#include "wayland_video_surface.h"

#include <EGL/eglext.h>
#include <gdk/gdkwayland.h>
#include <unistd.h>
#include <wayland-client.h>
#include <wayland-egl.h>

#include <cstring>
#include <limits>

#include "color-management-v1-client-protocol.h"
#include "plane_geometry.h"

namespace mpv {
namespace {

// The client understands up to this version of color-management-v1; KWin 6.4
// implements 1. Binding min(advertised, this) keeps newer compositors working
// without requiring them.
constexpr uint32_t kColorManagerMaxVersion = 3;

bool Fail(std::string* error, const char* message) {
  if (error) *error = message;
  return false;
}

// Scratch state for the registry listener only. The registry proxy is destroyed
// before BindGlobals returns, so a pointer to this frame cannot outlive it.
struct RegistryTarget {
  wl_subcompositor* subcompositor = nullptr;
  wp_color_manager_v1* color_manager = nullptr;
};

void RegistryGlobal(void* data, wl_registry* registry, uint32_t name, const char* interface, uint32_t version) {
  auto* target = static_cast<RegistryTarget*>(data);
  if (g_strcmp0(interface, "wl_subcompositor") == 0 && target->subcompositor == nullptr) {
    target->subcompositor =
        static_cast<wl_subcompositor*>(wl_registry_bind(registry, name, &wl_subcompositor_interface, 1));
  } else if (g_strcmp0(interface, "wp_color_manager_v1") == 0 && target->color_manager == nullptr) {
    const uint32_t bind_version = version < kColorManagerMaxVersion ? version : kColorManagerMaxVersion;
    target->color_manager = static_cast<wp_color_manager_v1*>(
        wl_registry_bind(registry, name, &wp_color_manager_v1_interface, bind_version));
  }
}

void RegistryGlobalRemove(void* data, wl_registry* registry, uint32_t name) {
  (void)data;
  (void)registry;
  (void)name;
}

const wl_registry_listener kRegistryListener = {RegistryGlobal, RegistryGlobalRemove};

wl_surface* ParentSurface(GtkWidget* view) {
  GtkWidget* toplevel = gtk_widget_get_toplevel(view);
  if (toplevel == nullptr) return nullptr;
  GdkWindow* window = gtk_widget_get_window(toplevel);
  if (window == nullptr || !GDK_IS_WAYLAND_WINDOW(window)) return nullptr;
  return gdk_wayland_window_get_wl_surface(GDK_WAYLAND_WINDOW(window));
}

}  // namespace

WaylandVideoSurface::~WaylandVideoSurface() { Destroy(); }

void WaylandVideoSurface::HandleManagerIntent(void* data, wp_color_manager_v1* manager, uint32_t intent) {
  (void)manager;
  // set_image_description raises the render_intent protocol error - fatal, not a
  // rejected description - for any intent the compositor did not advertise here.
  // Perceptual is the only one this plane ever asks for.
  if (intent == WP_COLOR_MANAGER_V1_RENDER_INTENT_PERCEPTUAL) {
    static_cast<WaylandVideoSurface*>(data)->manager_caps_.perceptual = true;
  }
}

void WaylandVideoSurface::HandleManagerFeature(void* data, wp_color_manager_v1* manager, uint32_t feature) {
  (void)manager;
  auto* self = static_cast<WaylandVideoSurface*>(data);
  if (feature == WP_COLOR_MANAGER_V1_FEATURE_PARAMETRIC) self->manager_caps_.parametric = true;
  // Gates set_mastering_luminance as well as the primaries request it is named
  // after. Sending either without this advertised is a fatal protocol error,
  // not a soft failure, so it has to be tracked rather than assumed.
  if (feature == WP_COLOR_MANAGER_V1_FEATURE_SET_MASTERING_DISPLAY_PRIMARIES) {
    self->manager_caps_.mastering = true;
  }
  // Whether a mastering display *larger* than the curve's primary colour volume
  // may be described. Without it the mastering advertisement only promises
  // volumes fully contained within it, and exceeding it is implementation
  // defined. This is what bounds HLG, whose primary volume stops at 1000 nits.
  if (feature == WP_COLOR_MANAGER_V1_FEATURE_EXTENDED_TARGET_VOLUME) {
    self->manager_caps_.extended_target_volume = true;
  }
}

void WaylandVideoSurface::HandleManagerTransferFunction(void* data, wp_color_manager_v1* manager, uint32_t tf) {
  (void)manager;
  auto* self = static_cast<WaylandVideoSurface*>(data);
  // Both HDR curves are tracked: which one a plane needs is decided per source,
  // since HLG content must be described as HLG and never re-labelled PQ.
  if (tf == WP_COLOR_MANAGER_V1_TRANSFER_FUNCTION_ST2084_PQ) self->manager_caps_.pq = true;
  if (tf == WP_COLOR_MANAGER_V1_TRANSFER_FUNCTION_HLG) self->manager_caps_.hlg = true;
}

void WaylandVideoSurface::HandleManagerPrimaries(void* data, wp_color_manager_v1* manager, uint32_t primaries) {
  (void)manager;
  if (primaries == WP_COLOR_MANAGER_V1_PRIMARIES_BT2020) {
    static_cast<WaylandVideoSurface*>(data)->manager_caps_.bt2020 = true;
  }
}

void WaylandVideoSurface::HandleManagerDone(void* data, wp_color_manager_v1* manager) {
  (void)manager;
  static_cast<WaylandVideoSurface*>(data)->manager_caps_.done = true;
}

bool WaylandVideoSurface::IsSupported(GdkDisplay* display) {
  return display != nullptr && GDK_IS_WAYLAND_DISPLAY(display);
}

bool WaylandVideoSurface::BindGlobals(GdkDisplay* display, std::string* error) {
  wl_display_ = gdk_wayland_display_get_wl_display(GDK_WAYLAND_DISPLAY(display));
  compositor_ = gdk_wayland_display_get_wl_compositor(GDK_WAYLAND_DISPLAY(display));
  if (wl_display_ == nullptr || compositor_ == nullptr) {
    return Fail(error, "Wayland display or compositor is unavailable");
  }

  // Bind on a private queue so the roundtrip cannot dispatch GDK's own events
  // from inside this call, then hand the bound global back to the default queue
  // that GDK's main-loop source already drives.
  wl_event_queue* queue = wl_display_create_queue(wl_display_);
  if (queue == nullptr) return Fail(error, "Failed to create a Wayland event queue");

  wl_registry* registry = wl_display_get_registry(wl_display_);
  if (registry == nullptr) {
    wl_event_queue_destroy(queue);
    return Fail(error, "Failed to obtain the Wayland registry");
  }
  wl_proxy_set_queue(reinterpret_cast<wl_proxy*>(registry), queue);

  RegistryTarget target;
  wl_registry_add_listener(registry, &kRegistryListener, &target);
  bool round_tripped = wl_display_roundtrip_queue(wl_display_, queue) >= 0;

