/*
 * This file is part of mpv.
 *
 * mpv is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * mpv 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 Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with mpv.  If not, see <http://www.gnu.org/licenses/>.
 */

#include <windows.h>
#include <EGL/egl.h>
#include <EGL/eglext.h>
#include <d3d11.h>
#include <dxgi1_2.h>
#include <dwmapi.h>

#include "angle_dynamic.h"
#include "egl_helpers.h"

#include "common/common.h"
#include "options/m_config.h"
#include "video/out/w32_common.h"
#include "osdep/windows_utils.h"
#include "context.h"

#ifndef EGL_D3D_TEXTURE_ANGLE
#define EGL_D3D_TEXTURE_ANGLE 0x33A3
#endif
#ifndef EGL_OPTIMAL_SURFACE_ORIENTATION_ANGLE
#define EGL_OPTIMAL_SURFACE_ORIENTATION_ANGLE 0x33A7
#define EGL_SURFACE_ORIENTATION_ANGLE 0x33A8
#define EGL_SURFACE_ORIENTATION_INVERT_Y_ANGLE 0x0002
#endif

// Windows 8 enum value, not present in mingw-w64 headers
#define DXGI_ADAPTER_FLAG_SOFTWARE (2)

enum {
    RENDERER_AUTO,
    RENDERER_D3D9,
    RENDERER_D3D11,
};

struct angle_opts {
    int renderer;
    int d3d11_warp;
    int d3d11_feature_level;
    int egl_windowing;
    int swapchain_length; // Currently only works with DXGI 1.2+
    int max_frame_latency;
};

#define OPT_BASE_STRUCT struct angle_opts
const struct m_sub_options angle_conf = {
    .opts = (const struct m_option[]) {
        OPT_CHOICE("angle-renderer", renderer, 0,
                   ({"auto", RENDERER_AUTO},
                    {"d3d9", RENDERER_D3D9},
                    {"d3d11", RENDERER_D3D11})),
        OPT_CHOICE("angle-d3d11-warp", d3d11_warp, 0,
                   ({"auto", -1},
                    {"no", 0},
                    {"yes", 1})),
        OPT_CHOICE("angle-d3d11-feature-level", d3d11_feature_level, 0,
                   ({"11_0", D3D_FEATURE_LEVEL_11_0},
                    {"10_1", D3D_FEATURE_LEVEL_10_1},
                    {"10_0", D3D_FEATURE_LEVEL_10_0},
                    {"9_3", D3D_FEATURE_LEVEL_9_3})),
        OPT_CHOICE("angle-egl-windowing", egl_windowing, 0,
                   ({"auto", -1},
                    {"no", 0},
                    {"yes", 1})),
        OPT_INTRANGE("angle-swapchain-length", swapchain_length, 0, 2, 16),
        OPT_INTRANGE("angle-max-frame-latency", max_frame_latency, 0, 1, 16),
        {0}
    },
    .defaults = &(const struct angle_opts) {
        .renderer = RENDERER_AUTO,
        .d3d11_warp = -1,
        .d3d11_feature_level = D3D_FEATURE_LEVEL_11_0,
        .egl_windowing = -1,
        .swapchain_length = 6,
        .max_frame_latency = 3,
    },
    .size = sizeof(struct angle_opts),
};

struct priv {
    IDXGIFactory1 *dxgi_factory;
    IDXGIFactory2 *dxgi_factory2;
    IDXGIAdapter1 *dxgi_adapter;
    IDXGIDevice1 *dxgi_device;
    IDXGISwapChain *dxgi_swapchain;
    IDXGISwapChain1 *dxgi_swapchain1;

    ID3D11Device *d3d11_device;
    ID3D11DeviceContext *d3d11_context;
    ID3D11Texture2D *d3d11_backbuffer;

