GPU: make using the glsl basic-shader a flag

This allows for it to be more easily tested.

source/blender/gpu/GPU_basic_shader.h

@@ -110,6 +110,9 @@ void GPU_basic_shader_stipple(GPUBasicShaderStipple stipple_id);
 void GPU_basic_shader_line_stipple(GLint stipple_factor, GLushort stipple_pattern);
 void GPU_basic_shader_line_width(float line_width);
 
+bool GPU_basic_shader_use_glsl_get(void);
+void GPU_basic_shader_use_glsl_set(bool enabled);
+
 #ifdef __cplusplus
 }
 #endif

source/blender/gpu/intern/gpu_basic_shader.c

@@ -51,8 +51,6 @@
 
 /* State */
 
-static const bool USE_GLSL = false;
-
 static struct {
 	GPUShader *cached_shaders[GPU_SHADER_OPTION_COMBINATIONS];
 	bool failed_shaders[GPU_SHADER_OPTION_COMBINATIONS];
@@ -269,6 +267,24 @@ const GLubyte stipple_hexagon[128] = {
 	0x22, 0x22, 0x22, 0x22, 0x22, 0x22, 0x22, 0x22};
 /* ********************************************* */
 
+/* GLSL State */
+
+static bool USE_GLSL = false;
+
+/**
+ * \note this isn't part of the basic shader API,
+ * only set from the command line once on startup.
+ */
+void GPU_basic_shader_use_glsl_set(bool enabled)
+{
+	USE_GLSL = enabled;
+}
+
+bool GPU_basic_shader_use_glsl_get(void)
+{
+	return USE_GLSL;
+}
+
 /* Init / exit */
 
 void GPU_basic_shaders_init(void)

source/creator/creator_args.c

@@ -72,6 +72,7 @@
 
 #include "WM_api.h"
 
+#include "GPU_basic_shader.h"
 #include "GPU_draw.h"
 #include "GPU_extensions.h"
 
@@ -591,6 +592,7 @@ static int arg_handle_print_help(int UNUSED(argc), const char **UNUSED(argv), vo
 	printf("\n");
 	printf("Experimental Features:\n");
 	BLI_argsPrintArgDoc(ba, "--enable-new-depsgraph");
+	BLI_argsPrintArgDoc(ba, "--enable-new-basic-shader-glsl");
 
 	printf("\n");
 	printf("Argument Parsing:\n");
@@ -1172,6 +1174,16 @@ static int arg_handle_depsgraph_use_new(int UNUSED(argc), const char **UNUSED(ar
 	return 0;
 }
 
+static const char arg_handle_basic_shader_glsl_use_new_doc[] =
+"\n\tUse new GLSL basic shader"
+;
+static int arg_handle_basic_shader_glsl_use_new(int UNUSED(argc), const char **UNUSED(argv), void *UNUSED(data))
+{
+	printf("Using new GLSL basic shader.\n");
+	GPU_basic_shader_use_glsl_set(true);
+	return 0;
+}
+
 static const char arg_handle_verbosity_set_doc[] =
 "<verbose>\n"
 "\tSet logging verbosity level."
@@ -1807,6 +1819,7 @@ void main_args_setup(bContext *C, bArgs *ba, SYS_SystemHandle *syshandle)
 	            CB_EX(arg_handle_debug_mode_generic_set, gpumem), (void *)G_DEBUG_GPU_MEM);
 
 	BLI_argsAdd(ba, 1, NULL, "--enable-new-depsgraph", CB(arg_handle_depsgraph_use_new), NULL);
+	BLI_argsAdd(ba, 1, NULL, "--enable-new-basic-shader-glsl", CB(arg_handle_basic_shader_glsl_use_new), NULL);
 
 	BLI_argsAdd(ba, 1, NULL, "--verbose", CB(arg_handle_verbosity_set), NULL);