  // The colour manager reports what it supports right after binding, so a
  // second roundtrip is needed before those answers can be trusted. The
  // listener is given `this`, not the local: the manager proxy is kept for the
  // life of the plane and libwayland cannot detach a listener, so a burst that
  // is still in flight when the loop below gives up would otherwise be
  // dispatched into a dead stack frame once GDK's queue picks it up.
  if (round_tripped && target.color_manager != nullptr) {
    static_assert(
        sizeof(wp_color_manager_v1_listener) == 5 * sizeof(void (*)()),
        "wp_color_manager_v1_listener gained an event; handle it here");
    static const wp_color_manager_v1_listener kManagerListener = {
        HandleManagerIntent,    HandleManagerFeature, HandleManagerTransferFunction,
        HandleManagerPrimaries, HandleManagerDone,
    };
    wp_color_manager_v1_add_listener(target.color_manager, &kManagerListener, this);
    for (int attempt = 0; attempt < kBootstrapRoundtrips && !manager_caps_.done; ++attempt) {
      if (wl_display_roundtrip_queue(wl_display_, queue) < 0) {
        round_tripped = false;
        break;
      }
    }
  }

  wl_registry_destroy(registry);

  // Both globals were bound from a registry on `queue`, so they inherited it.
  // They have to be moved off before it is destroyed: libwayland >= 1.22 warns
  // that a queue was destroyed with proxies still attached and nulls their
  // queue pointer, and a proxy with no queue is a null dereference the moment
  // anything is dispatched for it.
  if (target.subcompositor != nullptr) {
    wl_proxy_set_queue(reinterpret_cast<wl_proxy*>(target.subcompositor), nullptr);
  }
  if (target.color_manager != nullptr) {
    wl_proxy_set_queue(reinterpret_cast<wl_proxy*>(target.color_manager), nullptr);
  }
  wl_event_queue_destroy(queue);

  // Every failure below has to release both globals itself. They are not yet
  // owned by a member, so Destroy() would not see them. The caller turns the
  // message into a VIDEO_PLANE_UNSUPPORTED init failure - a compositor without
  // wl_subcompositor takes this route on every launch.
  auto abandon = [&](const char* message) {
    if (target.color_manager != nullptr) wp_color_manager_v1_destroy(target.color_manager);
    if (target.subcompositor != nullptr) wl_subcompositor_destroy(target.subcompositor);
    manager_caps_ = ManagerCaps{};
    return Fail(error, message);
  };
  if (!round_tripped) return abandon("Wayland roundtrip failed while binding globals");
  if (target.subcompositor == nullptr) return abandon("Compositor does not expose wl_subcompositor");

  subcompositor_ = target.subcompositor;

  if (target.color_manager != nullptr) {
    color_manager_ = target.color_manager;
    supports_pq_ = manager_caps_.pq;
    supports_hlg_ = manager_caps_.hlg;
    supports_bt2020_ = manager_caps_.bt2020;
    // BT.2020, at least one HDR curve, a parametric creator, and the perceptual
    // rendering intent. Either curve will do here; which one a given source needs
    // is checked per source. The intent belongs in this gate rather than at
    // attachment time because set_image_description raises a fatal protocol
    // error for an unadvertised intent, and perceptual is the only one the plane
    // ever asks for. Anything missing and the plane stays sRGB with mpv
    // tone-mapping as it does today.
    supports_hdr_ = manager_caps_.done && manager_caps_.parametric && manager_caps_.perceptual &&
                    manager_caps_.bt2020 && (manager_caps_.pq || manager_caps_.hlg);
    // Optional on top: without mastering the plane is still described by its
    // curve and gamut, the compositor just has to tone-map against its own
    // assumptions rather than the source's mastering display. The interface
    // version is recorded because version 1 imposes luminance rules version 2
    // dropped.
    luminance_support_.mastering = manager_caps_.mastering;
    luminance_support_.extended_target_volume = manager_caps_.extended_target_volume;
    luminance_support_.interface_version = wp_color_manager_v1_get_version(color_manager_);
    if (!supports_hdr_) {
      g_message(
          "MPV video plane: compositor colour management is incomplete "
          "(parametric=%d perceptual=%d pq=%d hlg=%d bt2020=%d); HDR passthrough unavailable",
          manager_caps_.parametric, manager_caps_.perceptual, manager_caps_.pq, manager_caps_.hlg,
          manager_caps_.bt2020);
    }
  }
  return true;
}

bool WaylandVideoSurface::InitEgl(std::string* error) {
  // The plane's EGL stack is deliberately independent of Flutter's: nothing is
  // shared, so the context is free to be ES 3.x (mpv wants compute shaders for
  // hdr-compute-peak, and the >8-bit render targets the 10-bit config chosen
  // below is there to provide).
  egl_display_ = eglGetDisplay(reinterpret_cast<EGLNativeDisplayType>(wl_display_));
  if (egl_display_ == EGL_NO_DISPLAY) return Fail(error, "No EGL display for the Wayland connection");
  if (!eglInitialize(egl_display_, nullptr, nullptr)) {
    egl_display_ = EGL_NO_DISPLAY;
    return Fail(error, "eglInitialize failed for the video plane");
  }

  // Video is opaque, so no alpha channel is requested. A config that carries
  // one anyway (the fp16 tier — no driver offers an alpha-less half-float
  // config) is still fine: Create() declares the whole surface opaque, so the
  // compositor never reads the alpha channel and may still promote the plane.
  //
  // Deepest first, because PQ quantised to 8 bits bands visibly. The middle
  // tier exists for NVIDIA: its Wayland EGL (through at least 610.xx) exposes
  // no 10-bit unorm window configs at all — only 8-bit unorm and half-float —
  // where Mesa offers ARGB2101010. fp16 exceeds 10-bit precision at twice the
  // bandwidth, so it ranks between the two unorm tiers rather than first.
  // 8 bits is the last resort and simply means HDR stays off.
  const char* extensions = eglQueryString(egl_display_, EGL_EXTENSIONS);
  const bool has_float_configs = extensions != nullptr && strstr(extensions, "EGL_EXT_pixel_format_float") != nullptr;
  auto choose = [this](const EGLint* attributes) {
    EGLConfig config = nullptr;
    EGLint count = 0;
    if (eglChooseConfig(egl_display_, attributes, &config, 1, &count) && count == 1) {
      egl_config_ = config;
      return true;
    }
    return false;
  };
  struct ConfigTier {
    EGLint bits;    // per-channel size requested, and the depth then reported
    bool floating;  // half-float rather than unorm
  };
  for (const ConfigTier tier : {ConfigTier{10, false}, ConfigTier{16, true}, ConfigTier{8, false}}) {
    if (tier.floating && !has_float_configs) continue;
    for (const EGLint renderable : {EGL_OPENGL_ES3_BIT, EGL_OPENGL_ES2_BIT}) {
      const EGLint attributes[] = {
          EGL_SURFACE_TYPE,
          EGL_WINDOW_BIT,
          EGL_RENDERABLE_TYPE,
          renderable,
          EGL_RED_SIZE,
          tier.bits,
          EGL_GREEN_SIZE,
          tier.bits,
          EGL_BLUE_SIZE,
          tier.bits,
          // Asking for zero alpha would reject every half-float config, since
          // no driver offers an alpha-less one.
          tier.floating ? EGL_COLOR_COMPONENT_TYPE_EXT : EGL_ALPHA_SIZE,
          tier.floating ? EGL_COLOR_COMPONENT_TYPE_FLOAT_EXT : 0,
          EGL_NONE,
      };
      if (choose(attributes)) {
        depth_bits_ = tier.bits;
        return true;
      }
    }
  }
  return Fail(error, "No matching EGL config for the video plane");
}