    EGLConfig egl_config;
    EGLDisplay egl_display;
    EGLDeviceEXT egl_device;
    EGLContext egl_context;
    EGLSurface egl_window; // For the EGL windowing surface only
    EGLSurface egl_backbuffer; // For the DXGI swap chain based surface

    int sc_width, sc_height; // Swap chain width and height
    int swapinterval;

    bool sw_adapter_msg_shown;

    struct angle_opts *opts;
};

static __thread struct MPGLContext *current_ctx;

static void update_sizes(MPGLContext *ctx)
{
    struct priv *p = ctx->priv;
    p->sc_width = ctx->vo->dwidth ? ctx->vo->dwidth : 1;
    p->sc_height = ctx->vo->dheight ? ctx->vo->dheight : 1;
}

static void d3d11_backbuffer_release(MPGLContext *ctx)
{
    struct priv *p = ctx->priv;

    if (p->egl_backbuffer) {
        eglMakeCurrent(p->egl_display, EGL_NO_SURFACE, EGL_NO_SURFACE,
                       EGL_NO_CONTEXT);
        eglDestroySurface(p->egl_display, p->egl_backbuffer);
    }
    p->egl_backbuffer = EGL_NO_SURFACE;

    SAFE_RELEASE(p->d3d11_backbuffer);
}

static bool d3d11_backbuffer_get(MPGLContext *ctx)
{
    struct priv *p = ctx->priv;
    struct vo *vo = ctx->vo;
    HRESULT hr;

    hr = IDXGISwapChain_GetBuffer(p->dxgi_swapchain, 0, &IID_ID3D11Texture2D,
        (void**)&p->d3d11_backbuffer);
    if (FAILED(hr)) {
        MP_FATAL(vo, "Couldn't get swap chain back buffer\n");
        return false;
    }

    EGLint pbuffer_attributes[] = {
        EGL_TEXTURE_FORMAT, EGL_TEXTURE_RGBA,
        EGL_TEXTURE_TARGET, EGL_TEXTURE_2D,
        EGL_NONE,
    };
    p->egl_backbuffer = eglCreatePbufferFromClientBuffer(p->egl_display,
        EGL_D3D_TEXTURE_ANGLE, p->d3d11_backbuffer, p->egl_config,
        pbuffer_attributes);
    if (!p->egl_backbuffer) {
        MP_FATAL(vo, "Couldn't create EGL pbuffer\n");
        return false;
    }

    eglMakeCurrent(p->egl_display, p->egl_backbuffer, p->egl_backbuffer,
                   p->egl_context);
    return true;
}

static void d3d11_backbuffer_resize(MPGLContext *ctx)
{
    struct priv *p = ctx->priv;
    struct vo *vo = ctx->vo;
    HRESULT hr;

    int old_sc_width = p->sc_width;
    int old_sc_height = p->sc_height;

    update_sizes(ctx);
    // Avoid unnecessary resizing
    if (old_sc_width == p->sc_width && old_sc_height == p->sc_height)
        return;

    // All references to backbuffers must be released before ResizeBuffers
    // (including references held by ANGLE)
    d3d11_backbuffer_release(ctx);

    // The DirectX runtime may report errors related to the device like
    // DXGI_ERROR_DEVICE_REMOVED at this point
    hr = IDXGISwapChain_ResizeBuffers(p->dxgi_swapchain, 0, p->sc_width,
        p->sc_height, DXGI_FORMAT_UNKNOWN, 0);
    if (FAILED(hr))
        MP_FATAL(vo, "Couldn't resize swapchain: %s\n", mp_HRESULT_to_str(hr));

    if (!d3d11_backbuffer_get(ctx))
        MP_FATAL(vo, "Couldn't get back buffer after resize\n");
}

static void d3d11_device_destroy(MPGLContext *ctx)
{
    struct priv *p = ctx->priv;

    PFNEGLRELEASEDEVICEANGLEPROC eglReleaseDeviceANGLE =
        (PFNEGLRELEASEDEVICEANGLEPROC)eglGetProcAddress("eglReleaseDeviceANGLE");

    if (p->egl_display)
        eglTerminate(p->egl_display);
    p->egl_display = EGL_NO_DISPLAY;

    if (p->egl_device && eglReleaseDeviceANGLE)
        eglReleaseDeviceANGLE(p->egl_device);
    p->egl_device = 0;

