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#include <QtGui/QOpenGLShaderProgram>
#include <QtGui/QOpenGLContext>

#include "qeglplatformbackingstore_p.h"
#include "qeglcompositor_p.h"
#include "qeglplatformwindow_p.h"
#include "qeglplatformscreen_p.h"

QT_BEGIN_NAMESPACE

/*!
    \class QEGLPlatformBackingStore
    \brief A backing store implementation for EGL and GLES.
    \since 5.2
    \internal
    \ingroup qpa

    This implementation uploads raster-rendered widget windows into
    textures and composites them onto a single native window using
    QEGLCompositor. This means that multiple top-level widgets are
    supported without creating actual native windows for each of them.

    The class is ready to be used as-is, the default
    QEGLPlatformIntegration::createPlatformBackingStore()
    implementation creates an instance which is ready to be used
    without further customization.

    If QEGLCompositor is not suitable, this backing store
    implementation can also be used without it. In this case a
    subclass must reimplement composite() and schedule an update in
    its custom compositor when this function is called. The textures
    are accessible via QEGLPlatformWindow::texture().
*/

QEGLPlatformBackingStore::QEGLPlatformBackingStore(QWindow *window)
    : QPlatformBackingStore(window),
      m_window(static_cast<QEGLPlatformWindow *>(window->handle())),
      m_texture(0)
{
    m_window->setBackingStore(this);
}

QPaintDevice *QEGLPlatformBackingStore::paintDevice()
{
    return &m_image;
}

void QEGLPlatformBackingStore::updateTexture()
{
    glBindTexture(GL_TEXTURE_2D, m_texture);

    if (!m_dirty.isNull()) {
        QRegion fixed;
        QRect imageRect = m_image.rect();
        m_dirty |= imageRect;

        foreach (const QRect &rect, m_dirty.rects()) {
            // intersect with image rect to be sure
            QRect r = imageRect & rect;

            // if the rect is wide enough it's cheaper to just
            // extend it instead of doing an image copy
            if (r.width() >= imageRect.width() / 2) {
                r.setX(0);
                r.setWidth(imageRect.width());
            }

            fixed |= r;
        }

        foreach (const QRect &rect, fixed.rects()) {
            // if the sub-rect is full-width we can pass the image data directly to
            // OpenGL instead of copying, since there's no gap between scanlines
            if (rect.width() == imageRect.width()) {
                glTexSubImage2D(GL_TEXTURE_2D, 0, 0, rect.y(), rect.width(), rect.height(), GL_RGBA, GL_UNSIGNED_BYTE,
                                m_image.constScanLine(rect.y()));
            } else {
                glTexSubImage2D(GL_TEXTURE_2D, 0, rect.x(), rect.y(), rect.width(), rect.height(), GL_RGBA, GL_UNSIGNED_BYTE,
                    m_image.copy(rect).constBits());
            }
        }

        m_dirty = QRegion();
    }
}

void QEGLPlatformBackingStore::flush(QWindow *window, const QRegion &region, const QPoint &offset)
{
    Q_UNUSED(window);
    Q_UNUSED(region);
    Q_UNUSED(offset);

#ifdef QEGL_EXTRA_DEBUG
    qWarning("QEglBackingStore::flush %p", window);
#endif

    QEGLPlatformScreen *screen = static_cast<QEGLPlatformScreen *>(m_window->screen());
    QEGLPlatformWindow *dstWin = screen->compositingWindow();
    if (!dstWin || !dstWin->isRaster())
        return;

    m_window->create();
    QOpenGLContext *context = screen->compositingContext();
    context->makeCurrent(dstWin->window());
    updateTexture();
    composite(context, dstWin);
}

void QEGLPlatformBackingStore::composite(QOpenGLContext *context, QEGLPlatformWindow *window)
{
    QEGLCompositor::instance()->schedule(context, window);
}

void QEGLPlatformBackingStore::beginPaint(const QRegion &rgn)
{
    m_dirty |= rgn;
}

void QEGLPlatformBackingStore::resize(const QSize &size, const QRegion &staticContents)
{
    Q_UNUSED(staticContents);

    QEGLPlatformScreen *screen = static_cast<QEGLPlatformScreen *>(m_window->screen());
    QEGLPlatformWindow *dstWin = screen->compositingWindow();
    if (!dstWin || !dstWin->isRaster())
        return;

    m_image = QImage(size, QImage::Format_RGB32);
    m_window->create();

    screen->compositingContext()->makeCurrent(dstWin->window());

    if (m_texture)
        glDeleteTextures(1, &m_texture);

    glGenTextures(1, &m_texture);
    glBindTexture(GL_TEXTURE_2D, m_texture);
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);

    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, size.width(), size.height(), 0, GL_RGBA, GL_UNSIGNED_BYTE, 0);
}

QT_END_NAMESPACE