bool WaylandVideoSurface::Create(GtkWidget* view, std::string* error) {
  if (view == nullptr) return Fail(error, "Video plane requires a realized view");
  GdkDisplay* display = gtk_widget_get_display(view);
  if (!IsSupported(display)) return Fail(error, "Not a Wayland display");

  wl_surface* parent = ParentSurface(view);
  if (parent == nullptr) return Fail(error, "Toplevel has no Wayland surface yet");

  view_ = view;
  if (!BindGlobals(display, error) || !InitEgl(error)) {
    Destroy();
    return false;
  }

  surface_ = wl_compositor_create_surface(compositor_);
  if (surface_ == nullptr) {
    Destroy();
    return Fail(error, "Failed to create the video wl_surface");
  }

  // Input belongs to the Flutter view, never to the video plane. An empty input
  // region makes the compositor route pointer and touch straight through — the
  // Wayland twin of keeping the Windows video child out of the hit-test path.
  //
  // The one allocation here that is survivable rather than fatal: without it the
  // plane still displays correctly and only input passthrough is lost, whereas
  // failing Create() would drop the whole window back to the Flutter texture
  // path and give up HDR and the per-frame upload saving to fix a stray hit-test.
  wl_region* empty = wl_compositor_create_region(compositor_);
  if (empty != nullptr) {
    wl_surface_set_input_region(surface_, empty);
    wl_region_destroy(empty);
  }

  // The plane carries opaque video, and saying so lets the compositor skip
  // blending it. It stops being merely helpful once the EGL config has an
  // alpha channel (the fp16 tier): without it the compositor would honour
  // whatever alpha mpv left in the buffer instead of treating video as solid.
  // The compositor clamps the region to the surface, so one maximal region
  // outlives every SetRect().
  wl_region* opaque = wl_compositor_create_region(compositor_);
  if (opaque != nullptr) {
    wl_region_add(opaque, 0, 0, std::numeric_limits<int32_t>::max(), std::numeric_limits<int32_t>::max());
    wl_surface_set_opaque_region(surface_, opaque);
    wl_region_destroy(opaque);
  }

  subsurface_ = wl_subcompositor_get_subsurface(subcompositor_, surface_, parent);
  if (subsurface_ == nullptr) {
    Destroy();
    return Fail(error, "Failed to create the video wl_subsurface");
  }
  wl_subsurface_place_below(subsurface_, parent);
  wl_subsurface_set_desync(subsurface_);

  // A 1x1 window keeps EGL happy until the first SetRect() arrives.
  egl_window_ = wl_egl_window_create(surface_, 1, 1);
  if (egl_window_ == nullptr) {
    Destroy();
    return Fail(error, "Failed to create the video wl_egl_window");
  }

  egl_surface_ =
      eglCreateWindowSurface(egl_display_, egl_config_, reinterpret_cast<EGLNativeWindowType>(egl_window_), nullptr);
  if (egl_surface_ == EGL_NO_SURFACE) {
    Destroy();
    return Fail(error, "Failed to create the video EGL surface");
  }

  // Note: the swap interval cannot be set here — eglSwapInterval acts on the
  // surface bound to the *current* context, and none is current yet. It is set
  // in MpvPlayer::InitRenderContextForSurface once the context is bound.

  if (color_manager_ != nullptr) {
    color_surface_ = wp_color_manager_v1_get_surface(color_manager_, surface_);
  }
  // PQ in 8 bits bands badly enough to be worse than tone-mapping to SDR, so
  // HDR is only offered when the plane actually got a deep config (10-bit
  // unorm or fp16).
  if (supports_hdr_ && (color_surface_ == nullptr || depth_bits_ < 10)) {
    supports_hdr_ = false;
    g_message(
        "MPV video plane: HDR unavailable (colour surface=%p, depth=%d bits)", static_cast<void*>(color_surface_),
        depth_bits_);
  }
  g_message("MPV video plane: %d bits per channel, HDR %s", depth_bits_, supports_hdr_ ? "available" : "unavailable");

  // Feedback tells us what the compositor would prefer for this surface, which
  // is the only channel that reveals the output's real peak luminance and
  // whether it is in HDR at all. Bootstrapped synchronously on a private queue
  // so callers - including Dart's isHDRSupported - see a populated answer as
  // soon as Create returns, then handed to the default queue that GDK drives so
  // later preferred_changed events keep arriving.
  if (supports_hdr_) {
    static_assert(
        sizeof(wp_color_management_surface_feedback_v1_listener) == 2 * sizeof(void (*)()),
        "wp_color_management_surface_feedback_v1_listener gained an event");
    static const wp_color_management_surface_feedback_v1_listener kFeedbackListener = {
        HandlePreferredChanged,
        HandlePreferredChanged2,
    };
    wl_event_queue* queue = wl_display_create_queue(wl_display_);
    color_feedback_ = wp_color_manager_v1_get_surface_feedback(color_manager_, surface_);
    if (color_feedback_ != nullptr) {
      wp_color_management_surface_feedback_v1_add_listener(color_feedback_, &kFeedbackListener, this);
      if (queue != nullptr) {
        // Children inherit the parent proxy's queue at creation, so putting the
        // feedback object here also lands the description and info objects on
        // this queue for the duration of the bootstrap.
        wl_proxy_set_queue(reinterpret_cast<wl_proxy*>(color_feedback_), queue);
        BeginPreferredQuery();
        // ready, then get_information's burst, then done; a compositor that
        // never answers just leaves preferred_ invalid.
        for (int attempt = 0; attempt < kBootstrapRoundtrips && !preferred_.valid; ++attempt) {
          if (wl_display_roundtrip_queue(wl_display_, queue) < 0) break;
        }
        // The description and info proxies must not outlive the queue they were
        // created on, so whatever is still in flight is abandoned here and
        // retried below on the default queue.
        //
        // The retry is keyed on there being an outstanding query rather than on
        // preferred_ being invalid, because those are not the same condition. A
        // preferred_changed dispatched in the *same* batch that completed the
        // first query re-arms BeginPreferredQuery on this queue after the loop's
        // condition has already gone false; ClearPreferredQuery then destroys
        // that new description, and a validity test would see the first,
        // superseded answer and skip the retry - leaving the plane reporting the
        // wrong output's peak, and possibly HDR-capable for an output that is
        // not. CommitPreferredQuery nulls the pointer on success, so a non-null
        // one means and only means "still outstanding".
        const bool query_outstanding = preferred_description_ != nullptr;
        ClearPreferredQuery();
        wl_proxy_set_queue(reinterpret_cast<wl_proxy*>(color_feedback_), nullptr);
        if (!preferred_.valid || query_outstanding) BeginPreferredQuery();
      } else {
        BeginPreferredQuery();
      }
    }
    if (queue != nullptr) wl_event_queue_destroy(queue);
    g_message("MPV video plane: output is %s", output_is_hdr() ? "in HDR" : "SDR or unknown");
  }