    SAFE_RELEASE(p->d3d11_device);
    SAFE_RELEASE(p->dxgi_device);
    SAFE_RELEASE(p->dxgi_adapter);
    SAFE_RELEASE(p->dxgi_factory);
    SAFE_RELEASE(p->dxgi_factory2);
}

static void show_sw_adapter_msg(MPGLContext *ctx)
{
    struct priv *p = ctx->priv;
    if (p->sw_adapter_msg_shown)
        return;
    MP_WARN(ctx->vo, "Using a software adapter\n");
    p->sw_adapter_msg_shown = true;
}

static bool d3d11_device_create(MPGLContext *ctx, int flags)
{
    struct priv *p = ctx->priv;
    struct vo *vo = ctx->vo;
    struct angle_opts *o = p->opts;
    HRESULT hr;

    HMODULE d3d11_dll = LoadLibraryW(L"d3d11.dll");
    if (!d3d11_dll) {
        MP_FATAL(vo, "Failed to load d3d11.dll\n");
        return false;
    }

    PFN_D3D11_CREATE_DEVICE D3D11CreateDevice = (PFN_D3D11_CREATE_DEVICE)
        GetProcAddress(d3d11_dll, "D3D11CreateDevice");
    if (!D3D11CreateDevice) {
        MP_FATAL(vo, "D3D11CreateDevice entry point not found\n");
        return false;
    }

    D3D_FEATURE_LEVEL *levels = (D3D_FEATURE_LEVEL[]) {
        D3D_FEATURE_LEVEL_11_0,
        D3D_FEATURE_LEVEL_10_1,
        D3D_FEATURE_LEVEL_10_0,
        D3D_FEATURE_LEVEL_9_3,
    };
    D3D_FEATURE_LEVEL selected_level;
    int level_count = 4;

    // Only try feature levels less than or equal to the user specified level
    while (level_count && levels[0] > o->d3d11_feature_level) {
        levels++;
        level_count--;
    }

    // Try a HW adapter first unless WARP is forced
    hr = E_FAIL;
    if ((FAILED(hr) && o->d3d11_warp == -1) || o->d3d11_warp == 0) {
        hr = D3D11CreateDevice(NULL, D3D_DRIVER_TYPE_HARDWARE, NULL, 0, levels,
            level_count, D3D11_SDK_VERSION, &p->d3d11_device, &selected_level,
            &p->d3d11_context);
    }
    // Try WARP if it is forced or if the HW adapter failed
    if ((FAILED(hr) && o->d3d11_warp == -1) || o->d3d11_warp == 1) {
        hr = D3D11CreateDevice(NULL, D3D_DRIVER_TYPE_WARP, NULL, 0, levels,
            level_count, D3D11_SDK_VERSION, &p->d3d11_device, &selected_level,
            &p->d3d11_context);
        if (SUCCEEDED(hr))
            show_sw_adapter_msg(ctx);
    }
    if (FAILED(hr)) {
        MP_FATAL(vo, "Couldn't create Direct3D 11 device: %s\n",
                 mp_HRESULT_to_str(hr));
        return false;
    }

    MP_VERBOSE(vo, "Using Direct3D 11 feature level %u_%u\n",
        ((unsigned)selected_level) >> 12,
        (((unsigned)selected_level) >> 8) & 0xf);

    hr = ID3D11Device_QueryInterface(p->d3d11_device, &IID_IDXGIDevice1,
        (void**)&p->dxgi_device);
    if (FAILED(hr)) {
        MP_FATAL(vo, "Couldn't get DXGI device\n");
        return false;
    }

    IDXGIDevice1_SetMaximumFrameLatency(p->dxgi_device, o->max_frame_latency);

    hr = IDXGIDevice1_GetParent(p->dxgi_device, &IID_IDXGIAdapter1,
        (void**)&p->dxgi_adapter);
    if (FAILED(hr)) {
        MP_FATAL(vo, "Couldn't get DXGI adapter\n");
        return false;
    }

    // Query some properties of the adapter in order to warn the user if they
    // are using a software adapter
    DXGI_ADAPTER_DESC1 desc;
    hr = IDXGIAdapter1_GetDesc1(p->dxgi_adapter, &desc);
    if (SUCCEEDED(hr)) {
        if (desc.Flags & DXGI_ADAPTER_FLAG_SOFTWARE)
            show_sw_adapter_msg(ctx);

