/* SPDX-FileCopyrightText: 2017 Blender Authors
 *
 * SPDX-License-Identifier: GPL-2.0-or-later */

/** \file
 * \ingroup draw
 */

#include "DRW_engine.hh"
#include "DRW_render.hh"

#include "ED_gpencil_legacy.hh"
#include "ED_view3d.hh"

#include "DNA_gpencil_legacy_types.h"
#include "DNA_view3d_types.h"

#include "BKE_gpencil_geom_legacy.h"
#include "BKE_gpencil_legacy.h"
#include "BKE_grease_pencil.hh"
#include "BKE_lib_id.hh"
#include "BKE_object.hh"

#include "BLI_hash.h"
#include "BLI_link_utils.h"
#include "BLI_math_color.h"
#include "BLI_math_vector.hh"
#include "BLI_memblock.h"

#include "gpencil_engine.h"

#include "draw_cache_impl.hh"

#include "DEG_depsgraph.hh"

/* -------------------------------------------------------------------- */
/** \name Object
 * \{ */

GPENCIL_tObject *gpencil_object_cache_add(GPENCIL_PrivateData *pd,
                                          Object *ob,
                                          const bool is_stroke_order_3d,
                                          const blender::Bounds<float3> bounds)
{
  using namespace blender;
  GPENCIL_tObject *tgp_ob = static_cast<GPENCIL_tObject *>(BLI_memblock_alloc(pd->gp_object_pool));

  tgp_ob->layers.first = tgp_ob->layers.last = nullptr;
  tgp_ob->vfx.first = tgp_ob->vfx.last = nullptr;
  tgp_ob->camera_z = dot_v3v3(pd->camera_z_axis, ob->object_to_world().location());
  tgp_ob->is_drawmode3d = is_stroke_order_3d || pd->draw_depth_only;
  tgp_ob->object_scale = mat4_to_scale(ob->object_to_world().ptr());

  /* Check if any material with holdout flag enabled. */
  tgp_ob->do_mat_holdout = false;
  const int tot_materials = BKE_object_material_count_eval(ob);
  for (int i = 0; i < tot_materials; i++) {
    MaterialGPencilStyle *gp_style = BKE_gpencil_material_settings(ob, i + 1);
    if (((gp_style != nullptr) && (gp_style->flag & GP_MATERIAL_IS_STROKE_HOLDOUT)) ||
        (gp_style->flag & GP_MATERIAL_IS_FILL_HOLDOUT))
    {
      tgp_ob->do_mat_holdout = true;
      break;
    }
  }

  /* Find the normal most likely to represent the gpObject. */
  /* TODO: This does not work quite well if you use
   * strokes not aligned with the object axes. Maybe we could try to
   * compute the minimum axis of all strokes. But this would be more
   * computationally heavy and should go into the GPData evaluation. */
  float3 size = (bounds.max - bounds.min) * 0.5f;
  float3 center = math::midpoint(bounds.min, bounds.max);
  /* Convert bbox to matrix */
  float mat[4][4];
  unit_m4(mat);
  copy_v3_v3(mat[3], center);
  /* Avoid division by 0.0 later. */
  add_v3_fl(size, 1e-8f);
  rescale_m4(mat, size);
  /* BBox space to World. */
  mul_m4_m4m4(mat, ob->object_to_world().ptr(), mat);
  if (DRW_view_is_persp_get(nullptr)) {
    /* BBox center to camera vector. */
    sub_v3_v3v3(tgp_ob->plane_normal, pd->camera_pos, mat[3]);
  }
  else {
    copy_v3_v3(tgp_ob->plane_normal, pd->camera_z_axis);
  }
  /* World to BBox space. */
  invert_m4(mat);
  /* Normalize the vector in BBox space. */
  mul_mat3_m4_v3(mat, tgp_ob->plane_normal);
  normalize_v3(tgp_ob->plane_normal);

  transpose_m4(mat);
  /* mat is now a "normal" matrix which will transform
   * BBox space normal to world space. */
  mul_mat3_m4_v3(mat, tgp_ob->plane_normal);
  normalize_v3(tgp_ob->plane_normal);