  RequestParentCommit();
  return true;
}

void WaylandVideoSurface::ClearPreferredQuery() {
  if (preferred_info_ != nullptr) {
    wp_image_description_info_v1_destroy(preferred_info_);
    preferred_info_ = nullptr;
  }
  if (preferred_description_ != nullptr) {
    wp_image_description_v1_destroy(preferred_description_);
    preferred_description_ = nullptr;
  }
}

void WaylandVideoSurface::BeginPreferredQuery() {
  if (color_feedback_ == nullptr) return;
  // The protocol asks clients to stop using descriptions from earlier
  // invocations, so a query in flight is abandoned rather than raced.
  ClearPreferredQuery();
  pending_preferred_ = PreferredColorDescription();

  static_assert(
      sizeof(wp_image_description_v1_listener) == 3 * sizeof(void (*)()),
      "wp_image_description_v1_listener gained an event; handle it here");
  static const wp_image_description_v1_listener kPreferredListener = {
      HandlePreferredFailed,
      HandlePreferredReady,
      HandlePreferredReady2,
  };
  // get_preferred_parametric rather than get_preferred: we can only read
  // parameters, and an ICC-based preferred description would tell us nothing.
  // It is gated on the parametric feature, which supports_hdr_ already implies.
  preferred_description_ = wp_color_management_surface_feedback_v1_get_preferred_parametric(color_feedback_);
  if (preferred_description_ == nullptr) return;
  wp_image_description_v1_add_listener(preferred_description_, &kPreferredListener, this);
}

void WaylandVideoSurface::CommitPreferredQuery() {
  pending_preferred_.valid = true;
  const bool changed = preferred_.valid != pending_preferred_.valid || preferred_.pq != pending_preferred_.pq ||
                       preferred_.bt2020 != pending_preferred_.bt2020 ||
                       preferred_.max_luminance != pending_preferred_.max_luminance ||
                       preferred_.min_luminance_scaled != pending_preferred_.min_luminance_scaled ||
                       preferred_.reference_luminance != pending_preferred_.reference_luminance;
  preferred_ = pending_preferred_;
  ClearPreferredQuery();
  g_message(
      "MPV video plane: compositor prefers %s / %s, target %u nits (floor %.4f), reference %u nits",
      preferred_.pq ? "PQ" : "non-PQ", preferred_.bt2020 ? "BT.2020" : "non-BT.2020", preferred_.max_luminance,
      static_cast<double>(preferred_.min_luminance_scaled) / kMinLuminanceScale, preferred_.reference_luminance);
  if (changed && on_preferred_changed_) on_preferred_changed_();
}

void WaylandVideoSurface::HandlePreferredChanged(
    void* data, wp_color_management_surface_feedback_v1* feedback, uint32_t identity) {
  (void)feedback;
  (void)identity;
  // The identity is only useful for skipping the re-query when it matches what
  // we already hold. We do not cache by identity, so always re-read.
  static_cast<WaylandVideoSurface*>(data)->BeginPreferredQuery();
}

void WaylandVideoSurface::HandlePreferredChanged2(
    void* data, wp_color_management_surface_feedback_v1* feedback, uint32_t identity_hi, uint32_t identity_lo) {
  (void)identity_hi;
  (void)identity_lo;
  HandlePreferredChanged(data, feedback, 0);
}

void WaylandVideoSurface::HandlePreferredReady(void* data, wp_image_description_v1* desc, uint32_t identity) {
  (void)identity;
  auto* self = static_cast<WaylandVideoSurface*>(data);
  if (self->preferred_description_ != desc) return;
  // get_information is allowed on descriptions from get_preferred, unlike the
  // ones we build ourselves, and is the only way to read the parameters out.
  self->preferred_info_ = wp_image_description_v1_get_information(desc);
  if (self->preferred_info_ == nullptr) return;
  static_assert(
      sizeof(wp_image_description_info_v1_listener) == 11 * sizeof(void (*)()),
      "wp_image_description_info_v1_listener gained an event; handle it here");
  static const wp_image_description_info_v1_listener kInfoListener = {
      HandleInfoDone,           HandleInfoIccFile,         HandleInfoPrimaries,
      HandleInfoPrimariesNamed, HandleInfoTfPower,         HandleInfoTfNamed,
      HandleInfoLuminances,     HandleInfoTargetPrimaries, HandleInfoTargetLuminance,
      HandleInfoTargetMaxCll,   HandleInfoTargetMaxFall,
  };
  wp_image_description_info_v1_add_listener(self->preferred_info_, &kInfoListener, self);
}

void WaylandVideoSurface::HandlePreferredReady2(
    void* data, wp_image_description_v1* desc, uint32_t identity_hi, uint32_t identity_lo) {
  (void)identity_hi;
  (void)identity_lo;
  HandlePreferredReady(data, desc, 0);
}

void WaylandVideoSurface::HandlePreferredFailed(
    void* data, wp_image_description_v1* desc, uint32_t cause, const char* message) {
  auto* self = static_cast<WaylandVideoSurface*>(data);
  // Wiping preferred_ drives output_is_hdr() false and would tear down a live
  // HDR plane, so this handler must not act on a superseded description.
  if (self->preferred_description_ != desc) return;
  // low_version means our vendored protocol is too old to be told the whole
  // description; no_output means the surface is not on one any more. Neither is
  // fatal - it only means we cannot claim to know the output's peak.
  g_message(
      "MPV video plane: no preferred colour description (cause %u): %s", cause, message ? message : "no reason given");
  const bool had_preference = self->preferred_.valid;
  self->ClearPreferredQuery();
  self->preferred_ = PreferredColorDescription();
  // Losing a preference we previously held is a state change like any other, and
  // a more urgent one: output_is_hdr() is now false, so the plane must stop being
  // described as HDR rather than keep a description for an output that is gone.
  // Silent during the initial bootstrap, where nothing was valid and no callback
  // is installed yet.
  if (had_preference && self->on_preferred_changed_) self->on_preferred_changed_();
}

void WaylandVideoSurface::HandleInfoDone(void* data, wp_image_description_info_v1* info) {
  auto* self = static_cast<WaylandVideoSurface*>(data);
  if (self->preferred_info_ != info) return;
  self->CommitPreferredQuery();
}

void WaylandVideoSurface::HandleInfoTfNamed(void* data, wp_image_description_info_v1* info, uint32_t tf) {
  (void)info;
  auto* self = static_cast<WaylandVideoSurface*>(data);
  self->pending_preferred_.pq = tf == WP_COLOR_MANAGER_V1_TRANSFER_FUNCTION_ST2084_PQ;
}

