Python GPU: Add reference of PyObject GPU object to the GPU object itself

Instead of creating different python wrappers for the same GPU object,
return the same `PyObject` created earlier.

This also allows for more secure access to existing GPU objects.

Reviewed By: brecht

Differential Revision: https://developer.blender.org/D11044

4 files changed, 76 insertions, 24 deletions

diff --git a/source/blender/python/gpu/gpu_py_framebuffer.c b/source/blender/python/gpu/gpu_py_framebuffer.c
index bc393aaafa4..0e58327737a 100644
--- a/source/blender/python/gpu/gpu_py_framebuffer.c
+++ b/source/blender/python/gpu/gpu_py_framebuffer.c
@@ -46,13 +46,7 @@
 static int pygpu_framebuffer_valid_check(BPyGPUFrameBuffer *bpygpu_fb)
 {
   if (UNLIKELY(bpygpu_fb->fb == NULL)) {
-    PyErr_SetString(PyExc_ReferenceError,
-#ifdef BPYGPU_USE_GPUOBJ_FREE_METHOD
-                    "GPU framebuffer was freed, no further access is valid"
-#else
-                    "GPU framebuffer: internal error"
-#endif
-    );
+    PyErr_SetString(PyExc_ReferenceError, "GPU framebuffer was freed, no further access is valid");
     return -1;
   }
   return 0;
@@ -68,10 +62,6 @@ static int pygpu_framebuffer_valid_check(BPyGPUFrameBuffer *bpygpu_fb)
 
 static void pygpu_framebuffer_free_if_possible(GPUFrameBuffer *fb)
 {
-  if (!fb) {
-    return;
-  }
-
   if (GPU_is_init()) {
     GPU_framebuffer_free(fb);
   }
@@ -80,6 +70,21 @@ static void pygpu_framebuffer_free_if_possible(GPUFrameBuffer *fb)
   }
 }
 
+static void pygpu_framebuffer_free_safe(BPyGPUFrameBuffer *self)
+{
+  if (self->fb) {
+#if GPU_USE_PY_REFERENCES
+    GPU_framebuffer_py_reference_set(self->fb, NULL);
+    if (!self->shared_reference)
+#endif
+    {
+      pygpu_framebuffer_free_if_possible(self->fb);
+    }
+
+    self->fb = NULL;
+  }
+}
+
 /* Keep less than or equal to #FRAMEBUFFER_STACK_DEPTH */
 #define GPU_PY_FRAMEBUFFER_STACK_LEN 16
 
@@ -336,7 +341,7 @@ static PyObject *pygpu_framebuffer__tp_new(PyTypeObject *UNUSED(self),
   GPUFrameBuffer *fb_python = GPU_framebuffer_create("fb_python");
   GPU_framebuffer_config_array(fb_python, config, color_attachements_len + 1);
 
-  return BPyGPUFrameBuffer_CreatePyObject(fb_python);
+  return BPyGPUFrameBuffer_CreatePyObject(fb_python, false);
 }
 
 PyDoc_STRVAR(pygpu_framebuffer_is_bound_doc,
@@ -459,15 +464,14 @@ PyDoc_STRVAR(pygpu_framebuffer_free_doc,
 static PyObject *pygpu_framebuffer_free(BPyGPUFrameBuffer *self)
 {
   PYGPU_FRAMEBUFFER_CHECK_OBJ(self);
-  pygpu_framebuffer_free_if_possible(self->fb);
-  self->fb = NULL;
+  pygpu_framebuffer_free_safe(self);
   Py_RETURN_NONE;
 }
 #endif
 
 static void BPyGPUFrameBuffer__tp_dealloc(BPyGPUFrameBuffer *self)
 {
-  pygpu_framebuffer_free_if_possible(self->fb);
+  pygpu_framebuffer_free_safe(self);
   Py_TYPE(self)->tp_free((PyObject *)self);
 }
 
@@ -531,13 +535,35 @@ PyTypeObject BPyGPUFrameBuffer_Type = {
 /** \name Public API
  * \{ */
 
-PyObject *BPyGPUFrameBuffer_CreatePyObject(GPUFrameBuffer *fb)
+PyObject *BPyGPUFrameBuffer_CreatePyObject(GPUFrameBuffer *fb, bool shared_reference)
 {
   BPyGPUFrameBuffer *self;
 
+#if GPU_USE_PY_REFERENCES
+  if (shared_reference) {
+    void **ref = GPU_framebuffer_py_reference_get(fb);
+    if (ref) {
+      /* Retrieve BPyGPUFrameBuffer reference. */
+      self = POINTER_OFFSET(ref, -offsetof(BPyGPUFrameBuffer, fb));
+      BLI_assert(self->fb == fb);
+      Py_INCREF(self);
+      return (PyObject *)self;
+    }
+  }
+#else
+  UNUSED_VARS(shared_reference);
+#endif
+
   self = PyObject_New(BPyGPUFrameBuffer, &BPyGPUFrameBuffer_Type);
   self->fb = fb;
 
