/*
 * ***** BEGIN GPL LICENSE BLOCK *****
 *
 * 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) 2008, Blender Foundation
 * This is a new part of Blender
 *
 * Contributor(s): Joshua Leung, Antonio Vazquez
 *
 * ***** END GPL LICENSE BLOCK *****
 */

/** \file blender/editors/gpencil/drawgpencil.c
 *  \ingroup edgpencil
 */


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

#include "MEM_guardedalloc.h"

#include "BLI_sys_types.h"

#include "BLI_math.h"
#include "BLI_utildefines.h"
#include "BLI_polyfill_2d.h"

#include "BLF_api.h"
#include "BLT_translation.h"

#include "DNA_brush_types.h"
#include "DNA_gpencil_types.h"
#include "DNA_scene_types.h"
#include "DNA_screen_types.h"
#include "DNA_space_types.h"
#include "DNA_view3d_types.h"
#include "DNA_userdef_types.h"
#include "DNA_object_types.h"

#include "BKE_context.h"
#include "BKE_brush.h"
#include "BKE_global.h"
#include "BKE_paint.h"
#include "BKE_gpencil.h"
#include "BKE_image.h"

#include "DEG_depsgraph.h"

#include "WM_api.h"

#include "BIF_glutil.h"

#include "GPU_immediate.h"
#include "GPU_draw.h"
#include "GPU_state.h"

#include "ED_gpencil.h"
#include "ED_screen.h"
#include "ED_view3d.h"
#include "ED_space_api.h"

#include "UI_interface_icons.h"
#include "UI_resources.h"

#include "IMB_imbuf_types.h"

#include "gpencil_intern.h"

/* ************************************************** */
/* GREASE PENCIL DRAWING */

/* ----- General Defines ------ */
/* flags for sflag */
typedef enum eDrawStrokeFlags {
	/** don't draw status info */
	GP_DRAWDATA_NOSTATUS    = (1 << 0),
	/** only draw 3d-strokes */
	GP_DRAWDATA_ONLY3D      = (1 << 1),
	/** only draw 'canvas' strokes */
	GP_DRAWDATA_ONLYV2D     = (1 << 2),
	/** only draw 'image' strokes */
	GP_DRAWDATA_ONLYI2D     = (1 << 3),
	/** special hack for drawing strokes in Image Editor (weird coordinates) */
	GP_DRAWDATA_IEDITHACK   = (1 << 4),
	/** don't draw xray in 3D view (which is default) */
	GP_DRAWDATA_NO_XRAY     = (1 << 5),
	/** no onionskins should be drawn (for animation playback) */
	GP_DRAWDATA_NO_ONIONS   = (1 << 6),
	/** draw strokes as "volumetric" circular billboards */
	GP_DRAWDATA_VOLUMETRIC	= (1 << 7),
	/** fill insides/bounded-regions of strokes */
	GP_DRAWDATA_FILL        = (1 << 8),
} eDrawStrokeFlags;



/* thickness above which we should use special drawing */
#if 0
#define GP_DRAWTHICKNESS_SPECIAL    3
#endif

/* conversion utility (float --> normalized unsigned byte) */
#define F2UB(x) (uchar)(255.0f * x)

/* ----- Tool Buffer Drawing ------ */
/* helper functions to set color of buffer point */

static void gp_set_tpoint_varying_color(const tGPspoint *pt, const float ink[4], uint attr_id)
{
	float alpha = ink[3] * pt->strength;
	CLAMP(alpha, GPENCIL_STRENGTH_MIN, 1.0f);
	immAttr4ub(attr_id, F2UB(ink[0]), F2UB(ink[1]), F2UB(ink[2]), F2UB(alpha));
}

static void gp_set_point_uniform_color(const bGPDspoint *pt, const float ink[4])
{
	float alpha = ink[3] * pt->strength;
	CLAMP(alpha, GPENCIL_STRENGTH_MIN, 1.0f);
	immUniformColor3fvAlpha(ink, alpha);
}

static void gp_set_point_varying_color(const bGPDspoint *pt, const float ink[4], uint attr_id)
{
	float alpha = ink[3] * pt->strength;
	CLAMP(alpha, GPENCIL_STRENGTH_MIN, 1.0f);
	immAttr4ub(attr_id, F2UB(ink[0]), F2UB(ink[1]), F2UB(ink[2]), F2UB(alpha));
}

/* draw fills for buffer stroke */
static void gp_draw_stroke_buffer_fill(const tGPspoint *points, int totpoints, float ink[4])
{
	if (totpoints < 3) {
		return;
	}
	int tot_triangles = totpoints - 2;
	/* allocate memory for temporary areas */
	uint(*tmp_triangles)[3] = MEM_mallocN(sizeof(*tmp_triangles) * tot_triangles, "GP Stroke buffer temp triangulation");
	float(*points2d)[2] = MEM_mallocN(sizeof(*points2d) * totpoints, "GP Stroke buffer temp 2d points");

	/* Convert points to array and triangulate
	 * Here a cache is not used because while drawing the information changes all the time, so the cache
	 * would be recalculated constantly, so it is better to do direct calculation for each function call
	 */
	for (int i = 0; i < totpoints; i++) {
		const tGPspoint *pt = &points[i];
		points2d[i][0] = pt->x;
		points2d[i][1] = pt->y;
	}
	BLI_polyfill_calc((const float(*)[2])points2d, (uint)totpoints, 0, (uint(*)[3])tmp_triangles);

	/* draw triangulation data */
	if (tot_triangles > 0) {
		GPUVertFormat *format = immVertexFormat();
		uint pos = GPU_vertformat_attr_add(format, "pos", GPU_COMP_I32, 2, GPU_FETCH_INT_TO_FLOAT);
		uint color = GPU_vertformat_attr_add(format, "color", GPU_COMP_U8, 4, GPU_FETCH_INT_TO_FLOAT_UNIT);

		immBindBuiltinProgram(GPU_SHADER_2D_SMOOTH_COLOR);

		/* Draw all triangles for filling the polygon */
		immBegin(GPU_PRIM_TRIS, tot_triangles * 3);
		/* TODO: use batch instead of immediate mode, to share vertices */

		const tGPspoint *pt;
		for (int i = 0; i < tot_triangles; i++) {
			/* vertex 1 */
			pt = &points[tmp_triangles[i][0]];
			gp_set_tpoint_varying_color(pt, ink, color);
			immVertex2fv(pos, &pt->x);
			/* vertex 2 */
			pt = &points[tmp_triangles[i][1]];
			gp_set_tpoint_varying_color(pt, ink, color);
			immVertex2fv(pos, &pt->x);
			/* vertex 3 */
			pt = &points[tmp_triangles[i][2]];
			gp_set_tpoint_varying_color(pt, ink, color);
			immVertex2fv(pos, &pt->x);
		}

		immEnd();
		immUnbindProgram();
	}

	/* clear memory */
	if (tmp_triangles) {
		MEM_freeN(tmp_triangles);
	}
	if (points2d) {
		MEM_freeN(points2d);
	}
}

/* draw stroke defined in buffer (simple ogl lines/points for now, as dotted lines) */
static void gp_draw_stroke_buffer(
        const tGPspoint *points, int totpoints, short thickness,
        short dflag, short sflag, float ink[4], float fill_ink[4])
{
	int draw_points = 0;

	/* error checking */
	if ((points == NULL) || (totpoints <= 0))
		return;

	/* check if buffer can be drawn */
	if (dflag & (GP_DRAWDATA_ONLY3D | GP_DRAWDATA_ONLYV2D))
		return;

	if (sflag & GP_STROKE_ERASER) {
		/* don't draw stroke at all! */
		return;
	}

	GPUVertFormat *format = immVertexFormat();
	uint pos = GPU_vertformat_attr_add(format, "pos", GPU_COMP_F32, 2, GPU_FETCH_FLOAT);
	uint color = GPU_vertformat_attr_add(format, "color", GPU_COMP_U8, 4, GPU_FETCH_INT_TO_FLOAT_UNIT);

	const tGPspoint *pt = points;

	if (totpoints == 1) {
		/* if drawing a single point, draw it larger */
		GPU_point_size((float)(thickness + 2) * points->pressure);
		immBindBuiltinProgram(GPU_SHADER_3D_POINT_FIXED_SIZE_VARYING_COLOR);
		immBegin(GPU_PRIM_POINTS, 1);
		gp_set_tpoint_varying_color(pt, ink, color);
		immVertex2fv(pos, &pt->x);
	}
	else {
		float oldpressure = points[0].pressure;

		/* draw stroke curve */
		GPU_line_width(max_ff(oldpressure * thickness, 1.0));
		immBindBuiltinProgram(GPU_SHADER_2D_SMOOTH_COLOR);
		immBeginAtMost(GPU_PRIM_LINE_STRIP, totpoints);