  /* Define a matrix that will be used to render a triangle to merge the depth of the rendered
   * gpencil object with the rest of the scene. */
  unit_m4(tgp_ob->plane_mat);
  copy_v3_v3(tgp_ob->plane_mat[2], tgp_ob->plane_normal);
  orthogonalize_m4(tgp_ob->plane_mat, 2);
  mul_mat3_m4_v3(ob->object_to_world().ptr(), size);
  float radius = len_v3(size);
  mul_m4_v3(ob->object_to_world().ptr(), center);
  rescale_m4(tgp_ob->plane_mat, blender::float3{radius, radius, radius});
  copy_v3_v3(tgp_ob->plane_mat[3], center);

  /* Add to corresponding list if is in front. */
  if (ob->dtx & OB_DRAW_IN_FRONT) {
    BLI_LINKS_APPEND(&pd->tobjects_infront, tgp_ob);
  }
  else {
    BLI_LINKS_APPEND(&pd->tobjects, tgp_ob);
  }

  return tgp_ob;
}

#define SORT_IMPL_LINKTYPE GPENCIL_tObject

#define SORT_IMPL_FUNC gpencil_tobject_sort_fn_r
#include "../../blenlib/intern/list_sort_impl.h"
#undef SORT_IMPL_FUNC

#undef SORT_IMPL_LINKTYPE

static int gpencil_tobject_dist_sort(const void *a, const void *b)
{
  const GPENCIL_tObject *ob_a = (const GPENCIL_tObject *)a;
  const GPENCIL_tObject *ob_b = (const GPENCIL_tObject *)b;
  /* Reminder, camera_z is negative in front of the camera. */
  if (ob_a->camera_z > ob_b->camera_z) {
    return 1;
  }
  if (ob_a->camera_z < ob_b->camera_z) {
    return -1;
  }

  return 0;
}

void gpencil_object_cache_sort(GPENCIL_PrivateData *pd)
{
  /* Sort object by distance to the camera. */
  if (pd->tobjects.first) {
    pd->tobjects.first = gpencil_tobject_sort_fn_r(pd->tobjects.first, gpencil_tobject_dist_sort);
    /* Relink last pointer. */
    while (pd->tobjects.last->next) {
      pd->tobjects.last = pd->tobjects.last->next;
    }
  }
  if (pd->tobjects_infront.first) {
    pd->tobjects_infront.first = gpencil_tobject_sort_fn_r(pd->tobjects_infront.first,
                                                           gpencil_tobject_dist_sort);
    /* Relink last pointer. */
    while (pd->tobjects_infront.last->next) {
      pd->tobjects_infront.last = pd->tobjects_infront.last->next;
    }
  }

  /* Join both lists, adding in front. */
  if (pd->tobjects_infront.first != nullptr) {
    if (pd->tobjects.last != nullptr) {
      pd->tobjects.last->next = pd->tobjects_infront.first;
      pd->tobjects.last = pd->tobjects_infront.last;
    }
    else {
      /* Only in front objects. */
      pd->tobjects.first = pd->tobjects_infront.first;
      pd->tobjects.last = pd->tobjects_infront.last;
    }
  }
}

/** \} */

/* -------------------------------------------------------------------- */
/** \name Layer
 * \{ */

static float gpencil_layer_final_opacity_get(const GPENCIL_PrivateData *pd,
                                             const Object *ob,
                                             const bGPDlayer *gpl)
{
  const bool is_obact = ((pd->obact) && (pd->obact == ob));
  const bool is_fade = ((pd->fade_layer_opacity > -1.0f) && (is_obact) &&
                        ((gpl->flag & GP_LAYER_ACTIVE) == 0));

  /* Defines layer opacity. For active object depends of layer opacity factor, and
   * for no active object, depends if the fade grease pencil objects option is enabled. */
  if (!pd->is_render) {
    if (is_obact && is_fade) {
      return gpl->opacity * pd->fade_layer_opacity;
    }
    if (!is_obact && (pd->fade_gp_object_opacity > -1.0f)) {
      return gpl->opacity * pd->fade_gp_object_opacity;
    }
  }
  return gpl->opacity;
}

static float grease_pencil_layer_final_opacity_get(const GPENCIL_PrivateData *pd,
                                                   const Object *ob,
                                                   const GreasePencil &grease_pencil,
                                                   const blender::bke::greasepencil::Layer &layer)
{
  const bool is_obact = ((pd->obact) && (pd->obact == ob));
  const bool is_fade = (pd->fade_layer_opacity > -1.0f) && (is_obact) &&
                       grease_pencil.is_layer_active(&layer);

