/********************************************************************
 KWin - the KDE window manager
 This file is part of the KDE project.

Copyright (C) 2010, 2012 Martin Gräßlin <mgraesslin@kde.org>

This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program.  If not, see <http://www.gnu.org/licenses/>.
*********************************************************************/
#include "eglonxbackend.h"
// kwin
#include "main.h"
#include "options.h"
#include "overlaywindow.h"
#include "screens.h"
#include "xcbutils.h"
// kwin libs
#include <kwinglplatform.h>
// Qt
#include <QDebug>
#include <QOpenGLContext>
// system
#include <unistd.h>

namespace KWin
{

EglOnXBackend::EglOnXBackend()
    : AbstractEglBackend()
    , m_overlayWindow(new OverlayWindow())
    , surfaceHasSubPost(0)
    , m_bufferAge(0)
    , m_usesOverlayWindow(true)
    , m_connection(connection())
    , m_x11Display(display())
    , m_rootWindow(rootWindow())
    , m_x11ScreenNumber(kwinApp()->x11ScreenNumber())
{
    init();
    // Egl is always direct rendering
    setIsDirectRendering(true);
}

EglOnXBackend::EglOnXBackend(xcb_connection_t *connection, Display *display, xcb_window_t rootWindow, int screenNumber, xcb_window_t renderingWindow)
    : AbstractEglBackend()
    , m_overlayWindow(nullptr)
    , surfaceHasSubPost(0)
    , m_bufferAge(0)
    , m_usesOverlayWindow(false)
    , m_connection(connection)
    , m_x11Display(display)
    , m_rootWindow(rootWindow)
    , m_x11ScreenNumber(screenNumber)
    , m_renderingWindow(renderingWindow)
{
    init();
    // Egl is always direct rendering
    setIsDirectRendering(true);
}

static bool gs_tripleBufferUndetected = true;
static bool gs_tripleBufferNeedsDetection = false;

EglOnXBackend::~EglOnXBackend()
{
    if (isFailed() && m_overlayWindow) {
        m_overlayWindow->destroy();
    }
    cleanup();

    gs_tripleBufferUndetected = true;
    gs_tripleBufferNeedsDetection = false;

    if (m_overlayWindow) {
        if (overlayWindow()->window()) {
            overlayWindow()->destroy();
        }
        delete m_overlayWindow;
    }
}

void EglOnXBackend::init()
{
    if (!initRenderingContext()) {
        setFailed(QStringLiteral("Could not initialize rendering context"));
        return;
    }

    initKWinGL();
    if (!hasGLExtension(QByteArrayLiteral("EGL_KHR_image")) &&
        (!hasGLExtension(QByteArrayLiteral("EGL_KHR_image_base")) ||
         !hasGLExtension(QByteArrayLiteral("EGL_KHR_image_pixmap")))) {
        setFailed(QStringLiteral("Required support for binding pixmaps to EGLImages not found, disabling compositing"));
        return;
    }
    if (!hasGLExtension(QByteArrayLiteral("GL_OES_EGL_image"))) {
        setFailed(QStringLiteral("Required extension GL_OES_EGL_image not found, disabling compositing"));
        return;
    }

    // check for EGL_NV_post_sub_buffer and whether it can be used on the surface
    if (hasGLExtension(QByteArrayLiteral("EGL_NV_post_sub_buffer"))) {
        if (eglQuerySurface(eglDisplay(), surface(), EGL_POST_SUB_BUFFER_SUPPORTED_NV, &surfaceHasSubPost) == EGL_FALSE) {
            EGLint error = eglGetError();
            if (error != EGL_SUCCESS && error != EGL_BAD_ATTRIBUTE) {
                setFailed(QStringLiteral("query surface failed"));
                return;
            } else {
                surfaceHasSubPost = EGL_FALSE;
            }
        }
    }

    initBufferAge();

    setSyncsToVBlank(false);
    setBlocksForRetrace(false);
    gs_tripleBufferNeedsDetection = false;
    m_swapProfiler.init();
    if (surfaceHasSubPost) {
        qCDebug(KWIN_CORE) << "EGL implementation and surface support eglPostSubBufferNV, let's use it";

