DRW: Refactor & Split draw_manager.c into multiple files.

Refactor include:
- Removal of DRWInterface. (was useless)
- Split DRWCallHeader into a new struct DRWCallState that will be reused in the future.
- Use BLI_link_utils for APPEND/PREPEND.
- Creation of the new DRWManager struct type. This will enable us to create more than one manager in the future.
- Removal of some dead code.

1 files changed, 747 insertions, 0 deletions

diff --git a/source/blender/draw/intern/draw_manager_exec.c b/source/blender/draw/intern/draw_manager_exec.c
new file mode 100644
index 00000000000..80c10d18bb0
--- /dev/null
+++ b/source/blender/draw/intern/draw_manager_exec.c
@@ -0,0 +1,747 @@
+/*
+ * Copyright 2016, Blender Foundation.
+ *
+ * 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.
+ *
+ * Contributor(s): Blender Institute
+ *
+ */
+
+/** \file blender/draw/intern/draw_manager_exec.c
+ *  \ingroup draw
+ */
+
+#include "draw_manager.h"
+
+#include "BIF_glutil.h"
+
+#include "BKE_global.h"
+
+#include "GPU_draw.h"
+#include "GPU_extensions.h"
+
+#ifdef USE_GPU_SELECT
+#  include "ED_view3d.h"
+#  include "ED_armature.h"
+#  include "GPU_select.h"
+#endif
+
+#ifdef USE_GPU_SELECT
+void DRW_select_load_id(unsigned int id)
+{
+	BLI_assert(G.f & G_PICKSEL);
+	DST.select_id = id;
+}
+#endif
+
+/* -------------------------------------------------------------------- */
+
+/** \name Draw State (DRW_state)
+ * \{ */
+
+void drw_state_set(DRWState state)
+{
+	if (DST.state == state) {
+		return;
+	}
+
+#define CHANGED_TO(f) \
+	((DST.state & (f)) ? \
+		((state & (f)) ?  0 : -1) : \
+		((state & (f)) ?  1 :  0))
+
+#define CHANGED_ANY(f) \
+	((DST.state & (f)) != (state & (f)))
+
+#define CHANGED_ANY_STORE_VAR(f, enabled) \
+	((DST.state & (f)) != (enabled = (state & (f))))
+
+	/* Depth Write */
+	{
+		int test;
+		if ((test = CHANGED_TO(DRW_STATE_WRITE_DEPTH))) {
+			if (test == 1) {
+				glDepthMask(GL_TRUE);
+			}
+			else {
+				glDepthMask(GL_FALSE);
+			}
+		}
+	}
+
+	/* Color Write */
+	{
+		int test;
+		if ((test = CHANGED_TO(DRW_STATE_WRITE_COLOR))) {
+			if (test == 1) {
+				glColorMask(GL_TRUE, GL_TRUE, GL_TRUE, GL_TRUE);
+			}
+			else {
+				glColorMask(GL_FALSE, GL_FALSE, GL_FALSE, GL_FALSE);
+			}
+		}
+	}
+
+	/* Cull */
+	{
+		DRWState test;
+		if (CHANGED_ANY_STORE_VAR(
+		        DRW_STATE_CULL_BACK | DRW_STATE_CULL_FRONT,
+		        test))
+		{
+			if (test) {
+				glEnable(GL_CULL_FACE);
+
+				if ((state & DRW_STATE_CULL_BACK) != 0) {
+					glCullFace(GL_BACK);
+				}
+				else if ((state & DRW_STATE_CULL_FRONT) != 0) {
+					glCullFace(GL_FRONT);
+				}
+				else {
+					BLI_assert(0);
+				}
+			}
+			else {
+				glDisable(GL_CULL_FACE);
+			}
+		}
+	}
+
+	/* Depth Test */
+	{
+		DRWState test;
+		if (CHANGED_ANY_STORE_VAR(
+		        DRW_STATE_DEPTH_LESS | DRW_STATE_DEPTH_EQUAL | DRW_STATE_DEPTH_GREATER | DRW_STATE_DEPTH_ALWAYS,
+		        test))
+		{
+			if (test) {
+				glEnable(GL_DEPTH_TEST);
+
+				if (state & DRW_STATE_DEPTH_LESS) {
+					glDepthFunc(GL_LEQUAL);
+				}
+				else if (state & DRW_STATE_DEPTH_EQUAL) {
+					glDepthFunc(GL_EQUAL);
+				}
+				else if (state & DRW_STATE_DEPTH_GREATER) {
+					glDepthFunc(GL_GREATER);
