/**
 * Looking Glass
 * Copyright (C) 2017-2021 The Looking Glass Authors
 * https://looking-glass.io
 *
 * 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, write to the Free Software Foundation, Inc., 59
 * Temple Place, Suite 330, Boston, MA 02111-1307 USA
 */

#include "interface/renderer.h"

#include "common/debug.h"
#include "common/KVMFR.h"
#include "common/option.h"
#include "common/sysinfo.h"
#include "common/time.h"
#include "common/locking.h"
#include "app.h"
#include "util.h"

#include <EGL/egl.h>
#include <GLES3/gl32.h>

#include "cimgui.h"
#include "generator/output/cimgui_impl.h"

#include <assert.h>
#include <math.h>
#include <string.h>

#include "app.h"
#include "egl_dynprocs.h"
#include "model.h"
#include "shader.h"
#include "damage.h"
#include "desktop.h"
#include "cursor.h"
#include "splash.h"

#define SPLASH_FADE_TIME 1000000

struct Options
{
  bool vsync;
  bool doubleBuffer;
};

struct Inst
{
  bool dmaSupport;
  LG_RendererParams params;
  struct Options    opt;

  EGLNativeWindowType  nativeWind;
  EGLDisplay           display;
  EGLConfig            configs;
  EGLSurface           surface;
  EGLContext           context, frameContext;

  EGL_Desktop     * desktop; // the desktop
  EGL_Cursor      * cursor;  // the mouse cursor
  EGL_Splash      * splash;  // the splash screen
  EGL_Damage      * damage;  // the damage display
  bool              imgui;   // if imgui was initialized

  LG_RendererFormat    format;
  bool                 formatValid;
  bool                 start;
  uint64_t             waitFadeTime;
  bool                 waitDone;

  int               width, height;
  float             uiScale;
  LG_RendererRect   destRect;
  LG_RendererRotate rotate; //client side rotation

  float translateX  , translateY;
  float scaleX      , scaleY;
  float splashRatio;
  float screenScaleX, screenScaleY;

  int viewportWidth, viewportHeight;
  enum EGL_DesktopScaleType scaleType;

  bool  cursorVisible;
  int   cursorX    , cursorY;
  float mouseWidth , mouseHeight;
  float mouseScaleX, mouseScaleY;
  bool  showDamage;

  struct CursorState cursorLast;

  bool                            hadOverlay;
  _Atomic(struct DesktopDamage *) desktopDamage;

  RingBuffer importTimings;
  GraphHandle importGraph;
};

static struct Option egl_options[] =
{
  {
    .module       = "egl",
    .name         = "vsync",
    .description  = "Enable vsync",
    .type         = OPTION_TYPE_BOOL,
    .value.x_bool = false,
  },
  {
    .module       = "egl",
    .name         = "doubleBuffer",
    .description  = "Enable double buffering",
    .type         = OPTION_TYPE_BOOL,
    .value.x_bool = false
  },
  {
    .module       = "egl",
    .name         = "multisample",
    .description  = "Enable Multisampling",
    .type         = OPTION_TYPE_BOOL,
    .value.x_bool = true
  },
  {
    .module       = "egl",
    .name         = "nvGainMax",
    .description  = "The maximum night vision gain",
    .type         = OPTION_TYPE_INT,
    .value.x_int  = 1
  },
  {
    .module       = "egl",
    .name         = "nvGain",
    .description  = "The initial night vision gain at startup",
    .type         = OPTION_TYPE_INT,
    .value.x_int  = 0
  },
  {
    .module       = "egl",
    .name         = "cbMode",
    .description  = "Color Blind Mode (0 = Off, 1 = Protanope, 2 = Deuteranope, 3 = Tritanope)",
    .type         = OPTION_TYPE_INT,
    .value.x_int  = 0
  },
  {
    .module       = "egl",
    .name         = "scale",
    .description  = "Set the scale algorithm (0 = auto, 1 = nearest, 2 = linear)",
    .type         = OPTION_TYPE_INT,
    .validator    = egl_desktop_scale_validate,
    .value.x_int  = 0
  },
  {
    .module       = "egl",
    .name         = "debug",
    .description  = "Enable debug output",
    .type         = OPTION_TYPE_BOOL,
    .value.x_bool = false
  },
  {0}
};