void WaylandVideoSurface::HandleInfoPrimariesNamed(void* data, wp_image_description_info_v1* info, uint32_t primaries) {
  (void)info;
  auto* self = static_cast<WaylandVideoSurface*>(data);
  self->pending_preferred_.bt2020 = primaries == WP_COLOR_MANAGER_V1_PRIMARIES_BT2020;
}

void WaylandVideoSurface::HandleInfoLuminances(
    void* data, wp_image_description_info_v1* info, uint32_t min_lum, uint32_t max_lum, uint32_t reference_lum) {
  (void)info;
  (void)min_lum;
  (void)max_lum;
  // These describe the transfer function's own encodable range - for PQ always
  // 0.005 to 10000 - so only the reference is informative. The panel's actual
  // peak arrives in target_luminance instead.
  static_cast<WaylandVideoSurface*>(data)->pending_preferred_.reference_luminance = reference_lum;
}

void WaylandVideoSurface::HandleInfoTargetLuminance(
    void* data, wp_image_description_info_v1* info, uint32_t min_lum, uint32_t max_lum) {
  (void)info;
  auto* self = static_cast<WaylandVideoSurface*>(data);
  self->pending_preferred_.min_luminance_scaled = min_lum;
  self->pending_preferred_.max_luminance = max_lum;
}

void WaylandVideoSurface::HandleInfoIccFile(
    void* data, wp_image_description_info_v1* info, int32_t icc, uint32_t icc_size) {
  (void)data;
  (void)info;
  (void)icc_size;
  // The fd is ours once received; leaking it would exhaust the process's fds
  // over repeated monitor changes.
  if (icc >= 0) close(icc);
}

// Events the plane has no use for. Present rather than omitted for the reason
// given beside the description listener in BuildImageDescription().
void WaylandVideoSurface::HandleInfoPrimaries(
    void* data, wp_image_description_info_v1* info, int32_t r_x, int32_t r_y, int32_t g_x, int32_t g_y, int32_t b_x,
    int32_t b_y, int32_t w_x, int32_t w_y) {
  (void)data;
  (void)info;
  (void)r_x;
  (void)r_y;
  (void)g_x;
  (void)g_y;
  (void)b_x;
  (void)b_y;
  (void)w_x;
  (void)w_y;
}

void WaylandVideoSurface::HandleInfoTfPower(void* data, wp_image_description_info_v1* info, uint32_t eexp) {
  (void)data;
  (void)info;
  (void)eexp;
}

void WaylandVideoSurface::HandleInfoTargetPrimaries(
    void* data, wp_image_description_info_v1* info, int32_t r_x, int32_t r_y, int32_t g_x, int32_t g_y, int32_t b_x,
    int32_t b_y, int32_t w_x, int32_t w_y) {
  (void)data;
  (void)info;
  (void)r_x;
  (void)r_y;
  (void)g_x;
  (void)g_y;
  (void)b_x;
  (void)b_y;
  (void)w_x;
  (void)w_y;
}

void WaylandVideoSurface::HandleInfoTargetMaxCll(void* data, wp_image_description_info_v1* info, uint32_t max_cll) {
  (void)data;
  (void)info;
  (void)max_cll;
}

void WaylandVideoSurface::HandleInfoTargetMaxFall(void* data, wp_image_description_info_v1* info, uint32_t max_fall) {
  (void)data;
  (void)info;
  (void)max_fall;
}

void WaylandVideoSurface::ClearStagedDescription() {
  if (staged_description_ != nullptr) {
    wp_image_description_v1_destroy(staged_description_);
    staged_description_ = nullptr;
  }
}

void WaylandVideoSurface::SettleTransition(bool ok) {
  if (!transition_staged_) return;
  // Re-armed, not cancelled. The compositor answering only ends the *first* of
  // two waits: the plane stays staged - and Present() stays held - until the
  // caller's mpv leg commits or aborts, which is a longer wait than this one and
  // has no timeout of its own. Cancelling here left exactly that window
  // unbounded, so a silent mpv froze the plane for good.
  ArmTransitionWatchdog();
  // Moved out first: the callback is entitled to start the next transition, and
  // it must not be running out of a member this object may reassign underneath it.
  auto settled = std::move(on_transition_settled_);
  on_transition_settled_ = nullptr;
  if (settled) settled(transition_token_, ok);
}

void WaylandVideoSurface::HandleImageDescriptionReady(void* data, wp_image_description_v1* desc, uint32_t identity) {
  (void)identity;
  auto* self = static_cast<WaylandVideoSurface*>(data);
  if (self->staged_description_ != desc) return;
  self->SettleTransition(true);
}

void WaylandVideoSurface::HandleImageDescriptionReady2(
    void* data, wp_image_description_v1* desc, uint32_t identity_hi, uint32_t identity_lo) {
  (void)identity_hi;
  (void)identity_lo;
  HandleImageDescriptionReady(data, desc, 0);
}

void WaylandVideoSurface::HandleImageDescriptionFailed(
    void* data, wp_image_description_v1* desc, uint32_t cause, const char* message) {
  auto* self = static_cast<WaylandVideoSurface*>(data);
  if (self->staged_description_ != desc) return;
  g_warning(
      "MPV video plane: compositor rejected the HDR image description (cause %u): %s", cause,
      message ? message : "no reason given");
  // Left staged so Abort - which the caller reaches via on_settled(false) - is the
  // single place that tears the transition down.
  self->SettleTransition(false);
}

bool WaylandVideoSurface::CanDescribeSource(const HdrMetadata& metadata) const {
  return SourceIsDescribable(metadata, {supports_bt2020_, supports_pq_, supports_hlg_});
}

void WaylandVideoSurface::BeginHdrTransition(
    bool describe, const HdrMetadata& metadata, std::function<void(uint64_t, bool)> on_settled) {
  // The two hard capabilities are still checked here: they are facts about this
  // surface rather than policy, and DecideHdr cannot know them.
  if (!supports_hdr_ || color_surface_ == nullptr) {
    if (on_settled) on_settled(0, !describe);
    return;
  }
  // One at a time; the caller serializes them. Superseding here cannot be made
  // safe: the displaced waiter is told synchronously, and anything it stages in
  // response would be clobbered as this call continues.
  if (transition_staged_) {
    if (on_settled) on_settled(0, false);
    return;
  }

  // Metadata matters only while described; otherwise every SDR source change
  // would stage a no-op transition that holds Present() and forces a render.
  if (describe == hdr_active_ && (!describe || metadata_ == metadata)) {
    if (on_settled) on_settled(0, true);
    return;
  }

  transition_staged_ = true;
  transition_token_ += 1;
  staged_describe_ = describe;
  staged_metadata_ = metadata;
  on_transition_settled_ = std::move(on_settled);

  if (!describe) {
    // Unsetting needs no validation, so it is settled at once; the request itself
    // is deferred to Commit so it still lands on the same commit as the first
    // buffer mpv renders in the new colour space.
    SettleTransition(true);
    return;
  }
  ArmTransitionWatchdog();
  BuildImageDescription();
}