  /* Defines layer opacity. For active object depends of layer opacity factor, and
   * for no active object, depends if the fade grease pencil objects option is enabled. */
  if (!pd->is_render) {
    if (is_obact && is_fade) {
      return layer.opacity * pd->fade_layer_opacity;
    }
    if (!is_obact && (pd->fade_gp_object_opacity > -1.0f)) {
      return layer.opacity * pd->fade_gp_object_opacity;
    }
  }
  return layer.opacity;
}

static void gpencil_layer_final_tint_and_alpha_get(const GPENCIL_PrivateData *pd,
                                                   const bGPdata *gpd,
                                                   const bGPDlayer *gpl,
                                                   const bGPDframe *gpf,
                                                   float r_tint[4],
                                                   float *r_alpha)
{
  const bool use_onion = (gpf != nullptr) && (gpf->runtime.onion_id != 0.0f);
  if (use_onion) {
    const bool use_onion_custom_col = (gpd->onion_flag & GP_ONION_GHOST_PREVCOL) != 0;
    const bool use_onion_fade = (gpd->onion_flag & GP_ONION_FADE) != 0;
    const bool use_next_col = gpf->runtime.onion_id > 0.0f;

    const float *onion_col_custom = (use_onion_custom_col) ?
                                        (use_next_col ? gpd->gcolor_next : gpd->gcolor_prev) :
                                        U.gpencil_new_layer_col;

    copy_v4_fl4(r_tint, UNPACK3(onion_col_custom), 1.0f);

    *r_alpha = use_onion_fade ? (1.0f / abs(gpf->runtime.onion_id)) : 0.5f;
    *r_alpha *= gpd->onion_factor;
    *r_alpha = (gpd->onion_factor > 0.0f) ? clamp_f(*r_alpha, 0.1f, 1.0f) :
                                            clamp_f(*r_alpha, 0.01f, 1.0f);
  }
  else {
    copy_v4_v4(r_tint, gpl->tintcolor);
    if (GPENCIL_SIMPLIFY_TINT(pd->scene)) {
      r_tint[3] = 0.0f;
    }
    *r_alpha = 1.0f;
  }

  *r_alpha *= pd->xray_alpha;
}

static float4 grease_pencil_layer_final_tint_and_alpha_get(const GPENCIL_PrivateData *pd,
                                                           const GreasePencil &grease_pencil,
                                                           const int onion_id,
                                                           float *r_alpha)
{
  const bool use_onion = (onion_id != 0);
  if (use_onion) {
    const bool use_onion_custom_col = (grease_pencil.onion_skinning_settings.flag &
                                       GP_ONION_SKINNING_USE_CUSTOM_COLORS) != 0;
    const bool use_onion_fade = (grease_pencil.onion_skinning_settings.flag &
                                 GP_ONION_SKINNING_USE_FADE) != 0;
    const bool use_next_col = onion_id > 0;

    const float onion_factor = grease_pencil.onion_skinning_settings.opacity;
    const float3 color_next(grease_pencil.onion_skinning_settings.color_after);
    const float3 color_prev(grease_pencil.onion_skinning_settings.color_before);

    const float4 onion_col_custom = (use_onion_custom_col) ?
                                        (use_next_col ? float4(color_next, 1.0f) :
                                                        float4(color_prev, 1.0f)) :
                                        float4(U.gpencil_new_layer_col);

    *r_alpha = use_onion_fade ? (1.0f / abs(onion_id)) : 0.5f;
    *r_alpha *= onion_factor;
    *r_alpha = (onion_factor > 0.0f) ? clamp_f(*r_alpha, 0.1f, 1.0f) :
                                       clamp_f(*r_alpha, 0.01f, 1.0f);
    *r_alpha *= pd->xray_alpha;

    return onion_col_custom;
  }

  /* Layer tint is not a property in GPv3 anymore. It's only used for onion skinning. The previous
   * property is replaced by a tint modifier during conversion. */
  float4 layer_tint(0.0f);
  if (GPENCIL_SIMPLIFY_TINT(pd->scene)) {
    layer_tint[3] = 0.0f;
  }
  *r_alpha = 1.0f;
  *r_alpha *= pd->xray_alpha;

  return layer_tint;
}

/* Random color by layer. */
static void gpencil_layer_random_color_get(const Object *ob,
                                           const bGPDlayer *gpl,
                                           float r_color[3])
{
  const float hsv_saturation = 0.7f;
  const float hsv_value = 0.6f;