		/* TODO: implement this with a geometry shader to draw one continuous tapered stroke */

		for (int i = 0; i < totpoints; i++, pt++) {
			/* if there was a significant pressure change, stop the curve, change the thickness of the stroke,
			 * and continue drawing again (since line-width cannot change in middle of GL_LINE_STRIP)
			 */
			if (fabsf(pt->pressure - oldpressure) > 0.2f) {
				/* need to have 2 points to avoid immEnd assert error */
				if (draw_points < 2) {
					gp_set_tpoint_varying_color(pt - 1, ink, color);
					immVertex2fv(pos, &(pt - 1)->x);
				}

				immEnd();
				draw_points = 0;

				GPU_line_width(max_ff(pt->pressure * thickness, 1.0f));
				immBeginAtMost(GPU_PRIM_LINE_STRIP, totpoints - i + 1);

				/* need to roll-back one point to ensure that there are no gaps in the stroke */
				if (i != 0) {
					gp_set_tpoint_varying_color(pt - 1, ink, color);
					immVertex2fv(pos, &(pt - 1)->x);
					draw_points++;
				}

				oldpressure = pt->pressure; /* reset our threshold */
			}

			/* now the point we want */
			gp_set_tpoint_varying_color(pt, ink, color);
			immVertex2fv(pos, &pt->x);
			draw_points++;
		}
		/* need to have 2 points to avoid immEnd assert error */
		if (draw_points < 2) {
			gp_set_tpoint_varying_color(pt - 1, ink, color);
			immVertex2fv(pos, &(pt - 1)->x);
		}
	}

	immEnd();
	immUnbindProgram();

	// draw fill
	if (fill_ink[3] > GPENCIL_ALPHA_OPACITY_THRESH) {
		gp_draw_stroke_buffer_fill(points, totpoints, fill_ink);
	}
}

/* --------- 2D Stroke Drawing Helpers --------- */
/* change in parameter list */
static void gp_calc_2d_stroke_fxy(const float pt[3], short sflag, int offsx, int offsy, int winx, int winy, float r_co[2])
{
	if (sflag & GP_STROKE_2DSPACE) {
		r_co[0] = pt[0];
		r_co[1] = pt[1];
	}
	else if (sflag & GP_STROKE_2DIMAGE) {
		const float x = (float)((pt[0] * winx) + offsx);
		const float y = (float)((pt[1] * winy) + offsy);

		r_co[0] = x;
		r_co[1] = y;
	}
	else {
		const float x = (float)(pt[0] / 100 * winx) + offsx;
		const float y = (float)(pt[1] / 100 * winy) + offsy;

		r_co[0] = x;
		r_co[1] = y;
	}
}
/* ----------- Volumetric Strokes --------------- */

/* draw a 2D buffer stroke in "volumetric" style
 * NOTE: the stroke buffer doesn't have any coordinate offsets/transforms
 */
static void gp_draw_stroke_volumetric_buffer(
        const tGPspoint *points, int totpoints, short thickness,
        short dflag, const float ink[4])
{
	/* error checking */
	if ((points == NULL) || (totpoints <= 0))
		return;

	/* check if buffer can be drawn */
	if (dflag & (GP_DRAWDATA_ONLY3D | GP_DRAWDATA_ONLYV2D))
		return;

	GPUVertFormat *format = immVertexFormat();
	uint pos = GPU_vertformat_attr_add(format, "pos", GPU_COMP_F32, 2, GPU_FETCH_FLOAT);
	uint size = GPU_vertformat_attr_add(format, "size", GPU_COMP_F32, 1, GPU_FETCH_FLOAT);
	uint color = GPU_vertformat_attr_add(format, "color", GPU_COMP_U8, 4, GPU_FETCH_INT_TO_FLOAT_UNIT);

	immBindBuiltinProgram(GPU_SHADER_3D_POINT_VARYING_SIZE_VARYING_COLOR);
	GPU_enable_program_point_size();
	immBegin(GPU_PRIM_POINTS, totpoints);

	const tGPspoint *pt = points;
	for (int i = 0; i < totpoints; i++, pt++) {
		gp_set_tpoint_varying_color(pt, ink, color);

		/* TODO: scale based on view transform (zoom level) */
		immAttr1f(size, pt->pressure * thickness);

		immVertex2f(pos, pt->x, pt->y);
	}

	immEnd();
	immUnbindProgram();
	GPU_disable_program_point_size();
}

/* draw a 2D strokes in "volumetric" style */
static void gp_draw_stroke_volumetric_2d(
        const bGPDspoint *points, int totpoints, short thickness,
        short UNUSED(dflag), short sflag,
        int offsx, int offsy, int winx, int winy,
        const float diff_mat[4][4], const float ink[4])
{
	GPUVertFormat *format = immVertexFormat();
	uint pos = GPU_vertformat_attr_add(format, "pos", GPU_COMP_F32, 2, GPU_FETCH_FLOAT);
	uint size = GPU_vertformat_attr_add(format, "size", GPU_COMP_F32, 1, GPU_FETCH_FLOAT);
	uint color = GPU_vertformat_attr_add(format, "color", GPU_COMP_U8, 4, GPU_FETCH_INT_TO_FLOAT_UNIT);

	immBindBuiltinProgram(GPU_SHADER_3D_POINT_VARYING_SIZE_VARYING_COLOR);
	GPU_enable_program_point_size();
	immBegin(GPU_PRIM_POINTS, totpoints);

	const bGPDspoint *pt = points;
	for (int i = 0; i < totpoints; i++, pt++) {
		/* transform position to 2D */
		float co[2];
		float fpt[3];

		mul_v3_m4v3(fpt, diff_mat, &pt->x);
		gp_calc_2d_stroke_fxy(fpt, sflag, offsx, offsy, winx, winy, co);

		gp_set_point_varying_color(pt, ink, color);
		immAttr1f(size, pt->pressure * thickness); /* TODO: scale based on view transform */
		immVertex2f(pos, co[0], co[1]);
	}

	immEnd();
	immUnbindProgram();
	GPU_disable_program_point_size();
}

/* draw a 3D stroke in "volumetric" style */
static void gp_draw_stroke_volumetric_3d(
        const bGPDspoint *points, int totpoints, short thickness,
        const float ink[4])
{
	GPUVertFormat *format = immVertexFormat();
	uint pos = GPU_vertformat_attr_add(format, "pos", GPU_COMP_F32, 3, GPU_FETCH_FLOAT);
	uint size = GPU_vertformat_attr_add(format, "size", GPU_COMP_F32, 1, GPU_FETCH_FLOAT);
	uint color = GPU_vertformat_attr_add(format, "color", GPU_COMP_U8, 4, GPU_FETCH_INT_TO_FLOAT_UNIT);

	immBindBuiltinProgram(GPU_SHADER_3D_POINT_VARYING_SIZE_VARYING_COLOR);
	GPU_enable_program_point_size();
	immBegin(GPU_PRIM_POINTS, totpoints);

	const bGPDspoint *pt = points;
	for (int i = 0; i < totpoints && pt; i++, pt++) {
		gp_set_point_varying_color(pt, ink, color);
		/* TODO: scale based on view transform */
		immAttr1f(size, pt->pressure * thickness);
		/* we can adjust size in vertex shader based on view/projection! */
		immVertex3fv(pos, &pt->x);
	}

	immEnd();
	immUnbindProgram();
	GPU_disable_program_point_size();
}


/* --------------- Stroke Fills ----------------- */
/* calc bounding box in 2d using flat projection data */
static void gp_calc_2d_bounding_box(const float(*points2d)[2], int totpoints, float minv[2], float maxv[2], bool expand)
{
	copy_v2_v2(minv, points2d[0]);
	copy_v2_v2(maxv, points2d[0]);

	for (int i = 1; i < totpoints; i++) {
		/* min */
		if (points2d[i][0] < minv[0]) {
			minv[0] = points2d[i][0];
		}
		if (points2d[i][1] < minv[1]) {
			minv[1] = points2d[i][1];
		}
		/* max */
		if (points2d[i][0] > maxv[0]) {
			maxv[0] = points2d[i][0];
		}
		if (points2d[i][1] > maxv[1]) {
			maxv[1] = points2d[i][1];
		}
	}
	/* If not expanded, use a perfect square */
	if (expand == false) {
		if (maxv[0] > maxv[1]) {
			maxv[1] = maxv[0];
		}
		else {
			maxv[0] = maxv[1];
		}
	}
}

/* calc texture coordinates using flat projected points */
static void gp_calc_stroke_text_coordinates(const float(*points2d)[2], int totpoints, float minv[2], float maxv[2], float(*r_uv)[2])
{
	float d[2];
	d[0] = maxv[0] - minv[0];
	d[1] = maxv[1] - minv[1];
	for (int i = 0; i < totpoints; i++) {
		r_uv[i][0] = (points2d[i][0] - minv[0]) / d[0];
		r_uv[i][1] = (points2d[i][1] - minv[1]) / d[1];
	}
}

