/* SPDX-License-Identifier: GPL-2.0-or-later */

/** \file
 * \ingroup spview3d
 */

#include "BLI_listbase.h"
#include "BLI_math.h"
#include "BLI_rect.h"
#include "BLI_string.h"
#include "BLI_utildefines.h"

#include "BLT_translation.h"

#include "BKE_context.h"
#include "BKE_gpencil.h"
#include "BKE_main.h"
#include "BKE_report.h"

#include "BKE_layer.h"
#include "BKE_material.h"
#include "BKE_object.h"
#include "BKE_scene.h"
#include "BKE_unit.h"

#include "DNA_gpencil_types.h"
#include "DNA_meshdata_types.h"
#include "DNA_object_types.h"
#include "DNA_view3d_types.h"

#include "ED_gizmo_library.h"
#include "ED_gizmo_utils.h"
#include "ED_gpencil.h"
#include "ED_screen.h"
#include "ED_transform.h"
#include "ED_transform_snap_object_context.h"
#include "ED_view3d.h"

#include "UI_interface.h"
#include "UI_resources.h"

#include "MEM_guardedalloc.h"

#include "RNA_access.h"

#include "WM_api.h"
#include "WM_toolsystem.h"
#include "WM_types.h"

#include "DEG_depsgraph_query.h"

#include "view3d_intern.h" /* own include */

#include "GPU_immediate.h"
#include "GPU_immediate_util.h"
#include "GPU_matrix.h"
#include "GPU_state.h"

#include "BLF_api.h"

/**
 * Supporting transform features could be removed if the actual transform system is used.
 * Keep the option open since each transform feature is duplicating logic.
 */
#define USE_AXIS_CONSTRAINTS

static const char *view3d_gzgt_ruler_id = "VIEW3D_GGT_ruler";

#define MVAL_MAX_PX_DIST 12.0f

/* -------------------------------------------------------------------- */
/* Ruler Item (we can have many) */

enum {
  /** Use protractor. */
  RULERITEM_USE_ANGLE = (1 << 0),
  /** Protractor vertex is selected (deleting removes it). */
  RULERITEM_USE_ANGLE_ACTIVE = (1 << 1),
};

/* keep smaller than selection, since we may want click elsewhere without selecting a ruler */
#define RULER_PICK_DIST 12.0f
#define RULER_PICK_DIST_SQ (RULER_PICK_DIST * RULER_PICK_DIST)

/* not clicking on a point */
#define PART_LINE 0xff

/* -------------------------------------------------------------------- */
/* Ruler Info (wmGizmoGroup customdata) */

enum {
  RULER_STATE_NORMAL = 0,
  RULER_STATE_DRAG,
};

#ifdef USE_AXIS_CONSTRAINTS
/* Constrain axes */
enum {
  CONSTRAIN_AXIS_NONE = -1,
  CONSTRAIN_AXIS_X = 0,
  CONSTRAIN_AXIS_Y = 1,
  CONSTRAIN_AXIS_Z = 2,
};

/**
 * Constraining modes.
 * Off / Scene orientation / Global (or Local if Scene orientation is Global).
 */
enum {
  CONSTRAIN_MODE_OFF = 0,
  CONSTRAIN_MODE_1 = 1,
  CONSTRAIN_MODE_2 = 2,
};
#endif /* USE_AXIS_CONSTRAINTS */

struct RulerItem;

typedef struct RulerInfo {
  struct RulerItem *item_active;
  int flag;
  int snap_flag;
  int state;

#ifdef USE_AXIS_CONSTRAINTS
  short constrain_axis, constrain_mode;
#endif

  /* wm state */
  wmWindowManager *wm;
  wmWindow *win;
  ScrArea *area;
  ARegion *region; /* re-assigned every modal update */

  /* Track changes in state. */
  struct {
#ifndef USE_SNAP_DETECT_FROM_KEYMAP_HACK
    bool do_snap;
#endif
    bool do_thickness;
  } drag_state_prev;

  struct {
    wmGizmo *gizmo;
    PropertyRNA *prop_prevpoint;
  } snap_data;

} RulerInfo;

/* -------------------------------------------------------------------- */
/* Ruler Item (two or three points) */

typedef struct RulerItem {
  wmGizmo gz;

  /** World-space coords, middle being optional. */
  float co[3][3];

  int flag;
  int raycast_dir; /* RULER_DIRECTION_* */
} RulerItem;

typedef struct RulerInteraction {
  /* selected coord */
  char co_index; /* 0 -> 2 */
  float drag_start_co[3];
} RulerInteraction;

/* -------------------------------------------------------------------- */
/** \name Internal Ruler Utilities
 * \{ */

static RulerItem *ruler_item_add(wmGizmoGroup *gzgroup)
{
  /* could pass this as an arg */
  const wmGizmoType *gzt_ruler = WM_gizmotype_find("VIEW3D_GT_ruler_item", true);
  RulerItem *ruler_item = (RulerItem *)WM_gizmo_new_ptr(gzt_ruler, gzgroup, NULL);
  WM_gizmo_set_flag(&ruler_item->gz, WM_GIZMO_DRAW_MODAL, true);
  return ruler_item;
}

static void ruler_item_remove(bContext *C, wmGizmoGroup *gzgroup, RulerItem *ruler_item)
{
  RulerInfo *ruler_info = gzgroup->customdata;
  if (ruler_info->item_active == ruler_item) {
    ruler_info->item_active = NULL;
  }
  WM_gizmo_unlink(&gzgroup->gizmos, gzgroup->parent_gzmap, &ruler_item->gz, C);
}

static void ruler_item_as_string(
    RulerItem *ruler_item, UnitSettings *unit, char *numstr, size_t numstr_size, int prec)
{
  if (ruler_item->flag & RULERITEM_USE_ANGLE) {
    const float ruler_angle = angle_v3v3v3(
        ruler_item->co[0], ruler_item->co[1], ruler_item->co[2]);

    if (unit->system == USER_UNIT_NONE) {
      BLI_snprintf(numstr, numstr_size, "%.*f°", prec, RAD2DEGF(ruler_angle));
    }
    else {
      BKE_unit_value_as_string(
          numstr, numstr_size, (double)ruler_angle, prec, B_UNIT_ROTATION, unit, false);
    }
  }
  else {
    const float ruler_len = len_v3v3(ruler_item->co[0], ruler_item->co[2]);

    if (unit->system == USER_UNIT_NONE) {
      BLI_snprintf(numstr, numstr_size, "%.*f", prec, ruler_len);
    }
    else {
      BKE_unit_value_as_string(numstr,
                               numstr_size,
                               (double)(ruler_len * unit->scale_length),
                               prec,
                               B_UNIT_LENGTH,
                               unit,
                               false);
    }
  }
}

static bool view3d_ruler_pick(wmGizmoGroup *gzgroup,
                              RulerItem *ruler_item,
                              const float mval[2],
                              int *r_co_index)
{
  RulerInfo *ruler_info = gzgroup->customdata;
  ARegion *region = ruler_info->region;
  bool found = false;

  float dist_best = RULER_PICK_DIST_SQ;
  int co_index_best = -1;