static const char * egl_get_name(void)
{
  return "EGL";
}

static void egl_setup(void)
{
  option_register(egl_options);
}

static bool egl_create(void ** opaque, const LG_RendererParams params, bool * needsOpenGL)
{
  // check if EGL is even available
  if (!eglQueryString(EGL_NO_DISPLAY, EGL_VERSION))
    return false;

  // create our local storage
  *opaque = calloc(1, sizeof(struct Inst));
  if (!*opaque)
  {
    DEBUG_INFO("Failed to allocate %lu bytes", sizeof(struct Inst));
    return false;
  }

  // safe off parameteres and init our default option values
  struct Inst * this = (struct Inst *)*opaque;
  memcpy(&this->params, &params, sizeof(LG_RendererParams));

  this->opt.vsync        = option_get_bool("egl", "vsync");
  this->opt.doubleBuffer = option_get_bool("egl", "doubleBuffer");

  this->translateX   = 0;
  this->translateY   = 0;
  this->scaleX       = 1.0f;
  this->scaleY       = 1.0f;
  this->screenScaleX = 1.0f;
  this->screenScaleY = 1.0f;
  this->uiScale      = 1.0;

  atomic_init(&this->desktopDamage, NULL);

  this->importTimings = ringbuffer_new(256, sizeof(float));
  this->importGraph   = app_registerGraph("IMPORT", this->importTimings, 0.0f, 5.0f);

  *needsOpenGL = false;
  return true;
}

static bool egl_initialize(void * opaque)
{
  struct Inst * this = (struct Inst *)opaque;
  DEBUG_INFO("Double buffering is %s", this->opt.doubleBuffer ? "on" : "off");
  return true;
}

static void egl_deinitialize(void * opaque)
{
  struct Inst * this = (struct Inst *)opaque;

  if (this->imgui)
    ImGui_ImplOpenGL3_Shutdown();

  app_unregisterGraph(this->importGraph);
  ringbuffer_free(&this->importTimings);

  egl_desktop_free(&this->desktop);
  egl_cursor_free (&this->cursor);
  egl_splash_free (&this->splash);
  egl_damage_free (&this->damage);

  LG_LOCK_FREE(this->lock);

  eglMakeCurrent(this->display, EGL_NO_SURFACE, EGL_NO_SURFACE, EGL_NO_CONTEXT);

  if (this->frameContext)
    eglDestroyContext(this->display, this->frameContext);

  if (this->context)
    eglDestroyContext(this->display, this->context);

  eglTerminate(this->display);

  free(this);
}

static bool egl_supports(void * opaque, LG_RendererSupport flag)
{
  struct Inst * this = (struct Inst *)opaque;

  switch(flag)
  {
    case LG_SUPPORTS_DMABUF:
      return this->dmaSupport;

    default:
      return false;
  }
}

static void egl_on_restart(void * opaque)
{
  struct Inst * this = (struct Inst *)opaque;

  eglDestroyContext(this->display, this->frameContext);
  this->frameContext = NULL;
  this->start        = false;
}

static void egl_calc_mouse_size(struct Inst * this)
{
  if (!this->formatValid)
    return;

  int w  = 0, h = 0;

  switch(this->format.rotate)
  {
    case LG_ROTATE_0:
    case LG_ROTATE_180:
      this->mouseScaleX = 2.0f / this->format.width;
      this->mouseScaleY = 2.0f / this->format.height;
      w = this->format.width;
      h = this->format.height;
      break;