/* Triangulate stroke for high quality fill (this is done only if cache is null or stroke was modified) */
static void gp_triangulate_stroke_fill(bGPDstroke *gps)
{
	BLI_assert(gps->totpoints >= 3);

	/* allocate memory for temporary areas */
	gps->tot_triangles = gps->totpoints - 2;
	uint (*tmp_triangles)[3] = MEM_mallocN(sizeof(*tmp_triangles) * gps->tot_triangles, "GP Stroke temp triangulation");
	float (*points2d)[2] = MEM_mallocN(sizeof(*points2d) * gps->totpoints, "GP Stroke temp 2d points");
	float(*uv)[2] = MEM_mallocN(sizeof(*uv) * gps->totpoints, "GP Stroke temp 2d uv data");

	int direction = 0;

	/* convert to 2d and triangulate */
	BKE_gpencil_stroke_2d_flat(gps->points, gps->totpoints, points2d, &direction);
	BLI_polyfill_calc(points2d, (uint)gps->totpoints, direction, tmp_triangles);

	/* calc texture coordinates automatically */
	float minv[2];
	float maxv[2];
	/* first needs bounding box data */
	gp_calc_2d_bounding_box((const float(*)[2])points2d, gps->totpoints, minv, maxv, false);
	/* calc uv data */
	gp_calc_stroke_text_coordinates((const float(*)[2])points2d, gps->totpoints, minv, maxv, uv);

	/* Number of triangles */
	gps->tot_triangles = gps->totpoints - 2;
	/* save triangulation data in stroke cache */
	if (gps->tot_triangles > 0) {
		if (gps->triangles == NULL) {
			gps->triangles = MEM_callocN(sizeof(*gps->triangles) * gps->tot_triangles, "GP Stroke triangulation");
		}
		else {
			gps->triangles = MEM_recallocN(gps->triangles, sizeof(*gps->triangles) * gps->tot_triangles);
		}

		for (int i = 0; i < gps->tot_triangles; i++) {
			bGPDtriangle *stroke_triangle = &gps->triangles[i];
			memcpy(stroke_triangle->verts, tmp_triangles[i], sizeof(uint[3]));
			/* copy texture coordinates */
			copy_v2_v2(stroke_triangle->uv[0], uv[tmp_triangles[i][0]]);
			copy_v2_v2(stroke_triangle->uv[1], uv[tmp_triangles[i][1]]);
			copy_v2_v2(stroke_triangle->uv[2], uv[tmp_triangles[i][2]]);
		}
	}
	else {
		/* No triangles needed - Free anything allocated previously */
		if (gps->triangles)
			MEM_freeN(gps->triangles);

		gps->triangles = NULL;
	}

	/* disable recalculation flag */
	if (gps->flag & GP_STROKE_RECALC_GEOMETRY) {
		gps->flag &= ~GP_STROKE_RECALC_GEOMETRY;
	}

	/* clear memory */
	MEM_SAFE_FREE(tmp_triangles);
	MEM_SAFE_FREE(points2d);
	MEM_SAFE_FREE(uv);
}

/* add a new fill point and texture coordinates to vertex buffer */
static void gp_add_filldata_tobuffer(
        const bGPDspoint *pt, const float uv[2], uint pos, uint texcoord, short flag,
        int offsx, int offsy, int winx, int winy, const float diff_mat[4][4])
{
	float fpt[3];
	float co[2];

	mul_v3_m4v3(fpt, diff_mat, &pt->x);
	/* if 2d, need conversion */
	if (!(flag & GP_STROKE_3DSPACE)) {
		gp_calc_2d_stroke_fxy(fpt, flag, offsx, offsy, winx, winy, co);
		copy_v2_v2(fpt, co);
		fpt[2] = 0.0f; /* 2d always is z=0.0f */
	}

	immAttr2f(texcoord, uv[0], uv[1]); /* texture coordinates */
	immVertex3fv(pos, fpt); /* position */
}

#if 0 /* GPXX disabled, not used in annotations */
/* assign image texture for filling stroke */
static int gp_set_filling_texture(Image *image, short flag)
{
	ImBuf *ibuf;
	uint *bind = &image->bindcode[TEXTARGET_TEXTURE_2D];
	int error = GL_NO_ERROR;
	ImageUser iuser = { NULL };
	void *lock;

	iuser.ok = true;

	ibuf = BKE_image_acquire_ibuf(image, &iuser, &lock);

	if (ibuf == NULL || ibuf->rect == NULL) {
		BKE_image_release_ibuf(image, ibuf, NULL);
		return (int)GL_INVALID_OPERATION;
	}

	GPU_create_gl_tex(bind, ibuf->rect, ibuf->rect_float, ibuf->x, ibuf->y, GL_TEXTURE_2D,
		false, false, image);

	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
	if (flag & GP_STYLE_COLOR_TEX_CLAMP) {
		glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP);
		glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP);
	}
	else {
		glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
		glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
	}
	BKE_image_release_ibuf(image, ibuf, NULL);

	return error;
}
#endif

/* draw fills for shapes */
static void gp_draw_stroke_fill(
        bGPdata *gpd, bGPDstroke *gps,
        int offsx, int offsy, int winx, int winy, const float diff_mat[4][4], const float color[4])
{
	BLI_assert(gps->totpoints >= 3);
	Material *ma = gpd->mat[gps->mat_nr];
	MaterialGPencilStyle *gp_style = (ma) ? ma->gp_style : NULL;

	/* Calculate triangles cache for filling area (must be done only after changes) */
	if ((gps->flag & GP_STROKE_RECALC_GEOMETRY) || (gps->tot_triangles == 0) || (gps->triangles == NULL)) {
		gp_triangulate_stroke_fill(gps);
	}
	BLI_assert(gps->tot_triangles >= 1);

	GPUVertFormat *format = immVertexFormat();
	uint pos = GPU_vertformat_attr_add(format, "pos", GPU_COMP_F32, 3, GPU_FETCH_FLOAT);
	uint texcoord = GPU_vertformat_attr_add(format, "texCoord", GPU_COMP_F32, 2, GPU_FETCH_FLOAT);
	immBindBuiltinProgram(GPU_SHADER_GPENCIL_FILL);

	immUniformColor4fv(color);
	immUniform4fv("color2", gp_style->mix_rgba);
	immUniform1i("fill_type", gp_style->fill_style);
	immUniform1f("mix_factor", gp_style->mix_factor);

	immUniform1f("gradient_angle", gp_style->gradient_angle);
	immUniform1f("gradient_radius", gp_style->gradient_radius);
	immUniform1f("pattern_gridsize", gp_style->pattern_gridsize);
	immUniform2fv("gradient_scale", gp_style->gradient_scale);
	immUniform2fv("gradient_shift", gp_style->gradient_shift);

	immUniform1f("texture_angle", gp_style->texture_angle);
	immUniform2fv("texture_scale", gp_style->texture_scale);
	immUniform2fv("texture_offset", gp_style->texture_offset);
	immUniform1f("texture_opacity", gp_style->texture_opacity);
	immUniform1i("t_mix", (gp_style->flag & GP_STYLE_COLOR_TEX_MIX) != 0);
	immUniform1i("t_flip", (gp_style->flag & GP_STYLE_COLOR_FLIP_FILL) != 0);
#if 0 /* GPXX disabled, not used in annotations */
	/* image texture */
	if ((gp_style->fill_style == GP_STYLE_FILL_STYLE_TEXTURE) || (gp_style->flag & GP_STYLE_COLOR_TEX_MIX)) {
		gp_set_filling_texture(gp_style->ima, gp_style->flag);
	}
#endif
	/* Draw all triangles for filling the polygon (cache must be calculated before) */
	immBegin(GPU_PRIM_TRIS, gps->tot_triangles * 3);
	/* TODO: use batch instead of immediate mode, to share vertices */

	const bGPDtriangle *stroke_triangle = gps->triangles;
	for (int i = 0; i < gps->tot_triangles; i++, stroke_triangle++) {
		for (int j = 0; j < 3; j++) {
			gp_add_filldata_tobuffer(
			        &gps->points[stroke_triangle->verts[j]], stroke_triangle->uv[j],
			        pos, texcoord, gps->flag,
			        offsx, offsy, winx, winy, diff_mat);
		}
	}

	immEnd();
	immUnbindProgram();
}

/* ----- Existing Strokes Drawing (3D and Point) ------ */

/* draw a given stroke - just a single dot (only one point) */
static void gp_draw_stroke_point(
        const bGPDspoint *points, short thickness, short UNUSED(dflag), short sflag,
        int offsx, int offsy, int winx, int winy, const float diff_mat[4][4], const float ink[4])
{
	const bGPDspoint *pt = points;

	/* get final position using parent matrix */
	float fpt[3];
	mul_v3_m4v3(fpt, diff_mat, &pt->x);