// Present() and the plugin's render path are both held while a transition is
// staged, so a compositor that accepts create() and then answers with neither
// ready nor failed freezes the plane on its last buffer for good, and every
// queued HDR method call behind it never answers. Everything else in this file
// that waits on the compositor is bounded; this is the one place that was not.
// Settling false is the same outcome as an explicit `failed`, which the caller
// already knows how to unwind.
void WaylandVideoSurface::ArmTransitionWatchdog() {
  CancelTransitionWatchdog();
  watchdog_source_ = g_timeout_add_seconds(
      kTransitionTimeoutSeconds,
      +[](gpointer data) -> gboolean {
        auto* self = static_cast<WaylandVideoSurface*>(data);
        self->watchdog_source_ = 0;
        // Every path out of the staged state cancels the watchdog first, so
        // reaching here at all means somebody went silent. Which one is still
        // owed an answer says which:
        if (!self->transition_staged_) return G_SOURCE_REMOVE;
        if (self->on_transition_settled_) {
          // Nothing has consumed the callback, so the compositor never answered
          // the description at all.
          g_warning(
              "MPV video plane: the compositor never answered the image description; "
              "abandoning the colour transition after %d seconds",
              kTransitionTimeoutSeconds);
          self->SettleTransition(false);
          return G_SOURCE_REMOVE;
        }
        // The compositor answered and the caller took the callback, but never
        // came back to commit or abort - mpv stopped answering its property
        // writes.
        //
        // Only unstage. The description *committed* right now is the one the
        // pixels on screen were rendered under, and it stays true precisely
        // because mpv has not finished moving off that colour space - the
        // staged one was never attached. Withdrawing would swap a claim that is
        // still accurate for one that is not: on a disable it would tell the
        // compositor a PQ buffer is undescribed, and on a re-describe the same
        // in miniature. Leaving it alone keeps the plane self-consistent for as
        // long as mpv is silent, and the caller's late commit is refused on its
        // stale token, which is what prompts the plugin to re-apply from
        // scratch.
        g_warning(
            "MPV video plane: the colour transition was never committed; "
            "resuming presentation on the description already in force after %d seconds",
            kTransitionTimeoutSeconds);
        self->DiscardTransition();
        // Present() was held for the whole staged window, so nothing else will
        // start it again: no frame callback is outstanding, and mpv - which by
        // definition has gone quiet - will not raise its redraw latch either.
        // That rules out the ordinary frame callback, whose handler skips unless
        // mpv has something new, and is why this needs the forcing one.
        if (self->on_forced_render_) self->on_forced_render_();
        return G_SOURCE_REMOVE;
      },
      this);
}

void WaylandVideoSurface::CancelTransitionWatchdog() {
  if (watchdog_source_ != 0) {
    g_source_remove(watchdog_source_);
    watchdog_source_ = 0;
  }
}

bool WaylandVideoSurface::CommitHdrTransition(uint64_t token) {
  // A stale token means the transition was torn down — teardown, or a forced
  // undescribe — while its caller's mpv request was still in flight. Committing
  // then would attach a description the plane no longer has pixels for. Token
  // zero is the "nothing was staged" case.
  if (!transition_staged_ || token == 0 || token != transition_token_) return false;
  // Load-bearing, not belt and braces: SettleTransition re-arms the watchdog to
  // bound this second wait, so committing is what finally disarms it.
  CancelTransitionWatchdog();

  const bool describe = staged_describe_;

  if (describe) {
    if (staged_description_ == nullptr) {
      DiscardTransition();
      return false;
    }
    // Copies (see staged_description_), so the surface's pending state carries
    // the description from here until the next commit.
    wp_color_management_surface_v1_set_image_description(
        color_surface_, staged_description_, WP_COLOR_MANAGER_V1_RENDER_INTENT_PERCEPTUAL);
    hdr_active_ = true;
    // Promoted here and nowhere earlier. This is the record BeginHdrTransition
    // compares a new request against to skip an identical one, so it has to name
    // a description that was actually attached - writing it before the bail-out
    // above would make the guard true for something the compositor was never
    // told, and never writing it at all leaves the guard permanently false, so
    // every playback-restart (i.e. every seek) stages a full transition and
    // holds the plane through a compositor round-trip it did not need.
    metadata_ = staged_metadata_;
    g_message("MPV video plane: image description attached");
  } else if (hdr_active_) {
    wp_color_management_surface_v1_unset_image_description(color_surface_);
    hdr_active_ = false;
    metadata_ = HdrMetadata();
    g_message("MPV video plane: image description cleared");
  }

  ClearStagedDescription();
  transition_staged_ = false;
  // Already moved out by SettleTransition, which is how the caller got here.
  on_transition_settled_ = nullptr;

  // The colour state is now pending on the child surface and lands on its next
  // commit, which only eglSwapBuffers performs. Telling the caller to render and
  // present now is what makes the pairing atomic: the buffer that carries the new
  // state is the first one rendered in it.
  //
  // The parent commit is for the subsurface's own state, not the child's, and is
  // requested separately once the child has committed.
  return true;
}

void WaylandVideoSurface::AbortHdrTransition(uint64_t token) {
  if (!transition_staged_ || token == 0 || token != transition_token_) return;
  DiscardTransition();
}

void WaylandVideoSurface::DiscardTransition() {
  if (!transition_staged_) return;
  CancelTransitionWatchdog();
  // The callback is moved out and the state torn down *before* it is invoked, so
  // a handler that aborts again finds nothing staged and the recursion stops.
  auto displaced = std::move(on_transition_settled_);
  const uint64_t token = transition_token_;
  on_transition_settled_ = nullptr;
  ClearStagedDescription();
  transition_staged_ = false;
  // A waiting caller must always hear an outcome. Silently dropping it strands
  // whatever it was going to answer - for the platform channel, a method call
  // that never responds and whose reference is never released. `false` is the
  // truth: this transition will not be committed.
  if (displaced) displaced(token, false);
}

bool WaylandVideoSurface::ForceUndescribed() {
  DiscardTransition();
  if (color_surface_ == nullptr || !hdr_active_) {
    return false;
  }
  wp_color_management_surface_v1_unset_image_description(color_surface_);
  hdr_active_ = false;
  // Cleared everywhere hdr_active_ goes false, not just on the commit path. A
  // stale record here is unobservable - the guard only reads it while
  // hdr_active_ is true - but three teardown paths disagreeing about it is a
  // thing the next reader has to re-derive rather than read.
  metadata_ = HdrMetadata();
  g_warning("MPV video plane: description withdrawn, mpv's colour space had to be forced to SDR");
  // Lands on the child surface's next commit, so the caller has to present for it
  // to take effect.
  return true;
}

void WaylandVideoSurface::BuildImageDescription() {
  // The staged metadata, not the committed one: this description belongs to the
  // transition being validated, and metadata_ only moves when it commits.
  const HdrMetadata& metadata = staged_metadata_;
  wp_image_description_creator_params_v1* creator = wp_color_manager_v1_create_parametric_creator(color_manager_);
  if (creator == nullptr) {
    g_warning("MPV video plane: compositor refused a parametric image-description creator");
    SettleTransition(false);
    return;
  }