        if (options->glPreferBufferSwap() != Options::NoSwapEncourage) {
            // check if swap interval 1 is supported
            EGLint val;
            eglGetConfigAttrib(eglDisplay(), config(), EGL_MAX_SWAP_INTERVAL, &val);
            if (val >= 1) {
                if (eglSwapInterval(eglDisplay(), 1)) {
                    qCDebug(KWIN_CORE) << "Enabled v-sync";
                    setSyncsToVBlank(true);
                    const QByteArray tripleBuffer = qgetenv("KWIN_TRIPLE_BUFFER");
                    if (!tripleBuffer.isEmpty()) {
                        setBlocksForRetrace(qstrcmp(tripleBuffer, "0") == 0);
                        gs_tripleBufferUndetected = false;
                    }
                    gs_tripleBufferNeedsDetection = gs_tripleBufferUndetected;
                }
            } else {
                qCWarning(KWIN_CORE) << "Cannot enable v-sync as max. swap interval is" << val;
            }
        } else {
            // disable v-sync
            eglSwapInterval(eglDisplay(), 0);
        }
    } else {
        /* In the GLX backend, we fall back to using glCopyPixels if we have no extension providing support for partial screen updates.
         * However, that does not work in EGL - glCopyPixels with glDrawBuffer(GL_FRONT); does nothing.
         * Hence we need EGL to preserve the backbuffer for us, so that we can draw the partial updates on it and call
         * eglSwapBuffers() for each frame. eglSwapBuffers() then does the copy (no page flip possible in this mode),
         * which means it is slow and not synced to the v-blank. */
        qCWarning(KWIN_CORE) << "eglPostSubBufferNV not supported, have to enable buffer preservation - which breaks v-sync and performance";
        eglSurfaceAttrib(eglDisplay(), surface(), EGL_SWAP_BEHAVIOR, EGL_BUFFER_PRESERVED);
    }

    initWayland();
}

bool EglOnXBackend::initRenderingContext()
{
    initClientExtensions();
    EGLDisplay dpy;

    // Use eglGetPlatformDisplayEXT() to get the display pointer
    // if the implementation supports it.
    const bool havePlatformBase = hasClientExtension(QByteArrayLiteral("EGL_EXT_platform_base"));
    if (havePlatformBase) {
        // Make sure that the X11 platform is supported
        if (!hasClientExtension(QByteArrayLiteral("EGL_EXT_platform_x11")))
            return false;

        const int attribs[] = {
            EGL_PLATFORM_X11_SCREEN_EXT, m_x11ScreenNumber,
            EGL_NONE
        };

        dpy = eglGetPlatformDisplayEXT(EGL_PLATFORM_X11_EXT, m_x11Display, attribs);
    } else {
        dpy = eglGetDisplay(m_x11Display);
    }

    if (dpy == EGL_NO_DISPLAY)
        return false;
    setEglDisplay(dpy);
    initEglAPI();

    initBufferConfigs();

    if (m_usesOverlayWindow) {
        if (!overlayWindow()->create()) {
            qCCritical(KWIN_CORE) << "Could not get overlay window";
            return false;
        } else {
            overlayWindow()->setup(None);
        }
    }

    xcb_window_t window = XCB_WINDOW_NONE;
    if (m_overlayWindow) {
        window = m_overlayWindow->window();
    } else if (m_renderingWindow) {
        window = m_renderingWindow;
    }
    if (window == XCB_WINDOW_NONE) {
        return false;
    }

    EGLSurface surface = EGL_NO_SURFACE;
    if (havePlatformBase) {
        // Note: Window is 64 bits on a 64-bit architecture whereas xcb_window_t is
        //       always 32 bits. eglCreatePlatformWindowSurfaceEXT() expects the
        //       native_window parameter to be pointer to a Window, so this variable
        //       cannot be an xcb_window_t.
        surface = eglCreatePlatformWindowSurfaceEXT(dpy, config(), (void *) &window, nullptr);
    } else {
        surface = eglCreateWindowSurface(dpy, config(), window, nullptr);
    }

    if (surface == EGL_NO_SURFACE) {
        return false;
    }
    setSurface(surface);

    EGLContext ctx = EGL_NO_CONTEXT;
    if (isOpenGLES()) {
        const EGLint context_attribs[] = {
            EGL_CONTEXT_CLIENT_VERSION, 2,
            EGL_NONE
        };

        ctx = eglCreateContext(dpy, config(), EGL_NO_CONTEXT, context_attribs);
    } else {
        const EGLint context_attribs_31_core[] = {
            EGL_CONTEXT_MAJOR_VERSION_KHR, 3,
            EGL_CONTEXT_MINOR_VERSION_KHR, 1,
            EGL_NONE
        };

        const EGLint context_attribs_legacy[] = {
            EGL_NONE
        };

        const QByteArray eglExtensions = eglQueryString(dpy, EGL_EXTENSIONS);
        const QList<QByteArray> extensions = eglExtensions.split(' ');

