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

20 files changed, 28 insertions, 53 deletions

diff --git a/intern/ghost/GHOST_C-api.h b/intern/ghost/GHOST_C-api.h
index 7fda535a7ac..62984c762c1 100644
--- a/intern/ghost/GHOST_C-api.h
+++ b/intern/ghost/GHOST_C-api.h
@@ -162,7 +162,6 @@ extern void GHOST_GetAllDisplayDimensions(GHOST_SystemHandle systemhandle,
  * \param height: The height the window.
  * \param state: The state of the window when opened.
  * \param is_dialog: Stay on top of parent window, no icon in taskbar, can't be minimized.
- * \param type: The type of drawing context installed in this window.
  * \param glSettings: Misc OpenGL options.
  * \return A handle to the new window ( == NULL if creation failed).
  */
@@ -175,7 +174,6 @@ extern GHOST_WindowHandle GHOST_CreateWindow(GHOST_SystemHandle systemhandle,
                                              uint32_t height,
                                              GHOST_TWindowState state,
                                              bool is_dialog,
-                                             GHOST_TDrawingContextType type,
                                              GHOST_GLSettings glSettings);
 
 /**
diff --git a/intern/ghost/GHOST_ISystem.h b/intern/ghost/GHOST_ISystem.h
index 9fb94ed1525..64b5f4ee496 100644
--- a/intern/ghost/GHOST_ISystem.h
+++ b/intern/ghost/GHOST_ISystem.h
@@ -232,7 +232,6 @@ class GHOST_ISystem {
    * \param width: The width the window.
    * \param height: The height the window.
    * \param state: The state of the window when opened.
-   * \param type: The type of drawing context installed in this window.
    * \param glSettings: Misc OpenGL settings.
    * \param exclusive: Use to show the window on top and ignore others (used full-screen).
    * \param is_dialog: Stay on top of parent window, no icon in taskbar, can't be minimized.
@@ -245,7 +244,6 @@ class GHOST_ISystem {
                                       uint32_t width,
                                       uint32_t height,
                                       GHOST_TWindowState state,
-                                      GHOST_TDrawingContextType type,
                                       GHOST_GLSettings glSettings,
                                       const bool exclusive = false,
                                       const bool is_dialog = false,
diff --git a/intern/ghost/GHOST_Types.h b/intern/ghost/GHOST_Types.h
index 2645ce448b0..db4eeff3122 100644
--- a/intern/ghost/GHOST_Types.h
+++ b/intern/ghost/GHOST_Types.h
@@ -60,10 +60,6 @@ typedef struct {
   int hot_spot[2];
 } GHOST_CursorBitmapRef;
 
-typedef struct {
-  int flags;
-} GHOST_GLSettings;
-
 typedef enum {
   GHOST_glStereoVisual = (1 << 0),
   GHOST_glDebugContext = (1 << 1),
@@ -157,6 +153,9 @@ typedef enum {
 #ifdef WIN32
   GHOST_kDrawingContextTypeD3D,
 #endif
+#ifdef __APPLE__
+  GHOST_kDrawingContextTypeMetal,
+#endif
 } GHOST_TDrawingContextType;
 
 typedef enum {
@@ -598,6 +597,11 @@ typedef struct {
   uint32_t frequency;
 } GHOST_DisplaySetting;
 
+typedef struct {
+  int flags;
+  GHOST_TDrawingContextType context_type;
+} GHOST_GLSettings;
+
 typedef enum {
   /** Axis that cursor grab will wrap. */
   GHOST_kDebugDefault = (1 << 1),
diff --git a/intern/ghost/intern/GHOST_C-api.cpp b/intern/ghost/intern/GHOST_C-api.cpp
index 158e979cdf2..aa2363c10b3 100644
--- a/intern/ghost/intern/GHOST_C-api.cpp
+++ b/intern/ghost/intern/GHOST_C-api.cpp
@@ -161,7 +161,6 @@ GHOST_WindowHandle GHOST_CreateWindow(GHOST_SystemHandle systemhandle,
                                       uint32_t height,
                                       GHOST_TWindowState state,
                                       bool is_dialog,
-                                      GHOST_TDrawingContextType type,
                                       GHOST_GLSettings glSettings)
 {
   GHOST_ISystem *system = (GHOST_ISystem *)systemhandle;
@@ -172,7 +171,6 @@ GHOST_WindowHandle GHOST_CreateWindow(GHOST_SystemHandle systemhandle,
                                                   width,
                                                   height,
                                                   state,
-                                                  type,
                                                   glSettings,
                                                   false,
                                                   is_dialog,
diff --git a/intern/ghost/intern/GHOST_ContextCGL.h b/intern/ghost/intern/GHOST_ContextCGL.h
index 130b926f25c..d19fffffb43 100644
--- a/intern/ghost/intern/GHOST_ContextCGL.h
+++ b/intern/ghost/intern/GHOST_ContextCGL.h
@@ -30,7 +30,8 @@ class GHOST_ContextCGL : public GHOST_Context {
   GHOST_ContextCGL(bool stereoVisual,
                    NSView *metalView,
                    CAMetalLayer *metalLayer,
-                   NSOpenGLView *openglView);
+                   NSOpenGLView *openglView,
+                   GHOST_TDrawingContextType type);
 