+				}
+				else if (state & DRW_STATE_DEPTH_ALWAYS) {
+					glDepthFunc(GL_ALWAYS);
+				}
+				else {
+					BLI_assert(0);
+				}
+			}
+			else {
+				glDisable(GL_DEPTH_TEST);
+			}
+		}
+	}
+
+	/* Wire Width */
+	{
+		if (CHANGED_ANY(DRW_STATE_WIRE)) {
+			if ((state & DRW_STATE_WIRE) != 0) {
+				glLineWidth(1.0f);
+			}
+			else {
+				/* do nothing */
+			}
+		}
+	}
+
+	/* Points Size */
+	{
+		int test;
+		if ((test = CHANGED_TO(DRW_STATE_POINT))) {
+			if (test == 1) {
+				GPU_enable_program_point_size();
+				glPointSize(5.0f);
+			}
+			else {
+				GPU_disable_program_point_size();
+			}
+		}
+	}
+
+	/* Blending (all buffer) */
+	{
+		int test;
+		if (CHANGED_ANY_STORE_VAR(
+		        DRW_STATE_BLEND | DRW_STATE_ADDITIVE | DRW_STATE_MULTIPLY | DRW_STATE_TRANSMISSION |
+		        DRW_STATE_ADDITIVE_FULL,
+		        test))
+		{
+			if (test) {
+				glEnable(GL_BLEND);
+
+				if ((state & DRW_STATE_BLEND) != 0) {
+					glBlendFuncSeparate(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA, /* RGB */
+					                    GL_ONE, GL_ONE_MINUS_SRC_ALPHA); /* Alpha */
+				}
+				else if ((state & DRW_STATE_MULTIPLY) != 0) {
+					glBlendFunc(GL_DST_COLOR, GL_ZERO);
+				}
+				else if ((state & DRW_STATE_TRANSMISSION) != 0) {
+					glBlendFunc(GL_ONE, GL_SRC_ALPHA);
+				}
+				else if ((state & DRW_STATE_ADDITIVE) != 0) {
+					/* Do not let alpha accumulate but premult the source RGB by it. */
+					glBlendFuncSeparate(GL_SRC_ALPHA, GL_ONE, /* RGB */
+					                    GL_ZERO, GL_ONE); /* Alpha */
+				}
+				else if ((state & DRW_STATE_ADDITIVE_FULL) != 0) {
+					/* Let alpha accumulate. */
+					glBlendFunc(GL_ONE, GL_ONE);
+				}
+				else {
+					BLI_assert(0);
+				}
+			}
+			else {
+				glDisable(GL_BLEND);
+			}
+		}
+	}
+
+	/* Clip Planes */
+	{
+		int test;
+		if ((test = CHANGED_TO(DRW_STATE_CLIP_PLANES))) {
+			if (test == 1) {
+				for (int i = 0; i < DST.num_clip_planes; ++i) {
+					glEnable(GL_CLIP_DISTANCE0 + i);
+				}
+			}
+			else {
+				for (int i = 0; i < MAX_CLIP_PLANES; ++i) {
+					glDisable(GL_CLIP_DISTANCE0 + i);
+				}
+			}
+		}
+	}
+
+	/* Line Stipple */
+	{
+		int test;
+		if (CHANGED_ANY_STORE_VAR(
+		        DRW_STATE_STIPPLE_2 | DRW_STATE_STIPPLE_3 | DRW_STATE_STIPPLE_4,
+		        test))
+		{
+			if (test) {
+				if ((state & DRW_STATE_STIPPLE_2) != 0) {
+					setlinestyle(2);
+				}
+				else if ((state & DRW_STATE_STIPPLE_3) != 0) {
+					setlinestyle(3);
+				}
+				else if ((state & DRW_STATE_STIPPLE_4) != 0) {
+					setlinestyle(4);
+				}
+				else {
+					BLI_assert(0);
+				}
+			}
+			else {
+				setlinestyle(0);
+			}
+		}
+	}
+
+	/* Stencil */
+	{
+		DRWState test;
+		if (CHANGED_ANY_STORE_VAR(
+		        DRW_STATE_WRITE_STENCIL |
+		        DRW_STATE_STENCIL_EQUAL,
+		        test))
+		{
+			if (test) {
+				glEnable(GL_STENCIL_TEST);
+
+				/* Stencil Write */
+				if ((state & DRW_STATE_WRITE_STENCIL) != 0) {
+					glStencilMask(0xFF);
+					glStencilOp(GL_KEEP, GL_KEEP, GL_REPLACE);
+				}
+				/* Stencil Test */
+				else if ((state & DRW_STATE_STENCIL_EQUAL) != 0) {
+					glStencilMask(0x00); /* disable write */
+					DST.stencil_mask = 0;
+				}
+				else {