  uint ob_hash = BLI_ghashutil_strhash_p_murmur(ob->id.name);
  uint gpl_hash = BLI_ghashutil_strhash_p_murmur(gpl->info);
  float hue = BLI_hash_int_01(ob_hash * gpl_hash);
  const float hsv[3] = {hue, hsv_saturation, hsv_value};
  hsv_to_rgb_v(hsv, r_color);
}

static void grease_pencil_layer_random_color_get(const Object *ob,
                                                 const blender::bke::greasepencil::Layer &layer,
                                                 float r_color[3])
{
  const float hsv_saturation = 0.7f;
  const float hsv_value = 0.6f;

  uint ob_hash = BLI_ghashutil_strhash_p_murmur(ob->id.name);
  uint gpl_hash = BLI_ghashutil_strhash_p_murmur(layer.name().c_str());
  float hue = BLI_hash_int_01(ob_hash * gpl_hash);
  const float hsv[3] = {hue, hsv_saturation, hsv_value};
  hsv_to_rgb_v(hsv, r_color);
}

GPENCIL_tLayer *gpencil_layer_cache_add(GPENCIL_PrivateData *pd,
                                        const Object *ob,
                                        const bGPDlayer *gpl,
                                        const bGPDframe *gpf,
                                        GPENCIL_tObject *tgp_ob)
{
  bGPdata *gpd = (bGPdata *)ob->data;

  const bool is_in_front = (ob->dtx & OB_DRAW_IN_FRONT);
  const bool is_screenspace = (gpd->flag & GP_DATA_STROKE_KEEPTHICKNESS) != 0;
  const bool override_vertcol = (pd->v3d_color_type != -1);
  const bool is_vert_col_mode = (pd->v3d_color_type == V3D_SHADING_VERTEX_COLOR) ||
                                GPENCIL_VERTEX_MODE(gpd) || pd->is_render;
  const bool is_viewlayer_render = pd->is_render && (gpl->viewlayername[0] != '\0') &&
                                   STREQ(pd->view_layer->name, gpl->viewlayername);
  const bool disable_masks_render = is_viewlayer_render &&
                                    (gpl->flag & GP_LAYER_DISABLE_MASKS_IN_VIEWLAYER);
  bool is_masked = disable_masks_render ? false :
                                          (gpl->flag & GP_LAYER_USE_MASK) &&
                                              !BLI_listbase_is_empty(&gpl->mask_layers);

  float vert_col_opacity = (override_vertcol) ?
                               (is_vert_col_mode ? pd->vertex_paint_opacity : 0.0f) :
                               (pd->is_render ? gpl->vertex_paint_opacity :
                                                pd->vertex_paint_opacity);
  /* Negate thickness sign to tag that strokes are in screen space.
   * Convert to world units (by default, 1 meter = 2000 pixels). */
  float thickness_scale = (is_screenspace) ? -1.0f : (gpd->pixfactor / GPENCIL_PIXEL_FACTOR);
  float layer_opacity = gpencil_layer_final_opacity_get(pd, ob, gpl);
  float layer_tint[4];
  float layer_alpha;
  gpencil_layer_final_tint_and_alpha_get(pd, gpd, gpl, gpf, layer_tint, &layer_alpha);

  /* Create the new layer descriptor. */
  GPENCIL_tLayer *tgp_layer = static_cast<GPENCIL_tLayer *>(BLI_memblock_alloc(pd->gp_layer_pool));
  BLI_LINKS_APPEND(&tgp_ob->layers, tgp_layer);
  tgp_layer->layer_id = BLI_findindex(&gpd->layers, gpl);
  tgp_layer->mask_bits = nullptr;
  tgp_layer->mask_invert_bits = nullptr;
  tgp_layer->blend_ps = nullptr;

  /* Masking: Go through mask list and extract valid masks in a bitmap. */
  if (is_masked) {
    bool valid_mask = false;
    /* WARNING: only #GP_MAX_MASKBITS amount of bits.
     * TODO(fclem): Find a better system without any limitation. */
    tgp_layer->mask_bits = static_cast<BLI_bitmap *>(BLI_memblock_alloc(pd->gp_maskbit_pool));
    tgp_layer->mask_invert_bits = static_cast<BLI_bitmap *>(
        BLI_memblock_alloc(pd->gp_maskbit_pool));
    BLI_bitmap_set_all(tgp_layer->mask_bits, false, GP_MAX_MASKBITS);

