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#include "qqnxrasterwindow.h"
#include "qqnxscreen.h"

#include <QDebug>

#include <errno.h>

#if defined(QQNXRASTERWINDOW_DEBUG)
#define qRasterWindowDebug qDebug
#else
#define qRasterWindowDebug QT_NO_QDEBUG_MACRO
#endif

QT_BEGIN_NAMESPACE

QQnxRasterWindow::QQnxRasterWindow(QWindow *window, screen_context_t context) :
    QQnxWindow(window, context),
    m_currentBufferIndex(-1),
    m_previousBufferIndex(-1)
{
    initWindow();
}

void QQnxRasterWindow::post(const QRegion &dirty)
{
    // How double-buffering works
    // --------------------------
    //
    // The are two buffers, the previous one and the current one.
    // The previous buffer always contains the complete, full image of the whole window when it
    // was last posted.
    // The current buffer starts with the complete, full image of the second to last posting
    // of the window.
    //
    // During painting, Qt paints on the current buffer. Thus, when Qt has finished painting, the
    // current buffer contains the second to last image plus the newly painted regions.
    // Since the second to last image is too old, we copy over the image from the previous buffer, but
    // only for those regions that Qt didn't paint (because that would overwrite what Qt has just
    // painted). This is the copyPreviousToCurrent() call below.
    //
    // After the call to copyPreviousToCurrent(), the current buffer contains the complete, full image of the
    // whole window in its current state, and we call screen_post_window() to make the new buffer
    // available to libscreen (called "posting"). There, only the regions that Qt painted on are
    // posted, as nothing else has changed.
    //
    // After that, the previous and the current buffers are swapped, and the whole cycle starts anew.

    // Check if render buffer exists and something was rendered
    if (m_currentBufferIndex != -1 && !dirty.isEmpty()) {
        qRasterWindowDebug() << Q_FUNC_INFO << "window =" << window();
        QQnxBuffer &currentBuffer = m_buffers[m_currentBufferIndex];

        // Copy unmodified region from old render buffer to new render buffer;
        // required to allow partial updates
        QRegion preserve = m_previousDirty - dirty - m_scrolled;
        blitPreviousToCurrent(preserve, 0, 0);

        // Calculate region that changed
        QRegion modified = preserve + dirty + m_scrolled;
        QRect rect = modified.boundingRect();
        int dirtyRect[4] = { rect.x(), rect.y(), rect.x() + rect.width(), rect.y() + rect.height() };

        // Update the display with contents of render buffer
        errno = 0;
        int result = screen_post_window(nativeHandle(), currentBuffer.nativeBuffer(), 1, dirtyRect, 0);
        if (result != 0)
            qFatal("QQnxWindow: failed to post window buffer, errno=%d", errno);

        // Advance to next nender buffer
        m_previousBufferIndex = m_currentBufferIndex++;
        if (m_currentBufferIndex >= MAX_BUFFER_COUNT)
            m_currentBufferIndex = 0;

        // Save modified region and clear scrolled region
        m_previousDirty = dirty;
        m_scrolled = QRegion();
        // Notify screen that window posted
        if (screen() != 0)
            screen()->onWindowPost(this);

        if (m_cover)
            m_cover->updateCover();
    }
}

void QQnxRasterWindow::scroll(const QRegion &region, int dx, int dy, bool flush)
{
    qRasterWindowDebug() << Q_FUNC_INFO << "window =" << window();
    blitPreviousToCurrent(region, dx, dy, flush);
    m_scrolled += region;
}

QQnxBuffer &QQnxRasterWindow::renderBuffer()
{
    qRasterWindowDebug() << Q_FUNC_INFO << "window =" << window();

    // Check if render buffer is invalid
    if (m_currentBufferIndex == -1) {
        // Get all buffers available for rendering
        errno = 0;
        screen_buffer_t buffers[MAX_BUFFER_COUNT];
        int result = screen_get_window_property_pv(nativeHandle(), SCREEN_PROPERTY_RENDER_BUFFERS, (void **)buffers);
        if (result != 0)
            qFatal("QQnxRasterWindow: failed to query window buffers, errno=%d", errno);

        // Wrap each buffer and clear
        for (int i = 0; i < MAX_BUFFER_COUNT; ++i) {
            m_buffers[i] = QQnxBuffer(buffers[i]);

            // Clear Buffer
            errno = 0;
            int bg[] = { SCREEN_BLIT_COLOR, 0x00000000, SCREEN_BLIT_END };
            result = screen_fill(screen()->nativeContext(), buffers[i], bg);
            if (result != 0)
                qFatal("QQnxWindow: failed to clear window buffer, errno=%d", errno);
        }

        errno = 0;
        result = screen_flush_blits(screen()->nativeContext(), 0);
        if (result != 0)
            qFatal("QQnxWindow: failed to flush blits, errno=%d", errno);

        // Use the first available render buffer
        m_currentBufferIndex = 0;
        m_previousBufferIndex = -1;
    }

    return m_buffers[m_currentBufferIndex];
}

int QQnxRasterWindow::pixelFormat() const
{
    return screen()->nativeFormat();
}

void QQnxRasterWindow::resetBuffers()
{
    // Buffers were destroyed; reacquire them
    m_currentBufferIndex = -1;
    m_previousDirty = QRegion();
    m_scrolled = QRegion();
}

void QQnxRasterWindow::blitPreviousToCurrent(const QRegion &region, int dx, int dy, bool flush)
{
    qRasterWindowDebug() << Q_FUNC_INFO << "window =" << window();

    // Abort if previous buffer is invalid or if nothing to copy
    if (m_previousBufferIndex == -1 || region.isEmpty())
        return;

    QQnxBuffer &currentBuffer = m_buffers[m_currentBufferIndex];
    QQnxBuffer &previousBuffer = m_buffers[m_previousBufferIndex];

    // Break down region into non-overlapping rectangles
    const QVector<QRect> rects = region.rects();
    for (int i = rects.size() - 1; i >= 0; i--) {
        // Clip rectangle to bounds of target
        const QRect rect = rects[i].intersected(currentBuffer.rect());

        if (rect.isEmpty())
            continue;

        // Setup blit operation
        int attribs[] = { SCREEN_BLIT_SOURCE_X, rect.x(),
                          SCREEN_BLIT_SOURCE_Y, rect.y(),
                          SCREEN_BLIT_SOURCE_WIDTH, rect.width(),
                          SCREEN_BLIT_SOURCE_HEIGHT, rect.height(),
                          SCREEN_BLIT_DESTINATION_X, rect.x() + dx,
                          SCREEN_BLIT_DESTINATION_Y, rect.y() + dy,
                          SCREEN_BLIT_DESTINATION_WIDTH, rect.width(),
                          SCREEN_BLIT_DESTINATION_HEIGHT, rect.height(),
                          SCREEN_BLIT_END };

        // Queue blit operation
        errno = 0;
        const int result = screen_blit(m_screenContext, currentBuffer.nativeBuffer(),
                                       previousBuffer.nativeBuffer(), attribs);
        if (result != 0)
            qFatal("QQnxWindow: failed to blit buffers, errno=%d", errno);
    }

    // Check if flush requested
    if (flush) {
        // Wait for all blits to complete
        errno = 0;
        const int result = screen_flush_blits(m_screenContext, SCREEN_WAIT_IDLE);
        if (result != 0)
            qFatal("QQnxWindow: failed to flush blits, errno=%d", errno);

        // Buffer was modified outside the CPU
        currentBuffer.invalidateInCache();
    }
}

QT_END_NAMESPACE