  {
    float co_ss[3][2];
    float dist;
    int j;

    /* should these be checked? - ok for now not to */
    for (j = 0; j < 3; j++) {
      ED_view3d_project_float_global(region, ruler_item->co[j], co_ss[j], V3D_PROJ_TEST_NOP);
    }

    if (ruler_item->flag & RULERITEM_USE_ANGLE) {
      dist = min_ff(dist_squared_to_line_segment_v2(mval, co_ss[0], co_ss[1]),
                    dist_squared_to_line_segment_v2(mval, co_ss[1], co_ss[2]));
      if (dist < dist_best) {
        dist_best = dist;
        found = true;

        {
          const float dist_points[3] = {
              len_squared_v2v2(co_ss[0], mval),
              len_squared_v2v2(co_ss[1], mval),
              len_squared_v2v2(co_ss[2], mval),
          };
          if (min_fff(UNPACK3(dist_points)) < RULER_PICK_DIST_SQ) {
            co_index_best = min_axis_v3(dist_points);
          }
          else {
            co_index_best = -1;
          }
        }
      }
    }
    else {
      dist = dist_squared_to_line_segment_v2(mval, co_ss[0], co_ss[2]);
      if (dist < dist_best) {
        dist_best = dist;
        found = true;

        {
          const float dist_points[2] = {
              len_squared_v2v2(co_ss[0], mval),
              len_squared_v2v2(co_ss[2], mval),
          };
          if (min_ff(UNPACK2(dist_points)) < RULER_PICK_DIST_SQ) {
            co_index_best = (dist_points[0] < dist_points[1]) ? 0 : 2;
          }
          else {
            co_index_best = -1;
          }
        }
      }
    }
  }

  *r_co_index = co_index_best;
  return found;
}

/**
 * Ensure the 'snap_context' is only cached while dragging,
 * needed since the user may toggle modes between tool use.
 */
static void ruler_state_set(RulerInfo *ruler_info, int state)
{
  if (state == ruler_info->state) {
    return;
  }

  if (state == RULER_STATE_NORMAL) {
    /* pass */
  }
  else if (state == RULER_STATE_DRAG) {
    memset(&ruler_info->drag_state_prev, 0x0, sizeof(ruler_info->drag_state_prev));
  }
  else {
    BLI_assert(0);
  }

  ruler_info->state = state;
}

static void view3d_ruler_item_project(RulerInfo *ruler_info, float r_co[3], const int xy[2])
{
  ED_view3d_win_to_3d_int(ruler_info->area->spacedata.first, ruler_info->region, r_co, xy, r_co);
}

/**
 * Use for mouse-move events.
 */
static bool view3d_ruler_item_mousemove(const bContext *C,
                                        struct Depsgraph *depsgraph,
                                        RulerInfo *ruler_info,
                                        RulerItem *ruler_item,
                                        const int mval[2],
                                        const bool do_thickness
#ifndef USE_SNAP_DETECT_FROM_KEYMAP_HACK
                                        ,
                                        const bool do_snap
#endif
)
{
  wmGizmo *snap_gizmo = ruler_info->snap_data.gizmo;
  const float eps_bias = 0.0002f;
  float dist_px = MVAL_MAX_PX_DIST * U.pixelsize; /* snap dist */

  if (ruler_item) {
    RulerInteraction *inter = ruler_item->gz.interaction_data;
    float *co = ruler_item->co[inter->co_index];
    /* restore the initial depth */
    copy_v3_v3(co, inter->drag_start_co);
    view3d_ruler_item_project(ruler_info, co, mval);
    if (do_thickness && inter->co_index != 1) {
      Scene *scene = DEG_get_input_scene(depsgraph);
      View3D *v3d = ruler_info->area->spacedata.first;
      SnapObjectContext *snap_context = ED_gizmotypes_snap_3d_context_ensure(scene, snap_gizmo);
      const float mval_fl[2] = {UNPACK2(mval)};
      float ray_normal[3];
      float ray_start[3];
      float *co_other;

      co_other = ruler_item->co[inter->co_index == 0 ? 2 : 0];

      if (ED_transform_snap_object_project_view3d(snap_context,
                                                  depsgraph,
                                                  ruler_info->region,
                                                  v3d,
                                                  SCE_SNAP_MODE_FACE_RAYCAST,
                                                  &(const struct SnapObjectParams){
                                                      .snap_target_select = SCE_SNAP_TARGET_ALL,
                                                      .edit_mode_type = SNAP_GEOM_CAGE,
                                                  },
                                                  NULL,
                                                  mval_fl,
                                                  NULL,
                                                  &dist_px,
                                                  co,
                                                  ray_normal)) {
        negate_v3(ray_normal);
        /* add some bias */
        madd_v3_v3v3fl(ray_start, co, ray_normal, eps_bias);
        ED_transform_snap_object_project_ray(snap_context,
                                             depsgraph,
                                             v3d,
                                             &(const struct SnapObjectParams){
                                                 .snap_target_select = SCE_SNAP_TARGET_ALL,
                                                 .edit_mode_type = SNAP_GEOM_CAGE,
                                             },
                                             ray_start,
                                             ray_normal,
                                             NULL,
                                             co_other,
                                             NULL);
      }
    }
    else
#ifndef USE_SNAP_DETECT_FROM_KEYMAP_HACK
        if (do_snap)
#endif
    {
      View3D *v3d = ruler_info->area->spacedata.first;
      float *prev_point = NULL;

      if (inter->co_index != 1) {
        if (ruler_item->flag & RULERITEM_USE_ANGLE) {
          prev_point = ruler_item->co[1];
        }
        else if (inter->co_index == 0) {
          prev_point = ruler_item->co[2];
        }
        else {
          prev_point = ruler_item->co[0];
        }
      }
      if (prev_point != NULL) {
        RNA_property_float_set_array(
            snap_gizmo->ptr, ruler_info->snap_data.prop_prevpoint, prev_point);
      }

      if (ED_gizmotypes_snap_3d_is_enabled(snap_gizmo)) {
        ED_gizmotypes_snap_3d_data_get(C, snap_gizmo, co, NULL, NULL, NULL);
      }

