Source/WebCore/platform/graphics/chromium/DrawingBufferChromium.cpp

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#include "config.h"

#include "DrawingBuffer.h"

#include "CanvasRenderingContext.h"
#include "Extensions3DChromium.h"
#include "GraphicsContext3D.h"
#include "GraphicsContext3DPrivate.h"
#include "GraphicsLayerChromium.h"
#include "TraceEvent.h"
#include <algorithm>
#include <public/Platform.h>
#include <public/WebCompositorSupport.h>
#include <public/WebExternalTextureLayer.h>
#include <public/WebExternalTextureLayerClient.h>
#include <public/WebGraphicsContext3D.h>

using namespace std;

namespace WebCore {

static unsigned generateColorTexture(GraphicsContext3D* context, const IntSize& size)
{
    unsigned offscreenColorTexture = context->createTexture();
    if (!offscreenColorTexture)
        return 0;

    context->bindTexture(GraphicsContext3D::TEXTURE_2D, offscreenColorTexture);
    context->texParameteri(GraphicsContext3D::TEXTURE_2D, GraphicsContext3D::TEXTURE_MAG_FILTER, GraphicsContext3D::LINEAR);
    context->texParameteri(GraphicsContext3D::TEXTURE_2D, GraphicsContext3D::TEXTURE_MIN_FILTER, GraphicsContext3D::LINEAR);
    context->texParameteri(GraphicsContext3D::TEXTURE_2D, GraphicsContext3D::TEXTURE_WRAP_S, GraphicsContext3D::CLAMP_TO_EDGE);
    context->texParameteri(GraphicsContext3D::TEXTURE_2D, GraphicsContext3D::TEXTURE_WRAP_T, GraphicsContext3D::CLAMP_TO_EDGE);
    context->texImage2DResourceSafe(GraphicsContext3D::TEXTURE_2D, 0, GraphicsContext3D::RGBA, size.width(), size.height(), 0, GraphicsContext3D::RGBA, GraphicsContext3D::UNSIGNED_BYTE);

    return offscreenColorTexture;
}

DrawingBuffer::DrawingBuffer(GraphicsContext3D* context,
                             const IntSize& size,
                             bool multisampleExtensionSupported,
                             bool packedDepthStencilExtensionSupported,
                             PreserveDrawingBuffer preserve,
                             AlphaRequirement alpha)
    : m_preserveDrawingBuffer(preserve)
    , m_alpha(alpha)
    , m_scissorEnabled(false)
    , m_texture2DBinding(0)
    , m_framebufferBinding(0)
    , m_activeTextureUnit(GraphicsContext3D::TEXTURE0)
    , m_context(context)
    , m_size(-1, -1)
    , m_multisampleExtensionSupported(multisampleExtensionSupported)
    , m_packedDepthStencilExtensionSupported(packedDepthStencilExtensionSupported)
    , m_fbo(0)
    , m_colorBuffer(0)
    , m_frontColorBuffer(0)
    , m_depthStencilBuffer(0)
    , m_depthBuffer(0)
    , m_stencilBuffer(0)
    , m_multisampleFBO(0)
    , m_multisampleColorBuffer(0)
    , m_contentsChanged(true)
{
    // Used by browser tests to detect the use of a DrawingBuffer.
    TRACE_EVENT_INSTANT0("test_gpu", "DrawingBufferCreation");

    // We need a separate front and back textures if ...
    m_separateFrontTexture = m_preserveDrawingBuffer == Preserve // ... we have to preserve contents after compositing, which is done with a copy or ...
                             || WebKit::Platform::current()->compositorSupport()->isThreadingEnabled(); // ... if we're in threaded mode and need to double buffer.
    initialize(size);
}

DrawingBuffer::~DrawingBuffer()
{
    if (!m_context)
        return;

    clear();
}

void DrawingBuffer::initialize(const IntSize& size)
{
    m_fbo = m_context->createFramebuffer();

    if (m_separateFrontTexture)
        m_frontColorBuffer = generateColorTexture(m_context.get(), size);

    m_context->bindFramebuffer(GraphicsContext3D::FRAMEBUFFER, m_fbo);
    m_colorBuffer = generateColorTexture(m_context.get(), size);
    m_context->framebufferTexture2D(GraphicsContext3D::FRAMEBUFFER, GraphicsContext3D::COLOR_ATTACHMENT0, GraphicsContext3D::TEXTURE_2D, m_colorBuffer, 0);
    createSecondaryBuffers();
    if (!reset(size)) {
        m_context.clear();
        return;
    }
}