   /**
    * Destructor.
diff --git a/intern/ghost/intern/GHOST_ContextCGL.mm b/intern/ghost/intern/GHOST_ContextCGL.mm
index ff53ecdbbba..9dad337a5d6 100644
--- a/intern/ghost/intern/GHOST_ContextCGL.mm
+++ b/intern/ghost/intern/GHOST_ContextCGL.mm
@@ -46,8 +46,10 @@ int GHOST_ContextCGL::s_sharedCount = 0;
 GHOST_ContextCGL::GHOST_ContextCGL(bool stereoVisual,
                                    NSView *metalView,
                                    CAMetalLayer *metalLayer,
-                                   NSOpenGLView *openGLView)
+                                   NSOpenGLView *openGLView,
+                                   GHOST_TDrawingContextType type)
     : GHOST_Context(stereoVisual),
+      m_useMetalForRendering(type == GHOST_kDrawingContextTypeMetal),
       m_metalView(metalView),
       m_metalLayer(metalLayer),
       m_metalCmdQueue(nil),
diff --git a/intern/ghost/intern/GHOST_System.cpp b/intern/ghost/intern/GHOST_System.cpp
index 94d021fd822..670ede35989 100644
--- a/intern/ghost/intern/GHOST_System.cpp
+++ b/intern/ghost/intern/GHOST_System.cpp
@@ -384,6 +384,7 @@ GHOST_TSuccess GHOST_System::createFullScreenWindow(GHOST_Window **window,
   if (stereoVisual) {
     glSettings.flags |= GHOST_glStereoVisual;
   }
+  glSettings.context_type = GHOST_kDrawingContextTypeOpenGL;
   /* NOTE: don't use #getCurrentDisplaySetting() because on X11 we may
    * be zoomed in and the desktop may be bigger than the viewport. */
   GHOST_ASSERT(m_displayManager,
@@ -395,7 +396,6 @@ GHOST_TSuccess GHOST_System::createFullScreenWindow(GHOST_Window **window,
                                          settings.xPixels,
                                          settings.yPixels,
                                          GHOST_kWindowStateNormal,
-                                         GHOST_kDrawingContextTypeOpenGL,
                                          glSettings,
                                          true /* exclusive */);
   return (*window == nullptr) ? GHOST_kFailure : GHOST_kSuccess;
diff --git a/intern/ghost/intern/GHOST_SystemCocoa.h b/intern/ghost/intern/GHOST_SystemCocoa.h
index dbb41c7fddf..0211694aad4 100644
--- a/intern/ghost/intern/GHOST_SystemCocoa.h
+++ b/intern/ghost/intern/GHOST_SystemCocoa.h
@@ -77,7 +77,6 @@ class GHOST_SystemCocoa : public GHOST_System {
    * \param width: The width the window.
    * \param height: The height the window.
    * \param state: The state of the window when opened.
-   * \param type: The type of drawing context installed in this window.
    * \param glSettings: Misc OpenGL settings.
    * \param exclusive: Use to show the window on top and ignore others (used full-screen).
    * \param parentWindow: Parent (embedder) window.
@@ -89,7 +88,6 @@ class GHOST_SystemCocoa : public GHOST_System {
                               uint32_t width,
                               uint32_t height,
                               GHOST_TWindowState state,
-                              GHOST_TDrawingContextType type,
                               GHOST_GLSettings glSettings,
                               const bool exclusive = false,
                               const bool is_dialog = false,
diff --git a/intern/ghost/intern/GHOST_SystemCocoa.mm b/intern/ghost/intern/GHOST_SystemCocoa.mm
index bfa90114e4c..a1016dd4843 100644
--- a/intern/ghost/intern/GHOST_SystemCocoa.mm
+++ b/intern/ghost/intern/GHOST_SystemCocoa.mm
@@ -689,7 +689,6 @@ GHOST_IWindow *GHOST_SystemCocoa::createWindow(const char *title,
                                                uint32_t width,
                                                uint32_t height,
                                                GHOST_TWindowState state,
-                                               GHOST_TDrawingContextType type,
                                                GHOST_GLSettings glSettings,
                                                const bool exclusive,
                                                const bool is_dialog,
@@ -719,7 +718,7 @@ GHOST_IWindow *GHOST_SystemCocoa::createWindow(const char *title,
                                    width,
                                    height,
                                    state,
-                                   type,
+                                   glSettings.context_type,
                                    glSettings.flags & GHOST_glStereoVisual,
                                    glSettings.flags & GHOST_glDebugContext,
                                    is_dialog,
@@ -751,7 +750,7 @@ GHOST_IWindow *GHOST_SystemCocoa::createWindow(const char *title,
  */
 GHOST_IContext *GHOST_SystemCocoa::createOffscreenContext(GHOST_GLSettings glSettings)
 {
-  GHOST_Context *context = new GHOST_ContextCGL(false, NULL, NULL, NULL);
+  GHOST_Context *context = new GHOST_ContextCGL(false, NULL, NULL, NULL, glSettings.context_type);
   if (context->initializeDrawingContext())
     return context;
   else
diff --git a/intern/ghost/intern/GHOST_SystemHeadless.h b/intern/ghost/intern/GHOST_SystemHeadless.h
index b02a82fc9eb..66af65f763d 100644
--- a/intern/ghost/intern/GHOST_SystemHeadless.h
+++ b/intern/ghost/intern/GHOST_SystemHeadless.h
@@ -142,7 +142,6 @@ class GHOST_SystemHeadless : public GHOST_System {
                               uint32_t width,
                               uint32_t height,
                               GHOST_TWindowState state,
-                              GHOST_TDrawingContextType type,
                               GHOST_GLSettings glSettings,
                               const bool /*exclusive*/,
                               const bool /*is_dialog*/,
@@ -155,7 +154,7 @@ class GHOST_SystemHeadless : public GHOST_System {
                                 height,
                                 state,
                                 parentWindow,
-                                type,
+                                glSettings.context_type,
                                 ((glSettings.flags & GHOST_glStereoVisual) != 0));
   }
 