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

	if (sflag & GP_STROKE_3DSPACE) {
		immBindBuiltinProgram(GPU_SHADER_3D_POINT_UNIFORM_SIZE_UNIFORM_COLOR_AA);
	}
	else {
		immBindBuiltinProgram(GPU_SHADER_2D_POINT_UNIFORM_SIZE_UNIFORM_COLOR_AA);

		/* get 2D coordinates of point */
		float co[3] = { 0.0f };
		gp_calc_2d_stroke_fxy(fpt, sflag, offsx, offsy, winx, winy, co);
		copy_v3_v3(fpt, co);
	}

	gp_set_point_uniform_color(pt, ink);
	/* set point thickness (since there's only one of these) */
	immUniform1f("size", (float)(thickness + 2) * pt->pressure);

	immBegin(GPU_PRIM_POINTS, 1);
	immVertex3fv(pos, fpt);
	immEnd();

	immUnbindProgram();
}

/* draw a given stroke in 3d (i.e. in 3d-space) */
static void gp_draw_stroke_3d(tGPDdraw *tgpw, short thickness, const float ink[4], bool cyclic)
{
	bGPDspoint *points = tgpw->gps->points;
	int totpoints = tgpw->gps->totpoints;

	const float viewport[2] = { (float)tgpw->winx, (float)tgpw->winy };
	float curpressure = points[0].pressure;
	float fpt[3];

	/* if cyclic needs more vertex */
	int cyclic_add = (cyclic) ? 1 : 0;

	GPUVertFormat *format = immVertexFormat();
	const struct {
		uint pos, color, thickness;
	} attr_id = {
		.pos = GPU_vertformat_attr_add(format, "pos", GPU_COMP_F32, 3, GPU_FETCH_FLOAT),
		.color = GPU_vertformat_attr_add(format, "color", GPU_COMP_U8, 4, GPU_FETCH_INT_TO_FLOAT_UNIT),
		.thickness = GPU_vertformat_attr_add(format, "thickness", GPU_COMP_F32, 1, GPU_FETCH_FLOAT),
	};

	immBindBuiltinProgram(GPU_SHADER_GPENCIL_STROKE);
	immUniform2fv("Viewport", viewport);
	immUniform1f("pixsize", tgpw->rv3d->pixsize);
	float obj_scale = tgpw->ob ? (tgpw->ob->size[0] + tgpw->ob->size[1] + tgpw->ob->size[2]) / 3.0f : 1.0f;

	immUniform1f("objscale", obj_scale);
	int keep_size = (int)((tgpw->gpd) && (tgpw->gpd->flag & GP_DATA_STROKE_KEEPTHICKNESS));
	immUniform1i("keep_size", keep_size);
	immUniform1i("pixfactor", tgpw->gpd->pixfactor);
	/* xray mode always to 3D space to avoid wrong zdepth calculation (T60051) */
	immUniform1i("xraymode", GP_XRAY_3DSPACE);

	/* draw stroke curve */
	GPU_line_width(max_ff(curpressure * thickness, 1.0f));
	immBeginAtMost(GPU_PRIM_LINE_STRIP_ADJ, totpoints + cyclic_add + 2);
	const bGPDspoint *pt = points;

	for (int i = 0; i < totpoints; i++, pt++) {
		/* first point for adjacency (not drawn) */
		if (i == 0) {
			gp_set_point_varying_color(points, ink, attr_id.color);
			immAttr1f(attr_id.thickness, max_ff(curpressure * thickness, 1.0f));
			if ((cyclic) && (totpoints > 2)) {
				mul_v3_m4v3(fpt, tgpw->diff_mat, &(points + totpoints - 1)->x);
			}
			else {
				mul_v3_m4v3(fpt, tgpw->diff_mat, &(points + 1)->x);
			}
			mul_v3_fl(fpt, -1.0f);
			immVertex3fv(attr_id.pos, fpt);
		}
		/* set point */
		gp_set_point_varying_color(pt, ink, attr_id.color);
		immAttr1f(attr_id.thickness, max_ff(curpressure * thickness, 1.0f));
		mul_v3_m4v3(fpt, tgpw->diff_mat, &pt->x);
		immVertex3fv(attr_id.pos, fpt);

		curpressure = pt->pressure;
	}

	if (cyclic && totpoints > 2) {
		/* draw line to first point to complete the cycle */
		immAttr1f(attr_id.thickness, max_ff(points->pressure * thickness, 1.0f));
		mul_v3_m4v3(fpt, tgpw->diff_mat, &points->x);
		immVertex3fv(attr_id.pos, fpt);

		/* now add adjacency point (not drawn) */
		immAttr1f(attr_id.thickness, max_ff((points + 1)->pressure * thickness, 1.0f));
		mul_v3_m4v3(fpt, tgpw->diff_mat, &(points + 1)->x);
		immVertex3fv(attr_id.pos, fpt);
	}
	/* last adjacency point (not drawn) */
	else {
		gp_set_point_varying_color(points + totpoints - 1, ink, attr_id.color);
		immAttr1f(attr_id.thickness, max_ff(curpressure * thickness, 1.0f));
		mul_v3_m4v3(fpt, tgpw->diff_mat, &(points + totpoints - 2)->x);
		mul_v3_fl(fpt, -1.0f);
		immVertex3fv(attr_id.pos, fpt);
	}

	immEnd();
	immUnbindProgram();
}

/* ----- Fancy 2D-Stroke Drawing ------ */

/* draw a given stroke in 2d */
static void gp_draw_stroke_2d(
        const bGPDspoint *points, int totpoints, short thickness_s, short dflag, short sflag,
        bool UNUSED(debug), int offsx, int offsy, int winx, int winy, const float diff_mat[4][4], const float ink[4])
{
	/* otherwise thickness is twice that of the 3D view */
	float thickness = (float)thickness_s * 0.5f;

	/* strokes in Image Editor need a scale factor, since units there are not pixels! */
	float scalefac  = 1.0f;
	if ((dflag & GP_DRAWDATA_IEDITHACK) && (dflag & GP_DRAWDATA_ONLYV2D)) {
		scalefac = 0.001f;
	}

	/* TODO: fancy++ with the magic of shaders */

	/* tessellation code - draw stroke as series of connected quads (triangle strips in fact) with connection
	 * edges rotated to minimize shrinking artifacts, and rounded endcaps
	 */
	{
		const bGPDspoint *pt1, *pt2;
		float s0[2], s1[2];     /* segment 'center' points */
		float pm[2];  /* normal from previous segment. */
		int i;
		float fpt[3];

		GPUVertFormat *format = immVertexFormat();
		const struct {
			uint pos, color;
		} attr_id = {
			.pos = GPU_vertformat_attr_add(format, "pos", GPU_COMP_F32, 2, GPU_FETCH_FLOAT),
			.color = GPU_vertformat_attr_add(format, "color", GPU_COMP_U8, 4, GPU_FETCH_INT_TO_FLOAT_UNIT),
		};

		immBindBuiltinProgram(GPU_SHADER_2D_FLAT_COLOR);
		immBegin(GPU_PRIM_TRI_STRIP, totpoints * 2 + 4);

		/* get x and y coordinates from first point */
		mul_v3_m4v3(fpt, diff_mat, &points->x);
		gp_calc_2d_stroke_fxy(fpt, sflag, offsx, offsy, winx, winy, s0);

		for (i = 0, pt1 = points, pt2 = points + 1; i < (totpoints - 1); i++, pt1++, pt2++) {
			float t0[2], t1[2];     /* tessellated coordinates */
			float m1[2], m2[2];     /* gradient and normal */
			float mt[2], sc[2];     /* gradient for thickness, point for end-cap */
			float pthick;           /* thickness at segment point */

			/* get x and y coordinates from point2 (point1 has already been computed in previous iteration). */
			mul_v3_m4v3(fpt, diff_mat, &pt2->x);
			gp_calc_2d_stroke_fxy(fpt, sflag, offsx, offsy, winx, winy, s1);

			/* calculate gradient and normal - 'angle'=(ny/nx) */
			m1[1] = s1[1] - s0[1];
			m1[0] = s1[0] - s0[0];
			normalize_v2(m1);
			m2[1] = -m1[0];
			m2[0] = m1[1];

			/* always use pressure from first point here */
			pthick = (pt1->pressure * thickness * scalefac);

			/* color of point */
			gp_set_point_varying_color(pt1, ink, attr_id.color);

			/* if the first segment, start of segment is segment's normal */
			if (i == 0) {
				/* draw start cap first
				 * - make points slightly closer to center (about halfway across)
				 */
				mt[0] = m2[0] * pthick * 0.5f;
				mt[1] = m2[1] * pthick * 0.5f;
				sc[0] = s0[0] - (m1[0] * pthick * 0.75f);
				sc[1] = s0[1] - (m1[1] * pthick * 0.75f);

				t0[0] = sc[0] - mt[0];
				t0[1] = sc[1] - mt[1];
				t1[0] = sc[0] + mt[0];
				t1[1] = sc[1] + mt[1];

