/*
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 *
 * The Original Code is Copyright (C) 2001-2002 by NaN Holding BV.
 * All rights reserved.
 */

/** \file
 * \ingroup edtransform
 */

#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "DNA_object_types.h"
#include "DNA_scene_types.h"
#include "DNA_screen_types.h"
#include "DNA_space_types.h"
#include "DNA_view3d_types.h"

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

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

#include "BKE_context.h"

#include "ED_view3d.h"

#include "BLT_translation.h"

#include "UI_resources.h"

#include "transform.h"
#include "transform_snap.h"

/* Own include. */
#include "transform_constraints.h"

static void drawObjectConstraint(TransInfo *t);

/* ************************** CONSTRAINTS ************************* */
static void constraintValuesFinal(TransInfo *t, float vec[3])
{
  int mode = t->con.mode;
  if (mode & CON_APPLY) {
    float nval = (t->flag & T_NULL_ONE) ? 1.0f : 0.0f;

    if ((mode & CON_AXIS0) == 0) {
      vec[0] = nval;
    }
    if ((mode & CON_AXIS1) == 0) {
      vec[1] = nval;
    }
    if ((mode & CON_AXIS2) == 0) {
      vec[2] = nval;
    }
  }
}

void constraintNumInput(TransInfo *t, float vec[3])
{
  int mode = t->con.mode;
  if (mode & CON_APPLY) {
    float nval = (t->flag & T_NULL_ONE) ? 1.0f : 0.0f;

    const int dims = getConstraintSpaceDimension(t);
    if (dims == 2) {
      int axis = mode & (CON_AXIS0 | CON_AXIS1 | CON_AXIS2);
      if (axis == (CON_AXIS0 | CON_AXIS1)) {
        /* vec[0] = vec[0]; */ /* same */
        /* vec[1] = vec[1]; */ /* same */
        vec[2] = nval;
      }
      else if (axis == (CON_AXIS1 | CON_AXIS2)) {
        vec[2] = vec[1];
        vec[1] = vec[0];
        vec[0] = nval;
      }
      else if (axis == (CON_AXIS0 | CON_AXIS2)) {
        /* vec[0] = vec[0]; */ /* same */
        vec[2] = vec[1];
        vec[1] = nval;
      }
    }
    else if (dims == 1) {
      if (mode & CON_AXIS0) {
        /* vec[0] = vec[0]; */ /* same */
        vec[1] = nval;
        vec[2] = nval;
      }
      else if (mode & CON_AXIS1) {
        vec[1] = vec[0];
        vec[0] = nval;
        vec[2] = nval;
      }
      else if (mode & CON_AXIS2) {
        vec[2] = vec[0];
        vec[0] = nval;
        vec[1] = nval;
      }
    }
  }
}

static void postConstraintChecks(TransInfo *t, float vec[3], float pvec[3])
{
  int i = 0;

  mul_m3_v3(t->con.imtx, vec);

  snapGridIncrement(t, vec);

  if (t->flag & T_NULL_ONE) {
    if (!(t->con.mode & CON_AXIS0)) {
      vec[0] = 1.0f;
    }

    if (!(t->con.mode & CON_AXIS1)) {
      vec[1] = 1.0f;
    }

    if (!(t->con.mode & CON_AXIS2)) {
      vec[2] = 1.0f;
    }
  }

  if (applyNumInput(&t->num, vec)) {
    constraintNumInput(t, vec);
    removeAspectRatio(t, vec);
  }

  /* If `t->values` is operator param, use that directly but not if snapping is forced */
  if (t->flag & T_INPUT_IS_VALUES_FINAL && (t->tsnap.status & SNAP_FORCED) == 0) {
    copy_v3_v3(vec, t->values);
    constraintValuesFinal(t, vec);
    /* inverse transformation at the end */
  }

  if (t->con.mode & CON_AXIS0) {
    pvec[i++] = vec[0];
  }
  if (t->con.mode & CON_AXIS1) {
    pvec[i++] = vec[1];
  }
  if (t->con.mode & CON_AXIS2) {
    pvec[i++] = vec[2];
  }

  mul_m3_v3(t->con.mtx, vec);
}

static void viewAxisCorrectCenter(const TransInfo *t, float t_con_center[3])
{
  if (t->spacetype == SPACE_VIEW3D) {
    // View3D *v3d = t->area->spacedata.first;
    const float min_dist = 1.0f; /* v3d->clip_start; */
    float dir[3];
    float l;

    sub_v3_v3v3(dir, t_con_center, t->viewinv[3]);
    if (dot_v3v3(dir, t->viewinv[2]) < 0.0f) {
      negate_v3(dir);
    }
    project_v3_v3v3(dir, dir, t->viewinv[2]);

    l = len_v3(dir);

    if (l < min_dist) {
      float diff[3];
      normalize_v3_v3_length(diff, t->viewinv[2], min_dist - l);
      sub_v3_v3(t_con_center, diff);
    }
  }
}