#if USE(ACCELERATED_COMPOSITING)
void DrawingBuffer::prepareBackBuffer()
{
    if (!m_contentsChanged)
        return;

    m_context->makeContextCurrent();

    if (multisample())
        commit();

    if (m_preserveDrawingBuffer == Discard && m_separateFrontTexture) {
        swap(m_frontColorBuffer, m_colorBuffer);
        // It appears safe to overwrite the context's framebuffer binding in the Discard case since there will always be a
        // WebGLRenderingContext::clearIfComposited() call made before the next draw call which restores the framebuffer binding.
        // If this stops being true at some point, we should track the current framebuffer binding in the DrawingBuffer and restore
        // it after attaching the new back buffer here.
        m_context->bindFramebuffer(GraphicsContext3D::FRAMEBUFFER, m_fbo);
        m_context->framebufferTexture2D(GraphicsContext3D::FRAMEBUFFER, GraphicsContext3D::COLOR_ATTACHMENT0, GraphicsContext3D::TEXTURE_2D, m_colorBuffer, 0);
    }

    if (multisample() && !m_framebufferBinding)
        bind();
    else
        restoreFramebufferBinding();

    m_contentsChanged = false;
}

bool DrawingBuffer::requiresCopyFromBackToFrontBuffer() const
{
    return m_separateFrontTexture && m_preserveDrawingBuffer == Preserve;
}

unsigned DrawingBuffer::frontColorBuffer() const
{
    return m_separateFrontTexture ? m_frontColorBuffer : m_colorBuffer;
}
#endif

class DrawingBufferPrivate : public WebKit::WebExternalTextureLayerClient {
    WTF_MAKE_NONCOPYABLE(DrawingBufferPrivate);
public:
    explicit DrawingBufferPrivate(DrawingBuffer* drawingBuffer)
        : m_drawingBuffer(drawingBuffer)
        , m_layer(adoptPtr(WebKit::Platform::current()->compositorSupport()->createExternalTextureLayer(this)))
    {

        GraphicsContext3D::Attributes attributes = m_drawingBuffer->graphicsContext3D()->getContextAttributes();
        m_layer->setOpaque(!attributes.alpha);
        m_layer->setPremultipliedAlpha(attributes.premultipliedAlpha);
        GraphicsLayerChromium::registerContentsLayer(m_layer->layer());
    }

    virtual ~DrawingBufferPrivate()
    {
        GraphicsLayerChromium::unregisterContentsLayer(m_layer->layer());
    }

    virtual unsigned prepareTexture(WebKit::WebTextureUpdater& updater) OVERRIDE
    {
        m_drawingBuffer->prepareBackBuffer();

        m_drawingBuffer->graphicsContext3D()->flush();
        m_drawingBuffer->graphicsContext3D()->markLayerComposited();

        unsigned textureId = m_drawingBuffer->frontColorBuffer();
        if (m_drawingBuffer->requiresCopyFromBackToFrontBuffer())
            updater.appendCopy(m_drawingBuffer->colorBuffer(), textureId, m_drawingBuffer->size());

        return textureId;
    }

    virtual WebKit::WebGraphicsContext3D* context() OVERRIDE
    {
        return GraphicsContext3DPrivate::extractWebGraphicsContext3D(m_drawingBuffer->graphicsContext3D());
    }

    WebKit::WebLayer* layer() { return m_layer->layer(); }

private:
    DrawingBuffer* m_drawingBuffer;
    OwnPtr<WebKit::WebExternalTextureLayer> m_layer;
};

#if USE(ACCELERATED_COMPOSITING)
PlatformLayer* DrawingBuffer::platformLayer()
{
    if (!m_private)
        m_private = adoptPtr(new DrawingBufferPrivate(this));

    return m_private->layer();
}
#endif

Platform3DObject DrawingBuffer::framebuffer() const
{
    return m_fbo;
}

#if USE(ACCELERATED_COMPOSITING)
void DrawingBuffer::paintCompositedResultsToCanvas(ImageBuffer* imageBuffer)
{
    if (!m_context->makeContextCurrent() || m_context->getExtensions()->getGraphicsResetStatusARB() != GraphicsContext3D::NO_ERROR)
        return;

    IntSize framebufferSize = m_context->getInternalFramebufferSize();

    // Since we're using the same context as WebGL, we have to restore any state we change (in this case, just the framebuffer binding).
    // FIXME: The WebGLRenderingContext tracks the current framebuffer binding, it would be slightly more efficient to use this value
    // rather than querying it off of the context.
    GC3Dint previousFramebuffer = 0;
    m_context->getIntegerv(GraphicsContext3D::FRAMEBUFFER_BINDING, &previousFramebuffer);

    Platform3DObject framebuffer = m_context->createFramebuffer();
    m_context->bindFramebuffer(GraphicsContext3D::FRAMEBUFFER, framebuffer);
    m_context->framebufferTexture2D(GraphicsContext3D::FRAMEBUFFER, GraphicsContext3D::COLOR_ATTACHMENT0, GraphicsContext3D::TEXTURE_2D, frontColorBuffer(), 0);

    Extensions3DChromium* extensions = static_cast<Extensions3DChromium*>(m_context->getExtensions());
    extensions->paintFramebufferToCanvas(framebuffer, framebufferSize.width(), framebufferSize.height(), !m_context->getContextAttributes().premultipliedAlpha, imageBuffer);
    m_context->deleteFramebuffer(framebuffer);

    m_context->bindFramebuffer(GraphicsContext3D::FRAMEBUFFER, previousFramebuffer);
}
#endif

}