diff --git a/intern/ghost/intern/GHOST_SystemSDL.cpp b/intern/ghost/intern/GHOST_SystemSDL.cpp
index ad5c4dc85fb..9174664adc4 100644
--- a/intern/ghost/intern/GHOST_SystemSDL.cpp
+++ b/intern/ghost/intern/GHOST_SystemSDL.cpp
@@ -42,7 +42,6 @@ GHOST_IWindow *GHOST_SystemSDL::createWindow(const char *title,
                                              uint32_t width,
                                              uint32_t height,
                                              GHOST_TWindowState state,
-                                             GHOST_TDrawingContextType type,
                                              GHOST_GLSettings glSettings,
                                              const bool exclusive,
                                              const bool /* is_dialog */,
@@ -57,7 +56,7 @@ GHOST_IWindow *GHOST_SystemSDL::createWindow(const char *title,
                                width,
                                height,
                                state,
-                               type,
+                               glSettings.context_type,
                                ((glSettings.flags & GHOST_glStereoVisual) != 0),
                                exclusive,
                                parentWindow);
diff --git a/intern/ghost/intern/GHOST_SystemSDL.h b/intern/ghost/intern/GHOST_SystemSDL.h
index bee277ba674..385bfb841e3 100644
--- a/intern/ghost/intern/GHOST_SystemSDL.h
+++ b/intern/ghost/intern/GHOST_SystemSDL.h
@@ -71,7 +71,6 @@ class GHOST_SystemSDL : public GHOST_System {
                               uint32_t width,
                               uint32_t height,
                               GHOST_TWindowState state,
-                              GHOST_TDrawingContextType type,
                               GHOST_GLSettings glSettings,
                               const bool exclusive = false,
                               const bool is_dialog = false,
diff --git a/intern/ghost/intern/GHOST_SystemWayland.cpp b/intern/ghost/intern/GHOST_SystemWayland.cpp
index 9f018d039b1..2d16fd4cff5 100644
--- a/intern/ghost/intern/GHOST_SystemWayland.cpp
+++ b/intern/ghost/intern/GHOST_SystemWayland.cpp
@@ -3813,7 +3813,6 @@ GHOST_IWindow *GHOST_SystemWayland::createWindow(const char *title,
                                                  const uint32_t width,
                                                  const uint32_t height,
                                                  const GHOST_TWindowState state,
-                                                 const GHOST_TDrawingContextType type,
                                                  const GHOST_GLSettings glSettings,
                                                  const bool exclusive,
                                                  const bool is_dialog,
@@ -3833,7 +3832,7 @@ GHOST_IWindow *GHOST_SystemWayland::createWindow(const char *title,
       height,
       state,
       parentWindow,
-      type,
+      glSettings.context_type,
       is_dialog,
       ((glSettings.flags & GHOST_glStereoVisual) != 0),
       exclusive);
diff --git a/intern/ghost/intern/GHOST_SystemWayland.h b/intern/ghost/intern/GHOST_SystemWayland.h
index 5d2cfe45582..ca78ccb89ab 100644
--- a/intern/ghost/intern/GHOST_SystemWayland.h
+++ b/intern/ghost/intern/GHOST_SystemWayland.h
@@ -128,7 +128,6 @@ class GHOST_SystemWayland : public GHOST_System {
                               uint32_t width,
                               uint32_t height,
                               GHOST_TWindowState state,
-                              GHOST_TDrawingContextType type,
                               GHOST_GLSettings glSettings,
                               const bool exclusive,
                               const bool is_dialog,
diff --git a/intern/ghost/intern/GHOST_SystemWin32.cpp b/intern/ghost/intern/GHOST_SystemWin32.cpp
index 667198241f0..54c892d296e 100644
--- a/intern/ghost/intern/GHOST_SystemWin32.cpp
+++ b/intern/ghost/intern/GHOST_SystemWin32.cpp
@@ -213,7 +213,6 @@ GHOST_IWindow *GHOST_SystemWin32::createWindow(const char *title,
                                                uint32_t width,
                                                uint32_t height,
                                                GHOST_TWindowState state,
-                                               GHOST_TDrawingContextType type,
                                                GHOST_GLSettings glSettings,
                                                const bool exclusive,
                                                const bool is_dialog,
@@ -227,7 +226,7 @@ GHOST_IWindow *GHOST_SystemWin32::createWindow(const char *title,