#ifdef USE_AXIS_CONSTRAINTS
      if (!(ruler_item->flag & RULERITEM_USE_ANGLE) &&
          ruler_info->constrain_mode != CONSTRAIN_MODE_OFF) {

        Scene *scene = DEG_get_input_scene(depsgraph);
        ViewLayer *view_layer = DEG_get_input_view_layer(depsgraph);
        RegionView3D *rv3d = ruler_info->region->regiondata;
        BKE_view_layer_synced_ensure(scene, view_layer);
        Object *ob = BKE_view_layer_active_object_get(view_layer);
        Object *obedit = OBEDIT_FROM_OBACT(ob);

        short orient_index = BKE_scene_orientation_get_index(scene, SCE_ORIENT_DEFAULT);

        if (ruler_info->constrain_mode == CONSTRAIN_MODE_2) {
          orient_index = (orient_index == V3D_ORIENT_GLOBAL) ? V3D_ORIENT_LOCAL :
                                                               V3D_ORIENT_GLOBAL;
        }

        const int pivot_point = scene->toolsettings->transform_pivot_point;
        float mat[3][3];

        ED_transform_calc_orientation_from_type_ex(
            scene, view_layer, v3d, rv3d, ob, obedit, orient_index, pivot_point, mat);

        invert_m3(mat);
        mul_m3_m3_pre(ruler_item->co, mat);

        /* Loop through the axes and constrain the dragged point to the current constrained axis.
         */
        for (int i = 0; i <= 2; i++) {
          if (ruler_info->constrain_axis != i) {
            ruler_item->co[inter->co_index][i] = ruler_item->co[(inter->co_index == 0) ? 2 : 0][i];
          }
        }
        invert_m3(mat);
        mul_m3_m3_pre(ruler_item->co, mat);
      }
#endif
    }
    return true;
  }
  return false;
}

/**
 * When the gizmo-group has been created immediately before running an operator
 * to manipulate rulers, it's possible the new gizmo-group has not yet been initialized.
 * in 3.0 this happened because left-click drag would both select and add a new ruler,
 * significantly increasing the likelihood of this happening.
 * Workaround this crash by checking the gizmo's custom-data has not been cleared.
 * The key-map has also been modified not to trigger this bug, see T95591.
 */
static bool gizmo_ruler_check_for_operator(const wmGizmoGroup *gzgroup)
{
  return gzgroup->customdata != NULL;
}

/** \} */

/* -------------------------------------------------------------------- */
/** \name Ruler/Grease Pencil Conversion
 * \{ */

/* Helper: Find the layer created as ruler. */
static bGPDlayer *view3d_ruler_layer_get(bGPdata *gpd)
{
  LISTBASE_FOREACH (bGPDlayer *, gpl, &gpd->layers) {
    if (gpl->flag & GP_LAYER_IS_RULER) {
      return gpl;
    }
  }
  return NULL;
}

static RulerItem *gzgroup_ruler_item_first_get(wmGizmoGroup *gzgroup)
{
#ifndef NDEBUG
  RulerInfo *ruler_info = gzgroup->customdata;
  BLI_assert(gzgroup->gizmos.first == ruler_info->snap_data.gizmo);
#endif
  return (RulerItem *)((wmGizmo *)gzgroup->gizmos.first)->next;
}

#define RULER_ID "RulerData3D"
static bool view3d_ruler_to_gpencil(bContext *C, wmGizmoGroup *gzgroup)
{
  // RulerInfo *ruler_info = gzgroup->customdata;
  Main *bmain = CTX_data_main(C);
  Scene *scene = CTX_data_scene(C);

  bGPdata *gpd;
  bGPDlayer *gpl;
  bGPDframe *gpf;
  bGPDstroke *gps;
  RulerItem *ruler_item;
  const char *ruler_name = RULER_ID;
  bool changed = false;

  if (scene->gpd == NULL) {
    scene->gpd = BKE_gpencil_data_addnew(bmain, "Annotations");
  }
  gpd = scene->gpd;

  gpl = view3d_ruler_layer_get(gpd);
  if (gpl == NULL) {
    gpl = BKE_gpencil_layer_addnew(gpd, ruler_name, false, false);
    copy_v4_v4(gpl->color, U.gpencil_new_layer_col);
    gpl->thickness = 1;
    gpl->flag |= GP_LAYER_HIDE | GP_LAYER_IS_RULER;
  }

  gpf = BKE_gpencil_layer_frame_get(gpl, scene->r.cfra, GP_GETFRAME_ADD_NEW);
  BKE_gpencil_free_strokes(gpf);

  for (ruler_item = gzgroup_ruler_item_first_get(gzgroup); ruler_item;
       ruler_item = (RulerItem *)ruler_item->gz.next) {
    bGPDspoint *pt;
    int j;

    /* allocate memory for a new stroke */
    gps = MEM_callocN(sizeof(bGPDstroke), "gp_stroke");
    if (ruler_item->flag & RULERITEM_USE_ANGLE) {
      gps->totpoints = 3;
      pt = gps->points = MEM_callocN(sizeof(bGPDspoint) * gps->totpoints, "gp_stroke_points");
      for (j = 0; j < 3; j++) {
        copy_v3_v3(&pt->x, ruler_item->co[j]);
        pt->pressure = 1.0f;
        pt->strength = 1.0f;
        pt++;
      }
    }
    else {
      gps->totpoints = 2;
      pt = gps->points = MEM_callocN(sizeof(bGPDspoint) * gps->totpoints, "gp_stroke_points");
      for (j = 0; j < 3; j += 2) {
        copy_v3_v3(&pt->x, ruler_item->co[j]);
        pt->pressure = 1.0f;
        pt->strength = 1.0f;
        pt++;
      }
    }
    gps->flag = GP_STROKE_3DSPACE;
    gps->thickness = 3;
    gps->hardeness = 1.0f;
    gps->fill_opacity_fac = 1.0f;
    copy_v2_fl(gps->aspect_ratio, 1.0f);
    gps->uv_scale = 1.0f;