+#if GPU_USE_PY_REFERENCES
+  self->shared_reference = shared_reference;
+
+  BLI_assert(GPU_framebuffer_py_reference_get(fb) == NULL);
+  GPU_framebuffer_py_reference_set(fb, &self->fb);
+#endif
+
   return (PyObject *)self;
 }
 
diff --git a/source/blender/python/gpu/gpu_py_framebuffer.h b/source/blender/python/gpu/gpu_py_framebuffer.h
index 7113e7c35aa..0049cc2fac7 100644
--- a/source/blender/python/gpu/gpu_py_framebuffer.h
+++ b/source/blender/python/gpu/gpu_py_framebuffer.h
@@ -28,6 +28,11 @@ extern PyTypeObject BPyGPUFrameBuffer_Type;
 
 typedef struct BPyGPUFrameBuffer {
   PyObject_HEAD struct GPUFrameBuffer *fb;
+
+#if GPU_USE_PY_REFERENCES
+  bool shared_reference;
+#endif
 } BPyGPUFrameBuffer;
 
-PyObject *BPyGPUFrameBuffer_CreatePyObject(struct GPUFrameBuffer *fb) ATTR_NONNULL(1);
+PyObject *BPyGPUFrameBuffer_CreatePyObject(struct GPUFrameBuffer *fb, bool shared_reference)
+    ATTR_NONNULL(1);
diff --git a/source/blender/python/gpu/gpu_py_texture.c b/source/blender/python/gpu/gpu_py_texture.c
index 1ae65c1dd11..9cc6a9df8fa 100644
--- a/source/blender/python/gpu/gpu_py_texture.c
+++ b/source/blender/python/gpu/gpu_py_texture.c
@@ -247,7 +247,7 @@ static PyObject *pygpu_texture__tp_new(PyTypeObject *UNUSED(self), PyObject *arg
     return NULL;
   }
 
-  return BPyGPUTexture_CreatePyObject(tex);
+  return BPyGPUTexture_CreatePyObject(tex, false);
 }
 
 PyDoc_STRVAR(pygpu_texture_width_doc, "Width of the texture.\n\n:type: `int`");
@@ -412,6 +412,9 @@ static PyObject *pygpu_texture_free(BPyGPUTexture *self)
 static void BPyGPUTexture__tp_dealloc(BPyGPUTexture *self)
 {
   if (self->tex) {
+#if GPU_USE_PY_REFERENCES
+    GPU_texture_py_reference_set(self->tex, NULL);
+#endif
     GPU_texture_free(self->tex);
   }
   Py_TYPE(self)->tp_free((PyObject *)self);
@@ -535,10 +538,7 @@ static PyObject *pygpu_texture_from_image(PyObject *UNUSED(self), PyObject *arg)
   BKE_imageuser_default(&iuser);
   GPUTexture *tex = BKE_image_get_gpu_texture(ima, &iuser, NULL);
 
-  /* Increase the texture reference count. */
-  GPU_texture_ref(tex);
-
-  return BPyGPUTexture_CreatePyObject(tex);
+  return BPyGPUTexture_CreatePyObject(tex, true);
 }
 
 static struct PyMethodDef pygpu_texture__m_methods[] = {
@@ -595,13 +595,33 @@ PyObject *bpygpu_texture_init(void)
 /** \name Public API
  * \{ */
 
-PyObject *BPyGPUTexture_CreatePyObject(GPUTexture *tex)
+PyObject *BPyGPUTexture_CreatePyObject(GPUTexture *tex, bool shared_reference)
 {
   BPyGPUTexture *self;
 
+  if (shared_reference) {
+#if GPU_USE_PY_REFERENCES
+    void **ref = GPU_texture_py_reference_get(tex);
+    if (ref) {
+      /* Retrieve BPyGPUTexture reference. */
+      self = POINTER_OFFSET(ref, -offsetof(BPyGPUTexture, tex));
+      BLI_assert(self->tex == tex);
+      Py_INCREF(self);
+      return (PyObject *)self;
+    }
+#endif
+
+    GPU_texture_ref(tex);
+  }
+
   self = PyObject_New(BPyGPUTexture, &BPyGPUTexture_Type);
   self->tex = tex;
 
+#if GPU_USE_PY_REFERENCES
+  BLI_assert(GPU_texture_py_reference_get(tex) == NULL);
+  GPU_texture_py_reference_set(tex, &self->tex);
+#endif
+
   return (PyObject *)self;
 }
 
diff --git a/source/blender/python/gpu/gpu_py_texture.h b/source/blender/python/gpu/gpu_py_texture.h
index 5130273f971..457ddcfc931 100644
--- a/source/blender/python/gpu/gpu_py_texture.h
+++ b/source/blender/python/gpu/gpu_py_texture.h
@@ -33,4 +33,5 @@ typedef struct BPyGPUTexture {
 int bpygpu_ParseTexture(PyObject *o, void *p);
 PyObject *bpygpu_texture_init(void);
 
-PyObject *BPyGPUTexture_CreatePyObject(struct GPUTexture *tex) ATTR_NONNULL(1);
+PyObject *BPyGPUTexture_CreatePyObject(struct GPUTexture *tex, bool weak_reference)
+    ATTR_NONNULL(1);