    LISTBASE_FOREACH (bGPDlayer_Mask *, mask, &gpl->mask_layers) {
      bGPDlayer *gpl_mask = BKE_gpencil_layer_named_get(gpd, mask->name);
      if (gpl_mask && (gpl_mask != gpl) && ((gpl_mask->flag & GP_LAYER_HIDE) == 0) &&
          ((mask->flag & GP_MASK_HIDE) == 0))
      {
        int index = BLI_findindex(&gpd->layers, gpl_mask);
        if (index < GP_MAX_MASKBITS) {
          const bool invert = (mask->flag & GP_MASK_INVERT) != 0;
          BLI_BITMAP_SET(tgp_layer->mask_bits, index, true);
          BLI_BITMAP_SET(tgp_layer->mask_invert_bits, index, invert);
          valid_mask = true;
        }
      }
    }

    if (valid_mask) {
      pd->use_mask_fb = true;
    }
    else {
      tgp_layer->mask_bits = nullptr;
    }
    is_masked = valid_mask;
  }

  /* Blending: Force blending for masked layer. */
  if (is_masked || (gpl->blend_mode != eGplBlendMode_Regular) || (layer_opacity < 1.0f)) {
    DRWState state = DRW_STATE_WRITE_COLOR | DRW_STATE_STENCIL_EQUAL;
    switch (gpl->blend_mode) {
      case eGplBlendMode_Regular:
        state |= DRW_STATE_BLEND_ALPHA_PREMUL;
        break;
      case eGplBlendMode_Add:
        state |= DRW_STATE_BLEND_ADD_FULL;
        break;
      case eGplBlendMode_Subtract:
        state |= DRW_STATE_BLEND_SUB;
        break;
      case eGplBlendMode_Multiply:
      case eGplBlendMode_Divide:
      case eGplBlendMode_HardLight:
        state |= DRW_STATE_BLEND_MUL;
        break;
    }

    if (ELEM(gpl->blend_mode, eGplBlendMode_Subtract, eGplBlendMode_HardLight)) {
      /* For these effect to propagate, we need a signed floating point buffer. */
      pd->use_signed_fb = true;
    }

    tgp_layer->blend_ps = DRW_pass_create("GPencil Blend Layer", state);

    GPUShader *sh = GPENCIL_shader_layer_blend_get();
    DRWShadingGroup *grp = DRW_shgroup_create(sh, tgp_layer->blend_ps);
    DRW_shgroup_uniform_int_copy(grp, "blendMode", gpl->blend_mode);
    DRW_shgroup_uniform_float_copy(grp, "blendOpacity", layer_opacity);
    DRW_shgroup_uniform_texture_ref(grp, "colorBuf", &pd->color_layer_tx);
    DRW_shgroup_uniform_texture_ref(grp, "revealBuf", &pd->reveal_layer_tx);
    DRW_shgroup_uniform_texture_ref(grp, "maskBuf", (is_masked) ? &pd->mask_tx : &pd->dummy_tx);
    DRW_shgroup_stencil_mask(grp, 0xFF);
    DRW_shgroup_call_procedural_triangles(grp, nullptr, 1);

    if (gpl->blend_mode == eGplBlendMode_HardLight) {
      /* We cannot do custom blending on Multi-Target frame-buffers.
       * Workaround by doing 2 passes. */
      grp = DRW_shgroup_create(sh, tgp_layer->blend_ps);
      DRW_shgroup_state_disable(grp, DRW_STATE_BLEND_MUL);
      DRW_shgroup_state_enable(grp, DRW_STATE_BLEND_ADD_FULL);
      DRW_shgroup_uniform_int_copy(grp, "blendMode", 999);
      DRW_shgroup_call_procedural_triangles(grp, nullptr, 1);
    }

    pd->use_layer_fb = true;
  }

  /* Geometry pass */
  {
    GPUTexture *depth_tex = (is_in_front) ? pd->dummy_tx : pd->scene_depth_tx;
    GPUTexture **mask_tex = (is_masked) ? &pd->mask_tx : &pd->dummy_tx;

