DRW: API for own versions of builtin GPU shaders

DRW_shader_get_builtin_shader can replace GPU_shader_get_builtin_shader
when we need to support clipping.

Use this for loose point & wire drawing in object mode,
clips edges in lattice edit mode.

3 files changed, 167 insertions, 0 deletions

diff --git a/source/blender/draw/intern/draw_builtin_shader.c b/source/blender/draw/intern/draw_builtin_shader.c
new file mode 100644
index 00000000000..3f49f9d2731
--- /dev/null
+++ b/source/blender/draw/intern/draw_builtin_shader.c
@@ -0,0 +1,131 @@
+/*
+ * ***** 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.
+ *
+ * ***** END GPL LICENSE BLOCK *****
+ *
+ */
+
+/** \file draw_armature.c
+ *  \ingroup draw
+ * Draw manager versions of #eGPUBuiltinShader, see #GPU_shader_get_builtin_shader.
+ *
+ * Allows for modifications to shaders (currently only clipping support).
+ * Follow GPU_shader.h conventions to avoid annoyance.
+ */
+
+#include "BLI_utildefines.h"
+
+#include "GPU_shader.h"
+
+#include "DRW_render.h"
+
+#include "draw_builtin_shader.h"  /* own include */
+
+
+extern char datatoc_common_world_clip_lib_glsl[];
+
+extern char datatoc_drw_shader_3D_vert_glsl[];
+extern char datatoc_drw_shader_3D_smooth_color_vert_glsl[];
+
+extern char datatoc_gpu_shader_uniform_color_frag_glsl[];
+extern char datatoc_gpu_shader_3D_smooth_color_frag_glsl[];
+
+
+/* cache of built-in shaders (each is created on first use) */
+static struct {
+	GPUShader *builtin_shaders[GPU_NUM_BUILTIN_SHADERS];
+} g_sh_data[DRW_SHADER_SLOT_LEN - 1] = {{{NULL}}};
+
+static GPUShader *drw_shader_get_builtin_shader_clipped(eGPUBuiltinShader shader_id, bool *r_test_only)
+{
+	const char *world_clip_lib = datatoc_common_world_clip_lib_glsl;
+	const char *world_clip_def = "#define USE_WORLD_CLIP_PLANES\n";
+
+	if (r_test_only) {
+		*r_test_only = true;
+	}
+
+	GPUShader *shader = NULL;
+	switch (shader_id) {
+		case GPU_SHADER_3D_UNIFORM_COLOR:
+			if (r_test_only) {
+				break;
+			}
+			shader = DRW_shader_create_from_arrays({
+			        .vert = (const char *[]){world_clip_lib, datatoc_drw_shader_3D_vert_glsl, NULL},
+			        .frag = (const char *[]){datatoc_gpu_shader_uniform_color_frag_glsl, NULL},
+			        .defs = (const char *[]){world_clip_def, NULL}});
+			break;
+		case GPU_SHADER_3D_SMOOTH_COLOR:
+			if (r_test_only) {
+				break;
+			}
+			shader = DRW_shader_create_from_arrays({
+			        .vert = (const char *[]){world_clip_lib, datatoc_drw_shader_3D_smooth_color_vert_glsl, NULL},
+			        .frag = (const char *[]){datatoc_gpu_shader_3D_smooth_color_frag_glsl, NULL},
+			        .defs = (const char *[]){world_clip_def, NULL}});
+			break;
+		default:
+			/* Unsupported, caller asserts. */
+			if (r_test_only) {
+				*r_test_only = false;
+			}
+	}
+	return shader;
+}
+
+static bool drw_shader_get_builtin_shader_test_all(eGPUBuiltinShader shader_id)
+{
+	bool test = false;
+	drw_shader_get_builtin_shader_clipped(shader_id, &test);
+	return test;
+}
+
+GPUShader *DRW_shader_get_builtin_shader(eGPUBuiltinShader shader_id, eDRW_ShaderSlot slot)
+{
+	BLI_assert(drw_shader_get_builtin_shader_test_all(shader_id));
+	if (slot == DRW_SHADER_SLOT_DEFAULT) {
+		return GPU_shader_get_builtin_shader(shader_id);
+	}
+
+	GPUShader **builtin_shaders = g_sh_data[slot - 1].builtin_shaders;
+
+	if (builtin_shaders[shader_id] != NULL) {
+		return builtin_shaders[shader_id];
+	}
+
+	if (slot == DRW_SHADER_SLOT_CLIPPED) {
+		builtin_shaders[shader_id] = drw_shader_get_builtin_shader_clipped(shader_id, NULL);
+		return builtin_shaders[shader_id];
+	}
+	else {
+		BLI_assert(0);
+	}
+}
+
+void DRW_shader_free_builtin_shaders(void)
+{
+	for (int j = 0; j < (DRW_SHADER_SLOT_LEN - 1); j++) {
+		GPUShader **builtin_shaders = g_sh_data[j].builtin_shaders;
+		for (int i = 0; i < GPU_NUM_BUILTIN_SHADERS; i++) {
+			if (builtin_shaders[i]) {
+				GPU_shader_free(builtin_shaders[i]);
+				builtin_shaders[i] = NULL;
+			}
+		}
+	}
+}
diff --git a/source/blender/draw/intern/draw_builtin_shader.h b/source/blender/draw/intern/draw_builtin_shader.h
new file mode 100644
index 00000000000..f9eb42a7026
--- /dev/null
+++ b/source/blender/draw/intern/draw_builtin_shader.h
@@ -0,0 +1,34 @@
+/*
+ * ***** 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.
+ *
+ * ***** END GPL LICENSE BLOCK *****
+ *
+ */
+
+/** \file draw_builtin_shader.h
+ *  \ingroup draw
+ */
+
+#ifndef __DRAW_BUILTIN_SHADER_H__
+#define __DRAW_BUILTIN_SHADER_H__
+
+struct GPUShader;
+
+struct GPUShader *DRW_shader_get_builtin_shader(eGPUBuiltinShader shader_id, eDRW_ShaderSlot slot);
+void DRW_shader_free_builtin_shaders(void);
+
+#endif  /* __DRAW_BUILTIN_SHADER_H__ */
diff --git a/source/blender/draw/intern/draw_manager.c b/source/blender/draw/intern/draw_manager.c
index c47ab00c841..d311b3e8156 100644
--- a/source/blender/draw/intern/draw_manager.c
+++ b/source/blender/draw/intern/draw_manager.c
@@ -82,6 +82,7 @@
 #include "draw_cache_impl.h"
 
 #include "draw_mode_engines.h"
+#include "draw_builtin_shader.h"
 #include "engines/eevee/eevee_engine.h"
 #include "engines/basic/basic_engine.h"
 #include "engines/workbench/workbench_engine.h"
@@ -2610,6 +2611,7 @@ void DRW_engines_free(void)
 	DRW_shape_cache_free();
 	DRW_stats_free();
 	DRW_globals_free();
+	DRW_shader_free_builtin_shaders();
 
 	DrawEngineType *next;
 	for (DrawEngineType *type = DRW_engines.first; type; type = next) {