/**
 * Axis calculation taking the view into account, correcting view-aligned axis.
 */
static void axisProjection(const TransInfo *t,
                           const float axis[3],
                           const float in[3],
                           float out[3])
{
  float norm[3], vec[3], factor, angle;
  float t_con_center[3];

  if (is_zero_v3(in)) {
    return;
  }

  copy_v3_v3(t_con_center, t->center_global);

  /* checks for center being too close to the view center */
  viewAxisCorrectCenter(t, t_con_center);

  angle = fabsf(angle_v3v3(axis, t->viewinv[2]));
  if (angle > (float)M_PI_2) {
    angle = (float)M_PI - angle;
  }

  /* For when view is parallel to constraint... will cause NaNs otherwise
   * So we take vertical motion in 3D space and apply it to the
   * constraint axis. Nice for camera grab + MMB */
  if (angle < DEG2RADF(5.0f)) {
    project_v3_v3v3(vec, in, t->viewinv[1]);
    factor = dot_v3v3(t->viewinv[1], vec) * 2.0f;
    /* Since camera distance is quite relative, use quadratic relationship.
     * holding shift can compensate. */
    if (factor < 0.0f) {
      factor *= -factor;
    }
    else {
      factor *= factor;
    }

    /* -factor makes move down going backwards */
    normalize_v3_v3_length(out, axis, -factor);
  }
  else {
    float v[3];
    float norm_center[3];
    float plane[3];

    getViewVector(t, t_con_center, norm_center);
    cross_v3_v3v3(plane, norm_center, axis);

    project_v3_v3v3(vec, in, plane);
    sub_v3_v3v3(vec, in, vec);

    add_v3_v3v3(v, vec, t_con_center);
    getViewVector(t, v, norm);

    /* give arbitrary large value if projection is impossible */
    factor = dot_v3v3(axis, norm);
    if (1.0f - fabsf(factor) < 0.0002f) {
      copy_v3_v3(out, axis);
      if (factor > 0) {
        mul_v3_fl(out, 1000000000.0f);
      }
      else {
        mul_v3_fl(out, -1000000000.0f);
      }
    }
    else {
      /* Use ray-ray intersection instead of line-line because this gave
       * precision issues adding small values to large numbers. */
      float mul;
      if (isect_ray_ray_v3(t_con_center, axis, v, norm, &mul, NULL)) {
        mul_v3_v3fl(out, axis, mul);
      }
      else {
        /* In practice this should never fail. */
        BLI_assert(0);
      }

      /* possible some values become nan when
       * viewpoint and object are both zero */
      if (!isfinite(out[0])) {
        out[0] = 0.0f;
      }
      if (!isfinite(out[1])) {
        out[1] = 0.0f;
      }
      if (!isfinite(out[2])) {
        out[2] = 0.0f;
      }
    }
  }
}

/**
 * Return true if the 2x axis are both aligned when projected into the view.
 * In this case, we can't usefully project the cursor onto the plane.
 */
static bool isPlaneProjectionViewAligned(const TransInfo *t)
{
  const float eps = 0.001f;
  const float *constraint_vector[2];
  int n = 0;
  for (int i = 0; i < 3; i++) {
    if (t->con.mode & (CON_AXIS0 << i)) {
      constraint_vector[n++] = t->con.mtx[i];
      if (n == 2) {
        break;
      }
    }
  }
  BLI_assert(n == 2);

  float view_to_plane[3], plane_normal[3];

  getViewVector(t, t->center_global, view_to_plane);

  cross_v3_v3v3(plane_normal, constraint_vector[0], constraint_vector[1]);
  normalize_v3(plane_normal);

  float factor = dot_v3v3(plane_normal, view_to_plane);
  return fabsf(factor) < eps;
}

static void planeProjection(const TransInfo *t, const float in[3], float out[3])
{
  float vec[3], factor, norm[3];

  add_v3_v3v3(vec, in, t->center_global);
  getViewVector(t, vec, norm);

  sub_v3_v3v3(vec, out, in);

  factor = dot_v3v3(vec, norm);
  if (factor == 0.0f) {
    return; /* prevent divide by zero */
  }
  factor = dot_v3v3(vec, vec) / factor;

  copy_v3_v3(vec, norm);
  mul_v3_fl(vec, factor);

  add_v3_v3v3(out, in, vec);
}

/*
 * Generic callback for constant spatial constraints applied to linear motion
 *
 * The IN vector in projected into the constrained space and then further
 * projected along the view vector.
 * (in perspective mode, the view vector is relative to the position on screen)
 */

static void applyAxisConstraintVec(TransInfo *t,
                                   TransDataContainer *UNUSED(tc),
                                   TransData *td,
                                   const float in[3],
                                   float out[3],
                                   float pvec[3])
{
  copy_v3_v3(out, in);
  if (!td && t->con.mode & CON_APPLY) {
    mul_m3_v3(t->con.pmtx, out);