    DRWState state = DRW_STATE_WRITE_COLOR | DRW_STATE_WRITE_DEPTH | DRW_STATE_BLEND_ALPHA_PREMUL;
    /* For 2D mode, we render all strokes with uniform depth (increasing with stroke id). */
    state |= tgp_ob->is_drawmode3d ? DRW_STATE_DEPTH_LESS_EQUAL : DRW_STATE_DEPTH_GREATER;
    /* Always write stencil. Only used as optimization for blending. */
    state |= DRW_STATE_WRITE_STENCIL | DRW_STATE_STENCIL_ALWAYS;

    tgp_layer->geom_ps = DRW_pass_create("GPencil Layer", state);

    GPUShader *sh = GPENCIL_shader_geometry_get();
    DRWShadingGroup *grp = tgp_layer->base_shgrp = DRW_shgroup_create(sh, tgp_layer->geom_ps);

    DRW_shgroup_uniform_texture(grp, "gpSceneDepthTexture", depth_tex);
    DRW_shgroup_uniform_texture_ref(grp, "gpMaskTexture", mask_tex);
    DRW_shgroup_uniform_vec3_copy(grp, "gpNormal", tgp_ob->plane_normal);
    DRW_shgroup_uniform_bool_copy(grp, "gpStrokeOrder3d", tgp_ob->is_drawmode3d);
    DRW_shgroup_uniform_float_copy(grp, "gpThicknessScale", tgp_ob->object_scale);
    DRW_shgroup_uniform_float_copy(grp, "gpThicknessOffset", float(gpl->line_change));
    DRW_shgroup_uniform_float_copy(grp, "gpThicknessWorldScale", thickness_scale);
    DRW_shgroup_uniform_float_copy(grp, "gpVertexColorOpacity", vert_col_opacity);

    /* If random color type, need color by layer. */
    float gpl_color[4];
    copy_v4_v4(gpl_color, layer_tint);
    if (pd->v3d_color_type == V3D_SHADING_RANDOM_COLOR) {
      gpencil_layer_random_color_get(ob, gpl, gpl_color);
      gpl_color[3] = 1.0f;
    }
    DRW_shgroup_uniform_vec4_copy(grp, "gpLayerTint", gpl_color);

    DRW_shgroup_uniform_float_copy(grp, "gpLayerOpacity", layer_alpha);
    DRW_shgroup_stencil_mask(grp, 0xFF);
  }

  return tgp_layer;
}

GPENCIL_tLayer *gpencil_layer_cache_get(GPENCIL_tObject *tgp_ob, int number)
{
  if (number >= 0) {
    GPENCIL_tLayer *layer = tgp_ob->layers.first;
    while (layer != nullptr) {
      if (layer->layer_id == number) {
        return layer;
      }
      layer = layer->next;
    }
  }
  return nullptr;
}

GPENCIL_tLayer *grease_pencil_layer_cache_add(GPENCIL_PrivateData *pd,
                                              const Object *ob,
                                              const blender::bke::greasepencil::Layer &layer,
                                              const int onion_id,
                                              const bool is_used_as_mask,
                                              GPENCIL_tObject *tgp_ob)

{
  using namespace blender::bke::greasepencil;
  const GreasePencil &grease_pencil = *static_cast<GreasePencil *>(ob->data);

  const bool is_in_front = (ob->dtx & OB_DRAW_IN_FRONT);

  const bool override_vertcol = (pd->v3d_color_type != -1);
  const bool is_vert_col_mode = (pd->v3d_color_type == V3D_SHADING_VERTEX_COLOR) ||
                                (ob->mode == OB_MODE_VERTEX_PAINT) || pd->is_render;
  const bool is_viewlayer_render = pd->is_render && !layer.view_layer_name().is_empty() &&
                                   STREQ(pd->view_layer->name, layer.view_layer_name().c_str());
  const bool disable_masks_render = is_viewlayer_render &&
                                    (layer.base.flag &
                                     GP_LAYER_TREE_NODE_DISABLE_MASKS_IN_VIEWLAYER) != 0;
  bool is_masked = !disable_masks_render && layer.use_masks() &&
                   !BLI_listbase_is_empty(&layer.masks);