				/* First two points of cap. */
				immVertex2fv(attr_id.pos, t0);
				immVertex2fv(attr_id.pos, t1);

				/* calculate points for start of segment */
				mt[0] = m2[0] * pthick;
				mt[1] = m2[1] * pthick;

				t0[0] = s0[0] - mt[0];
				t0[1] = s0[1] - mt[1];
				t1[0] = s0[0] + mt[0];
				t1[1] = s0[1] + mt[1];

				/* Last two points of start cap (and first two points of first segment). */
				immVertex2fv(attr_id.pos, t0);
				immVertex2fv(attr_id.pos, t1);
			}
			/* if not the first segment, use bisector of angle between segments */
			else {
				float mb[2];         /* bisector normal */
				float athick, dfac;  /* actual thickness, difference between thicknesses */

				/* calculate gradient of bisector (as average of normals) */
				mb[0] = (pm[0] + m2[0]) / 2;
				mb[1] = (pm[1] + m2[1]) / 2;
				normalize_v2(mb);

				/* calculate gradient to apply
				 * - as basis, use just pthick * bisector gradient
				 * - if cross-section not as thick as it should be, add extra padding to fix it
				 */
				mt[0] = mb[0] * pthick;
				mt[1] = mb[1] * pthick;
				athick = len_v2(mt);
				dfac = pthick - (athick * 2);

				if (((athick * 2.0f) < pthick) && (IS_EQF(athick, pthick) == 0)) {
					mt[0] += (mb[0] * dfac);
					mt[1] += (mb[1] * dfac);
				}

				/* calculate points for start of segment */
				t0[0] = s0[0] - mt[0];
				t0[1] = s0[1] - mt[1];
				t1[0] = s0[0] + mt[0];
				t1[1] = s0[1] + mt[1];

				/* Last two points of previous segment, and first two points of current segment. */
				immVertex2fv(attr_id.pos, t0);
				immVertex2fv(attr_id.pos, t1);
			}

			/* if last segment, also draw end of segment (defined as segment's normal) */
			if (i == totpoints - 2) {
				/* for once, we use second point's pressure (otherwise it won't be drawn) */
				pthick = (pt2->pressure * thickness * scalefac);

				/* color of point */
				gp_set_point_varying_color(pt2, ink, attr_id.color);

				/* calculate points for end of segment */
				mt[0] = m2[0] * pthick;
				mt[1] = m2[1] * pthick;

				t0[0] = s1[0] - mt[0];
				t0[1] = s1[1] - mt[1];
				t1[0] = s1[0] + mt[0];
				t1[1] = s1[1] + mt[1];

				/* Last two points of last segment (and first two points of end cap). */
				immVertex2fv(attr_id.pos, t0);
				immVertex2fv(attr_id.pos, t1);

				/* draw end cap as last step
				 * - make points slightly closer to center (about halfway across)
				 */
				mt[0] = m2[0] * pthick * 0.5f;
				mt[1] = m2[1] * pthick * 0.5f;
				sc[0] = s1[0] + (m1[0] * pthick * 0.75f);
				sc[1] = s1[1] + (m1[1] * pthick * 0.75f);

				t0[0] = sc[0] - mt[0];
				t0[1] = sc[1] - mt[1];
				t1[0] = sc[0] + mt[0];
				t1[1] = sc[1] + mt[1];

				/* Last two points of end cap. */
				immVertex2fv(attr_id.pos, t0);
				immVertex2fv(attr_id.pos, t1);
			}

			/* store computed point2 coordinates as point1 ones of next segment. */
			copy_v2_v2(s0, s1);
			/* store stroke's 'natural' normal for next stroke to use */
			copy_v2_v2(pm, m2);
		}

		immEnd();
		immUnbindProgram();
	}
}

/* ----- Strokes Drawing ------ */

/* Helper for doing all the checks on whether a stroke can be drawn */
static bool gp_can_draw_stroke(const bGPDstroke *gps, const int dflag)
{
	/* skip stroke if it isn't in the right display space for this drawing context */
	/* 1) 3D Strokes */
	if ((dflag & GP_DRAWDATA_ONLY3D) && !(gps->flag & GP_STROKE_3DSPACE))
		return false;
	if (!(dflag & GP_DRAWDATA_ONLY3D) && (gps->flag & GP_STROKE_3DSPACE))
		return false;

	/* 2) Screen Space 2D Strokes */
	if ((dflag & GP_DRAWDATA_ONLYV2D) && !(gps->flag & GP_STROKE_2DSPACE))
		return false;
	if (!(dflag & GP_DRAWDATA_ONLYV2D) && (gps->flag & GP_STROKE_2DSPACE))
		return false;

	/* 3) Image Space (2D) */
	if ((dflag & GP_DRAWDATA_ONLYI2D) && !(gps->flag & GP_STROKE_2DIMAGE))
		return false;
	if (!(dflag & GP_DRAWDATA_ONLYI2D) && (gps->flag & GP_STROKE_2DIMAGE))
		return false;

	/* skip stroke if it doesn't have any valid data */
	if ((gps->points == NULL) || (gps->totpoints < 1))
		return false;

	/* stroke can be drawn */
	return true;
}

/* draw a set of strokes */
static void gp_draw_strokes(tGPDdraw *tgpw)
{
	float tcolor[4];
	float tfill[4];
	short sthickness;
	float ink[4];

	GPU_enable_program_point_size();

	for (bGPDstroke *gps = tgpw->t_gpf->strokes.first; gps; gps = gps->next) {
		/* check if stroke can be drawn */
		if (gp_can_draw_stroke(gps, tgpw->dflag) == false) {
			continue;
		}
		/* check if the color is visible */
		Material *ma = tgpw->gpd->mat[gps->mat_nr];
		MaterialGPencilStyle *gp_style = (ma) ? ma->gp_style : NULL;

		if ((gp_style == NULL) ||
		    (gp_style->flag & GP_STYLE_COLOR_HIDE) ||
		    /* if onion and ghost flag do not draw*/
		    (tgpw->onion && (gp_style->flag & GP_STYLE_COLOR_ONIONSKIN)))
		{
			continue;
		}

		/* if disable fill, the colors with fill must be omitted too except fill boundary strokes */
		if ((tgpw->disable_fill == 1) &&
		    (gp_style->fill_rgba[3] > 0.0f) &&
		    ((gps->flag & GP_STROKE_NOFILL) == 0))
		{
			continue;
		}

		/* calculate thickness */
		sthickness = gps->thickness + tgpw->lthick;

		if (sthickness <= 0) {
			continue;
		}

		/* check which stroke-drawer to use */
		if (tgpw->dflag & GP_DRAWDATA_ONLY3D) {
			const int no_xray = (tgpw->dflag & GP_DRAWDATA_NO_XRAY);
			int mask_orig = 0;

			if (no_xray) {
				glGetIntegerv(GL_DEPTH_WRITEMASK, &mask_orig);
				glDepthMask(0);
				GPU_depth_test(true);

				/* first arg is normally rv3d->dist, but this isn't
				 * available here and seems to work quite well without */
				bglPolygonOffset(1.0f, 1.0f);
			}

			/* 3D Fill */
			//if ((dflag & GP_DRAWDATA_FILL) && (gps->totpoints >= 3)) {
			if ((gps->totpoints >= 3) && (tgpw->disable_fill != 1)) {
				/* set color using material, tint color and opacity */
				interp_v3_v3v3(tfill, gp_style->fill_rgba, tgpw->tintcolor, tgpw->tintcolor[3]);
				tfill[3] = gp_style->fill_rgba[3] * tgpw->opacity;
				if ((tfill[3] > GPENCIL_ALPHA_OPACITY_THRESH) || (gp_style->fill_style > 0)) {
					const float *color;
					if (!tgpw->onion) {
						color = tfill;
					}
					else {
						if (tgpw->custonion) {
							color = tgpw->tintcolor;
						}
						else {
							ARRAY_SET_ITEMS(tfill, UNPACK3(gp_style->fill_rgba), tgpw->tintcolor[3]);
							color = tfill;
						}
					}
					gp_draw_stroke_fill(
					        tgpw->gpd, gps,
					        tgpw->offsx, tgpw->offsy, tgpw->winx, tgpw->winy, tgpw->diff_mat, color);
				}
			}