+					BLI_assert(0);
+				}
+			}
+			else {
+				/* disable write & test */
+				DST.stencil_mask = 0;
+				glStencilMask(0x00);
+				glStencilFunc(GL_ALWAYS, 1, 0xFF);
+				glDisable(GL_STENCIL_TEST);
+			}
+		}
+	}
+
+#undef CHANGED_TO
+#undef CHANGED_ANY
+#undef CHANGED_ANY_STORE_VAR
+
+	DST.state = state;
+}
+
+static void drw_stencil_set(unsigned int mask)
+{
+	if (DST.stencil_mask != mask) {
+		/* Stencil Write */
+		if ((DST.state & DRW_STATE_WRITE_STENCIL) != 0) {
+			glStencilFunc(GL_ALWAYS, mask, 0xFF);
+			DST.stencil_mask = mask;
+		}
+		/* Stencil Test */
+		else if ((DST.state & DRW_STATE_STENCIL_EQUAL) != 0) {
+			glStencilFunc(GL_EQUAL, mask, 0xFF);
+			DST.stencil_mask = mask;
+		}
+	}
+}
+
+/* Reset state to not interfer with other UI drawcall */
+void DRW_state_reset_ex(DRWState state)
+{
+	DST.state = ~state;
+	drw_state_set(state);
+}
+
+void DRW_state_reset(void)
+{
+	/* Reset blending function */
+	glBlendFuncSeparate(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA, GL_ONE, GL_ONE_MINUS_SRC_ALPHA);
+
+	DRW_state_reset_ex(DRW_STATE_DEFAULT);
+}
+
+/* NOTE : Make sure to reset after use! */
+void DRW_state_invert_facing(void)
+{
+	SWAP(GLenum, DST.backface, DST.frontface);
+	glFrontFace(DST.frontface);
+}
+
+/**
+ * This only works if DRWPasses have been tagged with DRW_STATE_CLIP_PLANES,
+ * and if the shaders have support for it (see usage of gl_ClipDistance).
+ * Be sure to call DRW_state_clip_planes_reset() after you finish drawing.
+ **/
+void DRW_state_clip_planes_add(float plane_eq[4])
+{
+	BLI_assert(DST.num_clip_planes < MAX_CLIP_PLANES-1);
+	copy_v4_v4(DST.view_data.clip_planes_eq[DST.num_clip_planes++], plane_eq);
+}
+
+void DRW_state_clip_planes_reset(void)
+{
+	DST.num_clip_planes = 0;
+}
+
+/** \} */
+
+/* -------------------------------------------------------------------- */
+
+/** \name Draw (DRW_draw)
+ * \{ */
+
+static void draw_matrices_model_prepare(DRWCallState *st)
+{
+	/* OPTI : We can optimize further by sharing this computation for each call using the same object. */
+	/* Order matters */
+	if (st->matflag & (DRW_CALL_MODELVIEW | DRW_CALL_MODELVIEWINVERSE |
+	                  DRW_CALL_NORMALVIEW | DRW_CALL_EYEVEC))
+	{
+		mul_m4_m4m4(st->modelview, DST.view_data.mat[DRW_MAT_VIEW], st->model);
+	}
+	if (st->matflag & DRW_CALL_MODELVIEWINVERSE) {
+		invert_m4_m4(st->modelviewinverse, st->modelview);
+	}
+	if (st->matflag & DRW_CALL_MODELVIEWPROJECTION) {
+		mul_m4_m4m4(st->modelviewprojection, DST.view_data.mat[DRW_MAT_PERS], st->model);
+	}
+	if (st->matflag & DRW_CALL_NORMALVIEW) {
+		copy_m3_m4(st->normalview, st->modelview);
+		invert_m3(st->normalview);
+		transpose_m3(st->normalview);
+	}
+	if (st->matflag & DRW_CALL_EYEVEC) {
+		/* Used by orthographic wires */
+		float tmp[3][3];
+		copy_v3_fl3(st->eyevec, 0.0f, 0.0f, 1.0f);
+		invert_m3_m3(tmp, st->normalview);
+		/* set eye vector, transformed to object coords */
+		mul_m3_v3(tmp, st->eyevec);
+	}
+	/* Non view dependant */
+	if (st->matflag & DRW_CALL_MODELINVERSE) {
+		invert_m4_m4(st->modelinverse, st->model);
+		st->matflag &= ~DRW_CALL_MODELINVERSE;
+	}
+	if (st->matflag & DRW_CALL_NORMALWORLD) {
+		copy_m3_m4(st->normalworld, st->model);