    // With snap, a projection is alright, no need to correct for view alignment
    if (!validSnap(t)) {
      const int dims = getConstraintSpaceDimension(t);
      if (dims == 2) {
        if (!is_zero_v3(out)) {
          if (!isPlaneProjectionViewAligned(t)) {
            planeProjection(t, in, out);
          }
        }
      }
      else if (dims == 1) {
        float c[3];

        if (t->con.mode & CON_AXIS0) {
          copy_v3_v3(c, t->con.mtx[0]);
        }
        else if (t->con.mode & CON_AXIS1) {
          copy_v3_v3(c, t->con.mtx[1]);
        }
        else if (t->con.mode & CON_AXIS2) {
          copy_v3_v3(c, t->con.mtx[2]);
        }
        axisProjection(t, c, in, out);
      }
    }
    postConstraintChecks(t, out, pvec);
  }
}

/*
 * Generic callback for object based spatial constraints applied to linear motion
 *
 * At first, the following is applied to the first data in the array
 * The IN vector in projected into the constrained space and then further
 * projected along the view vector.
 * (in perspective mode, the view vector is relative to the position on screen)
 *
 * Further down, that vector is mapped to each data's space.
 */

static void applyObjectConstraintVec(TransInfo *t,
                                     TransDataContainer *tc,
                                     TransData *td,
                                     const float in[3],
                                     float out[3],
                                     float pvec[3])
{
  copy_v3_v3(out, in);
  if (t->con.mode & CON_APPLY) {
    if (!td) {
      mul_m3_v3(t->con.pmtx, out);

      const int dims = getConstraintSpaceDimension(t);
      if (dims == 2) {
        if (!is_zero_v3(out)) {
          if (!isPlaneProjectionViewAligned(t)) {
            planeProjection(t, in, out);
          }
        }
      }
      else if (dims == 1) {
        float c[3];

        if (t->con.mode & CON_AXIS0) {
          copy_v3_v3(c, t->con.mtx[0]);
        }
        else if (t->con.mode & CON_AXIS1) {
          copy_v3_v3(c, t->con.mtx[1]);
        }
        else if (t->con.mode & CON_AXIS2) {
          copy_v3_v3(c, t->con.mtx[2]);
        }
        axisProjection(t, c, in, out);
      }
      postConstraintChecks(t, out, pvec);
      copy_v3_v3(out, pvec);
    }
    else {
      int i = 0;

      out[0] = out[1] = out[2] = 0.0f;
      if (t->con.mode & CON_AXIS0) {
        out[0] = in[i++];
      }
      if (t->con.mode & CON_AXIS1) {
        out[1] = in[i++];
      }
      if (t->con.mode & CON_AXIS2) {
        out[2] = in[i++];
      }

      mul_m3_v3(td->axismtx, out);
      if (t->flag & T_EDIT) {
        mul_m3_v3(tc->mat3_unit, out);
      }
    }
  }
}

/*
 * Generic callback for constant spatial constraints applied to resize motion
 */

static void applyAxisConstraintSize(TransInfo *t,
                                    TransDataContainer *UNUSED(tc),
                                    TransData *td,
                                    float smat[3][3])
{
  if (!td && t->con.mode & CON_APPLY) {
    float tmat[3][3];

    if (!(t->con.mode & CON_AXIS0)) {
      smat[0][0] = 1.0f;
    }
    if (!(t->con.mode & CON_AXIS1)) {
      smat[1][1] = 1.0f;
    }
    if (!(t->con.mode & CON_AXIS2)) {
      smat[2][2] = 1.0f;
    }

    mul_m3_m3m3(tmat, smat, t->con.imtx);
    mul_m3_m3m3(smat, t->con.mtx, tmat);
  }
}

/*
 * Callback for object based spatial constraints applied to resize motion
 */

static void applyObjectConstraintSize(TransInfo *t,
                                      TransDataContainer *tc,
                                      TransData *td,
                                      float smat[3][3])
{
  if (td && t->con.mode & CON_APPLY) {
    float tmat[3][3];
    float imat[3][3];

    invert_m3_m3(imat, td->axismtx);

    if (!(t->con.mode & CON_AXIS0)) {
      smat[0][0] = 1.0f;
    }
    if (!(t->con.mode & CON_AXIS1)) {
      smat[1][1] = 1.0f;
    }
    if (!(t->con.mode & CON_AXIS2)) {
      smat[2][2] = 1.0f;
    }

    mul_m3_m3m3(tmat, smat, imat);
    if (t->flag & T_EDIT) {
      mul_m3_m3m3(smat, tc->mat3_unit, smat);
    }
    mul_m3_m3m3(smat, td->axismtx, tmat);
  }
}