  const float vert_col_opacity = (override_vertcol) ?
                                     (is_vert_col_mode ? pd->vertex_paint_opacity : 0.0f) :
                                     (pd->is_render ? 1.0f : pd->vertex_paint_opacity);
  /* Negate thickness sign to tag that strokes are in screen space (this is no longer used in
   * GPv3). Convert to world units (by default, 1 meter = 1000 pixels). */
  const float thickness_scale = blender::bke::greasepencil::LEGACY_RADIUS_CONVERSION_FACTOR;
  /* If the layer is used as a mask (but is otherwise not visible in the render), render it with a
   * opacity of 0 so that it can still mask other layers. */
  const float layer_opacity = !is_used_as_mask ? grease_pencil_layer_final_opacity_get(
                                                     pd, ob, grease_pencil, layer) :
                                                 0.0f;

  float layer_alpha = pd->xray_alpha;
  const float4 layer_tint = grease_pencil_layer_final_tint_and_alpha_get(
      pd, grease_pencil, onion_id, &layer_alpha);

  /* Create the new layer descriptor. */
  GPENCIL_tLayer *tgp_layer = static_cast<GPENCIL_tLayer *>(BLI_memblock_alloc(pd->gp_layer_pool));
  BLI_LINKS_APPEND(&tgp_ob->layers, tgp_layer);
  tgp_layer->layer_id = *grease_pencil.get_layer_index(layer);
  tgp_layer->mask_bits = nullptr;
  tgp_layer->mask_invert_bits = nullptr;
  tgp_layer->blend_ps = nullptr;

  /* Masking: Go through mask list and extract valid masks in a bitmap. */
  if (is_masked) {
    bool valid_mask = false;
    /* WARNING: only #GP_MAX_MASKBITS amount of bits.
     * TODO(fclem): Find a better system without any limitation. */
    tgp_layer->mask_bits = static_cast<BLI_bitmap *>(BLI_memblock_alloc(pd->gp_maskbit_pool));
    tgp_layer->mask_invert_bits = static_cast<BLI_bitmap *>(
        BLI_memblock_alloc(pd->gp_maskbit_pool));
    BLI_bitmap_set_all(tgp_layer->mask_bits, false, GP_MAX_MASKBITS);

    LISTBASE_FOREACH (GreasePencilLayerMask *, mask, &layer.masks) {
      if (mask->flag & GP_LAYER_MASK_HIDE) {
        continue;
      }
      const TreeNode *node = grease_pencil.find_node_by_name(mask->layer_name);
      if (node == nullptr) {
        continue;
      }
      const Layer &mask_layer = node->as_layer();
      if ((&mask_layer == &layer) || !mask_layer.is_visible()) {
        continue;
      }
      const int index = *grease_pencil.get_layer_index(mask_layer);
      if (index < GP_MAX_MASKBITS) {
        const bool invert = (mask->flag & GP_LAYER_MASK_INVERT) != 0;
        BLI_BITMAP_SET(tgp_layer->mask_bits, index, true);
        BLI_BITMAP_SET(tgp_layer->mask_invert_bits, index, invert);
        valid_mask = true;
      }
    }

    if (valid_mask) {
      pd->use_mask_fb = true;
    }
    else {
      tgp_layer->mask_bits = nullptr;
    }
    is_masked = valid_mask;
  }

  /* Blending: Force blending for masked layer. */
  if (is_masked || (layer.blend_mode != GP_LAYER_BLEND_NONE) || (layer_opacity < 1.0f)) {
    DRWState state = DRW_STATE_WRITE_COLOR | DRW_STATE_STENCIL_EQUAL;
    switch (layer.blend_mode) {
      case GP_LAYER_BLEND_NONE:
        state |= DRW_STATE_BLEND_ALPHA_PREMUL;
        break;
      case GP_LAYER_BLEND_ADD:
        state |= DRW_STATE_BLEND_ADD_FULL;
        break;
      case GP_LAYER_BLEND_SUBTRACT:
        state |= DRW_STATE_BLEND_SUB;
        break;
      case GP_LAYER_BLEND_MULTIPLY:
      case GP_LAYER_BLEND_DIVIDE:
      case GP_LAYER_BLEND_HARDLIGHT:
        state |= DRW_STATE_BLEND_MUL;
        break;
    }

    if (ELEM(layer.blend_mode, GP_LAYER_BLEND_SUBTRACT, GP_LAYER_BLEND_HARDLIGHT)) {
      /* For these effect to propagate, we need a signed floating point buffer. */
      pd->use_signed_fb = true;
    }

    tgp_layer->blend_ps = DRW_pass_create("GPencil Blend Layer", state);