        // Try to create a 3.1 core context
        if (options->glCoreProfile() && extensions.contains("EGL_KHR_create_context"))
            ctx = eglCreateContext(dpy, config(), EGL_NO_CONTEXT, context_attribs_31_core);

        if (ctx == EGL_NO_CONTEXT)
            ctx = eglCreateContext(dpy, config(), EGL_NO_CONTEXT, context_attribs_legacy);
    }

    if (ctx == EGL_NO_CONTEXT) {
        qCCritical(KWIN_CORE) << "Create Context failed";
        return false;
    }
    setContext(ctx);

    if (eglMakeCurrent(dpy, surface, surface, ctx) == EGL_FALSE) {
        qCCritical(KWIN_CORE) << "Make Context Current failed";
        return false;
    }

    EGLint error = eglGetError();
    if (error != EGL_SUCCESS) {
        qCWarning(KWIN_CORE) << "Error occurred while creating context " << error;
        return false;
    }

    return true;
}

bool EglOnXBackend::initBufferConfigs()
{
    const EGLint config_attribs[] = {
        EGL_SURFACE_TYPE,         EGL_WINDOW_BIT|EGL_SWAP_BEHAVIOR_PRESERVED_BIT,
        EGL_RED_SIZE,             1,
        EGL_GREEN_SIZE,           1,
        EGL_BLUE_SIZE,            1,
        EGL_ALPHA_SIZE,           0,
        EGL_RENDERABLE_TYPE,      isOpenGLES() ? EGL_OPENGL_ES2_BIT : EGL_OPENGL_BIT,
        EGL_CONFIG_CAVEAT,        EGL_NONE,
        EGL_NONE,
    };

    EGLint count;
    EGLConfig configs[1024];
    if (eglChooseConfig(eglDisplay(), config_attribs, configs, 1024, &count) == EGL_FALSE) {
        qCCritical(KWIN_CORE) << "choose config failed";
        return false;
    }

    ScopedCPointer<xcb_get_window_attributes_reply_t> attribs(xcb_get_window_attributes_reply(m_connection,
                                                                                              xcb_get_window_attributes_unchecked(m_connection, m_rootWindow),
                                                                                              nullptr));
    if (!attribs) {
        qCCritical(KWIN_CORE) << "Failed to get window attributes of root window";
        return false;
    }

    setConfig(configs[0]);
    for (int i = 0; i < count; i++) {
        EGLint val;
        if (eglGetConfigAttrib(eglDisplay(), configs[i], EGL_NATIVE_VISUAL_ID, &val) == EGL_FALSE) {
            qCCritical(KWIN_CORE) << "egl get config attrib failed";
        }
        if (uint32_t(val) == attribs->visual) {
            setConfig(configs[i]);
            break;
        }
    }
    return true;
}

void EglOnXBackend::present()
{
    if (lastDamage().isEmpty())
        return;

    const QSize screenSize = screens()->size();
    const QRegion displayRegion(0, 0, screenSize.width(), screenSize.height());
    const bool fullRepaint = supportsBufferAge() || (lastDamage() == displayRegion);

    if (fullRepaint || !surfaceHasSubPost) {
        if (gs_tripleBufferNeedsDetection) {
            eglWaitGL();
            m_swapProfiler.begin();
        }
        // the entire screen changed, or we cannot do partial updates (which implies we enabled surface preservation)
        eglSwapBuffers(eglDisplay(), surface());
        if (gs_tripleBufferNeedsDetection) {
            eglWaitGL();
            if (char result = m_swapProfiler.end()) {
                gs_tripleBufferUndetected = gs_tripleBufferNeedsDetection = false;
                if (result == 'd' && GLPlatform::instance()->driver() == Driver_NVidia) {
                    // TODO this is a workaround, we should get __GL_YIELD set before libGL checks it
                    if (qstrcmp(qgetenv("__GL_YIELD"), "USLEEP")) {
                        options->setGlPreferBufferSwap(0);
                        eglSwapInterval(eglDisplay(), 0);
                        result = 0; // hint proper behavior
                        qCWarning(KWIN_CORE) << "\nIt seems you are using the nvidia driver without triple buffering\n"
                                          "You must export __GL_YIELD=\"USLEEP\" to prevent large CPU overhead on synced swaps\n"
                                          "Preferably, enable the TripleBuffer Option in the xorg.conf Device\n"
                                          "For this reason, the tearing prevention has been disabled.\n"
                                          "See https://bugs.kde.org/show_bug.cgi?id=322060\n";
                    }
                }
                setBlocksForRetrace(result == 'd');
            }
        }
        if (supportsBufferAge()) {
            eglQuerySurface(eglDisplay(), surface(), EGL_BUFFER_AGE_EXT, &m_bufferAge);
        }
    } else {
        // a part of the screen changed, and we can use eglPostSubBufferNV to copy the updated area
        foreach (const QRect & r, lastDamage().rects()) {
            eglPostSubBufferNV(eglDisplay(), surface(), r.left(), screenSize.height() - r.bottom() - 1, r.width(), r.height());
        }
    }