    BLI_addtail(&gpf->strokes, gps);
    changed = true;
  }

  return changed;
}

static bool view3d_ruler_from_gpencil(const bContext *C, wmGizmoGroup *gzgroup)
{
  Scene *scene = CTX_data_scene(C);
  bool changed = false;

  if (scene->gpd) {
    bGPDlayer *gpl;
    gpl = view3d_ruler_layer_get(scene->gpd);
    if (gpl) {
      bGPDframe *gpf;
      gpf = BKE_gpencil_layer_frame_get(gpl, scene->r.cfra, GP_GETFRAME_USE_PREV);
      if (gpf) {
        bGPDstroke *gps;
        for (gps = gpf->strokes.first; gps; gps = gps->next) {
          bGPDspoint *pt = gps->points;
          int j;
          RulerItem *ruler_item = NULL;
          if (gps->totpoints == 3) {
            ruler_item = ruler_item_add(gzgroup);
            for (j = 0; j < 3; j++) {
              copy_v3_v3(ruler_item->co[j], &pt->x);
              pt++;
            }
            ruler_item->flag |= RULERITEM_USE_ANGLE;
            changed = true;
          }
          else if (gps->totpoints == 2) {
            ruler_item = ruler_item_add(gzgroup);
            for (j = 0; j < 3; j += 2) {
              copy_v3_v3(ruler_item->co[j], &pt->x);
              pt++;
            }
            changed = true;
          }
        }
      }
    }
  }

  return changed;
}

/** \} */

/* -------------------------------------------------------------------- */
/** \name Ruler Item Gizmo Type
 * \{ */

static void gizmo_ruler_draw(const bContext *C, wmGizmo *gz)
{
  Scene *scene = CTX_data_scene(C);
  UnitSettings *unit = &scene->unit;
  RulerInfo *ruler_info = gz->parent_gzgroup->customdata;
  RulerItem *ruler_item = (RulerItem *)gz;
  ARegion *region = ruler_info->region;
  RegionView3D *rv3d = region->regiondata;
  const float cap_size = 4.0f * U.dpi_fac;
  const float bg_margin = 4.0f * U.dpi_fac;
  const float arc_size = 64.0f * U.dpi_fac;
#define ARC_STEPS 24
  const int arc_steps = ARC_STEPS;
  const float color_act[4] = {1.0f, 1.0f, 1.0f, 1.0f};
  const float color_base[4] = {0.0f, 0.0f, 0.0f, 1.0f};
  uchar color_text[3];
  uchar color_wire[3];
  float color_back[4] = {1.0f, 1.0f, 1.0f, 0.5f};

  /* Pixel Space. */
  GPU_matrix_push_projection();
  GPU_matrix_push();
  GPU_matrix_identity_set();
  wmOrtho2_region_pixelspace(region);

  /* anti-aliased lines for more consistent appearance */
  GPU_line_smooth(true);
  GPU_line_width(1.0f);

  BLF_enable(blf_mono_font, BLF_ROTATION);
  BLF_size(blf_mono_font, 14.0f * U.dpi_fac);
  BLF_rotation(blf_mono_font, 0.0f);

  UI_GetThemeColor3ubv(TH_TEXT, color_text);
  UI_GetThemeColor3ubv(TH_WIRE, color_wire);

  /* Avoid white on white text. (TODO: Fix by using theme). */
  if ((int)color_text[0] + (int)color_text[1] + (int)color_text[2] > 127 * 3 * 0.6f) {
    copy_v3_fl(color_back, 0.0f);
  }

  const bool is_act = (ruler_info->item_active == ruler_item);
  float dir_ruler[2];
  float co_ss[3][2];
  bool proj_ok[3];
  int j;

  /* Check if each corner is behind the near plane. If it is, we do not draw certain lines. */
  for (j = 0; j < 3; j++) {
    eV3DProjStatus status = ED_view3d_project_float_global(
        region, ruler_item->co[j], co_ss[j], V3D_PROJ_TEST_CLIP_NEAR);
    proj_ok[j] = (status == V3D_PROJ_RET_OK);
  }

  /* 3d drawing. */

  GPU_matrix_push_projection();
  GPU_matrix_push();
  GPU_matrix_projection_set(rv3d->winmat);
  GPU_matrix_set(rv3d->viewmat);

  GPU_blend(GPU_BLEND_ALPHA);

  const uint shdr_pos_3d = GPU_vertformat_attr_add(
      immVertexFormat(), "pos", GPU_COMP_F32, 3, GPU_FETCH_FLOAT);

  if (ruler_item->flag & RULERITEM_USE_ANGLE) {
    immBindBuiltinProgram(GPU_SHADER_3D_LINE_DASHED_UNIFORM_COLOR);

    float viewport_size[4];
    GPU_viewport_size_get_f(viewport_size);
    immUniform2f("viewport_size", viewport_size[2], viewport_size[3]);

    immUniform1i("colors_len", 2); /* "advanced" mode */
    const float *col = is_act ? color_act : color_base;
    immUniform4f("color", 0.67f, 0.67f, 0.67f, 1.0f);
    immUniform4f("color2", col[0], col[1], col[2], col[3]);
    immUniform1f("dash_width", 6.0f);
    immUniform1f("dash_factor", 0.5f);

    immBegin(GPU_PRIM_LINE_STRIP, 3);

    immVertex3fv(shdr_pos_3d, ruler_item->co[0]);
    immVertex3fv(shdr_pos_3d, ruler_item->co[1]);
    immVertex3fv(shdr_pos_3d, ruler_item->co[2]);

    immEnd();

    immUnbindProgram();

    immBindBuiltinProgram(GPU_SHADER_3D_UNIFORM_COLOR);

    /* arc */
    {
      float dir_tmp[3];
      float ar_coord[3];

      float dir_a[3];
      float dir_b[3];
      float quat[4];
      float axis[3];
      float angle;
      const float px_scale = (ED_view3d_pixel_size_no_ui_scale(rv3d, ruler_item->co[1]) *
                              min_fff(arc_size,
                                      len_v2v2(co_ss[0], co_ss[1]) / 2.0f,
                                      len_v2v2(co_ss[2], co_ss[1]) / 2.0f));

      sub_v3_v3v3(dir_a, ruler_item->co[0], ruler_item->co[1]);
      sub_v3_v3v3(dir_b, ruler_item->co[2], ruler_item->co[1]);
      normalize_v3(dir_a);
      normalize_v3(dir_b);

      cross_v3_v3v3(axis, dir_a, dir_b);
      angle = angle_normalized_v3v3(dir_a, dir_b);

      axis_angle_to_quat(quat, axis, angle / arc_steps);

      copy_v3_v3(dir_tmp, dir_a);

      immUniformColor3ubv(color_wire);

      immBegin(GPU_PRIM_LINE_STRIP, arc_steps + 1);

      for (j = 0; j <= arc_steps; j++) {
        madd_v3_v3v3fl(ar_coord, ruler_item->co[1], dir_tmp, px_scale);
        mul_qt_v3(quat, dir_tmp);

        immVertex3fv(shdr_pos_3d, ar_coord);
      }

      immEnd();
    }

    immUnbindProgram();
  }
  else {
    immBindBuiltinProgram(GPU_SHADER_3D_LINE_DASHED_UNIFORM_COLOR);