			/* 3D Stroke */
			/* set color using material tint color and opacity */
			if (!tgpw->onion) {
				interp_v3_v3v3(tcolor, gp_style->stroke_rgba, tgpw->tintcolor, tgpw->tintcolor[3]);
				tcolor[3] = gp_style->stroke_rgba[3] * tgpw->opacity;
				copy_v4_v4(ink, tcolor);
			}
			else {
				if (tgpw->custonion) {
					copy_v4_v4(ink, tgpw->tintcolor);
				}
				else {
					ARRAY_SET_ITEMS(tcolor, UNPACK3(gp_style->stroke_rgba), tgpw->opacity);
					copy_v4_v4(ink, tcolor);
				}
			}
			if (gp_style->mode == GP_STYLE_MODE_DOTS) {
				/* volumetric stroke drawing */
				if (tgpw->disable_fill != 1) {
					gp_draw_stroke_volumetric_3d(gps->points, gps->totpoints, sthickness, ink);
				}
			}
			else {
				/* 3D Lines - OpenGL primitives-based */
				if (gps->totpoints == 1) {
					if (tgpw->disable_fill != 1) {
						gp_draw_stroke_point(gps->points, sthickness, tgpw->dflag, gps->flag,
							tgpw->offsx, tgpw->offsy, tgpw->winx, tgpw->winy,
							tgpw->diff_mat, ink);
					}
				}
				else {
					tgpw->gps = gps;
					gp_draw_stroke_3d(tgpw, sthickness, ink, gps->flag & GP_STROKE_CYCLIC);
				}
			}
			if (no_xray) {
				glDepthMask(mask_orig);
				GPU_depth_test(false);

				bglPolygonOffset(0.0, 0.0);
			}
		}
		else {
			/* 2D - Fill */
			if (gps->totpoints >= 3) {
				/* set color using material, tint color and opacity */
				interp_v3_v3v3(tfill, gp_style->fill_rgba, tgpw->tintcolor, tgpw->tintcolor[3]);
				tfill[3] = gp_style->fill_rgba[3] * tgpw->opacity;
				if ((tfill[3] > GPENCIL_ALPHA_OPACITY_THRESH) || (gp_style->fill_style > 0)) {
					const float *color;
					if (!tgpw->onion) {
						color = tfill;
					}
					else {
						if (tgpw->custonion) {
							color = tgpw->tintcolor;
						}
						else {
							ARRAY_SET_ITEMS(tfill, UNPACK3(gp_style->fill_rgba), tgpw->tintcolor[3]);
							color = tfill;
						}
					}
					gp_draw_stroke_fill(
					        tgpw->gpd, gps,
					        tgpw->offsx, tgpw->offsy, tgpw->winx, tgpw->winy, tgpw->diff_mat, color);
				}
			}

			/* 2D Strokes... */
			/* set color using material, tint color and opacity */
			if (!tgpw->onion) {
				interp_v3_v3v3(tcolor, gp_style->stroke_rgba, tgpw->tintcolor, tgpw->tintcolor[3]);
				tcolor[3] = gp_style->stroke_rgba[3] * tgpw->opacity;
				copy_v4_v4(ink, tcolor);
			}
			else {
				if (tgpw->custonion) {
					copy_v4_v4(ink, tgpw->tintcolor);
				}
				else {
					ARRAY_SET_ITEMS(tcolor, UNPACK3(gp_style->stroke_rgba), tgpw->opacity);
					copy_v4_v4(ink, tcolor);
				}
			}
			if (gp_style->mode == GP_STYLE_MODE_DOTS) {
				/* blob/disk-based "volumetric" drawing */
				gp_draw_stroke_volumetric_2d(
				        gps->points, gps->totpoints, sthickness, tgpw->dflag, gps->flag,
				        tgpw->offsx, tgpw->offsy, tgpw->winx, tgpw->winy, tgpw->diff_mat, ink);
			}
			else {
				/* normal 2D strokes */
				if (gps->totpoints == 1) {
					gp_draw_stroke_point(
					        gps->points, sthickness, tgpw->dflag, gps->flag,
					        tgpw->offsx, tgpw->offsy, tgpw->winx, tgpw->winy,
					        tgpw->diff_mat, ink);
				}
				else {
					gp_draw_stroke_2d(
					        gps->points, gps->totpoints, sthickness, tgpw->dflag, gps->flag, false,
					        tgpw->offsx, tgpw->offsy, tgpw->winx, tgpw->winy, tgpw->diff_mat, ink);
				}
			}
		}
	}

	GPU_disable_program_point_size();
}

/* Draw selected verts for strokes being edited */
static void gp_draw_strokes_edit(
        bGPdata *gpd, const bGPDframe *gpf, int offsx, int offsy, int winx, int winy, short dflag,
        short lflag, const float diff_mat[4][4], float alpha)
{
	/* if alpha 0 do not draw */
	if (alpha == 0.0f)
		return;

	const bool no_xray = (dflag & GP_DRAWDATA_NO_XRAY) != 0;
	int mask_orig = 0;

	/* set up depth masks... */
	if (dflag & GP_DRAWDATA_ONLY3D) {
		if (no_xray) {
			glGetIntegerv(GL_DEPTH_WRITEMASK, &mask_orig);
			glDepthMask(0);
			GPU_depth_test(true);

			/* first arg is normally rv3d->dist, but this isn't
			 * available here and seems to work quite well without */
			bglPolygonOffset(1.0f, 1.0f);
		}
	}

	GPU_enable_program_point_size();

	/* draw stroke verts */
	for (bGPDstroke *gps = gpf->strokes.first; gps; gps = gps->next) {
		/* check if stroke can be drawn */
		if (gp_can_draw_stroke(gps, dflag) == false)
			continue;

		/* Optimisation: only draw points for selected strokes
		 * We assume that selected points can only occur in
		 * strokes that are selected too.
		 */
		if ((gps->flag & GP_STROKE_SELECT) == 0)
			continue;

		/* verify color lock */
		{
			Material *ma = gpd->mat[gps->mat_nr];
			MaterialGPencilStyle *gp_style = (ma) ? ma->gp_style : NULL;

			if (gp_style != NULL) {
				if (gp_style->flag & GP_STYLE_COLOR_HIDE) {
					continue;
				}
				if (((lflag & GP_LAYER_UNLOCK_COLOR) == 0) && (gp_style->flag & GP_STYLE_COLOR_LOCKED)) {
					continue;
				}
			}
		}

		/* Get size of verts:
		 * - The selected state needs to be larger than the unselected state so that
		 *   they stand out more.
		 * - We use the theme setting for size of the unselected verts
		 */
		float bsize = UI_GetThemeValuef(TH_GP_VERTEX_SIZE);
		float vsize;
		if ((int)bsize > 8) {
			vsize = 10.0f;
			bsize = 8.0f;
		}
		else {
			vsize = bsize + 2;
		}

		/* for now, we assume that the base color of the points is not too close to the real color */
		/* set color using material */
		Material *ma = gpd->mat[gps->mat_nr];
		MaterialGPencilStyle *gp_style = (ma) ? ma->gp_style : NULL;

		float selectColor[4];
		UI_GetThemeColor3fv(TH_GP_VERTEX_SELECT, selectColor);
		selectColor[3] = alpha;

		GPUVertFormat *format = immVertexFormat();
		uint pos; /* specified later */
		uint size = GPU_vertformat_attr_add(format, "size", GPU_COMP_F32, 1, GPU_FETCH_FLOAT);
		uint color = GPU_vertformat_attr_add(format, "color", GPU_COMP_U8, 3, GPU_FETCH_INT_TO_FLOAT_UNIT);

		if (gps->flag & GP_STROKE_3DSPACE) {
			pos = GPU_vertformat_attr_add(format, "pos", GPU_COMP_F32, 3, GPU_FETCH_FLOAT);
			immBindBuiltinProgram(GPU_SHADER_3D_POINT_VARYING_SIZE_VARYING_COLOR);
		}
		else {
			pos = GPU_vertformat_attr_add(format, "pos", GPU_COMP_F32, 2, GPU_FETCH_FLOAT);
			immBindBuiltinProgram(GPU_SHADER_2D_POINT_VARYING_SIZE_VARYING_COLOR);
		}

		immBegin(GPU_PRIM_POINTS, gps->totpoints);

		/* Draw start and end point differently if enabled stroke direction hint */
		bool show_direction_hint = (gpd->flag & GP_DATA_SHOW_DIRECTION) && (gps->totpoints > 1);

		/* Draw all the stroke points (selected or not) */
		bGPDspoint *pt = gps->points;
		float fpt[3];
		for (int i = 0; i < gps->totpoints; i++, pt++) {
			/* size and color first */
			if (show_direction_hint && i == 0) {
				/* start point in green bigger */
				immAttr3f(color, 0.0f, 1.0f, 0.0f);
				immAttr1f(size, vsize + 4);
			}
			else if (show_direction_hint && (i == gps->totpoints - 1)) {
				/* end point in red smaller */
				immAttr3f(color, 1.0f, 0.0f, 0.0f);
				immAttr1f(size, vsize + 1);
			}
			else if (pt->flag & GP_SPOINT_SELECT) {
				immAttr3fv(color, selectColor);
				immAttr1f(size, vsize);
			}
			else if (gp_style) {
				immAttr3fv(color, gp_style->stroke_rgba);
				immAttr1f(size, bsize);
			}
			else {
				immAttr3f(color, 0.0f, 0.0f, 0.0f);
				immAttr1f(size, bsize);
			}