    case LG_ROTATE_90:
    case LG_ROTATE_270:
      this->mouseScaleX = 2.0f / this->format.height;
      this->mouseScaleY = 2.0f / this->format.width;
      w = this->format.height;
      h = this->format.width;
      break;

    default:
      assert(!"unreachable");
  }

  switch((this->format.rotate + this->rotate) % LG_ROTATE_MAX)
  {
    case LG_ROTATE_0:
    case LG_ROTATE_180:
      egl_cursor_set_size(this->cursor,
        (this->mouseWidth  * (1.0f / w)) * this->scaleX,
        (this->mouseHeight * (1.0f / h)) * this->scaleY
      );
      break;

    case LG_ROTATE_90:
    case LG_ROTATE_270:
      egl_cursor_set_size(this->cursor,
        (this->mouseWidth  * (1.0f / w)) * this->scaleY,
        (this->mouseHeight * (1.0f / h)) * this->scaleX
      );
      break;
  }
}

static void egl_calc_mouse_state(struct Inst * this)
{
  if (!this->formatValid)
    return;

  switch((this->format.rotate + this->rotate) % LG_ROTATE_MAX)
  {
    case LG_ROTATE_0:
    case LG_ROTATE_180:
      egl_cursor_set_state(
        this->cursor,
        this->cursorVisible,
        (((float)this->cursorX * this->mouseScaleX) - 1.0f) * this->scaleX,
        (((float)this->cursorY * this->mouseScaleY) - 1.0f) * this->scaleY
      );
      break;

    case LG_ROTATE_90:
    case LG_ROTATE_270:
      egl_cursor_set_state(
        this->cursor,
        this->cursorVisible,
        (((float)this->cursorX * this->mouseScaleX) - 1.0f) * this->scaleY,
        (((float)this->cursorY * this->mouseScaleY) - 1.0f) * this->scaleX
      );
      break;
  }
}

static void egl_update_scale_type(struct Inst * this)
{
  int width = 0, height = 0;

  switch (this->rotate)
  {
    case LG_ROTATE_0:
    case LG_ROTATE_180:
      width  = this->format.width;
      height = this->format.height;
      break;

    case LG_ROTATE_90:
    case LG_ROTATE_270:
      width  = this->format.height;
      height = this->format.width;
      break;
  }

  if (width == this->viewportWidth || height == this->viewportHeight)
    this->scaleType = EGL_DESKTOP_NOSCALE;
  else if (width > this->viewportWidth || height > this->viewportHeight)
    this->scaleType = EGL_DESKTOP_DOWNSCALE;
  else
    this->scaleType = EGL_DESKTOP_UPSCALE;
}

static void egl_on_resize(void * opaque, const int width, const int height, const double scale,
    const LG_RendererRect destRect, LG_RendererRotate rotate)
{
  struct Inst * this = (struct Inst *)opaque;

  this->width   = width * scale;
  this->height  = height * scale;
  this->uiScale = (float) scale;
  this->rotate  = rotate;

  this->destRect.x = destRect.x * scale;
  this->destRect.y = destRect.y * scale;
  this->destRect.w = destRect.w * scale;
  this->destRect.h = destRect.h * scale;

  glViewport(0, 0, this->width, this->height);

  if (destRect.valid)
  {
    this->translateX     = 1.0f - (((this->destRect.w / 2) + this->destRect.x) * 2) / (float)this->width;
    this->translateY     = 1.0f - (((this->destRect.h / 2) + this->destRect.y) * 2) / (float)this->height;
    this->scaleX         = (float)this->destRect.w / (float)this->width;
    this->scaleY         = (float)this->destRect.h / (float)this->height;
    this->viewportWidth  = this->destRect.w;
    this->viewportHeight = this->destRect.h;
  }

  egl_update_scale_type(this);
  egl_calc_mouse_size(this);

  this->splashRatio  = (float)width / (float)height;
  this->screenScaleX = 1.0f / this->width;
  this->screenScaleY = 1.0f / this->height;

  egl_calc_mouse_state(this);

  struct DesktopDamage * damage = malloc(sizeof(struct DesktopDamage));
  if (!damage)
  {
    DEBUG_FATAL("Out of memory");
    abort();
  }
  damage->count = 0;
  free(atomic_exchange(&this->desktopDamage, damage));