/*
 * Generic callback for constant spatial constraints applied to rotations
 *
 * The rotation axis is copied into VEC.
 *
 * In the case of single axis constraints, the rotation axis is directly the one constrained to.
 * For planar constraints (2 axis), the rotation axis is the normal of the plane.
 *
 * The following only applies when CON_NOFLIP is not set.
 * The vector is then modified to always point away from the screen (in global space)
 * This insures that the rotation is always logically following the mouse.
 * (ie: not doing counterclockwise rotations when the mouse moves clockwise).
 */

static void applyAxisConstraintRot(
    TransInfo *t, TransDataContainer *UNUSED(tc), TransData *td, float vec[3], float *angle)
{
  if (!td && t->con.mode & CON_APPLY) {
    int mode = t->con.mode & (CON_AXIS0 | CON_AXIS1 | CON_AXIS2);

    switch (mode) {
      case CON_AXIS0:
      case (CON_AXIS1 | CON_AXIS2):
        copy_v3_v3(vec, t->con.mtx[0]);
        break;
      case CON_AXIS1:
      case (CON_AXIS0 | CON_AXIS2):
        copy_v3_v3(vec, t->con.mtx[1]);
        break;
      case CON_AXIS2:
      case (CON_AXIS0 | CON_AXIS1):
        copy_v3_v3(vec, t->con.mtx[2]);
        break;
    }
    /* don't flip axis if asked to or if num input */
    if (angle && (mode & CON_NOFLIP) == 0 && hasNumInput(&t->num) == 0) {
      if (dot_v3v3(vec, t->viewinv[2]) > 0.0f) {
        *angle = -(*angle);
      }
    }
  }
}

/*
 * Callback for object based spatial constraints applied to rotations
 *
 * The rotation axis is copied into VEC.
 *
 * In the case of single axis constraints, the rotation axis is directly the one constrained to.
 * For planar constraints (2 axis), the rotation axis is the normal of the plane.
 *
 * The following only applies when CON_NOFLIP is not set.
 * The vector is then modified to always point away from the screen (in global space)
 * This insures that the rotation is always logically following the mouse.
 * (ie: not doing counterclockwise rotations when the mouse moves clockwise).
 */

static void applyObjectConstraintRot(
    TransInfo *t, TransDataContainer *tc, TransData *td, float vec[3], float *angle)
{
  if (t->con.mode & CON_APPLY) {
    int mode = t->con.mode & (CON_AXIS0 | CON_AXIS1 | CON_AXIS2);
    float tmp_axismtx[3][3];
    float(*axismtx)[3];

    /* on setup call, use first object */
    if (td == NULL) {
      BLI_assert(tc == NULL);
      tc = TRANS_DATA_CONTAINER_FIRST_OK(t);
      td = tc->data;
    }

    if (t->flag & T_EDIT) {
      mul_m3_m3m3(tmp_axismtx, tc->mat3_unit, td->axismtx);
      axismtx = tmp_axismtx;
    }
    else {
      axismtx = td->axismtx;
    }

    switch (mode) {
      case CON_AXIS0:
      case (CON_AXIS1 | CON_AXIS2):
        copy_v3_v3(vec, axismtx[0]);
        break;
      case CON_AXIS1:
      case (CON_AXIS0 | CON_AXIS2):
        copy_v3_v3(vec, axismtx[1]);
        break;
      case CON_AXIS2:
      case (CON_AXIS0 | CON_AXIS1):
        copy_v3_v3(vec, axismtx[2]);
        break;
    }
    if (angle && (mode & CON_NOFLIP) == 0 && hasNumInput(&t->num) == 0) {
      if (dot_v3v3(vec, t->viewinv[2]) > 0.0f) {
        *angle = -(*angle);
      }
    }
  }
}

/*--------------------- INTERNAL SETUP CALLS ------------------*/

void setConstraint(TransInfo *t, float space[3][3], int mode, const char text[])
{
  BLI_strncpy(t->con.text + 1, text, sizeof(t->con.text) - 1);
  copy_m3_m3(t->con.mtx, space);
  t->con.mode = mode;
  getConstraintMatrix(t);

  startConstraint(t);

  t->con.drawExtra = NULL;
  t->con.applyVec = applyAxisConstraintVec;
  t->con.applySize = applyAxisConstraintSize;
  t->con.applyRot = applyAxisConstraintRot;
  t->redraw = TREDRAW_HARD;
}