+		invert_m3(st->normalworld);
+		transpose_m3(st->normalworld);
+		st->matflag &= ~DRW_CALL_NORMALWORLD;
+	}
+}
+
+static void draw_geometry_prepare(DRWShadingGroup *shgroup, DRWCallState *state)
+{
+	/* step 1 : bind object dependent matrices */
+	if (state != NULL) {
+		/* OPTI/IDEA(clem): Do this preparation in another thread. */
+		draw_matrices_model_prepare(state);
+		GPU_shader_uniform_vector(shgroup->shader, shgroup->model, 16, 1, (float *)state->model);
+		GPU_shader_uniform_vector(shgroup->shader, shgroup->modelinverse, 16, 1, (float *)state->modelinverse);
+		GPU_shader_uniform_vector(shgroup->shader, shgroup->modelview, 16, 1, (float *)state->modelview);
+		GPU_shader_uniform_vector(shgroup->shader, shgroup->modelviewinverse, 16, 1, (float *)state->modelviewinverse);
+		GPU_shader_uniform_vector(shgroup->shader, shgroup->modelviewprojection, 16, 1, (float *)state->modelviewprojection);
+		GPU_shader_uniform_vector(shgroup->shader, shgroup->normalview, 9, 1, (float *)state->normalview);
+		GPU_shader_uniform_vector(shgroup->shader, shgroup->normalworld, 9, 1, (float *)state->normalworld);
+		GPU_shader_uniform_vector(shgroup->shader, shgroup->orcotexfac, 3, 2, (float *)state->orcotexfac);
+		GPU_shader_uniform_vector(shgroup->shader, shgroup->eye, 3, 1, (float *)state->eyevec);
+	}
+	else {
+		BLI_assert((shgroup->normalview == -1) && (shgroup->normalworld == -1) && (shgroup->eye == -1));
+		/* For instancing and batching. */
+		float unitmat[4][4];
+		unit_m4(unitmat);
+		GPU_shader_uniform_vector(shgroup->shader, shgroup->model, 16, 1, (float *)unitmat);
+		GPU_shader_uniform_vector(shgroup->shader, shgroup->modelinverse, 16, 1, (float *)unitmat);
+		GPU_shader_uniform_vector(shgroup->shader, shgroup->modelview, 16, 1, (float *)DST.view_data.mat[DRW_MAT_VIEW]);
+		GPU_shader_uniform_vector(shgroup->shader, shgroup->modelviewinverse, 16, 1, (float *)DST.view_data.mat[DRW_MAT_VIEWINV]);
+		GPU_shader_uniform_vector(shgroup->shader, shgroup->modelviewprojection, 16, 1, (float *)DST.view_data.mat[DRW_MAT_PERS]);
+		GPU_shader_uniform_vector(shgroup->shader, shgroup->orcotexfac, 3, 2, (float *)shgroup->instance_orcofac);
+	}
+}
+
+static void draw_geometry_execute_ex(
+        DRWShadingGroup *shgroup, Gwn_Batch *geom, unsigned int start, unsigned int count)
+{
+	/* Special case: empty drawcall, placement is done via shader, don't bind anything. */
+	if (geom == NULL) {
+		BLI_assert(shgroup->type == DRW_SHG_TRIANGLE_BATCH); /* Add other type if needed. */
+		/* Shader is already bound. */
+		GWN_draw_primitive(GWN_PRIM_TRIS, count);
+		return;
+	}
+
+	/* step 2 : bind vertex array & draw */
+	GWN_batch_program_set_no_use(geom, GPU_shader_get_program(shgroup->shader), GPU_shader_get_interface(shgroup->shader));
+	/* XXX hacking gawain. we don't want to call glUseProgram! (huge performance loss) */
+	geom->program_in_use = true;
+	if (ELEM(shgroup->type, DRW_SHG_INSTANCE, DRW_SHG_INSTANCE_EXTERNAL)) {
+		GWN_batch_draw_range_ex(geom, start, count, true);
+	}
+	else {
+		GWN_batch_draw_range(geom, start, count);
+	}
+	geom->program_in_use = false; /* XXX hacking gawain */
+}
+