    GPUShader *sh = GPENCIL_shader_layer_blend_get();
    DRWShadingGroup *grp = DRW_shgroup_create(sh, tgp_layer->blend_ps);
    DRW_shgroup_uniform_int_copy(grp, "blendMode", layer.blend_mode);
    DRW_shgroup_uniform_float_copy(grp, "blendOpacity", layer_opacity);
    DRW_shgroup_uniform_texture_ref(grp, "colorBuf", &pd->color_layer_tx);
    DRW_shgroup_uniform_texture_ref(grp, "revealBuf", &pd->reveal_layer_tx);
    DRW_shgroup_uniform_texture_ref(grp, "maskBuf", (is_masked) ? &pd->mask_tx : &pd->dummy_tx);
    DRW_shgroup_stencil_mask(grp, 0xFF);
    DRW_shgroup_call_procedural_triangles(grp, nullptr, 1);

    if (layer.blend_mode == GP_LAYER_BLEND_HARDLIGHT) {
      /* We cannot do custom blending on Multi-Target frame-buffers.
       * Workaround by doing 2 passes. */
      grp = DRW_shgroup_create(sh, tgp_layer->blend_ps);
      DRW_shgroup_state_disable(grp, DRW_STATE_BLEND_MUL);
      DRW_shgroup_state_enable(grp, DRW_STATE_BLEND_ADD_FULL);
      DRW_shgroup_uniform_int_copy(grp, "blendMode", 999);
      DRW_shgroup_call_procedural_triangles(grp, nullptr, 1);
    }

    pd->use_layer_fb = true;
  }

  /* Geometry pass */
  {
    GPUTexture *depth_tex = (is_in_front) ? pd->dummy_tx : pd->scene_depth_tx;
    GPUTexture **mask_tex = (is_masked) ? &pd->mask_tx : &pd->dummy_tx;

    DRWState state = DRW_STATE_WRITE_COLOR | DRW_STATE_WRITE_DEPTH | DRW_STATE_BLEND_ALPHA_PREMUL;
    /* For 2D mode, we render all strokes with uniform depth (increasing with stroke id). */
    state |= tgp_ob->is_drawmode3d ? DRW_STATE_DEPTH_LESS_EQUAL : DRW_STATE_DEPTH_GREATER;
    /* Always write stencil. Only used as optimization for blending. */
    state |= DRW_STATE_WRITE_STENCIL | DRW_STATE_STENCIL_ALWAYS;

    tgp_layer->geom_ps = DRW_pass_create("GPencil Layer", state);

    GPUShader *sh = GPENCIL_shader_geometry_get();
    DRWShadingGroup *grp = tgp_layer->base_shgrp = DRW_shgroup_create(sh, tgp_layer->geom_ps);

    DRW_shgroup_uniform_texture(grp, "gpSceneDepthTexture", depth_tex);
    DRW_shgroup_uniform_texture_ref(grp, "gpMaskTexture", mask_tex);
    DRW_shgroup_uniform_vec3_copy(grp, "gpNormal", tgp_ob->plane_normal);
    DRW_shgroup_uniform_bool_copy(grp, "gpStrokeOrder3d", tgp_ob->is_drawmode3d);
    DRW_shgroup_uniform_float_copy(grp, "gpThicknessScale", tgp_ob->object_scale);
    /* Replaced by a modifier in GPv3. */
    DRW_shgroup_uniform_float_copy(grp, "gpThicknessOffset", 0.0f);
    DRW_shgroup_uniform_float_copy(grp, "gpThicknessWorldScale", thickness_scale);
    DRW_shgroup_uniform_float_copy(grp, "gpVertexColorOpacity", vert_col_opacity);

    /* If random color type, need color by layer. */
    float gpl_color[4];
    copy_v4_v4(gpl_color, layer_tint);
    if (pd->v3d_color_type == V3D_SHADING_RANDOM_COLOR) {
      grease_pencil_layer_random_color_get(ob, layer, gpl_color);
      gpl_color[3] = 1.0f;
    }
    DRW_shgroup_uniform_vec4_copy(grp, "gpLayerTint", gpl_color);

    DRW_shgroup_uniform_float_copy(grp, "gpLayerOpacity", layer_alpha);
    DRW_shgroup_stencil_mask(grp, 0xFF);
  }

  return tgp_layer;
}
/** \} */