/* applies individual td->axismtx constraints */
void setAxisMatrixConstraint(TransInfo *t, int mode, const char text[])
{
  TransDataContainer *tc = t->data_container;
  if (t->data_len_all == 1) {
    float axismtx[3][3];
    if (t->flag & T_EDIT) {
      mul_m3_m3m3(axismtx, tc->mat3_unit, tc->data->axismtx);
    }
    else {
      copy_m3_m3(axismtx, tc->data->axismtx);
    }

    setConstraint(t, axismtx, mode, text);
  }
  else {
    BLI_strncpy(t->con.text + 1, text, sizeof(t->con.text) - 1);
    copy_m3_m3(t->con.mtx, tc->data->axismtx);
    t->con.mode = mode;
    getConstraintMatrix(t);

    startConstraint(t);

    t->con.drawExtra = drawObjectConstraint;
    t->con.applyVec = applyObjectConstraintVec;
    t->con.applySize = applyObjectConstraintSize;
    t->con.applyRot = applyObjectConstraintRot;
    t->redraw = TREDRAW_HARD;
  }
}

void setLocalConstraint(TransInfo *t, int mode, const char text[])
{
  /* edit-mode now allows local transforms too */
  if (t->flag & T_EDIT) {
    /* Use the active (first) edit object. */
    TransDataContainer *tc = t->data_container;
    setConstraint(t, tc->mat3_unit, mode, text);
  }
  else {
    setAxisMatrixConstraint(t, mode, text);
  }
}

/*
 * Set the constraint according to the user defined orientation
 *
 * ftext is a format string passed to BLI_snprintf. It will add the name of
 * the orientation where %s is (logically).
 */
void setUserConstraint(TransInfo *t, short orientation, int mode, const char ftext[])
{
  char text[256];

  switch (orientation) {
    case V3D_ORIENT_GLOBAL: {
      float mtx[3][3];
      BLI_snprintf(text, sizeof(text), ftext, TIP_("global"));
      unit_m3(mtx);
      setConstraint(t, mtx, mode, text);
      break;
    }
    case V3D_ORIENT_LOCAL:
      BLI_snprintf(text, sizeof(text), ftext, TIP_("local"));
      setLocalConstraint(t, mode, text);
      break;
    case V3D_ORIENT_NORMAL:
      BLI_snprintf(text, sizeof(text), ftext, TIP_("normal"));
      if (checkUseAxisMatrix(t)) {
        setAxisMatrixConstraint(t, mode, text);
      }
      else {
        setConstraint(t, t->spacemtx, mode, text);
      }
      break;
    case V3D_ORIENT_VIEW:
      BLI_snprintf(text, sizeof(text), ftext, TIP_("view"));
      setConstraint(t, t->spacemtx, mode, text);
      break;
    case V3D_ORIENT_CURSOR:
      BLI_snprintf(text, sizeof(text), ftext, TIP_("cursor"));
      setConstraint(t, t->spacemtx, mode, text);
      break;
    case V3D_ORIENT_GIMBAL:
      BLI_snprintf(text, sizeof(text), ftext, TIP_("gimbal"));
      setConstraint(t, t->spacemtx, mode, text);
      break;
    case V3D_ORIENT_CUSTOM_MATRIX:
      BLI_snprintf(text, sizeof(text), ftext, TIP_("custom matrix"));
      setConstraint(t, t->spacemtx, mode, text);
      break;
    case V3D_ORIENT_CUSTOM: {
      char orientation_str[128];
      BLI_snprintf(orientation_str,
                   sizeof(orientation_str),
                   "%s \"%s\"",
                   TIP_("custom orientation"),
                   t->orientation.custom->name);
      BLI_snprintf(text, sizeof(text), ftext, orientation_str);
      setConstraint(t, t->spacemtx, mode, text);
      break;
    }
  }

  t->con.orientation = orientation;

  t->con.mode |= CON_USER;
}

/*----------------- DRAWING CONSTRAINTS -------------------*/

void drawConstraint(TransInfo *t)
{
  TransCon *tc = &(t->con);

  if (!ELEM(t->spacetype, SPACE_VIEW3D, SPACE_IMAGE, SPACE_NODE)) {
    return;
  }
  if (!(tc->mode & CON_APPLY)) {
    return;
  }
  if (t->flag & T_NO_CONSTRAINT) {
    return;
  }

  if (tc->drawExtra) {
    tc->drawExtra(t);
  }
  else {
    if (tc->mode & CON_SELECT) {
      float vec[3];
      int depth_test_enabled;

      convertViewVec(t, vec, (t->mval[0] - t->con.imval[0]), (t->mval[1] - t->con.imval[1]));
      add_v3_v3(vec, t->center_global);

      drawLine(t, t->center_global, tc->mtx[0], 'X', 0);
      drawLine(t, t->center_global, tc->mtx[1], 'Y', 0);
      drawLine(t, t->center_global, tc->mtx[2], 'Z', 0);

      depth_test_enabled = GPU_depth_test_enabled();
      if (depth_test_enabled) {
        GPU_depth_test(false);
      }