			/* then position */
			if (gps->flag & GP_STROKE_3DSPACE) {
				mul_v3_m4v3(fpt, diff_mat, &pt->x);
				immVertex3fv(pos, fpt);
			}
			else {
				float co[2];
				mul_v3_m4v3(fpt, diff_mat, &pt->x);
				gp_calc_2d_stroke_fxy(fpt, gps->flag, offsx, offsy, winx, winy, co);
				immVertex2fv(pos, co);
			}
		}

		immEnd();
		immUnbindProgram();
	}

	GPU_disable_program_point_size();

	/* clear depth mask */
	if (dflag & GP_DRAWDATA_ONLY3D) {
		if (no_xray) {
			glDepthMask(mask_orig);
			GPU_depth_test(false);

			bglPolygonOffset(0.0, 0.0);
#if 0
			glDisable(GL_POLYGON_OFFSET_LINE);
			glPolygonOffset(0, 0);
#endif
		}
	}
}

/* ----- General Drawing ------ */


/* draw interpolate strokes (used only while operator is running) */
void ED_gp_draw_interpolation(const bContext *C, tGPDinterpolate *tgpi, const int type)
{
	tGPDdraw tgpw;
	ARegion *ar = CTX_wm_region(C);
	RegionView3D *rv3d = ar->regiondata;
	tGPDinterpolate_layer *tgpil;
	Object *obact = CTX_data_active_object(C);
	Depsgraph *depsgraph = CTX_data_depsgraph(C);

	float color[4];

	UI_GetThemeColor3fv(TH_GP_VERTEX_SELECT, color);
	color[3] = 0.6f;
	int dflag = 0;
	/* if 3d stuff, enable flags */
	if (type == REGION_DRAW_POST_VIEW) {
		dflag |= (GP_DRAWDATA_ONLY3D | GP_DRAWDATA_NOSTATUS);
	}

	tgpw.rv3d = rv3d;
	tgpw.depsgraph = depsgraph;
	tgpw.ob = obact;
	tgpw.gpd = tgpi->gpd;
	tgpw.offsx = 0;
	tgpw.offsy = 0;
	tgpw.winx = tgpi->ar->winx;
	tgpw.winy = tgpi->ar->winy;
	tgpw.dflag = dflag;

	/* turn on alpha-blending */
	glEnable(GL_BLEND);
	for (tgpil = tgpi->ilayers.first; tgpil; tgpil = tgpil->next) {
		/* calculate parent position */
		ED_gpencil_parent_location(depsgraph, obact, tgpi->gpd, tgpil->gpl, tgpw.diff_mat);
		if (tgpil->interFrame) {
			tgpw.gpl = tgpil->gpl;
			tgpw.gpf = tgpil->interFrame;
			tgpw.t_gpf = tgpil->interFrame;

			tgpw.lthick = tgpil->gpl->line_change;
			tgpw.opacity = 1.0;
			copy_v4_v4(tgpw.tintcolor, color);
			tgpw.onion = true;
			tgpw.custonion = true;

			gp_draw_strokes(&tgpw);
		}
	}
	glDisable(GL_BLEND);
}

/* wrapper to draw strokes for filling operator */
void ED_gp_draw_fill(tGPDdraw *tgpw)
{
	gp_draw_strokes(tgpw);
}

/* loop over gpencil data layers, drawing them */
static void gp_draw_data_layers(RegionView3D *rv3d,
        const Brush *brush, float alpha, Object *ob, bGPdata *gpd,
        int offsx, int offsy, int winx, int winy, int cfra, int dflag)
{
	float diff_mat[4][4];
	tGPDdraw tgpw;

	tgpw.rv3d = rv3d;
	tgpw.depsgraph = NULL; /* XXX: This is not used here */
	tgpw.ob = ob;
	tgpw.gpd = gpd;
	tgpw.gpl = NULL;
	tgpw.gpf = NULL;
	tgpw.t_gpf = NULL;
	tgpw.offsx = offsx;
	tgpw.offsy = offsy;
	tgpw.winx = winx;
	tgpw.winy = winy;
	tgpw.dflag = dflag;

	for (bGPDlayer *gpl = gpd->layers.first; gpl; gpl = gpl->next) {
		/* calculate parent position */
		ED_gpencil_parent_location(tgpw.depsgraph, ob, gpd, gpl, diff_mat);

		short lthick = brush->size + gpl->line_change;

		/* don't draw layer if hidden */
		if (gpl->flag & GP_LAYER_HIDE)
			continue;

		/* get frame to draw */
		bGPDframe *gpf = BKE_gpencil_layer_getframe(gpl, cfra, GP_GETFRAME_USE_PREV);
		if (gpf == NULL)
			continue;

		/* set basic stroke thickness */
		GPU_line_width(lthick);

		/* Add layer drawing settings to the set of "draw flags"
		 * NOTE: If the setting doesn't apply, it *must* be cleared,
		 *       as dflag's carry over from the previous layer
		 */

		/* xray... */
		SET_FLAG_FROM_TEST(dflag, gpl->flag & GP_LAYER_NO_XRAY, GP_DRAWDATA_NO_XRAY);

		/* volumetric strokes... */
		SET_FLAG_FROM_TEST(dflag, gpl->flag & GP_LAYER_VOLUMETRIC, GP_DRAWDATA_VOLUMETRIC);

		tgpw.gpl = gpl;
		tgpw.gpf = gpf;
		tgpw.t_gpf = gpf; // XXX?
		tgpw.lthick = gpl->line_change;
		tgpw.opacity = gpl->opacity;
		copy_v4_v4(tgpw.tintcolor, gpl->tintcolor);
		tgpw.onion = false;
		tgpw.custonion = false;
		copy_m4_m4(tgpw.diff_mat, diff_mat);

		/* draw the strokes already in active frame */
		gp_draw_strokes(&tgpw);

		/* Draw verts of selected strokes
		 * - when doing OpenGL renders, we don't want to be showing these, as that ends up flickering
		 *   - locked layers can't be edited, so there's no point showing these verts
		 *     as they will have no bearings on what gets edited
		 * - only show when in editmode, since operators shouldn't work otherwise
		 *   (NOTE: doing it this way means that the toggling editmode shows visible change immediately)
		 */
		/* XXX: perhaps we don't want to show these when users are drawing... */
		if ((G.f & G_RENDER_OGL) == 0 &&
		    (gpl->flag & GP_LAYER_LOCKED) == 0 &&
		    (gpd->flag & GP_DATA_STROKE_EDITMODE))
		{
			gp_draw_strokes_edit(gpd, gpf, offsx, offsy, winx, winy, dflag, gpl->flag, diff_mat, alpha);
		}

		/* Check if may need to draw the active stroke cache, only if this layer is the active layer
		 * that is being edited. (Stroke buffer is currently stored in gp-data)
		 */
		if (ED_gpencil_session_active() && (gpl->flag & GP_LAYER_ACTIVE) &&
		    (gpf->flag & GP_FRAME_PAINT))
		{
			/* Buffer stroke needs to be drawn with a different linestyle
			 * to help differentiate them from normal strokes.
			 *
			 * It should also be noted that sbuffer contains temporary point types
			 * i.e. tGPspoints NOT bGPDspoints
			 */
			if (gpd->runtime.mode == GP_STYLE_MODE_DOTS) {
				gp_draw_stroke_volumetric_buffer(
				        gpd->runtime.sbuffer,
				        gpd->runtime.sbuffer_size, lthick,
				        dflag, gpd->runtime.scolor);
			}
			else {
				gp_draw_stroke_buffer(
				        gpd->runtime.sbuffer,
				        gpd->runtime.sbuffer_size, lthick,
				        dflag, gpd->runtime.sbuffer_sflag,
				        gpd->runtime.scolor, gpd->runtime.sfill);
			}
		}
	}
}

/* draw a short status message in the top-right corner */
static void UNUSED_FUNCTION(gp_draw_status_text)(const bGPdata *gpd, ARegion *ar)
{
	rcti rect;

	/* Cannot draw any status text when drawing OpenGL Renders */
	if (G.f & G_RENDER_OGL)
		return;

	/* Get bounds of region - Necessary to avoid problems with region overlap */
	ED_region_visible_rect(ar, &rect);

	/* for now, this should only be used to indicate when we are in stroke editmode */
	if (gpd->flag & GP_DATA_STROKE_EDITMODE) {
		const char *printable = IFACE_("GPencil Stroke Editing");
		float       printable_size[2];

		int font_id = BLF_default();

		BLF_width_and_height(font_id, printable, BLF_DRAW_STR_DUMMY_MAX, &printable_size[0], &printable_size[1]);

		int xco = (rect.xmax - U.widget_unit) - (int)printable_size[0];
		int yco = (rect.ymax - U.widget_unit);