  // this is needed to refresh the font atlas texture
  ImGui_ImplOpenGL3_Shutdown();
  ImGui_ImplOpenGL3_NewFrame();

  egl_damage_resize(this->damage, this->translateX, this->translateY, this->scaleX, this->scaleY);
}

static bool egl_on_mouse_shape(void * opaque, const LG_RendererCursor cursor,
    const int width, const int height,
    const int pitch, const uint8_t * data)
{
  struct Inst * this = (struct Inst *)opaque;

  if (!egl_cursor_set_shape(this->cursor, cursor, width, height, pitch, data))
  {
    DEBUG_ERROR("Failed to update the cursor shape");
    return false;
  }

  this->mouseWidth  = width;
  this->mouseHeight = height;
  egl_calc_mouse_size(this);

  return true;
}

static bool egl_on_mouse_event(void * opaque, const bool visible, const int x, const int y)
{
  struct Inst * this = (struct Inst *)opaque;
  this->cursorVisible = visible;
  this->cursorX       = x;
  this->cursorY       = y;
  egl_calc_mouse_state(this);
  return true;
}

static bool egl_on_frame_format(void * opaque, const LG_RendererFormat format, bool useDMA)
{
  struct Inst * this = (struct Inst *)opaque;
  memcpy(&this->format, &format, sizeof(LG_RendererFormat));
  this->formatValid = true;

  /* this event runs in a second thread so we need to init it here */
  if (!this->frameContext)
  {
    static EGLint attrs[] = {
      EGL_CONTEXT_CLIENT_VERSION, 2,
      EGL_NONE
    };

    if (!(this->frameContext = eglCreateContext(this->display, this->configs, this->context, attrs)))
    {
      DEBUG_ERROR("Failed to create the frame context");
      return false;
    }

    if (!eglMakeCurrent(this->display, EGL_NO_SURFACE, EGL_NO_SURFACE, this->frameContext))
    {
      DEBUG_ERROR("Failed to make the frame context current");
      return false;
    }
  }

  egl_update_scale_type(this);
  egl_damage_setup(this->damage, format.width, format.height);

  return egl_desktop_setup(this->desktop, format, useDMA);
}

static bool egl_on_frame(void * opaque, const FrameBuffer * frame, int dmaFd,
    const FrameDamageRect * damageRects, int damageRectsCount)
{
  struct Inst * this = (struct Inst *)opaque;

  uint64_t start = nanotime();
  if (!egl_desktop_update(this->desktop, frame, dmaFd))
  {
    DEBUG_INFO("Failed to to update the desktop");
    return false;
  }
  ringbuffer_push(this->importTimings, &(float){ (nanotime() - start) * 1e-6f });

  this->start = true;

  struct DesktopDamage * damage = malloc(sizeof(struct DesktopDamage));
  if (!damage)
  {
    DEBUG_FATAL("Out of memory");
    abort();
  }
  damage->count = damageRectsCount;
  memcpy(damage->rects, damageRects, damageRectsCount * sizeof(FrameDamageRect));
  free(atomic_exchange(&this->desktopDamage, damage));

  return true;
}

static void debugCallback(GLenum source, GLenum type, GLuint id,
    GLenum severity, GLsizei length, const GLchar * message,
    const void * userParam)
{
  enum DebugLevel level = DEBUG_LEVEL_FIXME;
  switch (severity)
  {
    case GL_DEBUG_SEVERITY_HIGH:
      level = DEBUG_LEVEL_ERROR;
      break;
    case GL_DEBUG_SEVERITY_MEDIUM:
      level = DEBUG_LEVEL_WARN;
      break;
    case GL_DEBUG_SEVERITY_LOW:
    case GL_DEBUG_SEVERITY_NOTIFICATION:
      level = DEBUG_LEVEL_INFO;
      break;
  }