    float viewport_size[4];
    GPU_viewport_size_get_f(viewport_size);
    immUniform2f("viewport_size", viewport_size[2], viewport_size[3]);

    immUniform1i("colors_len", 2); /* "advanced" mode */
    const float *col = is_act ? color_act : color_base;
    immUniform4f("color", 0.67f, 0.67f, 0.67f, 1.0f);
    immUniform4f("color2", col[0], col[1], col[2], col[3]);
    immUniform1f("dash_width", 6.0f);
    immUniform1f("dash_factor", 0.5f);

    immBegin(GPU_PRIM_LINES, 2);

    immVertex3fv(shdr_pos_3d, ruler_item->co[0]);
    immVertex3fv(shdr_pos_3d, ruler_item->co[2]);

    immEnd();

    immUnbindProgram();
  }

  /* 2d drawing. */

  GPU_matrix_pop();
  GPU_matrix_pop_projection();

  const uint shdr_pos_2d = GPU_vertformat_attr_add(
      immVertexFormat(), "pos", GPU_COMP_F32, 2, GPU_FETCH_FLOAT);

  if (ruler_item->flag & RULERITEM_USE_ANGLE) {
    immBindBuiltinProgram(GPU_SHADER_3D_UNIFORM_COLOR);
    /* capping */
    {
      float rot_90_vec_a[2];
      float rot_90_vec_b[2];
      float cap[2];

      sub_v2_v2v2(dir_ruler, co_ss[0], co_ss[1]);
      rot_90_vec_a[0] = -dir_ruler[1];
      rot_90_vec_a[1] = dir_ruler[0];
      normalize_v2(rot_90_vec_a);

      sub_v2_v2v2(dir_ruler, co_ss[1], co_ss[2]);
      rot_90_vec_b[0] = -dir_ruler[1];
      rot_90_vec_b[1] = dir_ruler[0];
      normalize_v2(rot_90_vec_b);

      GPU_blend(GPU_BLEND_ALPHA);

      if (proj_ok[1] && is_act && (ruler_item->flag & RULERITEM_USE_ANGLE_ACTIVE)) {
        GPU_line_width(3.0f);
        immUniformColor3fv(color_act);
        immBegin(GPU_PRIM_LINES, 4);
        /* angle vertex */
        immVertex2f(shdr_pos_2d, co_ss[1][0] - cap_size, co_ss[1][1] - cap_size);
        immVertex2f(shdr_pos_2d, co_ss[1][0] + cap_size, co_ss[1][1] + cap_size);
        immVertex2f(shdr_pos_2d, co_ss[1][0] - cap_size, co_ss[1][1] + cap_size);
        immVertex2f(shdr_pos_2d, co_ss[1][0] + cap_size, co_ss[1][1] - cap_size);

        immEnd();
        GPU_line_width(1.0f);
      }

      immUniformColor3ubv(color_wire);

      if (proj_ok[0] || proj_ok[2] || proj_ok[1]) {
        immBegin(GPU_PRIM_LINES, proj_ok[0] * 2 + proj_ok[2] * 2 + proj_ok[1] * 4);

        if (proj_ok[0]) {
          madd_v2_v2v2fl(cap, co_ss[0], rot_90_vec_a, cap_size);
          immVertex2fv(shdr_pos_2d, cap);
          madd_v2_v2v2fl(cap, co_ss[0], rot_90_vec_a, -cap_size);
          immVertex2fv(shdr_pos_2d, cap);
        }

        if (proj_ok[2]) {
          madd_v2_v2v2fl(cap, co_ss[2], rot_90_vec_b, cap_size);
          immVertex2fv(shdr_pos_2d, cap);
          madd_v2_v2v2fl(cap, co_ss[2], rot_90_vec_b, -cap_size);
          immVertex2fv(shdr_pos_2d, cap);
        }

        /* angle vertex */
        if (proj_ok[1]) {
          immVertex2f(shdr_pos_2d, co_ss[1][0] - cap_size, co_ss[1][1] - cap_size);
          immVertex2f(shdr_pos_2d, co_ss[1][0] + cap_size, co_ss[1][1] + cap_size);
          immVertex2f(shdr_pos_2d, co_ss[1][0] - cap_size, co_ss[1][1] + cap_size);
          immVertex2f(shdr_pos_2d, co_ss[1][0] + cap_size, co_ss[1][1] - cap_size);
        }

        immEnd();
      }

      GPU_blend(GPU_BLEND_NONE);
    }

    /* text */
    char numstr[256];
    float numstr_size[2];
    float posit[2];
    const int prec = 2; /* XXX, todo, make optional */

    ruler_item_as_string(ruler_item, unit, numstr, sizeof(numstr), prec);

    BLF_width_and_height(blf_mono_font, numstr, sizeof(numstr), &numstr_size[0], &numstr_size[1]);

    posit[0] = co_ss[1][0] + (cap_size * 2.0f);
    posit[1] = co_ss[1][1] - (numstr_size[1] / 2.0f);

    /* draw text (bg) */
    if (proj_ok[1]) {
      immUniformColor4fv(color_back);
      GPU_blend(GPU_BLEND_ALPHA);
      immRectf(shdr_pos_2d,
               posit[0] - bg_margin,
               posit[1] - bg_margin,
               posit[0] + bg_margin + numstr_size[0],
               posit[1] + bg_margin + numstr_size[1]);
      GPU_blend(GPU_BLEND_NONE);
    }

    immUnbindProgram();

    /* draw text */
    if (proj_ok[1]) {
      BLF_color3ubv(blf_mono_font, color_text);
      BLF_position(blf_mono_font, posit[0], posit[1], 0.0f);
      BLF_rotation(blf_mono_font, 0.0f);
      BLF_draw(blf_mono_font, numstr, sizeof(numstr));
    }
  }
  else {
    immBindBuiltinProgram(GPU_SHADER_3D_UNIFORM_COLOR);

    sub_v2_v2v2(dir_ruler, co_ss[0], co_ss[2]);

    /* capping */
    {
      float rot_90_vec[2] = {-dir_ruler[1], dir_ruler[0]};
      float cap[2];

      normalize_v2(rot_90_vec);