       width,
       height,
       state,
-      type,
+      glSettings.context_type,
       ((glSettings.flags & GHOST_glStereoVisual) != 0),
       false,
       (GHOST_WindowWin32 *)parentWindow,
diff --git a/intern/ghost/intern/GHOST_SystemWin32.h b/intern/ghost/intern/GHOST_SystemWin32.h
index f5cd0055b34..98a7e5dfb35 100644
--- a/intern/ghost/intern/GHOST_SystemWin32.h
+++ b/intern/ghost/intern/GHOST_SystemWin32.h
@@ -103,7 +103,6 @@ class GHOST_SystemWin32 : public GHOST_System {
    * \param width: The width the window.
    * \param height: The height the window.
    * \param state: The state of the window when opened.
-   * \param type: The type of drawing context installed in this window.
    * \param glSettings: Misc OpenGL settings.
    * \param exclusive: Use to show the window on top and ignore others (used full-screen).
    * \param parentWindow: Parent window.
@@ -115,7 +114,6 @@ class GHOST_SystemWin32 : public GHOST_System {
                               uint32_t width,
                               uint32_t height,
                               GHOST_TWindowState state,
-                              GHOST_TDrawingContextType type,
                               GHOST_GLSettings glSettings,
                               const bool exclusive = false,
                               const bool is_dialog = false,
diff --git a/intern/ghost/intern/GHOST_SystemX11.cpp b/intern/ghost/intern/GHOST_SystemX11.cpp
index 4523f6fa37c..5c89febe97c 100644
--- a/intern/ghost/intern/GHOST_SystemX11.cpp
+++ b/intern/ghost/intern/GHOST_SystemX11.cpp
@@ -308,7 +308,6 @@ void GHOST_SystemX11::getAllDisplayDimensions(uint32_t &width, uint32_t &height)
  * \param width: The width the window.
  * \param height: The height the window.
  * \param state: The state of the window when opened.
- * \param type: The type of drawing context installed in this window.
  * \param glSettings: Misc OpenGL settings.
  * \param exclusive: Use to show the window on top and ignore others (used full-screen).
  * \param parentWindow: Parent window.
@@ -320,7 +319,6 @@ GHOST_IWindow *GHOST_SystemX11::createWindow(const char *title,
                                              uint32_t width,
                                              uint32_t height,
                                              GHOST_TWindowState state,
-                                             GHOST_TDrawingContextType type,
                                              GHOST_GLSettings glSettings,
                                              const bool exclusive,
                                              const bool is_dialog,
@@ -341,7 +339,7 @@ GHOST_IWindow *GHOST_SystemX11::createWindow(const char *title,
                                height,
                                state,
                                (GHOST_WindowX11 *)parentWindow,
-                               type,
+                               glSettings.context_type,
                                is_dialog,
                                ((glSettings.flags & GHOST_glStereoVisual) != 0),
                                exclusive,
diff --git a/intern/ghost/intern/GHOST_SystemX11.h b/intern/ghost/intern/GHOST_SystemX11.h
index 572be30174d..1f071da6da7 100644
--- a/intern/ghost/intern/GHOST_SystemX11.h
+++ b/intern/ghost/intern/GHOST_SystemX11.h
@@ -113,7 +113,6 @@ class GHOST_SystemX11 : public GHOST_System {
    * \param width: The width the window.
    * \param height: The height the window.
    * \param state: The state of the window when opened.
-   * \param type: The type of drawing context installed in this window.
    * \param stereoVisual: Create a stereo visual for quad buffered stereo.
    * \param exclusive: Use to show the window on top and ignore others (used full-screen).
    * \param parentWindow: Parent (embedder) window.
@@ -125,7 +124,6 @@ class GHOST_SystemX11 : public GHOST_System {
                               uint32_t width,
                               uint32_t height,
                               GHOST_TWindowState state,
-                              GHOST_TDrawingContextType type,
                               GHOST_GLSettings glSettings,
                               const bool exclusive = false,
                               const bool is_dialog = false,
diff --git a/intern/ghost/intern/GHOST_WindowCocoa.mm b/intern/ghost/intern/GHOST_WindowCocoa.mm
index 737fd64bdf0..bc1f1e99a3a 100644
--- a/intern/ghost/intern/GHOST_WindowCocoa.mm
+++ b/intern/ghost/intern/GHOST_WindowCocoa.mm
@@ -803,10 +803,10 @@ GHOST_TSuccess GHOST_WindowCocoa::setOrder(GHOST_TWindowOrder order)
 