+static void draw_geometry_execute(DRWShadingGroup *shgroup, Gwn_Batch *geom)
+{
+	draw_geometry_execute_ex(shgroup, geom, 0, 0);
+}
+
+static void bind_texture(GPUTexture *tex)
+{
+	int bind_num = GPU_texture_bound_number(tex);
+	if (bind_num == -1) {
+		for (int i = 0; i < GPU_max_textures(); ++i) {
+			DST.RST.bind_tex_inc = (DST.RST.bind_tex_inc + 1) % GPU_max_textures();
+			if (DST.RST.bound_tex_slots[DST.RST.bind_tex_inc] == false) {
+				if (DST.RST.bound_texs[DST.RST.bind_tex_inc] != NULL) {
+					GPU_texture_unbind(DST.RST.bound_texs[DST.RST.bind_tex_inc]);
+				}
+				GPU_texture_bind(tex, DST.RST.bind_tex_inc);
+				DST.RST.bound_texs[DST.RST.bind_tex_inc] = tex;
+				DST.RST.bound_tex_slots[DST.RST.bind_tex_inc] = true;
+				// printf("Binds Texture %d %p\n", DST.RST.bind_tex_inc, tex);
+				return;
+			}
+		}
+
+		printf("Not enough texture slots! Reduce number of textures used by your shader.\n");
+	}
+	DST.RST.bound_tex_slots[bind_num] = true;
+}
+
+static void bind_ubo(GPUUniformBuffer *ubo)
+{
+	if (DST.RST.bind_ubo_inc < GPU_max_ubo_binds()) {
+		GPU_uniformbuffer_bind(ubo, DST.RST.bind_ubo_inc);
+		DST.RST.bind_ubo_inc++;
+	}
+	else {
+		/* This is not depending on user input.
+		 * It is our responsability to make sure there enough slots. */
+		BLI_assert(0 && "Not enough ubo slots! This should not happen!\n");
+
+		/* printf so user can report bad behaviour */
+		printf("Not enough ubo slots! This should not happen!\n");
+	}
+}
+
+static void release_texture_slots(void)
+{
+	memset(DST.RST.bound_tex_slots, 0x0, sizeof(bool) * GPU_max_textures());
+}
+
+static void release_ubo_slots(void)
+{
+	DST.RST.bind_ubo_inc = 0;
+}
+
+static void draw_shgroup(DRWShadingGroup *shgroup, DRWState pass_state)
+{
+	BLI_assert(shgroup->shader);
+
+	GPUTexture *tex;
+	GPUUniformBuffer *ubo;
+	int val;
+	float fval;
+
+	if (DST.shader != shgroup->shader) {
+		if (DST.shader) GPU_shader_unbind();
+		GPU_shader_bind(shgroup->shader);
+		DST.shader = shgroup->shader;
+	}
+
+	release_texture_slots();
+	release_ubo_slots();
+
+	drw_state_set((pass_state & shgroup->state_extra_disable) | shgroup->state_extra);
+	drw_stencil_set(shgroup->stencil_mask);
+
+	/* Binding Uniform */
+	/* Don't check anything, Interface should already contain the least uniform as possible */
+	for (DRWUniform *uni = shgroup->uniforms; uni; uni = uni->next) {
+		switch (uni->type) {
+			case DRW_UNIFORM_SHORT_TO_INT:
+				val = (int)*((short *)uni->value);
+				GPU_shader_uniform_vector_int(
+				        shgroup->shader, uni->location, uni->length, uni->arraysize, (int *)&val);
+				break;
+			case DRW_UNIFORM_SHORT_TO_FLOAT:
+				fval = (float)*((short *)uni->value);
+				GPU_shader_uniform_vector(
+				        shgroup->shader, uni->location, uni->length, uni->arraysize, (float *)&fval);
+				break;
+			case DRW_UNIFORM_BOOL:
+			case DRW_UNIFORM_INT:
+				GPU_shader_uniform_vector_int(
+				        shgroup->shader, uni->location, uni->length, uni->arraysize, (int *)uni->value);
+				break;
+			case DRW_UNIFORM_FLOAT:
+				GPU_shader_uniform_vector(
+				        shgroup->shader, uni->location, uni->length, uni->arraysize, (float *)uni->value);
+				break;
+			case DRW_UNIFORM_TEXTURE:
+				tex = (GPUTexture *)uni->value;