      GPU_blend(GPU_BLEND_ALPHA);

      immUniformColor3ubv(color_wire);

      if (proj_ok[0] || proj_ok[2]) {
        immBegin(GPU_PRIM_LINES, proj_ok[0] * 2 + proj_ok[2] * 2);

        if (proj_ok[0]) {
          madd_v2_v2v2fl(cap, co_ss[0], rot_90_vec, cap_size);
          immVertex2fv(shdr_pos_2d, cap);
          madd_v2_v2v2fl(cap, co_ss[0], rot_90_vec, -cap_size);
          immVertex2fv(shdr_pos_2d, cap);
        }

        if (proj_ok[2]) {
          madd_v2_v2v2fl(cap, co_ss[2], rot_90_vec, cap_size);
          immVertex2fv(shdr_pos_2d, cap);
          madd_v2_v2v2fl(cap, co_ss[2], rot_90_vec, -cap_size);
          immVertex2fv(shdr_pos_2d, cap);
        }

        immEnd();
      }

      GPU_blend(GPU_BLEND_NONE);
    }

    /* text */
    char numstr[256];
    float numstr_size[2];
    const int prec = 6; /* XXX, todo, make optional */
    float posit[2];

    ruler_item_as_string(ruler_item, unit, numstr, sizeof(numstr), prec);

    BLF_width_and_height(blf_mono_font, numstr, sizeof(numstr), &numstr_size[0], &numstr_size[1]);

    mid_v2_v2v2(posit, co_ss[0], co_ss[2]);

    /* center text */
    posit[0] -= numstr_size[0] / 2.0f;
    posit[1] -= numstr_size[1] / 2.0f;

    /* draw text (bg) */
    if (proj_ok[0] && proj_ok[2]) {
      immUniformColor4fv(color_back);
      GPU_blend(GPU_BLEND_ALPHA);
      immRectf(shdr_pos_2d,
               posit[0] - bg_margin,
               posit[1] - bg_margin,
               posit[0] + bg_margin + numstr_size[0],
               posit[1] + bg_margin + numstr_size[1]);
      GPU_blend(GPU_BLEND_NONE);
    }

    immUnbindProgram();

    /* draw text */
    if (proj_ok[0] && proj_ok[2]) {
      BLF_color3ubv(blf_mono_font, color_text);
      BLF_position(blf_mono_font, posit[0], posit[1], 0.0f);
      BLF_draw(blf_mono_font, numstr, sizeof(numstr));
    }
  }

  GPU_line_smooth(false);

  BLF_disable(blf_mono_font, BLF_ROTATION);

  GPU_matrix_pop();
  GPU_matrix_pop_projection();

#undef ARC_STEPS
}

static int gizmo_ruler_test_select(bContext *UNUSED(C), wmGizmo *gz, const int mval[2])
{
  RulerItem *ruler_item_pick = (RulerItem *)gz;
  const float mval_fl[2] = {UNPACK2(mval)};
  int co_index;

  /* select and drag */
  if (view3d_ruler_pick(gz->parent_gzgroup, ruler_item_pick, mval_fl, &co_index)) {
    if (co_index == -1) {
      if ((ruler_item_pick->flag & RULERITEM_USE_ANGLE) == 0) {
        return PART_LINE;
      }
    }
    else {
      return co_index;
    }
  }
  return -1;
}

static int gizmo_ruler_modal(bContext *C,
                             wmGizmo *gz,
                             const wmEvent *event,
                             eWM_GizmoFlagTweak tweak_flag)
{
  bool do_draw = false;
  int exit_code = OPERATOR_RUNNING_MODAL;
  RulerInfo *ruler_info = gz->parent_gzgroup->customdata;
  RulerItem *ruler_item = (RulerItem *)gz;
  ARegion *region = CTX_wm_region(C);
  bool do_cursor_update = (event->val == KM_RELEASE) || (event->type == MOUSEMOVE);

  ruler_info->region = region;

#ifdef USE_AXIS_CONSTRAINTS
  if ((event->val == KM_PRESS) && ELEM(event->type, EVT_XKEY, EVT_YKEY, EVT_ZKEY)) {
    /* Go to Mode 1 if a new axis is selected. */
    if (event->type == EVT_XKEY && ruler_info->constrain_axis != CONSTRAIN_AXIS_X) {
      ruler_info->constrain_axis = CONSTRAIN_AXIS_X;
      ruler_info->constrain_mode = CONSTRAIN_MODE_1;
    }
    else if (event->type == EVT_YKEY && ruler_info->constrain_axis != CONSTRAIN_AXIS_Y) {
      ruler_info->constrain_axis = CONSTRAIN_AXIS_Y;
      ruler_info->constrain_mode = CONSTRAIN_MODE_1;
    }
    else if (event->type == EVT_ZKEY && ruler_info->constrain_axis != CONSTRAIN_AXIS_Z) {
      ruler_info->constrain_axis = CONSTRAIN_AXIS_Z;
      ruler_info->constrain_mode = CONSTRAIN_MODE_1;
    }
    else {
      /* Cycle to the next mode if the same key is pressed again. */
      if (ruler_info->constrain_mode != CONSTRAIN_MODE_2) {
        ruler_info->constrain_mode++;
      }
      else {
        ruler_info->constrain_mode = CONSTRAIN_MODE_OFF;
        ruler_info->constrain_axis = CONSTRAIN_AXIS_NONE;
      }
    }
    do_cursor_update = true;
  }
#endif

#ifndef USE_SNAP_DETECT_FROM_KEYMAP_HACK
  const bool do_snap = !(tweak_flag & WM_GIZMO_TWEAK_SNAP);
#endif
  const bool do_thickness = tweak_flag & WM_GIZMO_TWEAK_PRECISE;
  if (ruler_info->drag_state_prev.do_thickness != do_thickness) {
    do_cursor_update = true;
  }

  if (do_cursor_update) {
    if (ruler_info->state == RULER_STATE_DRAG) {
      struct Depsgraph *depsgraph = CTX_data_ensure_evaluated_depsgraph(C);
      if (view3d_ruler_item_mousemove(C,
                                      depsgraph,
                                      ruler_info,
                                      ruler_item,
                                      event->mval,
                                      do_thickness
#ifndef USE_SNAP_DETECT_FROM_KEYMAP_HACK
                                      ,
                                      do_snap
#endif
                                      )) {
        do_draw = true;
      }
    }
  }

  ruler_info->drag_state_prev.do_thickness = do_thickness;

  if (do_draw) {
    ED_region_tag_redraw_editor_overlays(region);
  }
  return exit_code;
}

static int gizmo_ruler_invoke(bContext *C, wmGizmo *gz, const wmEvent *event)
{
  wmGizmoGroup *gzgroup = gz->parent_gzgroup;
  RulerInfo *ruler_info = gzgroup->customdata;
  RulerItem *ruler_item_pick = (RulerItem *)gz;
  RulerInteraction *inter = MEM_callocN(sizeof(RulerInteraction), __func__);
  gz->interaction_data = inter;

  ARegion *region = ruler_info->region;

  float mval_fl[2];
  WM_event_drag_start_mval_fl(event, region, mval_fl);