        // If the primary display adapter is a software adapter, the
        // DXGI_ADAPTER_FLAG_SOFTWARE won't be set, but the device IDs
        // should still match the Microsoft Basic Render Driver
        if (desc.VendorId == 0x1414 && desc.DeviceId == 0x8c)
            show_sw_adapter_msg(ctx);
    }

    hr = IDXGIAdapter1_GetParent(p->dxgi_adapter, &IID_IDXGIFactory1,
        (void**)&p->dxgi_factory);
    if (FAILED(hr)) {
        MP_FATAL(vo, "Couldn't get DXGI factory\n");
        return false;
    }

    IDXGIFactory1_QueryInterface(p->dxgi_factory, &IID_IDXGIFactory2,
        (void**)&p->dxgi_factory2);

    PFNEGLGETPLATFORMDISPLAYEXTPROC eglGetPlatformDisplayEXT =
        (PFNEGLGETPLATFORMDISPLAYEXTPROC)eglGetProcAddress("eglGetPlatformDisplayEXT");
    if (!eglGetPlatformDisplayEXT) {
        MP_FATAL(vo, "Missing EGL_EXT_platform_base\n");
        return false;
    }
    PFNEGLCREATEDEVICEANGLEPROC eglCreateDeviceANGLE =
        (PFNEGLCREATEDEVICEANGLEPROC)eglGetProcAddress("eglCreateDeviceANGLE");
    if (!eglCreateDeviceANGLE) {
        MP_FATAL(vo, "Missing EGL_EXT_platform_device\n");
        return false;
    }

    p->egl_device = eglCreateDeviceANGLE(EGL_D3D11_DEVICE_ANGLE,
        p->d3d11_device, NULL);
    if (!p->egl_device) {
        MP_FATAL(vo, "Couldn't create EGL device\n");
        return false;
    }

    p->egl_display = eglGetPlatformDisplayEXT(EGL_PLATFORM_DEVICE_EXT,
        p->egl_device, NULL);
    if (!p->egl_display) {
        MP_FATAL(vo, "Couldn't get EGL display\n");
        return false;
    }

    return true;
}

static void d3d11_swapchain_surface_destroy(MPGLContext *ctx)
{
    struct priv *p = ctx->priv;
    SAFE_RELEASE(p->dxgi_swapchain);
    SAFE_RELEASE(p->dxgi_swapchain1);
    d3d11_backbuffer_release(ctx);
}

static bool d3d11_swapchain_create_1_2(MPGLContext *ctx, int flags)
{
    struct priv *p = ctx->priv;
    struct vo *vo = ctx->vo;
    HRESULT hr;

    update_sizes(ctx);
    DXGI_SWAP_CHAIN_DESC1 desc1 = {
        .Width = p->sc_width,
        .Height = p->sc_height,
        .Format = DXGI_FORMAT_R8G8B8A8_UNORM,
        .SampleDesc = { .Count = 1 },
        .BufferUsage = DXGI_USAGE_RENDER_TARGET_OUTPUT |
                       DXGI_USAGE_SHADER_INPUT,
        .BufferCount = p->opts->swapchain_length,
        .SwapEffect = DXGI_SWAP_EFFECT_FLIP_SEQUENTIAL,
    };

    hr = IDXGIFactory2_CreateSwapChainForHwnd(p->dxgi_factory2,
        (IUnknown*)p->d3d11_device, vo_w32_hwnd(vo), &desc1, NULL, NULL,
        &p->dxgi_swapchain1);
    if (FAILED(hr)) {
        MP_FATAL(vo, "Couldn't create DXGI 1.2+ swap chain: %s\n",
                 mp_HRESULT_to_str(hr));
        return false;
    }

    hr = IDXGISwapChain1_QueryInterface(p->dxgi_swapchain1,
        &IID_IDXGISwapChain, (void**)&p->dxgi_swapchain);
    if (FAILED(hr)) {
        MP_FATAL(vo, "Couldn't create DXGI 1.2+ swap chain\n");
        return false;
    }