+				BLI_assert(tex);
+				bind_texture(tex);
+				GPU_shader_uniform_texture(shgroup->shader, uni->location, tex);
+				break;
+			case DRW_UNIFORM_BUFFER:
+				if (!DRW_state_is_fbo()) {
+					break;
+				}
+				tex = *((GPUTexture **)uni->value);
+				BLI_assert(tex);
+				bind_texture(tex);
+				GPU_shader_uniform_texture(shgroup->shader, uni->location, tex);
+				break;
+			case DRW_UNIFORM_BLOCK:
+				ubo = (GPUUniformBuffer *)uni->value;
+				bind_ubo(ubo);
+				GPU_shader_uniform_buffer(shgroup->shader, uni->location, ubo);
+				break;
+		}
+	}
+
+#ifdef USE_GPU_SELECT
+	/* use the first item because of selection we only ever add one */
+#  define GPU_SELECT_LOAD_IF_PICKSEL(_call) \
+	if ((G.f & G_PICKSEL) && (_call)) { \
+		GPU_select_load_id((_call)->head.select_id); \
+	} ((void)0)
+
+#  define GPU_SELECT_LOAD_IF_PICKSEL_LIST(_shgroup, _start, _count)  \
+	_start = 0;                                                      \
+	_count = _shgroup->instance_count;                     \
+	int *select_id = NULL;                                           \
+	if (G.f & G_PICKSEL) {                                           \
+		if (_shgroup->override_selectid == -1) {                        \
+			select_id = DRW_instance_data_get(_shgroup->inst_selectid); \
+			switch (_shgroup->type) {                                             \
+				case DRW_SHG_TRIANGLE_BATCH: _count = 3; break;                   \
+				case DRW_SHG_LINE_BATCH: _count = 2; break;                       \
+				default: _count = 1; break;                                       \
+			}                                                                     \
+		}                                                                         \
+		else {                                                                    \
+			GPU_select_load_id(_shgroup->override_selectid);            \
+		}                                                                         \
+	}                                                                \
+	while (_start < _shgroup->instance_count) {            \
+		if (select_id) {                                             \
+			GPU_select_load_id(select_id[_start]);                   \
+		}
+
+# define GPU_SELECT_LOAD_IF_PICKSEL_LIST_END(_start, _count) \
+		_start += _count;                                    \
+	}
+
+#else
+#  define GPU_SELECT_LOAD_IF_PICKSEL(call)
+#  define GPU_SELECT_LOAD_IF_PICKSEL_LIST_END(start, count)
+#  define GPU_SELECT_LOAD_IF_PICKSEL_LIST(_shgroup, _start, _count) \
+	_start = 0;                                                     \
+	_count = _shgroup->interface.instance_count;
+
+#endif
+
+	/* Rendering Calls */
+	if (!ELEM(shgroup->type, DRW_SHG_NORMAL)) {
+		/* Replacing multiple calls with only one */
+		if (ELEM(shgroup->type, DRW_SHG_INSTANCE, DRW_SHG_INSTANCE_EXTERNAL)) {
+			if (shgroup->type == DRW_SHG_INSTANCE_EXTERNAL) {
+				if (shgroup->instance_geom != NULL) {
+					unsigned int count, start;
+					draw_geometry_prepare(shgroup, NULL);
+					/* This will only load override_selectid */
+					GPU_SELECT_LOAD_IF_PICKSEL_LIST(shgroup, start, count)
+					{
+						draw_geometry_execute(shgroup, shgroup->instance_geom);