		/* text label */
		UI_FontThemeColor(font_id, TH_TEXT_HI);
#ifdef WITH_INTERNATIONAL
		BLF_draw_default(xco, yco, 0.0f, printable, BLF_DRAW_STR_DUMMY_MAX);
#else
		BLF_draw_default_ascii(xco, yco, 0.0f, printable, BLF_DRAW_STR_DUMMY_MAX);
#endif

		/* grease pencil icon... */
		// XXX: is this too intrusive?
		GPU_blend_set_func_separate(GPU_SRC_ALPHA, GPU_ONE_MINUS_SRC_ALPHA, GPU_ONE, GPU_ONE_MINUS_SRC_ALPHA);
		GPU_blend(true);

		xco -= U.widget_unit;
		yco -= (int)printable_size[1] / 2;

		UI_icon_draw(xco, yco, ICON_GREASEPENCIL);

		GPU_blend(false);
	}
}

/* draw grease-pencil datablock */
static void gp_draw_data(RegionView3D *rv3d,
        const Brush *brush, float alpha, Object *ob, bGPdata *gpd,
        int offsx, int offsy, int winx, int winy, int cfra, int dflag)
{
	/* turn on smooth lines (i.e. anti-aliasing) */
	GPU_line_smooth(true);

	/* XXX: turn on some way of ensuring that the polygon edges get smoothed
	 *      GL_POLYGON_SMOOTH is nasty and shouldn't be used, as it ends up
	 *      creating internal white rays due to the ways it accumulates stuff
	 */

	/* turn on alpha-blending */
	GPU_blend_set_func_separate(GPU_SRC_ALPHA, GPU_ONE_MINUS_SRC_ALPHA, GPU_ONE, GPU_ONE_MINUS_SRC_ALPHA);
	GPU_blend(true);

	/* draw! */
	gp_draw_data_layers(rv3d, brush, alpha, ob, gpd, offsx, offsy, winx, winy, cfra, dflag);

	/* turn off alpha blending, then smooth lines */
	GPU_blend(false); // alpha blending
	GPU_line_smooth(false); // smooth lines
}

/* if we have strokes for scenes (3d view)/clips (movie clip editor)
 * and objects/tracks, multiple data blocks have to be drawn */
static void gp_draw_data_all(
        ViewLayer *view_layer, RegionView3D *rv3d, Scene *scene, bGPdata *gpd,
        int offsx, int offsy, int winx, int winy,
        int cfra, int dflag, const char UNUSED(spacetype))
{
	bGPdata *gpd_source = NULL;
	Brush *brush = NULL;
	Object *ob = OBACT(view_layer);
	if (scene) {
		ToolSettings *ts = scene->toolsettings;
		brush = BKE_paint_brush(&ts->gp_paint->paint);

		if (gpd_source) {
			if (brush != NULL) {
				gp_draw_data(
				        rv3d, brush, 1.0f, ob, gpd_source,
				        offsx, offsy, winx, winy, cfra, dflag);
			}
		}
	}

	/* scene/clip data has already been drawn, only object/track data is drawn here
	 * if gpd_source == gpd, we don't have any object/track data and we can skip */
	if (gpd_source == NULL || (gpd_source && gpd_source != gpd)) {
		if (brush != NULL) {
			gp_draw_data(
			        rv3d, brush, 1.0f, ob, gpd,
			        offsx, offsy, winx, winy, cfra, dflag);
		}
	}
}

/* ----- Grease Pencil Sketches Drawing API ------ */


/* draw grease-pencil sketches to specified 3d-view assuming that matrices are already set correctly
 * Note: this gets called twice - first time with only3d=true to draw 3d-strokes,
 * second time with only3d=false for screen-aligned strokes */
void ED_gpencil_draw_view3d(
        wmWindowManager *wm,
        Scene *scene,
        ViewLayer *view_layer,
        struct Depsgraph *depsgraph,
        View3D *v3d,
        ARegion *ar,
        bool only3d)
{
	int dflag = 0;
	RegionView3D *rv3d = ar->regiondata;
	int offsx,  offsy,  winx,  winy;

	/* check that we have grease-pencil stuff to draw */
	// XXX: This is the only place that still uses this function
	bGPdata *gpd = ED_gpencil_data_get_active_v3d(view_layer, v3d);
	if (gpd == NULL) return;

	/* when rendering to the offscreen buffer we don't want to
	 * deal with the camera border, otherwise map the coords to the camera border. */
	if ((rv3d->persp == RV3D_CAMOB) && !(G.f & G_RENDER_OGL)) {
		rctf rectf;
		ED_view3d_calc_camera_border(scene, depsgraph, ar, v3d, rv3d, &rectf, true); /* no shift */

		offsx = round_fl_to_int(rectf.xmin);
		offsy = round_fl_to_int(rectf.ymin);
		winx  = round_fl_to_int(rectf.xmax - rectf.xmin);
		winy  = round_fl_to_int(rectf.ymax - rectf.ymin);
	}
	else {
		offsx = 0;
		offsy = 0;
		winx  = ar->winx;
		winy  = ar->winy;
	}

	/* set flags */
	if (only3d) {
		/* 3D strokes/3D space:
		 * - only 3D space points
		 * - don't status text either (as it's the wrong space)
		 */
		dflag |= (GP_DRAWDATA_ONLY3D | GP_DRAWDATA_NOSTATUS);
	}

	if (v3d->flag2 & V3D_RENDER_OVERRIDE) {
		/* don't draw status text when "only render" flag is set */
		dflag |= GP_DRAWDATA_NOSTATUS;
	}

	if ((wm == NULL) || ED_screen_animation_playing(wm)) {
		/* don't show onion-skins during animation playback/scrub (i.e. it obscures the poses)
		 * OpenGL Renders (i.e. final output), or depth buffer (i.e. not real strokes)
		 */
		dflag |= GP_DRAWDATA_NO_ONIONS;
	}

	/* draw it! */
	gp_draw_data_all(view_layer, rv3d, scene, gpd, offsx, offsy, winx, winy, CFRA, dflag, v3d->spacetype);
}

/* draw grease-pencil sketches to specified 3d-view for gp object
 * assuming that matrices are already set correctly
 */
void ED_gpencil_draw_view3d_object(wmWindowManager *wm, Scene *scene, Depsgraph *depsgraph, Object *ob, View3D *v3d, ARegion *ar, bool only3d)
{
	int dflag = 0;
	RegionView3D *rv3d = ar->regiondata;
	int offsx, offsy, winx, winy;

	/* check that we have grease-pencil stuff to draw */
	bGPdata *gpd = ob->data;
	if (gpd == NULL) return;

	/* when rendering to the offscreen buffer we don't want to
	 * deal with the camera border, otherwise map the coords to the camera border. */
	if ((rv3d->persp == RV3D_CAMOB) && !(G.f & G_RENDER_OGL)) {
		rctf rectf;
		ED_view3d_calc_camera_border(scene, depsgraph, ar, v3d, rv3d, &rectf, true); /* no shift */

		offsx = round_fl_to_int(rectf.xmin);
		offsy = round_fl_to_int(rectf.ymin);
		winx = round_fl_to_int(rectf.xmax - rectf.xmin);
		winy = round_fl_to_int(rectf.ymax - rectf.ymin);
	}
	else {
		offsx = 0;
		offsy = 0;
		winx = ar->winx;
		winy = ar->winy;
	}

	/* set flags */
	if (only3d) {
		/* 3D strokes/3D space:
		 * - only 3D space points
		 * - don't status text either (as it's the wrong space)
		 */
		dflag |= (GP_DRAWDATA_ONLY3D | GP_DRAWDATA_NOSTATUS);
	}

	if (v3d->flag2 & V3D_RENDER_OVERRIDE) {
		/* don't draw status text when "only render" flag is set */
		dflag |= GP_DRAWDATA_NOSTATUS;
	}

	if ((wm == NULL) || ED_screen_animation_playing(wm)) {
		/* don't show onionskins during animation playback/scrub (i.e. it obscures the poses)
		 * OpenGL Renders (i.e. final output), or depth buffer (i.e. not real strokes)
		 */
		dflag |= GP_DRAWDATA_NO_ONIONS;
	}

	/* draw it! */
	ToolSettings *ts = scene->toolsettings;
	Brush *brush = BKE_paint_brush(&ts->gp_paint->paint);
	if (brush != NULL) {
		gp_draw_data(rv3d, brush, 1.0f, ob, gpd,
			offsx, offsy, winx, winy, CFRA, dflag);
	}
}

void ED_gpencil_draw_ex(
	ViewLayer *view_layer, RegionView3D *rv3d, Scene *scene,
	bGPdata *gpd, int winx, int winy, const int cfra, const char spacetype)
{
	int dflag = GP_DRAWDATA_NOSTATUS | GP_DRAWDATA_ONLYV2D;

	gp_draw_data_all(view_layer, rv3d, scene, gpd, 0, 0, winx, winy, cfra, dflag, spacetype);
}