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

      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", 0); /* "simple" mode */
      immUniformColor4f(1.0f, 1.0f, 1.0f, 1.0f);
      immUniform1f("dash_width", 2.0f);
      immUniform1f("dash_factor", 0.5f);

      immBegin(GPU_PRIM_LINES, 2);
      immVertex3fv(shdr_pos, t->center_global);
      immVertex3fv(shdr_pos, vec);
      immEnd();

      immUnbindProgram();

      if (depth_test_enabled) {
        GPU_depth_test(true);
      }
    }

    if (tc->mode & CON_AXIS0) {
      drawLine(t, t->center_global, tc->mtx[0], 'X', DRAWLIGHT);
    }
    if (tc->mode & CON_AXIS1) {
      drawLine(t, t->center_global, tc->mtx[1], 'Y', DRAWLIGHT);
    }
    if (tc->mode & CON_AXIS2) {
      drawLine(t, t->center_global, tc->mtx[2], 'Z', DRAWLIGHT);
    }
  }
}

/* called from drawview.c, as an extra per-window draw option */
void drawPropCircle(const struct bContext *C, TransInfo *t)
{
  if (t->flag & T_PROP_EDIT) {
    RegionView3D *rv3d = CTX_wm_region_view3d(C);
    float tmat[4][4], imat[4][4];
    int depth_test_enabled;

    if (t->spacetype == SPACE_VIEW3D && rv3d != NULL) {
      copy_m4_m4(tmat, rv3d->viewmat);
      invert_m4_m4(imat, tmat);
    }
    else {
      unit_m4(tmat);
      unit_m4(imat);
    }

    GPU_matrix_push();

    if (t->spacetype == SPACE_VIEW3D) {
      /* pass */
    }
    else if (t->spacetype == SPACE_IMAGE) {
      GPU_matrix_scale_2f(1.0f / t->aspect[0], 1.0f / t->aspect[1]);
    }
    else if (ELEM(t->spacetype, SPACE_GRAPH, SPACE_ACTION)) {
      /* only scale y */
      rcti *mask = &t->region->v2d.mask;
      rctf *datamask = &t->region->v2d.cur;
      float xsize = BLI_rctf_size_x(datamask);
      float ysize = BLI_rctf_size_y(datamask);
      float xmask = BLI_rcti_size_x(mask);
      float ymask = BLI_rcti_size_y(mask);
      GPU_matrix_scale_2f(1.0f, (ysize / xsize) * (xmask / ymask));
    }

    depth_test_enabled = GPU_depth_test_enabled();
    if (depth_test_enabled) {
      GPU_depth_test(false);
    }

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

    immBindBuiltinProgram(GPU_SHADER_3D_UNIFORM_COLOR);
    immUniformThemeColor(TH_GRID);

    GPU_logic_op_invert_set(true);
    imm_drawcircball(t->center_global, t->prop_size, imat, pos);
    GPU_logic_op_invert_set(false);

    immUnbindProgram();

    if (depth_test_enabled) {
      GPU_depth_test(true);
    }

    GPU_matrix_pop();
  }
}

static void drawObjectConstraint(TransInfo *t)
{
  /* Draw the first one lighter because that's the one who controls the others.
   * Meaning the transformation is projected on that one and just copied on the others
   * constraint space.
   * In a nutshell, the object with light axis is controlled by the user and the others follow.
   * Without drawing the first light, users have little clue what they are doing.
   */
  short options = DRAWLIGHT;
  int i;
  float tmp_axismtx[3][3];

  FOREACH_TRANS_DATA_CONTAINER (t, tc) {
    TransData *td = tc->data;
    for (i = 0; i < tc->data_len; i++, td++) {
      float co[3];
      float(*axismtx)[3];

      if (t->flag & T_PROP_EDIT) {
        /* we're sorted, so skip the rest */
        if (td->factor == 0.0f) {
          break;
        }
      }

      if (t->options & CTX_GPENCIL_STROKES) {
        /* only draw a constraint line for one point, otherwise we can't see anything */
        if ((options & DRAWLIGHT) == 0) {
          break;
        }
      }

      if (t->flag & T_OBJECT) {
        copy_v3_v3(co, td->ob->obmat[3]);
        axismtx = td->axismtx;
      }
      else if (t->flag & T_EDIT) {
        mul_v3_m4v3(co, tc->mat, td->center);

        mul_m3_m3m3(tmp_axismtx, tc->mat3_unit, td->axismtx);
        axismtx = tmp_axismtx;
      }
      else if (t->flag & T_POSE) {
        mul_v3_m4v3(co, tc->mat, td->center);
        axismtx = td->axismtx;
      }
      else {
        copy_v3_v3(co, td->center);
        axismtx = td->axismtx;
      }

      if (t->con.mode & CON_AXIS0) {
        drawLine(t, co, axismtx[0], 'X', options);
      }
      if (t->con.mode & CON_AXIS1) {
        drawLine(t, co, axismtx[1], 'Y', options);
      }
      if (t->con.mode & CON_AXIS2) {
        drawLine(t, co, axismtx[2], 'Z', options);
      }
      options &= ~DRAWLIGHT;
    }
  }
}

