Blender: Add command line argument to switch gpu backends.

Add command line argument to switch gpu backend. Add `--gpu-backend` option to
override the gpu backend selected by Blender.

Values for this option that will be available in releases for now are:
* opengl: Force blender to select OpenGL backend.

During development and depending on compile options additional values can exist:
* metal: Force Blender to select Metal backend.

When this option isn't provided the internal logic for GPU backend selection will be used.
Note that this is at the time of writing the same as always selecting the opengl backend.

Reviewed By: fclem, brecht, MichaelPW

Differential Revision: https://developer.blender.org/D16297

1 files changed, 44 insertions, 0 deletions

diff --git a/source/creator/creator_args.c b/source/creator/creator_args.c
index 06b898587bf..4144603555b 100644
--- a/source/creator/creator_args.c
+++ b/source/creator/creator_args.c
@@ -42,6 +42,8 @@
 #  include "BKE_scene.h"
 #  include "BKE_sound.h"
 
+#  include "GPU_context.h"
+
 #  ifdef WITH_FFMPEG
 #    include "IMB_imbuf.h"
 #  endif
@@ -1111,6 +1113,44 @@ static int arg_handle_debug_gpu_set(int UNUSED(argc),
   return 0;
 }
 
+static const char arg_handle_gpu_backend_set_doc[] =
+    "\n"
+    "\tForce to use a specific GPU backend. Valid options: "
+#  ifdef WITH_METAL_BACKEND
+    "'metal',  "
+#  endif
+    "'opengl').";
+static int arg_handle_gpu_backend_set(int argc, const char **argv, void *UNUSED(data))
+{
+  if (argc == 0) {
+    printf("\nError: GPU backend must follow '--gpu-backend'.\n");
+    return 0;
+  }
+
+  eGPUBackendType gpu_backend = GPU_BACKEND_NONE;
+
+  if (STREQ(argv[1], "opengl")) {
+    gpu_backend = GPU_BACKEND_OPENGL;
+  }
+#  ifdef WITH_METAL_BACKEND
+  else if (STREQ(argv[1], "metal")) {
+    gpu_backend = GPU_BACKEND_METAL;
+  }
+#  endif
+  else {
+    printf("\nError: Unrecognized GPU backend for '--gpu-backend'.\n");
+    return 0;
+  }
+
+  GPU_backend_type_selection_set(gpu_backend);
+  if (!GPU_backend_supported()) {
+    printf("\nError: GPU backend not supported.\n");
+    return 0;
+  }
+
+  return 1;
+}
+
 static const char arg_handle_debug_fpe_set_doc[] =
     "\n\t"
     "Enable floating-point exceptions.";
@@ -2074,6 +2114,10 @@ void main_args_setup(bContext *C, bArgs *ba)
   BLI_args_add(ba, NULL, "--log-show-timestamp", CB(arg_handle_log_show_timestamp_set), ba);
   BLI_args_add(ba, NULL, "--log-file", CB(arg_handle_log_file_set), ba);
 
+  /* GPU backend selection should be part of ARG_PASS_ENVIRONMENT for correct GPU context selection
+   * for anim player. */
+  BLI_args_add(ba, NULL, "--gpu-backend", CB(arg_handle_gpu_backend_set), NULL);
+
   /* Pass: Background Mode & Settings
    *
    * Also and commands that exit after usage. */