  // Describe the source's own curve and gamut, never a fixed PQ / BT.2020. The
  // compositor is being told what the buffer holds, so anything else is a lie
  // that it will faithfully act on.
  //
  // Both arms below assume CanDescribeSource() already accepted this source, so
  // an SDR transfer cannot reach here - the ternary would otherwise label SDR
  // pixels as PQ, which is the one wrong value in this function that the
  // compositor cannot detect.
  wp_image_description_creator_params_v1_set_tf_named(
      creator, metadata.transfer == SourceTransfer::kHlg ? WP_COLOR_MANAGER_V1_TRANSFER_FUNCTION_HLG
                                                         : WP_COLOR_MANAGER_V1_TRANSFER_FUNCTION_ST2084_PQ);
  // BT.2020 is the only gamut CanDescribeSource() lets through.
  wp_image_description_creator_params_v1_set_primaries_named(creator, WP_COLOR_MANAGER_V1_PRIMARIES_BT2020);

  // Only forward metadata the source actually carried, and only in a
  // combination the protocol accepts. Inventing values would have the
  // compositor tone-map against a mastering display that never existed, and
  // forwarding an incoherent set is worse still: every luminance rule here is a
  // protocol *error* on create(), so a badly authored file would disconnect the
  // whole client rather than merely fail the description.
  //
  // Note that omitting all of it is not neutral either - the compositor then
  // has to assume the worst case the PQ curve allows, 10000 nits, and rolls the
  // highlights off far harder than the content needs. So send as much as is
  // legal, and no more. PlanHdrLuminance decides; see hdr_metadata.h.
  const HdrLuminancePlan plan = PlanHdrLuminance(metadata, luminance_support_);
  if (plan.send_mastering) {
    wp_image_description_creator_params_v1_set_mastering_luminance(
        creator, plan.mastering_min_scaled, plan.mastering_max);
  }
  if (plan.send_max_cll) {
    wp_image_description_creator_params_v1_set_max_cll(creator, plan.max_cll);
  }
  if (plan.send_max_fall) {
    wp_image_description_creator_params_v1_set_max_fall(creator, plan.max_fall);
  }
  if (plan.send_max_cll != (metadata.max_cll > 0) || plan.send_max_fall != (metadata.max_fall > 0)) {
    g_message(
        "MPV video plane: dropped source light levels the protocol would reject "
        "(MaxCLL %u kept=%d, MaxFALL %u kept=%d, mastering max %u kept=%d)",
        metadata.max_cll, plan.send_max_cll, metadata.max_fall, plan.send_max_fall, plan.mastering_max,
        plan.send_mastering);
  }

  // Every member must be filled in. libwayland calls implementation[opcode]
  // through libffi with no null check, so a listener that is short by one
  // member is a segfault on the first compositor that sends that event - not a
  // dropped notification. The static_assert is the tripwire for re-vendoring a
  // newer color-management-v1.xml: if the generated struct grows an event,
  // the build fails here instead of the app crashing in the field.
  static_assert(
      sizeof(wp_image_description_v1_listener) == 3 * sizeof(void (*)()),
      "wp_image_description_v1_listener gained an event; handle it below");
  static const wp_image_description_v1_listener kDescriptionListener = {
      HandleImageDescriptionFailed,
      HandleImageDescriptionReady,
      HandleImageDescriptionReady2,
  };
  // create() consumes the creator, so it must not be destroyed afterwards.
  staged_description_ = wp_image_description_creator_params_v1_create(creator);
  if (staged_description_ == nullptr) {
    g_warning("MPV video plane: could not create the HDR image description");
    SettleTransition(false);
    return;
  }
  wp_image_description_v1_add_listener(staged_description_, &kDescriptionListener, this);
}

void WaylandVideoSurface::ClearFrameCallback() {
  if (frame_callback_ != nullptr) {
    wl_callback_destroy(frame_callback_);
    frame_callback_ = nullptr;
  }
  frame_pending_ = false;
}

void WaylandVideoSurface::HandleFrameDone(void* data, wl_callback* callback, uint32_t time) {
  (void)time;
  auto* self = static_cast<WaylandVideoSurface*>(data);
  // Always the callback we hold: Present() is the only place one is created and
  // it early-returns while frame_pending_, so a second is never armed over a
  // live one, and libwayland delivers nothing for a proxy we already destroyed.
  if (self->frame_callback_ == callback) {
    wl_callback_destroy(self->frame_callback_);
    self->frame_callback_ = nullptr;
  }
  self->frame_pending_ = false;
  // Rendering resumes from here, not from mpv: its redraw latch is still set
  // from the update we declined to serve, so it will not notify again.
  if (self->on_frame_) self->on_frame_();
}

void WaylandVideoSurface::Destroy() {
  // Unconditionally, ahead of everything: the timeout closure captures `this`,
  // and DiscardTransition below only cancels it when a transition is actually
  // staged.
  CancelTransitionWatchdog();
  if (egl_surface_ != EGL_NO_SURFACE) {
    if (eglGetCurrentSurface(EGL_DRAW) == egl_surface_ || eglGetCurrentSurface(EGL_READ) == egl_surface_) {
      eglMakeCurrent(egl_display_, EGL_NO_SURFACE, EGL_NO_SURFACE, EGL_NO_CONTEXT);
    }
    eglDestroySurface(egl_display_, egl_surface_);
    egl_surface_ = EGL_NO_SURFACE;
  }
  if (egl_window_ != nullptr) {
    wl_egl_window_destroy(egl_window_);
    egl_window_ = nullptr;
  }
  ClearFrameCallback();
  on_frame_ = nullptr;
  // Same rule as on_frame_: the forced-render callback captures the plugin,
  // and nothing may invoke it once teardown has begun.
  on_forced_render_ = nullptr;
  // Drops the staged description and, importantly, the settled callback: it
  // captures the plugin, which is being torn down alongside this.
  DiscardTransition();
  // Before the colour surface and manager: these are children of the manager
  // and reference the wl_surface.
  ClearPreferredQuery();
  on_preferred_changed_ = nullptr;
  if (color_feedback_ != nullptr) {
    wp_color_management_surface_feedback_v1_destroy(color_feedback_);
    color_feedback_ = nullptr;
  }
  preferred_ = PreferredColorDescription();
  pending_preferred_ = PreferredColorDescription();
  if (color_surface_ != nullptr) {
    wp_color_management_surface_v1_destroy(color_surface_);
    color_surface_ = nullptr;
  }
  if (color_manager_ != nullptr) {
    wp_color_manager_v1_destroy(color_manager_);
    color_manager_ = nullptr;
  }
  // Every advertised capability, not just the aggregate: CanDescribeSource()
  // reads the per-curve flags directly, and a partial recreate would otherwise
  // consult what the *previous* compositor connection offered.
  supports_hdr_ = false;
  supports_pq_ = false;
  supports_hlg_ = false;
  supports_bt2020_ = false;
  luminance_support_ = CompositorLuminanceSupport();
  manager_caps_ = ManagerCaps();
  hdr_active_ = false;
  metadata_ = HdrMetadata();
  depth_bits_ = 8;
  if (subsurface_ != nullptr) {
    wl_subsurface_destroy(subsurface_);
    subsurface_ = nullptr;
  }
  if (surface_ != nullptr) {
    wl_surface_destroy(surface_);
    surface_ = nullptr;
  }
  if (subcompositor_ != nullptr) {
    wl_subcompositor_destroy(subcompositor_);
    subcompositor_ = nullptr;
  }
  // compositor_, wl_display_ and the EGLDisplay itself are owned by GDK/EGL and
  // are shared process-wide; only our own references are dropped here.
  compositor_ = nullptr;
  wl_display_ = nullptr;
  egl_config_ = nullptr;
  egl_display_ = EGL_NO_DISPLAY;
  view_ = nullptr;
  // All of it, not just the size: SetRect() early-returns when nothing changed,
  // so stale geometry surviving here would leave a recreated subsurface never
  // positioned or scaled. The zeroed size alone happens to prevent that today,
  // which is not a thing to rely on.
  x_ = 0;
  y_ = 0;
  width_ = 0;
  height_ = 0;
  scale_ = 1;
  visible_ = false;
  rect_valid_ = false;
  buffer_attached_ = false;
}

