GLContext: extract __init_try_backend() (readability + try-return)

comfy_extras/nodes_glsl.py

@@ -315,16 +315,18 @@ class GLContext:
     Tries backends in order: GLFW (desktop) → EGL (headless GPU) → OSMesa (software).
     """
 
-    _instance = None
-    _initialized = False
+    __instance: 'GLContext' = None  # The singleton
 
     def __new__(cls):
-        if cls._instance is None:
-            cls._instance = super().__new__(cls)
-        return cls._instance
+        # Since ``GLContext`` is a singleton anyway, we should store it
+        # explicitly in ``GLContext.__instance``, NOT in ``cls.__instance``.
+        if GLContext.__instance is None:
+            GLContext.__instance = super().__new__(cls)
+            assert isinstance(GLContext.__instance, GLContext)
+        return GLContext.__instance
 
     def __init__(self):
-        if GLContext._initialized:
+        if GLContext.__instance is not None:
             logger.debug("GLContext.__init__: already initialized, skipping")
             return
 
@@ -333,7 +335,7 @@ class GLContext:
         global glfw, EGL
 
         import time
-        start = time.perf_counter()
+        start_time: float = time.perf_counter()
 
         self._backend = None
         self._window = None
@@ -344,64 +346,7 @@ class GLContext:
         self._osmesa_buffer = None
         self._vao = None
 
-        # Try backends in order: GLFW → EGL → OSMesa
-        errors = []
-
-        logger.debug("GLContext.__init__: trying GLFW backend")
-        try:
-            self._window, glfw = _init_glfw()
-            self._backend = "glfw"
-            logger.debug("GLContext.__init__: GLFW backend succeeded")
-        except Exception as e:
-            logger.debug(f"GLContext.__init__: GLFW backend failed: {e}")
-            errors.append(("GLFW", e))
-
-        if self._backend is None:
-            logger.debug("GLContext.__init__: trying EGL backend")
-            try:
-                self._egl_display, self._egl_context, self._egl_surface, EGL = _init_egl()
-                self._backend = "egl"
-                logger.debug("GLContext.__init__: EGL backend succeeded")
-            except Exception as e:
-                logger.debug(f"GLContext.__init__: EGL backend failed: {e}")
-                errors.append(("EGL", e))
-
-        if self._backend is None:
-            logger.debug("GLContext.__init__: trying OSMesa backend")
-            try:
-                self._osmesa_ctx, self._osmesa_buffer = _init_osmesa()
-                self._backend = "osmesa"
-                logger.debug("GLContext.__init__: OSMesa backend succeeded")
-            except Exception as e:
-                logger.debug(f"GLContext.__init__: OSMesa backend failed: {e}")
-                errors.append(("OSMesa", e))
-
-        if self._backend is None:
-            if sys.platform == "win32":
-                platform_help = (
-                    "Windows: Ensure GPU drivers are installed and display is available.\n"
-                    "         CPU-only/headless mode is not supported on Windows."
-                )
-            elif sys.platform == "darwin":
-                platform_help = (
-                    "macOS: GLFW is not supported.\n"
-                    "  Install OSMesa via Homebrew: brew install mesa\n"
-                    "  Then: pip install PyOpenGL PyOpenGL-accelerate"
-                )
-            else:
-                platform_help = (
-                    "Linux: Install one of these backends:\n"
-                    "  Desktop:           sudo apt install libgl1-mesa-glx libglfw3\n"
-                    "  Headless with GPU: sudo apt install libegl1-mesa libgl1-mesa-dri\n"
-                    "  Headless (CPU):    sudo apt install libosmesa6"
-                )
-
-            error_details = "\n".join(f"  {name}: {err}" for name, err in errors)
-            raise RuntimeError(
-                f"Failed to create OpenGL context.\n\n"
-                f"Backend errors:\n{error_details}\n\n"
-                f"{platform_help}"
-            )
+        self._init_try_backend()
 
         # Now import OpenGL.GL (after context is current)
         logger.debug("GLContext.__init__: importing OpenGL.GL")
@@ -424,7 +369,7 @@ class GLContext:
                 except Exception:
                     pass
 
-        elapsed = (time.perf_counter() - start) * 1000
+        elapsed = (time.perf_counter() - start_time) * 1000
 
         # Log device info
         renderer = gl.glGetString(gl.GL_RENDERER)
@@ -434,9 +379,75 @@ class GLContext:
         vendor = vendor.decode() if vendor else "Unknown"
         version = version.decode() if version else "Unknown"
 
-        GLContext._initialized = True
         logger.info(f"GLSL context initialized in {elapsed:.1f}ms ({self._backend}) - {renderer} ({vendor}), GL {version}")
 
+    def _init_try_backend(self):
+        """Try to init backends in fallback order: GLFW → EGL → OSMesa. Raises RuntimeError on failure.
+        """
+        global glfw, EGL
+
+        errors = []
+        self._backend = None
+
+        logger.debug("GLContext.__init__: trying GLFW backend")
+        try:
+            self._window, glfw = _init_glfw()
+            self._backend = "glfw"
+            logger.debug("GLContext.__init__: GLFW backend succeeded")
+            return
+        except Exception as e:
+            logger.debug(f"GLContext.__init__: GLFW backend failed: {e}")
+            errors.append(("GLFW", e))
+
+        logger.debug("GLContext.__init__: trying EGL backend")
+        try:
+            self._egl_display, self._egl_context, self._egl_surface, EGL = _init_egl()
+            self._backend = "egl"
+            logger.debug("GLContext.__init__: EGL backend succeeded")
+            return
+        except Exception as e:
+            logger.debug(f"GLContext.__init__: EGL backend failed: {e}")
+            errors.append(("EGL", e))
+
+        logger.debug("GLContext.__init__: trying OSMesa backend")
+        try:
+            self._osmesa_ctx, self._osmesa_buffer = _init_osmesa()
+            self._backend = "osmesa"
+            logger.debug("GLContext.__init__: OSMesa backend succeeded")
+            return
+        except Exception as e:
+            logger.debug(f"GLContext.__init__: OSMesa backend failed: {e}")
+            errors.append(("OSMesa", e))
+
+        # If we still haven't returned, none of the backends succeeded.
+        # Let's raise the error.
+
+        if sys.platform == "win32":
+            platform_help = (
+                "Windows: Ensure GPU drivers are installed and display is available.\n"
+                "         CPU-only/headless mode is not supported on Windows."
+            )
+        elif sys.platform == "darwin":
+            platform_help = (
+                "macOS: GLFW is not supported.\n"
+                "  Install OSMesa via Homebrew: brew install mesa\n"
+                "  Then: pip install PyOpenGL PyOpenGL-accelerate"
+            )
+        else:
+            platform_help = (
+                "Linux: Install one of these backends:\n"
+                "  Desktop:           sudo apt install libgl1-mesa-glx libglfw3\n"
+                "  Headless with GPU: sudo apt install libegl1-mesa libgl1-mesa-dri\n"
+                "  Headless (CPU):    sudo apt install libosmesa6"
+            )
+
+        error_details = "\n".join(f"  {name}: {err}" for name, err in errors)
+        raise RuntimeError(
+            f"Failed to create OpenGL context.\n\n"
+            f"Backend errors:\n{error_details}\n\n"
+            f"{platform_help}"
+        )
+
     def make_current(self):
         if self._backend == "glfw":
             glfw.make_context_current(self._window)