    return true;
}

static bool d3d11_swapchain_create_1_1(MPGLContext *ctx, int flags)
{
    struct priv *p = ctx->priv;
    struct vo *vo = ctx->vo;
    HRESULT hr;

    update_sizes(ctx);
    DXGI_SWAP_CHAIN_DESC desc = {
        .BufferDesc = {
            .Width = p->sc_width,
            .Height = p->sc_height,
            .Format = DXGI_FORMAT_R8G8B8A8_UNORM
        },
        .SampleDesc = { .Count = 1 },
        .BufferUsage = DXGI_USAGE_RENDER_TARGET_OUTPUT |
                       DXGI_USAGE_SHADER_INPUT,
        .BufferCount = 1,
        .OutputWindow = vo_w32_hwnd(vo),
        .Windowed = TRUE,
        .SwapEffect = DXGI_SWAP_EFFECT_DISCARD,
    };

    hr = IDXGIFactory1_CreateSwapChain(p->dxgi_factory,
        (IUnknown*)p->d3d11_device, &desc, &p->dxgi_swapchain);
    if (FAILED(hr)) {
        MP_FATAL(vo, "Couldn't create DXGI 1.1 swap chain: %s\n",
                 mp_HRESULT_to_str(hr));
        return false;
    }

    return true;
}

static bool d3d11_swapchain_surface_create(MPGLContext *ctx, int flags)
{
    struct priv *p = ctx->priv;
    struct vo *vo = ctx->vo;

    if (p->dxgi_factory2) {
        // Create a DXGI 1.2+ (Windows 8+) swap chain if possible
        if (!d3d11_swapchain_create_1_2(ctx, flags))
            goto fail;
        MP_VERBOSE(vo, "Using DXGI 1.2+\n");
    } else if (p->dxgi_factory) {
        // Fall back to DXGI 1.1 (Windows 7)
        if (!d3d11_swapchain_create_1_1(ctx, flags))
            goto fail;
        MP_VERBOSE(vo, "Using DXGI 1.1\n");
    } else {
        goto fail;
    }
    // Prevent DXGI from making changes to the VO window, otherwise it will
    // hook the Alt+Enter keystroke and make it trigger an ugly transition to
    // exclusive fullscreen mode instead of running the user-set command.
    IDXGIFactory_MakeWindowAssociation(p->dxgi_factory, vo_w32_hwnd(vo),
        DXGI_MWA_NO_WINDOW_CHANGES | DXGI_MWA_NO_ALT_ENTER |
        DXGI_MWA_NO_PRINT_SCREEN);

    if (!d3d11_backbuffer_get(ctx))
        goto fail;

    // EGL_D3D_TEXTURE_ANGLE pbuffers are always flipped vertically
    ctx->flip_v = true;
    return true;

fail:
    d3d11_swapchain_surface_destroy(ctx);
    return false;
}

static void d3d9_device_destroy(MPGLContext *ctx)
{
    struct priv *p = ctx->priv;

    if (p->egl_display)
        eglTerminate(p->egl_display);
    p->egl_display = EGL_NO_DISPLAY;
}

static bool d3d9_device_create(MPGLContext *ctx, int flags)
{
    struct priv *p = ctx->priv;
    struct vo *vo = ctx->vo;

    PFNEGLGETPLATFORMDISPLAYEXTPROC eglGetPlatformDisplayEXT =
        (PFNEGLGETPLATFORMDISPLAYEXTPROC)eglGetProcAddress("eglGetPlatformDisplayEXT");
    if (!eglGetPlatformDisplayEXT) {
        MP_FATAL(vo, "Missing EGL_EXT_platform_base\n");
        return false;
    }