 GHOST_Context *GHOST_WindowCocoa::newDrawingContext(GHOST_TDrawingContextType type)
 {
-  if (type == GHOST_kDrawingContextTypeOpenGL) {
+  if (type == GHOST_kDrawingContextTypeOpenGL || type == GHOST_kDrawingContextTypeMetal) {
 
     GHOST_Context *context = new GHOST_ContextCGL(
-        m_wantStereoVisual, m_metalView, m_metalLayer, m_openGLView);
+        m_wantStereoVisual, m_metalView, m_metalLayer, m_openGLView, type);
 
     if (context->initializeDrawingContext())
       return context;
diff --git a/intern/ghost/test/gears/GHOST_Test.cpp b/intern/ghost/test/gears/GHOST_Test.cpp
index 1891f1eca77..3c9206b2010 100644
--- a/intern/ghost/test/gears/GHOST_Test.cpp
+++ b/intern/ghost/test/gears/GHOST_Test.cpp
@@ -407,17 +407,12 @@ Application::Application(GHOST_ISystem *system)
       stereo(false)
 {
   GHOST_GLSettings glSettings = {0};
+  glSettings.context_type = GHOST_kDrawingContextTypeOpenGL;
   fApp = this;
 
   // Create the main window
-  m_mainWindow = system->createWindow("gears - main window",
-                                      10,
-                                      64,
-                                      320,
-                                      200,
-                                      GHOST_kWindowStateNormal,
-                                      GHOST_kDrawingContextTypeOpenGL,
-                                      glSettings);
+  m_mainWindow = system->createWindow(
+      "gears - main window", 10, 64, 320, 200, GHOST_kWindowStateNormal, glSettings);
 
   if (!m_mainWindow) {
     std::cout << "could not create main window\n";
@@ -425,14 +420,8 @@ Application::Application(GHOST_ISystem *system)
   }
 
   // Create a secondary window
-  m_secondaryWindow = system->createWindow("gears - secondary window",
-                                           340,
-                                           64,
-                                           320,
-                                           200,
-                                           GHOST_kWindowStateNormal,
-                                           GHOST_kDrawingContextTypeOpenGL,
-                                           glSettings);
+  m_secondaryWindow = system->createWindow(
+      "gears - secondary window", 340, 64, 320, 200, GHOST_kWindowStateNormal, glSettings);
   if (!m_secondaryWindow) {
     std::cout << "could not create secondary window\n";
     exit(-1);