#ifdef USE_AXIS_CONSTRAINTS
  ruler_info->constrain_axis = CONSTRAIN_AXIS_NONE;
  ruler_info->constrain_mode = CONSTRAIN_MODE_OFF;
#endif

  /* select and drag */
  if (gz->highlight_part == PART_LINE) {
    if ((ruler_item_pick->flag & RULERITEM_USE_ANGLE) == 0) {
      /* Add Center Point */
      ruler_item_pick->flag |= RULERITEM_USE_ANGLE;
      inter->co_index = 1;
      ruler_state_set(ruler_info, RULER_STATE_DRAG);

      /* find the factor */
      {
        float co_ss[2][2];
        float fac;

        ED_view3d_project_float_global(
            region, ruler_item_pick->co[0], co_ss[0], V3D_PROJ_TEST_NOP);
        ED_view3d_project_float_global(
            region, ruler_item_pick->co[2], co_ss[1], V3D_PROJ_TEST_NOP);

        fac = line_point_factor_v2(mval_fl, co_ss[0], co_ss[1]);
        CLAMP(fac, 0.0f, 1.0f);

        interp_v3_v3v3(
            ruler_item_pick->co[1], ruler_item_pick->co[0], ruler_item_pick->co[2], fac);
      }

      /* update the new location */
      struct Depsgraph *depsgraph = CTX_data_ensure_evaluated_depsgraph(C);
      view3d_ruler_item_mousemove(C,
                                  depsgraph,
                                  ruler_info,
                                  ruler_item_pick,
                                  event->mval,
                                  false
#ifndef USE_SNAP_DETECT_FROM_KEYMAP_HACK
                                  ,
                                  false
#endif
      );
    }
  }
  else {
    inter->co_index = gz->highlight_part;
    ruler_state_set(ruler_info, RULER_STATE_DRAG);

    /* store the initial depth */
    copy_v3_v3(inter->drag_start_co, ruler_item_pick->co[inter->co_index]);
  }

  if (inter->co_index == 1) {
    ruler_item_pick->flag |= RULERITEM_USE_ANGLE_ACTIVE;
  }
  else {
    ruler_item_pick->flag &= ~RULERITEM_USE_ANGLE_ACTIVE;
  }

  {
    /* Set Snap prev point. */
    float *prev_point;
    if (ruler_item_pick->flag & RULERITEM_USE_ANGLE) {
      prev_point = (inter->co_index != 1) ? ruler_item_pick->co[1] : NULL;
    }
    else if (inter->co_index == 0) {
      prev_point = ruler_item_pick->co[2];
    }
    else {
      prev_point = ruler_item_pick->co[0];
    }

    if (prev_point) {
      RNA_property_float_set_array(
          ruler_info->snap_data.gizmo->ptr, ruler_info->snap_data.prop_prevpoint, prev_point);
    }
    else {
      RNA_property_unset(ruler_info->snap_data.gizmo->ptr, ruler_info->snap_data.prop_prevpoint);
    }
  }

  ruler_info->item_active = ruler_item_pick;

  return OPERATOR_RUNNING_MODAL;
}

static void gizmo_ruler_exit(bContext *C, wmGizmo *gz, const bool cancel)
{
  wmGizmoGroup *gzgroup = gz->parent_gzgroup;
  RulerInfo *ruler_info = gzgroup->customdata;

  if (!cancel) {
    if (ruler_info->state == RULER_STATE_DRAG) {
      RNA_property_unset(ruler_info->snap_data.gizmo->ptr, ruler_info->snap_data.prop_prevpoint);
      ruler_state_set(ruler_info, RULER_STATE_NORMAL);
    }
    /* We could convert only the current gizmo, for now just re-generate. */
    view3d_ruler_to_gpencil(C, gzgroup);
  }

  MEM_SAFE_FREE(gz->interaction_data);

  ruler_state_set(ruler_info, RULER_STATE_NORMAL);
}

static int gizmo_ruler_cursor_get(wmGizmo *gz)
{
  if (gz->highlight_part == PART_LINE) {
    return WM_CURSOR_CROSS;
  }
  return WM_CURSOR_NSEW_SCROLL;
}

void VIEW3D_GT_ruler_item(wmGizmoType *gzt)
{
  /* identifiers */
  gzt->idname = "VIEW3D_GT_ruler_item";

  /* api callbacks */
  gzt->draw = gizmo_ruler_draw;
  gzt->test_select = gizmo_ruler_test_select;
  gzt->modal = gizmo_ruler_modal;
  gzt->invoke = gizmo_ruler_invoke;
  gzt->exit = gizmo_ruler_exit;
  gzt->cursor_get = gizmo_ruler_cursor_get;

  gzt->struct_size = sizeof(RulerItem);
}

/** \} */

/* -------------------------------------------------------------------- */
/** \name Ruler Gizmo Group
 * \{ */

static void WIDGETGROUP_ruler_setup(const bContext *C, wmGizmoGroup *gzgroup)
{
  RulerInfo *ruler_info = MEM_callocN(sizeof(RulerInfo), __func__);

  wmGizmo *gizmo;
  {
    /* The gizmo snap has to be the first gizmo. */
    const wmGizmoType *gzt_snap;
    gzt_snap = WM_gizmotype_find("GIZMO_GT_snap_3d", true);
    gizmo = WM_gizmo_new_ptr(gzt_snap, gzgroup, NULL);

    RNA_enum_set(gizmo->ptr, "snap_elements_force", SCE_SNAP_MODE_GEOM);
    ED_gizmotypes_snap_3d_flag_set(gizmo, V3D_SNAPCURSOR_SNAP_EDIT_GEOM_CAGE);
    WM_gizmo_set_color(gizmo, (float[4]){1.0f, 1.0f, 1.0f, 1.0f});

    wmOperatorType *ot = WM_operatortype_find("VIEW3D_OT_ruler_add", true);
    WM_gizmo_operator_set(gizmo, 0, ot, NULL);
  }

  if (view3d_ruler_from_gpencil(C, gzgroup)) {
    /* nop */
  }

  wmWindowManager *wm = CTX_wm_manager(C);
  wmWindow *win = CTX_wm_window(C);
  ScrArea *area = CTX_wm_area(C);
  ARegion *region = CTX_wm_region(C);

  ruler_info->wm = wm;
  ruler_info->win = win;
  ruler_info->area = area;
  ruler_info->region = region;
  ruler_info->snap_data.gizmo = gizmo;
  ruler_info->snap_data.prop_prevpoint = RNA_struct_find_property(gizmo->ptr, "prev_point");

  gzgroup->customdata = ruler_info;
}

void VIEW3D_GGT_ruler(wmGizmoGroupType *gzgt)
{
  gzgt->name = "Ruler Widgets";
  gzgt->idname = view3d_gzgt_ruler_id;

  gzgt->flag |= WM_GIZMOGROUPTYPE_3D | WM_GIZMOGROUPTYPE_SCALE | WM_GIZMOGROUPTYPE_DRAW_MODAL_ALL;

  gzgt->gzmap_params.spaceid = SPACE_VIEW3D;
  gzgt->gzmap_params.regionid = RGN_TYPE_WINDOW;

  gzgt->poll = ED_gizmo_poll_or_unlink_delayed_from_tool;
  gzgt->setup = WIDGETGROUP_ruler_setup;
}