+					}
+					GPU_SELECT_LOAD_IF_PICKSEL_LIST_END(start, count)
+				}
+			}
+			else {
+				if (shgroup->instance_count > 0) {
+					unsigned int count, start;
+					draw_geometry_prepare(shgroup, NULL);
+					GPU_SELECT_LOAD_IF_PICKSEL_LIST(shgroup, start, count)
+					{
+						draw_geometry_execute_ex(shgroup, shgroup->instance_geom, start, count);
+					}
+					GPU_SELECT_LOAD_IF_PICKSEL_LIST_END(start, count)
+				}
+			}
+		}
+		else { /* DRW_SHG_***_BATCH */
+			/* Some dynamic batch can have no geom (no call to aggregate) */
+			if (shgroup->instance_count > 0) {
+				unsigned int count, start;
+				draw_geometry_prepare(shgroup, NULL);
+				GPU_SELECT_LOAD_IF_PICKSEL_LIST(shgroup, start, count)
+				{
+					draw_geometry_execute_ex(shgroup, shgroup->batch_geom, start, count);
+				}
+				GPU_SELECT_LOAD_IF_PICKSEL_LIST_END(start, count)
+			}
+		}
+	}
+	else {
+		bool prev_neg_scale = false;
+		for (DRWCall *call = (DRWCall *)shgroup->calls.first; call; call = (DRWCall *)call->head.next) {
+			if ((call->state.flag & DRW_CALL_CULLED) != 0)
+				continue;
+
+			/* Negative scale objects */
+			bool neg_scale = call->state.flag & DRW_CALL_NEGSCALE;
+			if (neg_scale != prev_neg_scale) {
+				glFrontFace((neg_scale) ? DST.backface : DST.frontface);
+				prev_neg_scale = neg_scale;
+			}
+
+			GPU_SELECT_LOAD_IF_PICKSEL(call);
+
+			if (call->head.type == DRW_CALL_SINGLE) {
+				draw_geometry_prepare(shgroup, &call->state);
+				draw_geometry_execute(shgroup, call->geometry);
+			}
+			else {
+				BLI_assert(call->head.type == DRW_CALL_GENERATE);
+				DRWCallGenerate *callgen = ((DRWCallGenerate *)call);
+				draw_geometry_prepare(shgroup, &callgen->state);
+				callgen->geometry_fn(shgroup, draw_geometry_execute, callgen->user_data);
+			}
+		}
+		/* Reset state */
+		glFrontFace(DST.frontface);
+	}
+
+	/* TODO: remove, (currently causes alpha issue with sculpt, need to investigate) */
+	DRW_state_reset();
+}
+
+static void drw_draw_pass_ex(DRWPass *pass, DRWShadingGroup *start_group, DRWShadingGroup *end_group)
+{
+	/* Start fresh */
+	DST.shader = NULL;
+
+	BLI_assert(DST.buffer_finish_called && "DRW_render_instance_buffer_finish had not been called before drawing");
+
+	drw_state_set(pass->state);
+
+	DRW_stats_query_start(pass->name);
+
+	for (DRWShadingGroup *shgroup = start_group; shgroup; shgroup = shgroup->next) {
+		draw_shgroup(shgroup, pass->state);
+		/* break if upper limit */
+		if (shgroup == end_group) {
+			break;
+		}
+	}
+
+	/* Clear Bound textures */
+	for (int i = 0; i < GPU_max_textures(); i++) {
+		if (DST.RST.bound_texs[i] != NULL) {
+			GPU_texture_unbind(DST.RST.bound_texs[i]);
+			DST.RST.bound_texs[i] = NULL;
+		}
+	}
+
+	if (DST.shader) {
+		GPU_shader_unbind();
+		DST.shader = NULL;
+	}
+
+	DRW_stats_query_end();
+}
+
+void DRW_draw_pass(DRWPass *pass)
+{
+	drw_draw_pass_ex(pass, pass->shgroups.first, pass->shgroups.last);
+}
+
+/* Draw only a subset of shgroups. Used in special situations as grease pencil strokes */
+void DRW_draw_pass_subset(DRWPass *pass, DRWShadingGroup *start_group, DRWShadingGroup *end_group)
+{
+	drw_draw_pass_ex(pass, start_group, end_group);
+}
+
+/** \} */