    EGLint display_attributes[] = {
        EGL_PLATFORM_ANGLE_TYPE_ANGLE,
            EGL_PLATFORM_ANGLE_TYPE_D3D9_ANGLE,
        EGL_PLATFORM_ANGLE_DEVICE_TYPE_ANGLE,
            EGL_PLATFORM_ANGLE_DEVICE_TYPE_HARDWARE_ANGLE,
        EGL_NONE,
    };
    p->egl_display = eglGetPlatformDisplayEXT(EGL_PLATFORM_ANGLE_ANGLE,
        EGL_DEFAULT_DISPLAY, display_attributes);
    if (p->egl_display == EGL_NO_DISPLAY) {
        MP_FATAL(vo, "Couldn't get display\n");
        return false;
    }

    return true;
}

static void egl_window_surface_destroy(MPGLContext *ctx)
{
    struct priv *p = ctx->priv;
    if (p->egl_window) {
        eglMakeCurrent(p->egl_display, EGL_NO_SURFACE, EGL_NO_SURFACE,
                       EGL_NO_CONTEXT);
    }
}

static bool egl_window_surface_create(MPGLContext *ctx, int flags)
{
    struct priv *p = ctx->priv;
    struct vo *vo = ctx->vo;

    int window_attribs_len = 0;
    EGLint *window_attribs = NULL;

    EGLint flip_val;
    if (eglGetConfigAttrib(p->egl_display, p->egl_config,
                           EGL_OPTIMAL_SURFACE_ORIENTATION_ANGLE, &flip_val))
    {
        if (flip_val == EGL_SURFACE_ORIENTATION_INVERT_Y_ANGLE) {
            MP_TARRAY_APPEND(NULL, window_attribs, window_attribs_len,
                EGL_SURFACE_ORIENTATION_ANGLE);
            MP_TARRAY_APPEND(NULL, window_attribs, window_attribs_len,
                EGL_SURFACE_ORIENTATION_INVERT_Y_ANGLE);
            ctx->flip_v = true;
            MP_VERBOSE(vo, "Rendering flipped.\n");
        }
    }

    MP_TARRAY_APPEND(NULL, window_attribs, window_attribs_len, EGL_NONE);
    p->egl_window = eglCreateWindowSurface(p->egl_display, p->egl_config,
                                           vo_w32_hwnd(vo), window_attribs);
    talloc_free(window_attribs);
    if (!p->egl_window) {
        MP_FATAL(vo, "Could not create EGL surface!\n");
        goto fail;
    }

    eglMakeCurrent(p->egl_display, p->egl_window, p->egl_window,
                   p->egl_context);
    return true;
fail:
    egl_window_surface_destroy(ctx);
    return false;
}

static void angle_uninit(struct MPGLContext *ctx)
{
    struct priv *p = ctx->priv;

    DwmEnableMMCSS(FALSE);

    // Uninit the EGL surface implementation that is being used. Note: This may
    // result in the *_destroy function being called twice since it is also
    // called when the surface create function fails. This is fine because the
    // *_destroy functions are idempotent.
    if (p->dxgi_swapchain)
        d3d11_swapchain_surface_destroy(ctx);
    else
        egl_window_surface_destroy(ctx);

    if (p->egl_context) {
        eglMakeCurrent(p->egl_display, EGL_NO_SURFACE, EGL_NO_SURFACE,
                       EGL_NO_CONTEXT);
        eglDestroyContext(p->egl_display, p->egl_context);
    }
    p->egl_context = EGL_NO_CONTEXT;

    // Uninit the EGL device implementation that is being used
    if (p->d3d11_device)
        d3d11_device_destroy(ctx);
    else
        d3d9_device_destroy(ctx);

    vo_w32_uninit(ctx->vo);
}

static int GLAPIENTRY angle_swap_interval(int interval)
{
    if (!current_ctx)
        return 0;
    struct priv *p = current_ctx->priv;

    if (p->dxgi_swapchain) {
        p->swapinterval = MPCLAMP(interval, 0, 4);
        return 1;
    } else {
        return eglSwapInterval(p->egl_display, interval);
    }
}

static void *get_proc_address(const GLubyte *proc_name)
{
    return eglGetProcAddress(proc_name);
}

static int angle_init(struct MPGLContext *ctx, int flags)
{
    struct priv *p = ctx->priv;
    struct vo *vo = ctx->vo;

    p->opts = mp_get_config_group(ctx, ctx->global, &angle_conf);
    struct angle_opts *o = p->opts;