  const char * sourceName = "unknown";
  switch (source)
  {
    case GL_DEBUG_SOURCE_API:
      sourceName = "OpenGL API";
      break;
    case GL_DEBUG_SOURCE_WINDOW_SYSTEM:
      sourceName = "window system";
      break;
    case GL_DEBUG_SOURCE_SHADER_COMPILER:
      sourceName = "shader compiler";
      break;
    case GL_DEBUG_SOURCE_THIRD_PARTY:
      sourceName = "third party";
      break;
    case GL_DEBUG_SOURCE_APPLICATION:
      sourceName = "application";
      break;
    case GL_DEBUG_SOURCE_OTHER:
      sourceName = "other";
      break;
  }

  const char * typeName = "unknown";
  switch (type)
  {
    case GL_DEBUG_TYPE_ERROR:
      typeName = "error";
      break;
    case GL_DEBUG_TYPE_DEPRECATED_BEHAVIOR:
      typeName = "deprecated behaviour";
      break;
    case GL_DEBUG_TYPE_UNDEFINED_BEHAVIOR:
      typeName = "undefined behaviour";
      break;
    case GL_DEBUG_TYPE_PORTABILITY:
      typeName = "portability";
      break;
    case GL_DEBUG_TYPE_PERFORMANCE:
      typeName = "performance";
      break;
    case GL_DEBUG_TYPE_MARKER:
      typeName = "marker";
      break;
    case GL_DEBUG_TYPE_PUSH_GROUP:
      typeName = "group pushing";
      break;
    case GL_DEBUG_TYPE_POP_GROUP:
      typeName = "group popping";
      break;
    case GL_DEBUG_TYPE_OTHER:
      typeName = "other";
      break;
  }

  DEBUG_PRINT(level, "GL message (source: %s, type: %s): %s", sourceName, typeName, message);
}

static bool egl_render_startup(void * opaque)
{
  struct Inst * this = (struct Inst *)opaque;

  this->nativeWind = app_getEGLNativeWindow();
  if (!this->nativeWind)
    return false;

  this->display = app_getEGLDisplay();
  if (this->display == EGL_NO_DISPLAY)
    return false;

  int maj, min;
  if (!eglInitialize(this->display, &maj, &min))
  {
    DEBUG_ERROR("Unable to initialize EGL");
    return false;
  }

  int maxSamples = 1;
  if (option_get_bool("egl", "multisample"))
  {
    if (app_getProp(LG_DS_MAX_MULTISAMPLE, &maxSamples) && maxSamples > 1)
    {
      if (maxSamples > 4)
        maxSamples = 4;

      DEBUG_INFO("Multisampling enabled, max samples: %d", maxSamples);
    }
  }

  EGLint attr[] =
  {
    EGL_BUFFER_SIZE    , 24,
    EGL_RENDERABLE_TYPE, EGL_OPENGL_ES2_BIT,
    EGL_SAMPLE_BUFFERS , maxSamples > 0 ? 1 : 0,
    EGL_SAMPLES        , maxSamples,
    EGL_NONE
  };