/*--------------------- START / STOP CONSTRAINTS ---------------------- */

void startConstraint(TransInfo *t)
{
  t->con.mode |= CON_APPLY;
  *t->con.text = ' ';
  t->num.idx_max = min_ii(getConstraintSpaceDimension(t) - 1, t->idx_max);
}

void stopConstraint(TransInfo *t)
{
  t->con.mode &= ~(CON_APPLY | CON_SELECT);
  *t->con.text = '\0';
  t->num.idx_max = t->idx_max;
}

void getConstraintMatrix(TransInfo *t)
{
  float mat[3][3];
  invert_m3_m3(t->con.imtx, t->con.mtx);
  unit_m3(t->con.pmtx);

  if (!(t->con.mode & CON_AXIS0)) {
    zero_v3(t->con.pmtx[0]);
  }

  if (!(t->con.mode & CON_AXIS1)) {
    zero_v3(t->con.pmtx[1]);
  }

  if (!(t->con.mode & CON_AXIS2)) {
    zero_v3(t->con.pmtx[2]);
  }

  mul_m3_m3m3(mat, t->con.pmtx, t->con.imtx);
  mul_m3_m3m3(t->con.pmtx, t->con.mtx, mat);
}

/*------------------------- MMB Select -------------------------------*/

void initSelectConstraint(TransInfo *t, float mtx[3][3])
{
  copy_m3_m3(t->con.mtx, mtx);
  t->con.mode |= CON_APPLY;
  t->con.mode |= CON_SELECT;

  setNearestAxis(t);
  t->con.drawExtra = NULL;
  t->con.applyVec = applyAxisConstraintVec;
  t->con.applySize = applyAxisConstraintSize;
  t->con.applyRot = applyAxisConstraintRot;
}

void selectConstraint(TransInfo *t)
{
  if (t->con.mode & CON_SELECT) {
    setNearestAxis(t);
    startConstraint(t);
  }
}

void postSelectConstraint(TransInfo *t)
{
  if (!(t->con.mode & CON_SELECT)) {
    return;
  }

  t->con.mode &= ~CON_AXIS0;
  t->con.mode &= ~CON_AXIS1;
  t->con.mode &= ~CON_AXIS2;
  t->con.mode &= ~CON_SELECT;

  setNearestAxis(t);

  startConstraint(t);
  t->redraw = TREDRAW_HARD;
}

static void setNearestAxis2d(TransInfo *t)
{
  /* no correction needed... just use whichever one is lower */
  if (abs(t->mval[0] - t->con.imval[0]) < abs(t->mval[1] - t->con.imval[1])) {
    t->con.mode |= CON_AXIS1;
    BLI_strncpy(t->con.text, TIP_(" along Y axis"), sizeof(t->con.text));
  }
  else {
    t->con.mode |= CON_AXIS0;
    BLI_strncpy(t->con.text, TIP_(" along X axis"), sizeof(t->con.text));
  }
}

static void setNearestAxis3d(TransInfo *t)
{
  float zfac;
  float mvec[3], proj[3];
  float len[3];
  int i;

  /* calculate mouse movement */
  mvec[0] = (float)(t->mval[0] - t->con.imval[0]);
  mvec[1] = (float)(t->mval[1] - t->con.imval[1]);
  mvec[2] = 0.0f;

  /* We need to correct axis length for the current zoom-level of view,
   * this to prevent projected values to be clipped behind the camera
   * and to overflow the short integers.
   * The formula used is a bit stupid, just a simplification of the subtraction
   * of two 2D points 30 pixels apart (that's the last factor in the formula) after
   * projecting them with ED_view3d_win_to_delta and then get the length of that vector.
   */
  zfac = mul_project_m4_v3_zfac(t->persmat, t->center_global);
  zfac = len_v3(t->persinv[0]) * 2.0f / t->region->winx * zfac * 30.0f;

  for (i = 0; i < 3; i++) {
    float axis[3], axis_2d[2];

    copy_v3_v3(axis, t->con.mtx[i]);

    mul_v3_fl(axis, zfac);
    /* now we can project to get window coordinate */
    add_v3_v3(axis, t->center_global);
    projectFloatView(t, axis, axis_2d);

    sub_v2_v2v2(axis, axis_2d, t->center2d);
    axis[2] = 0.0f;