    // DWM MMCSS cargo-cult. The dxinterop backend also does this.
    DwmEnableMMCSS(TRUE);

    if (!angle_load()) {
        MP_VERBOSE(vo, "Failed to load LIBEGL.DLL\n");
        goto fail;
    }

    // Create the underlying EGL device implementation
    bool device_ok = false;
    if ((!device_ok && !o->renderer) || o->renderer == RENDERER_D3D11)
        device_ok = d3d11_device_create(ctx, flags);
    if ((!device_ok && !o->renderer) || o->renderer == RENDERER_D3D9)
        device_ok = d3d9_device_create(ctx, flags);
    if (!device_ok)
        goto fail;

    if (!eglInitialize(p->egl_display, NULL, NULL)) {
        MP_FATAL(vo, "Couldn't initialize EGL\n");
        return false;
    }

    if (!vo_w32_init(vo))
        goto fail;

    const char *exts = eglQueryString(p->egl_display, EGL_EXTENSIONS);
    if (exts)
        MP_DBG(ctx->vo, "EGL extensions: %s\n", exts);

    if (!mpegl_create_context(p->egl_display, vo->log, flags | VOFLAG_GLES,
                              &p->egl_context, &p->egl_config))
    {
        MP_FATAL(vo, "Could not create EGL context!\n");
        goto fail;
    }

    // Create the underlying EGL surface implementation
    bool surface_ok = false;
    if ((!surface_ok && o->egl_windowing == -1) || o->egl_windowing == 0)
        surface_ok = d3d11_swapchain_surface_create(ctx, flags);
    if ((!surface_ok && o->egl_windowing == -1) || o->egl_windowing == 1)
        surface_ok = egl_window_surface_create(ctx, flags);
    if (!surface_ok)
        goto fail;

    mpgl_load_functions(ctx->gl, get_proc_address, NULL, vo->log);

    current_ctx = ctx;
    ctx->gl->SwapInterval = angle_swap_interval;

    return 0;
fail:
    angle_uninit(ctx);
    return -1;
}

static int angle_reconfig(struct MPGLContext *ctx)
{
    vo_w32_config(ctx->vo);
    return 0;
}

static struct mp_image *d3d11_screenshot(MPGLContext *ctx)
{
    struct priv *p = ctx->priv;
    ID3D11Texture2D *frontbuffer = NULL;
    ID3D11Texture2D *staging = NULL;
    struct mp_image *img = NULL;
    HRESULT hr;

    if (!p->dxgi_swapchain1)
        goto done;

    // Validate the swap chain. This screenshot method will only work on DXGI
    // 1.2+ flip/sequential swap chains. It's probably not possible at all with
    // discard swap chains, since by definition, the backbuffer contents is
    // discarded on Present().
    DXGI_SWAP_CHAIN_DESC1 scd;
    hr = IDXGISwapChain1_GetDesc1(p->dxgi_swapchain1, &scd);
    if (FAILED(hr))
        goto done;
    if (scd.SwapEffect != DXGI_SWAP_EFFECT_FLIP_SEQUENTIAL)
        goto done;

    // Get the last buffer that was presented with Present(). This should be
    // the n-1th buffer for a swap chain of length n.
    hr = IDXGISwapChain_GetBuffer(p->dxgi_swapchain, scd.BufferCount - 1,
        &IID_ID3D11Texture2D, (void**)&frontbuffer);
    if (FAILED(hr))
        goto done;

    D3D11_TEXTURE2D_DESC td;
    ID3D11Texture2D_GetDesc(frontbuffer, &td);
    if (td.SampleDesc.Count > 1)
        goto done;

    // Validate the backbuffer format and convert to an mpv IMGFMT
    enum mp_imgfmt fmt;
    switch (td.Format) {
    case DXGI_FORMAT_B8G8R8A8_UNORM: fmt = IMGFMT_BGR0; break;
    case DXGI_FORMAT_R8G8B8A8_UNORM: fmt = IMGFMT_RGB0; break;
    default:
        goto done;
    }