void WaylandVideoSurface::RequestParentCommit() {
  // Subsurface position and stacking are double-buffered *parent* state: they
  // only land when the parent surface commits. Asking the view to redraw is the
  // one way to make GTK do that without reaching into its pending state.
  if (view_ != nullptr) gtk_widget_queue_draw(view_);
}

void WaylandVideoSurface::SetRect(int32_t x, int32_t y, int32_t width, int32_t height, int32_t scale) {
  scale = NormalizePlaneScale(scale);
  // Whether Dart has given us a rect worth showing. Tracked from the *requested*
  // size, before the rounding below: that floor would otherwise make a 0x0
  // layout - which Dart does send, ahead of the first real one - look like a
  // usable one-pixel plane, and has_size() means "there is a rect", not "the
  // numbers are non-zero".
  const bool was_valid = rect_valid_;
  rect_valid_ = width > 0 && height > 0;
  // Losing the rect has to take the pixels down, not just stop drawing new ones.
  // render_video_plane skips a plane with no size, so without this the last
  // frame stays on screen - and it stays *at its old geometry*, over whatever
  // Flutter laid out in the space the video no longer occupies. A widget
  // animating to zero height is the ordinary way in; hiding the plane is the
  // separate call Dart does not have to make first.
  if (was_valid && !rect_valid_) DetachBuffer();

  // Sized from the *origin* as well as the extent, so the plane covers the rect
  // on both edges once the origin is floored; PlaneBufferExtent explains why the
  // two roundings have to compose, and why one is not enough.
  width = PlaneBufferExtent(x, width, scale);
  height = PlaneBufferExtent(y, height, scale);
  // Flutter's rect is relative to the FlView; wl_subsurface_set_position is
  // relative to the *toplevel's* surface, which is what ParentSurface() returns.
  // Those differ whenever the view is inset inside the toplevel: a GtkHeaderBar
  // titlebar, or GTK3 drawing client-side decorations because the compositor
  // offers none of its own - on Mutter that is every window, where the invisible
  // resize shadow alone shifts the plane. Server-side decorations make it zero,
  // which is why a KWin session cannot show the difference.
  //
  // Read before the early return and compared like any other input: maximising a
  // CSD window drops the shadow, which moves the view without Flutter's rect
  // necessarily changing.
  int32_t view_x = 0;
  int32_t view_y = 0;
  if (view_ != nullptr) {
    GtkWidget* toplevel = gtk_widget_get_toplevel(view_);
    gint offset_x = 0;
    gint offset_y = 0;
    if (toplevel != nullptr && gtk_widget_translate_coordinates(view_, toplevel, 0, 0, &offset_x, &offset_y)) {
      view_x = offset_x;
      view_y = offset_y;
    }
  }
  if (x == x_ && y == y_ && width == width_ && height == height_ && scale == scale_ && view_x == view_x_ &&
      view_y == view_y_) {
    return;
  }

  const bool size_changed = width != width_ || height != height_;
  const bool scale_changed = scale != scale_;
  x_ = x;
  y_ = y;
  width_ = width;
  height_ = height;
  scale_ = scale;
  view_x_ = view_x;
  view_y_ = view_y;

  if (surface_ == nullptr || subsurface_ == nullptr || egl_window_ == nullptr) return;

  if (scale_changed) wl_surface_set_buffer_scale(surface_, scale_);
  if (size_changed || scale_changed) wl_egl_window_resize(egl_window_, width_, height_, 0, 0);
  // Both axes are floored into surface-local units and then offset by the
  // view's position inside the toplevel; PlaneSurfacePosition explains why.
  wl_subsurface_set_position(
      subsurface_, PlaneSurfacePosition(x_, scale_, view_x_), PlaneSurfacePosition(y_, scale_, view_y_));
  RequestParentCommit();
}

void WaylandVideoSurface::DetachBuffer() {
  // The only way to take pixels off screen. Hiding the subsurface is not enough
  // on its own: a subsurface has no visibility of its own, so what "hidden"
  // means here is "carrying no buffer", and the content stays up until the
  // compositor is told to drop it. The pending frame callback goes too - it
  // would otherwise fire against a surface with nothing to present.
  if (surface_ == nullptr) return;
  ClearFrameCallback();
  wl_surface_attach(surface_, nullptr, 0, 0);
  wl_surface_commit(surface_);
  buffer_attached_ = false;
}

void WaylandVideoSurface::SetVisible(bool visible) {
  if (visible == visible_) return;
  visible_ = visible;
  if (surface_ == nullptr) return;
  if (!visible) DetachBuffer();
  // Becoming visible needs no action here: the next Present() attaches a buffer.
  RequestParentCommit();
}

bool WaylandVideoSurface::Present() {
  if (!visible_ || egl_surface_ == EGL_NO_SURFACE || frame_pending_) return false;
  // Held while a colour transition is staged. eglSwapBuffers is the child
  // surface's commit, so presenting now would publish a buffer paired with a
  // colour state it was not rendered for - the flash this whole two-phase dance
  // exists to avoid. The previously presented frame stays up for the duration of
  // one property round-trip.
  if (transition_staged_) return false;

  // Ask for the acknowledgement before the commit that eglSwapBuffers performs,
  // so the callback belongs to this frame.
  static const wl_callback_listener kFrameListener = {HandleFrameDone};
  frame_callback_ = wl_surface_frame(surface_);
  if (frame_callback_ != nullptr) {
    wl_callback_add_listener(frame_callback_, &kFrameListener, this);
    frame_pending_ = true;
  }

  if (eglSwapBuffers(egl_display_, egl_surface_) != EGL_TRUE) {
    ClearFrameCallback();
    g_warning("MPV video plane: eglSwapBuffers failed: 0x%x", eglGetError());
    return false;
  }
  if (!buffer_attached_) {
    buffer_attached_ = true;
    // The first buffer changes what the plane occludes; make sure the parent's
    // view of the subsurface is up to date.
    RequestParentCommit();
  }
  return true;
}

}  // namespace mpv