  EGLint num_config;
  if (!eglChooseConfig(this->display, attr, &this->configs, 1, &num_config))
  {
    DEBUG_ERROR("Failed to choose config (eglError: 0x%x)", eglGetError());
    return false;
  }

  const EGLint surfattr[] =
  {
    EGL_RENDER_BUFFER, this->opt.doubleBuffer ? EGL_BACK_BUFFER : EGL_SINGLE_BUFFER,
    EGL_NONE
  };

  this->surface = eglCreateWindowSurface(this->display, this->configs, this->nativeWind, surfattr);
  if (this->surface == EGL_NO_SURFACE)
  {
    DEBUG_ERROR("Failed to create EGL surface (eglError: 0x%x)", eglGetError());
    return false;
  }

  bool debugContext = option_get_bool("egl", "debug");
  EGLint ctxattr[] =
  {
    EGL_CONTEXT_CLIENT_VERSION, 2,
    EGL_CONTEXT_OPENGL_DEBUG  , debugContext ? EGL_TRUE : EGL_FALSE,
    EGL_NONE
  };

  this->context = eglCreateContext(this->display, this->configs, EGL_NO_CONTEXT, ctxattr);
  if (this->context == EGL_NO_CONTEXT)
  {
    DEBUG_ERROR("Failed to create EGL context (eglError: 0x%x)", eglGetError());
    return false;
  }

  EGLint rb = 0;
  eglQuerySurface(this->display, this->surface, EGL_RENDER_BUFFER, &rb);
  switch(rb)
  {
    case EGL_SINGLE_BUFFER:
      DEBUG_INFO("Single buffer mode");
      break;

    case EGL_BACK_BUFFER:
      DEBUG_INFO("Back buffer mode");
      break;

    default:
      DEBUG_WARN("Unknown render buffer mode: %d", rb);
      break;
  }

  eglMakeCurrent(this->display, this->surface, this->surface, this->context);
  const char *client_exts = eglQueryString(this->display, EGL_EXTENSIONS);
  const char *gl_exts     = (const char *)glGetString(GL_EXTENSIONS);
  const char *vendor      = (const char *)glGetString(GL_VENDOR);

  DEBUG_INFO("EGL     : %d.%d", maj, min);
  DEBUG_INFO("Vendor  : %s", vendor);
  DEBUG_INFO("Renderer: %s", glGetString(GL_RENDERER));
  DEBUG_INFO("Version : %s", glGetString(GL_VERSION ));
  DEBUG_INFO("EGL APIs: %s", eglQueryString(this->display, EGL_CLIENT_APIS));
  DEBUG_INFO("EGL Exts: %s", client_exts);
  DEBUG_INFO("GL Exts : %s", gl_exts);

  GLint esMaj, esMin;
  glGetIntegerv(GL_MAJOR_VERSION, &esMaj);
  glGetIntegerv(GL_MINOR_VERSION, &esMin);

  if (!util_hasGLExt(gl_exts, "GL_EXT_buffer_storage"))
  {
    DEBUG_ERROR("GL_EXT_buffer_storage is needed to use EGL backend");
    return false;
  }

  if (!util_hasGLExt(gl_exts, "GL_EXT_texture_format_BGRA8888"))
  {
    DEBUG_ERROR("GL_EXT_texture_format_BGRA8888 is needed to use EGL backend");
    return false;
  }

  if (g_egl_dynProcs.glEGLImageTargetTexture2DOES)
  {
    if (util_hasGLExt(client_exts, "EGL_EXT_image_dma_buf_import"))
    {
      /*
       * As of version 455.45.01 NVidia started advertising support for this
       * feature, however even on the latest version 460.27.04 this is still
       * broken and does not work, until this is fixed and we have way to detect
       * this early just disable dma for all NVIDIA devices.
       *
       * ref: https://forums.developer.nvidia.com/t/egl-ext-image-dma-buf-import-broken-egl-bad-alloc-with-tons-of-free-ram/165552
       */
      if (strstr(vendor, "NVIDIA") != NULL)
        DEBUG_WARN("NVIDIA driver detected, ignoring broken DMA support");
      else
        this->dmaSupport = true;
    }
    else
      DEBUG_INFO("EGL_EXT_image_dma_buf_import unavailable, DMA support disabled");
  }
  else
    DEBUG_INFO("glEGLImageTargetTexture2DOES unavilable, DMA support disabled");

