamTrack.h"

#include "GraphicsContext.h"
#include "HTMLCanvasElement.h"
#include "WebGLRenderingContextBase.h"

#if ENABLE(MEDIA_STREAM)

namespace WebCore {

Ref<CanvasCaptureMediaStreamTrack> CanvasCaptureMediaStreamTrack::create(ScriptExecutionContext& context, Ref<HTMLCanvasElement>&& canvas, std::optional<double>&& frameRequestRate)
{
    auto source = CanvasCaptureMediaStreamTrack::Source::create(canvas.get(), WTFMove(frameRequestRate));
    return adoptRef(*new CanvasCaptureMediaStreamTrack(context, WTFMove(canvas), WTFMove(source)));
}

CanvasCaptureMediaStreamTrack::CanvasCaptureMediaStreamTrack(ScriptExecutionContext& context, Ref<HTMLCanvasElement>&& canvas, Ref<CanvasCaptureMediaStreamTrack::Source>&& source)
    : MediaStreamTrack(context, MediaStreamTrackPrivate::create(source.copyRef()))
    , m_canvas(WTFMove(canvas))
    , m_source(WTFMove(source))
{
}

Ref<CanvasCaptureMediaStreamTrack::Source> CanvasCaptureMediaStreamTrack::Source::create(HTMLCanvasElement& canvas, std::optional<double>&& frameRequestRate)
{
    auto source = adoptRef(*new Source(canvas, WTFMove(frameRequestRate)));
    source->start();

    callOnMainThread([source = source.copyRef()] {
        if (!source->m_canvas)
            return;
        source->captureCanvas();
    });
    return source;
}

// FIXME: Give source id and name
CanvasCaptureMediaStreamTrack::Source::Source(HTMLCanvasElement& canvas, std::optional<double>&& frameRequestRate)
    : RealtimeMediaSource(String(), Type::Video, String())
    , m_frameRequestRate(WTFMove(frameRequestRate))
    , m_requestFrameTimer(*this, &Source::requestFrameTimerFired)
    , m_canvasChangedTimer(*this, &Source::captureCanvas)
    , m_canvas(&canvas)
{
    m_settings.setWidth(canvas.width());
    m_settings.setHeight(canvas.height());
    RealtimeMediaSourceSupportedConstraints constraints;
    constraints.setSupportsWidth(true);
    constraints.setSupportsHeight(true);
    m_settings.setSupportedConstraints(constraints);
}

void CanvasCaptureMediaStreamTrack::Source::startProducingData()
{
    if (!m_canvas)
        return;
    m_canvas->addObserver(*this);

    if (!m_frameRequestRate)
        return;

    if (m_frameRequestRate.value())
        m_requestFrameTimer.startRepeating(1_s / m_frameRequestRate.value());
}

void CanvasCaptureMediaStreamTrack::Source::stopProducingData()
{
    m_requestFrameTimer.stop();

    if (!m_canvas)
        return;
    m_canvas->removeObserver(*this);
}

void CanvasCaptureMediaStreamTrack::Source::requestFrameTimerFired()
{
    requestFrame();
}

void CanvasCaptureMediaStreamTrack::Source::canvasDestroyed(CanvasBase& canvas)
{
    ASSERT_UNUSED(canvas, m_canvas == &canvas);

    stop();
    m_canvas = nullptr;
}

void CanvasCaptureMediaStreamTrack::Source::canvasResized(CanvasBase& canvas)
{
    ASSERT_UNUSED(canvas, m_canvas == &canvas);

    m_settings.setWidth(m_canvas->width());
    m_settings.setHeight(m_canvas->height());

    settingsDidChange();
}

void CanvasCaptureMediaStreamTrack::Source::canvasChanged(CanvasBase& canvas, const FloatRect&)
{
    ASSERT_UNUSED(canvas, m_canvas == &canvas);

    // FIXME: We need to preserve drawing buffer as we are currently grabbing frames asynchronously.
    // We should instead add an anchor point for both 2d and 3d contexts where canvas will actually paint.
    // And call canvas observers from that point.
    if (is<WebGLRenderingContextBase>(canvas.renderingContext())) {
        auto& context = downcast<WebGLRenderingContextBase>(*canvas.renderingContext());
        if (!context.isPreservingDrawingBuffer()) {
            canvas.scriptExecutionContext()->addConsoleMessage(MessageSource::JS, MessageLevel::Warning, ASCIILiteral("Turning drawing buffer preservation for the WebGL canvas being captured"));
            context.setPreserveDrawingBuffer(true);
        }
    }

    // FIXME: We should try to generate the frame at the time the screen is being updated.
    if (m_canvasChangedTimer.isActive())
        return;
    m_canvasChangedTimer.startOneShot(0_s);
}

void CanvasCaptureMediaStreamTrack::Source::captureCanvas()
{
    ASSERT(m_canvas);

    if (!isProducingData())
        return;

    if (m_frameRequestRate) {
        if (!m_shouldEmitFrame)
            return;
        m_shouldEmitFrame = false;
    }

    if (!m_canvas->originClean())
        return;

    auto sample = m_canvas->toMediaSample();
    if (!sample)
        return;

    videoSampleAvailable(*sample);
}

RefPtr<MediaStreamTrack> CanvasCaptureMediaStreamTrack::clone()
{
    if (!scriptExecutionContext())
        return nullptr;

    return CanvasCaptureMediaStreamTrack::create(*scriptExecutionContext(), m_canvas.copyRef(), m_source->frameRequestRate());
}

}

#endif // ENABLE(MEDIA_STREAM)