    setLastDamage(QRegion());
    if (!supportsBufferAge()) {
        eglWaitGL();
        xcb_flush(m_connection);
    }
}

void EglOnXBackend::screenGeometryChanged(const QSize &size)
{
    Q_UNUSED(size)

    // TODO: base implementation in OpenGLBackend

    // The back buffer contents are now undefined
    m_bufferAge = 0;
}

SceneOpenGL::TexturePrivate *EglOnXBackend::createBackendTexture(SceneOpenGL::Texture *texture)
{
    return new EglTexture(texture, this);
}

QRegion EglOnXBackend::prepareRenderingFrame()
{
    QRegion repaint;

    if (gs_tripleBufferNeedsDetection) {
        // the composite timer floors the repaint frequency. This can pollute our triple buffering
        // detection because the glXSwapBuffers call for the new frame has to wait until the pending
        // one scanned out.
        // So we compensate for that by waiting an extra milisecond to give the driver the chance to
        // fllush the buffer queue
        usleep(1000);
    }

    present();

    if (supportsBufferAge())
        repaint = accumulatedDamageHistory(m_bufferAge);

    startRenderTimer();
    eglWaitNative(EGL_CORE_NATIVE_ENGINE);

    return repaint;
}

void EglOnXBackend::endRenderingFrame(const QRegion &renderedRegion, const QRegion &damagedRegion)
{
    if (damagedRegion.isEmpty()) {
        setLastDamage(QRegion());

        // If the damaged region of a window is fully occluded, the only
        // rendering done, if any, will have been to repair a reused back
        // buffer, making it identical to the front buffer.
        //
        // In this case we won't post the back buffer. Instead we'll just
        // set the buffer age to 1, so the repaired regions won't be
        // rendered again in the next frame.
        if (!renderedRegion.isEmpty())
            glFlush();

        m_bufferAge = 1;
        return;
    }

    setLastDamage(renderedRegion);

    if (!blocksForRetrace()) {
        // This also sets lastDamage to empty which prevents the frame from
        // being posted again when prepareRenderingFrame() is called.
        present();
    } else {
        // Make sure that the GPU begins processing the command stream
        // now and not the next time prepareRenderingFrame() is called.
        glFlush();
    }

    if (m_overlayWindow && overlayWindow()->window())  // show the window only after the first pass,
        overlayWindow()->show();   // since that pass may take long

    // Save the damaged region to history
    if (supportsBufferAge())
        addToDamageHistory(damagedRegion);
}

bool EglOnXBackend::usesOverlayWindow() const
{
    return m_usesOverlayWindow;
}

OverlayWindow* EglOnXBackend::overlayWindow()
{
    return m_overlayWindow;
}

/************************************************
 * EglTexture
 ************************************************/

EglTexture::EglTexture(KWin::SceneOpenGL::Texture *texture, KWin::EglOnXBackend *backend)
    : AbstractEglTexture(texture, backend)
{
}

EglTexture::~EglTexture() = default;

void KWin::EglTexture::onDamage()
{
    if (options->isGlStrictBinding()) {
        // This is just implemented to be consistent with
        // the example in mesa/demos/src/egl/opengles1/texture_from_pixmap.c
        eglWaitNative(EGL_CORE_NATIVE_ENGINE);
        glEGLImageTargetTexture2DOES(GL_TEXTURE_2D, (GLeglImageOES) image());
    }
    GLTexturePrivate::onDamage();
}

} // namespace