  if (debugContext)
  {
    if ((esMaj > 3 || (esMaj == 3 && esMin >= 2)) && g_egl_dynProcs.glDebugMessageCallback)
    {
      g_egl_dynProcs.glDebugMessageCallback(debugCallback, NULL);
      DEBUG_INFO("Using debug message callback from OpenGL ES 3.2+");
    }
    else if (util_hasGLExt(gl_exts, "GL_KHR_debug") && g_egl_dynProcs.glDebugMessageCallbackKHR)
    {
      g_egl_dynProcs.glDebugMessageCallbackKHR(debugCallback, NULL);
      DEBUG_INFO("Using debug message callback from GL_KHR_debug");
    }
    else
      DEBUG_INFO("Debug message callback not supported");
  }
  else
    DEBUG_INFO("Debug messages disabled, enable with egl:debug=true");

  eglSwapInterval(this->display, this->opt.vsync ? 1 : 0);

  if (!egl_desktop_init(&this->desktop, this->display))
  {
    DEBUG_ERROR("Failed to initialize the desktop");
    return false;
  }

  if (!egl_cursor_init(&this->cursor))
  {
    DEBUG_ERROR("Failed to initialize the cursor");
    return false;
  }

  if (!egl_splash_init(&this->splash))
  {
    DEBUG_ERROR("Failed to initialize the splash screen");
    return false;
  }

  if (!egl_damage_init(&this->damage))
  {
    DEBUG_ERROR("Failed to initialize the damage display");
    return false;
  }

  if (!ImGui_ImplOpenGL3_Init("#version 300 es"))
  {
    DEBUG_ERROR("Failed to initialize ImGui");
    return false;
  }

  this->imgui = true;
  return true;
}

static bool egl_render(void * opaque, LG_RendererRotate rotate, const bool newFrame,
    const bool invalidateWindow)
{
  struct Inst * this = (struct Inst *)opaque;

  glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
  glClear(GL_COLOR_BUFFER_BIT);

  bool hasOverlay = false;
  struct CursorState cursorState = { .visible = false };
  struct DesktopDamage * desktopDamage = NULL;

  if (this->start)
  {
    desktopDamage = atomic_exchange(&this->desktopDamage, NULL);
    if (egl_desktop_render(this->desktop,
        this->translateX, this->translateY,
        this->scaleX    , this->scaleY    ,
        this->scaleType , rotate))
    {
      if (!this->waitFadeTime)
      {
        if (!this->params.quickSplash)
          this->waitFadeTime = microtime() + SPLASH_FADE_TIME;
        else
          this->waitDone = true;
      }

      cursorState = egl_cursor_render(this->cursor,
          (this->format.rotate + rotate) % LG_ROTATE_MAX,
          this->width, this->height);
    }
    else
      desktopDamage->count = 0;
  }

  if (!this->waitDone)
  {
    float a = 1.0f;
    if (!this->waitFadeTime)
      a = 1.0f;
    else
    {
      uint64_t t = microtime();
      if (t > this->waitFadeTime)
        this->waitDone = true;
      else
      {
        uint64_t delta = this->waitFadeTime - t;
        a = 1.0f / SPLASH_FADE_TIME * delta;
      }
    }

    if (!this->waitDone)
    {
      egl_splash_render(this->splash, a, this->splashRatio);
      hasOverlay = true;
    }
  }
  else if (!this->start)
  {
    egl_splash_render(this->splash, 1.0f, this->splashRatio);
    hasOverlay = true;
  }

  if (desktopDamage && rotate != LG_ROTATE_0)
  {
    for (int i = 0; i < desktopDamage->count; ++i)
    {
      FrameDamageRect * r = desktopDamage->rects + i;

      switch (rotate)
      {
        case LG_ROTATE_90:
          *r = (FrameDamageRect) {
            .x = this->format.height - r->y - r->height,
            .y = r->x,
            .width = r->height,
            .height = r->width,
          };
          break;