/** \} */

/* -------------------------------------------------------------------- */
/** \name Add Ruler Operator
 * \{ */

static bool view3d_ruler_poll(bContext *C)
{
  bToolRef_Runtime *tref_rt = WM_toolsystem_runtime_from_context((bContext *)C);
  if ((tref_rt == NULL) || !STREQ(view3d_gzgt_ruler_id, tref_rt->gizmo_group) ||
      CTX_wm_region_view3d(C) == NULL) {
    return false;
  }
  return true;
}

static int view3d_ruler_add_invoke(bContext *C, wmOperator *op, const wmEvent *event)
{
  ARegion *region = CTX_wm_region(C);
  View3D *v3d = CTX_wm_view3d(C);
  RegionView3D *rv3d = region->regiondata;

  if (v3d->gizmo_flag & (V3D_GIZMO_HIDE | V3D_GIZMO_HIDE_TOOL)) {
    BKE_report(op->reports, RPT_WARNING, "Gizmos hidden in this view");
    return OPERATOR_CANCELLED;
  }

  wmGizmoMap *gzmap = region->gizmo_map;
  wmGizmoGroup *gzgroup = WM_gizmomap_group_find(gzmap, view3d_gzgt_ruler_id);
  const bool use_depth = (v3d->shading.type >= OB_SOLID);

  if (!gizmo_ruler_check_for_operator(gzgroup)) {
    return OPERATOR_CANCELLED;
  }

  int mval[2];
  WM_event_drag_start_mval(event, region, mval);

  /* Create new line */
  RulerItem *ruler_item;
  ruler_item = ruler_item_add(gzgroup);

  /* This is a little weak, but there is no real good way to tweak directly. */
  WM_gizmo_highlight_set(gzmap, &ruler_item->gz);
  if (WM_operator_name_call(
          C, "GIZMOGROUP_OT_gizmo_tweak", WM_OP_INVOKE_REGION_WIN, NULL, event) ==
      OPERATOR_RUNNING_MODAL) {
    RulerInfo *ruler_info = gzgroup->customdata;
    RulerInteraction *inter = ruler_item->gz.interaction_data;
    if (use_depth) {
      struct Depsgraph *depsgraph = CTX_data_ensure_evaluated_depsgraph(C);
      /* snap the first point added, not essential but handy */
      inter->co_index = 0;
      view3d_ruler_item_mousemove(C,
                                  depsgraph,
                                  ruler_info,
                                  ruler_item,
                                  mval,
                                  false
#ifndef USE_SNAP_DETECT_FROM_KEYMAP_HACK
                                  ,
                                  true
#endif
      );
      copy_v3_v3(inter->drag_start_co, ruler_item->co[inter->co_index]);
      RNA_property_float_set_array(ruler_info->snap_data.gizmo->ptr,
                                   ruler_info->snap_data.prop_prevpoint,
                                   inter->drag_start_co);
    }
    else {
      negate_v3_v3(inter->drag_start_co, rv3d->ofs);
      copy_v3_v3(ruler_item->co[0], inter->drag_start_co);
      view3d_ruler_item_project(ruler_info, ruler_item->co[0], mval);
    }

    copy_v3_v3(ruler_item->co[2], ruler_item->co[0]);
    ruler_item->gz.highlight_part = inter->co_index = 2;
  }
  return OPERATOR_FINISHED;
}

void VIEW3D_OT_ruler_add(wmOperatorType *ot)
{
  /* identifiers */
  ot->name = "Ruler Add";
  ot->idname = "VIEW3D_OT_ruler_add";
  ot->description = "Add ruler";

  ot->invoke = view3d_ruler_add_invoke;
  ot->poll = view3d_ruler_poll;

  /* flags */
  ot->flag = OPTYPE_UNDO | OPTYPE_INTERNAL;
}

/** \} */

/* -------------------------------------------------------------------- */
/** \name Remove Ruler Operator
 * \{ */

static int view3d_ruler_remove_invoke(bContext *C, wmOperator *op, const wmEvent *UNUSED(event))
{
  ARegion *region = CTX_wm_region(C);
  View3D *v3d = CTX_wm_view3d(C);

  if (v3d->gizmo_flag & (V3D_GIZMO_HIDE | V3D_GIZMO_HIDE_TOOL)) {
    BKE_report(op->reports, RPT_WARNING, "Gizmos hidden in this view");
    return OPERATOR_CANCELLED;
  }

  wmGizmoMap *gzmap = region->gizmo_map;
  wmGizmoGroup *gzgroup = WM_gizmomap_group_find(gzmap, view3d_gzgt_ruler_id);
  if (gzgroup) {
    if (!gizmo_ruler_check_for_operator(gzgroup)) {
      return OPERATOR_CANCELLED;
    }
    RulerInfo *ruler_info = gzgroup->customdata;
    if (ruler_info->item_active) {
      RulerItem *ruler_item = ruler_info->item_active;
      if ((ruler_item->flag & RULERITEM_USE_ANGLE) &&
          (ruler_item->flag & RULERITEM_USE_ANGLE_ACTIVE)) {
        ruler_item->flag &= ~(RULERITEM_USE_ANGLE | RULERITEM_USE_ANGLE_ACTIVE);
      }
      else {
        ruler_item_remove(C, gzgroup, ruler_item);
      }

      /* Update the annotation layer. */
      view3d_ruler_to_gpencil(C, gzgroup);

      ED_region_tag_redraw_editor_overlays(region);
      return OPERATOR_FINISHED;
    }
  }
  return OPERATOR_PASS_THROUGH;
}

void VIEW3D_OT_ruler_remove(wmOperatorType *ot)
{
  /* identifiers */
  ot->name = "Ruler Remove";
  ot->idname = "VIEW3D_OT_ruler_remove";

  ot->invoke = view3d_ruler_remove_invoke;
  ot->poll = view3d_ruler_poll;

  /* flags */
  ot->flag = OPTYPE_UNDO | OPTYPE_INTERNAL;
}

/** \} */