    if (normalize_v3(axis) > 1e-3f) {
      project_v3_v3v3(proj, mvec, axis);
      sub_v3_v3v3(axis, mvec, proj);
      len[i] = normalize_v3(axis);
    }
    else {
      len[i] = 1e10f;
    }
  }

  if (len[0] <= len[1] && len[0] <= len[2]) {
    if (t->modifiers & MOD_CONSTRAINT_PLANE) {
      t->con.mode |= (CON_AXIS1 | CON_AXIS2);
      BLI_snprintf(t->con.text, sizeof(t->con.text), TIP_(" locking %s X axis"), t->spacename);
    }
    else {
      t->con.mode |= CON_AXIS0;
      BLI_snprintf(t->con.text, sizeof(t->con.text), TIP_(" along %s X axis"), t->spacename);
    }
  }
  else if (len[1] <= len[0] && len[1] <= len[2]) {
    if (t->modifiers & MOD_CONSTRAINT_PLANE) {
      t->con.mode |= (CON_AXIS0 | CON_AXIS2);
      BLI_snprintf(t->con.text, sizeof(t->con.text), TIP_(" locking %s Y axis"), t->spacename);
    }
    else {
      t->con.mode |= CON_AXIS1;
      BLI_snprintf(t->con.text, sizeof(t->con.text), TIP_(" along %s Y axis"), t->spacename);
    }
  }
  else if (len[2] <= len[1] && len[2] <= len[0]) {
    if (t->modifiers & MOD_CONSTRAINT_PLANE) {
      t->con.mode |= (CON_AXIS0 | CON_AXIS1);
      BLI_snprintf(t->con.text, sizeof(t->con.text), TIP_(" locking %s Z axis"), t->spacename);
    }
    else {
      t->con.mode |= CON_AXIS2;
      BLI_snprintf(t->con.text, sizeof(t->con.text), TIP_(" along %s Z axis"), t->spacename);
    }
  }
}

void setNearestAxis(TransInfo *t)
{
  /* clear any prior constraint flags */
  t->con.mode &= ~CON_AXIS0;
  t->con.mode &= ~CON_AXIS1;
  t->con.mode &= ~CON_AXIS2;

  /* constraint setting - depends on spacetype */
  if (t->spacetype == SPACE_VIEW3D) {
    /* 3d-view */
    setNearestAxis3d(t);
  }
  else {
    /* assume that this means a 2D-Editor */
    setNearestAxis2d(t);
  }

  getConstraintMatrix(t);
}

/*-------------- HELPER FUNCTIONS ----------------*/

int constraintModeToIndex(const TransInfo *t)
{
  if ((t->con.mode & CON_APPLY) == 0) {
    return -1;
  }
  switch (t->con.mode & (CON_AXIS0 | CON_AXIS1 | CON_AXIS2)) {
    case (CON_AXIS0):
    case (CON_AXIS1 | CON_AXIS2):
      return 0;
    case (CON_AXIS1):
    case (CON_AXIS0 | CON_AXIS2):
      return 1;
    case (CON_AXIS2):
    case (CON_AXIS0 | CON_AXIS1):
      return 2;
    default:
      return -1;
  }
}

char constraintModeToChar(const TransInfo *t)
{
  int index = constraintModeToIndex(t);
  if (index == -1) {
    return '\0';
  }
  BLI_assert((uint)index < 3);
  return 'X' + index;
}

bool isLockConstraint(TransInfo *t)
{
  int mode = t->con.mode;

  if ((mode & (CON_AXIS0 | CON_AXIS1)) == (CON_AXIS0 | CON_AXIS1)) {
    return true;
  }

  if ((mode & (CON_AXIS1 | CON_AXIS2)) == (CON_AXIS1 | CON_AXIS2)) {
    return true;
  }

  if ((mode & (CON_AXIS0 | CON_AXIS2)) == (CON_AXIS0 | CON_AXIS2)) {
    return true;
  }

  return false;
}

/*
 * Returns the dimension of the constraint space.
 *
 * For that reason, the flags always needs to be set to properly evaluate here,
 * even if they aren't actually used in the callback function. (Which could happen
 * for weird constraints not yet designed. Along a path for example.)
 */

int getConstraintSpaceDimension(TransInfo *t)
{
  int n = 0;

  if (t->con.mode & CON_AXIS0) {
    n++;
  }

  if (t->con.mode & CON_AXIS1) {
    n++;
  }

  if (t->con.mode & CON_AXIS2) {
    n++;
  }

  return n;
  /*
   * Someone willing to do it cryptically could do the following instead:
   *
   * return t->con & (CON_AXIS0|CON_AXIS1|CON_AXIS2);
   *
   * Based on the assumptions that the axis flags are one after the other and start at 1
   */
}