        case LG_ROTATE_180:
          r->x = this->format.width  - r->x - r->width;
          r->y = this->format.height - r->y - r->height;
          break;

        case LG_ROTATE_270:
          *r = (FrameDamageRect) {
            .x = r->y,
            .y = this->format.width - r->x - r->width,
            .width = r->height,
            .height = r->width,
          };
          break;

        case LG_ROTATE_0:
        default:
          assert(!"unreachable");
      }
    }
  }

  double scaleX = 0;
  double scaleY = 0;
  bool rotated = false;

  switch (rotate)
  {
    case LG_ROTATE_0:
    case LG_ROTATE_180:
      scaleX = (double) this->destRect.w / this->format.width;
      scaleY = (double) this->destRect.h / this->format.height;
      rotated = false;
      break;

    case LG_ROTATE_90:
    case LG_ROTATE_270:
      scaleX = (double) this->destRect.w / this->format.height;
      scaleY = (double) this->destRect.h / this->format.width;
      rotated = true;
      break;

    default:
      assert(!"unreachable");
  }

  hasOverlay |= egl_damage_render(this->damage, rotated, newFrame ? desktopDamage : NULL);
  hasOverlay |= invalidateWindow;

  struct Rect damage[KVMFR_MAX_DAMAGE_RECTS + MAX_OVERLAY_RECTS + 2];
  int damageIdx = app_renderOverlay(damage, MAX_OVERLAY_RECTS);

  switch (damageIdx)
  {
    case 0: // no overlay
      break;
    case -1: // full damage
      hasOverlay = true;
      // fallthrough
    default:
      ImGui_ImplOpenGL3_NewFrame();
      ImGui_ImplOpenGL3_RenderDrawData(igGetDrawData());

      for (int i = 0; i < damageIdx; ++i)
        damage[i].y = this->height - damage[i].y - damage[i].h;
  }

  if (!hasOverlay && !this->hadOverlay)
  {
    if (this->cursorLast.visible)
      damage[damageIdx++] = this->cursorLast.rect;

    if (cursorState.visible)
      damage[damageIdx++] = cursorState.rect;

    this->cursorLast = cursorState;

    if (desktopDamage)
    {
      if (desktopDamage->count == 0)
        // Zero damage count means invalidating entire window.
        damageIdx = 0;
      else
      {
        for (int i = 0; i < desktopDamage->count; ++i)
        {
          FrameDamageRect rect = desktopDamage->rects[i];
          int x1 = (int) (rect.x * scaleX);
          int y1 = (int) (rect.y * scaleY);
          int x2 = (int) ceil((rect.x + rect.width) * scaleX);
          int y2 = (int) ceil((rect.y + rect.height) * scaleY);
          damage[damageIdx++] = (struct Rect) {
            .x = this->destRect.x + x1,
            .y = this->height - (this->destRect.y + y2),
            .w = x2 - x1,
            .h = y2 - y1,
          };
        }
      }
    }
  }
  else
    damageIdx = 0;
  this->hadOverlay = hasOverlay;
  free(desktopDamage);

  app_eglSwapBuffers(this->display, this->surface, damage, damageIdx);
  return true;
}

struct LG_Renderer LGR_EGL =
{
  .get_name        = egl_get_name,
  .setup           = egl_setup,
  .create          = egl_create,
  .initialize      = egl_initialize,
  .deinitialize    = egl_deinitialize,
  .supports        = egl_supports,
  .on_restart      = egl_on_restart,
  .on_resize       = egl_on_resize,
  .on_mouse_shape  = egl_on_mouse_shape,
  .on_mouse_event  = egl_on_mouse_event,
  .on_frame_format = egl_on_frame_format,
  .on_frame        = egl_on_frame,
  .render_startup  = egl_render_startup,
  .render          = egl_render
};