    // Create a staging texture based on the frontbuffer with CPU access
    td.BindFlags = 0;
    td.MiscFlags = 0;
    td.CPUAccessFlags = D3D11_CPU_ACCESS_READ;
    td.Usage = D3D11_USAGE_STAGING;
    hr = ID3D11Device_CreateTexture2D(p->d3d11_device, &td, 0, &staging);
    if (FAILED(hr))
        goto done;

    ID3D11DeviceContext_CopyResource(p->d3d11_context,
        (ID3D11Resource*)staging, (ID3D11Resource*)frontbuffer);

    // Attempt to map the staging texture to CPU-accessible memory
    D3D11_MAPPED_SUBRESOURCE lock;
    hr = ID3D11DeviceContext_Map(p->d3d11_context, (ID3D11Resource*)staging,
                                 0, D3D11_MAP_READ, 0, &lock);
    if (FAILED(hr))
        goto done;

    img = mp_image_alloc(fmt, td.Width, td.Height);
    if (!img)
        return NULL;
    for (int i = 0; i < td.Height; i++) {
        memcpy(img->planes[0] + img->stride[0] * i,
               (char*)lock.pData + lock.RowPitch * i, td.Width * 4);
    }

    ID3D11DeviceContext_Unmap(p->d3d11_context, (ID3D11Resource*)staging, 0);

done:
    SAFE_RELEASE(frontbuffer);
    SAFE_RELEASE(staging);
    return img;
}

static int angle_control(MPGLContext *ctx, int *events, int request, void *arg)
{
    struct priv *p = ctx->priv;

    // Try a D3D11-specific method of taking a window screenshot
    if (request == VOCTRL_SCREENSHOT_WIN) {
        struct mp_image *img = d3d11_screenshot(ctx);
        if (img) {
            *(struct mp_image **)arg = img;
            return true;
        }
    }

    int r = vo_w32_control(ctx->vo, events, request, arg);
    if (*events & VO_EVENT_RESIZE) {
        if (p->dxgi_swapchain)
            d3d11_backbuffer_resize(ctx);
        else
            eglWaitClient(); // Should get ANGLE to resize its swapchain
    }
    return r;
}

static void d3d11_swap_buffers(MPGLContext *ctx)
{
    struct priv *p = ctx->priv;

    // Calling Present() on a flip-sequential swap chain will silently change
    // the underlying storage of the back buffer to point to the next buffer in
    // the chain. This results in the RTVs for the back buffer becoming
    // unbound. Since ANGLE doesn't know we called Present(), it will continue
    // using the unbound RTVs, so we must save and restore them ourselves.
    ID3D11RenderTargetView *rtvs[D3D11_SIMULTANEOUS_RENDER_TARGET_COUNT] = {0};
    ID3D11DepthStencilView *dsv = NULL;
    ID3D11DeviceContext_OMGetRenderTargets(p->d3d11_context,
        MP_ARRAY_SIZE(rtvs), rtvs, &dsv);

    HRESULT hr = IDXGISwapChain_Present(p->dxgi_swapchain, p->swapinterval, 0);
    if (FAILED(hr))
        MP_FATAL(ctx->vo, "Couldn't present: %s\n", mp_HRESULT_to_str(hr));

    // Restore the RTVs and release the objects
    ID3D11DeviceContext_OMSetRenderTargets(p->d3d11_context,
        MP_ARRAY_SIZE(rtvs), rtvs, dsv);
    for (int i = 0; i < 8; i++)
        SAFE_RELEASE(rtvs[i]);
    SAFE_RELEASE(dsv);
}

static void egl_swap_buffers(MPGLContext *ctx)
{
    struct priv *p = ctx->priv;
    eglSwapBuffers(p->egl_display, p->egl_window);
}

static void angle_swap_buffers(MPGLContext *ctx)
{
    struct priv *p = ctx->priv;
    if (p->dxgi_swapchain)
        d3d11_swap_buffers(ctx);
    else
        egl_swap_buffers(ctx);
}

const struct mpgl_driver mpgl_driver_angle = {
    .name           = "angle",
    .priv_size      = sizeof(struct priv),
    .init           = angle_init,
    .reconfig       = angle_reconfig,
    .swap_buffers   = angle_swap_buffers,
    .control        = angle_control,
    .uninit         = angle_uninit,
};