BGE: scene.pre_draw_setup[] callback

This callback allows the user to change the camera data right before the
rendering calculations.

scene.pre_draw[] is not enough here, because if you want to change the
camera matrices (projection/modelview) the culling test is done before
that (after pre_draw_setup[] though).

Reviewers: moguri, campbellbarton

Differential Revision: https://developer.blender.org/D1251

Python sample code using this. The sample scene would need a default
camera (not used for rendering), a dummy camera ('Camera.VR'), and two
cameras ('Camera.Left', 'Camera.Right') that will be used for the actual
rendering.

```
import bge

def callback():
    scene = bge.logic.getCurrentScene()
    objects = scene.objects

    vr_camera = objects.get('Camera.VR')

    if bge.render.getStereoEye() ==  bge.render.LEFT_EYE:
        camera = objects.get('Camera.Left')
    else:
        camera = objects.get('Camera.Right')

    vr_camera.worldOrientation = camera.worldOrientation
    vr_camera.worldPosition =  camera.worldPosition

def init():
    scene = bge.logic.getCurrentScene()
    main_camera = scene.active_camera
    main_camera.useViewport = True

   scene.pre_draw_setup.append(callback)

    objects = scene.objects
    vr_camera = objects.get('Camera.VR')
    vr_camera.useViewport = True
    vr_camera.setViewport(
            0,
            0,
            bge.render.getWindowWidth(),
            bge.render.getWindowHeight() )
```

1 files changed, 29 insertions, 0 deletions

diff --git a/source/gameengine/Ketsji/KX_Scene.cpp b/source/gameengine/Ketsji/KX_Scene.cpp
index a3e1d1562c9..ca4d017fe8c 100644
--- a/source/gameengine/Ketsji/KX_Scene.cpp
+++ b/source/gameengine/Ketsji/KX_Scene.cpp
@@ -238,6 +238,7 @@ KX_Scene::KX_Scene(class SCA_IInputDevice* keyboarddevice,
 	m_attr_dict = NULL;
 	m_draw_call_pre = NULL;
 	m_draw_call_post = NULL;
+	m_draw_setup_call_pre = NULL;
 #endif
 }
 
@@ -2399,6 +2400,17 @@ PyObject *KX_Scene::pyattr_get_drawing_callback_post(void *self_v, const KX_PYAT
 	return self->m_draw_call_post;
 }
 
+PyObject *KX_Scene::pyattr_get_drawing_setup_callback_pre(void *self_v, const KX_PYATTRIBUTE_DEF *attrdef)
+{
+	KX_Scene* self = static_cast<KX_Scene*>(self_v);
+
+	if (self->m_draw_setup_call_pre == NULL)
+		self->m_draw_setup_call_pre = PyList_New(0);
+
+	Py_INCREF(self->m_draw_setup_call_pre);
+	return self->m_draw_setup_call_pre;
+}
+
 int KX_Scene::pyattr_set_drawing_callback_pre(void *self_v, const KX_PYATTRIBUTE_DEF *attrdef, PyObject *value)
 {
 	KX_Scene* self = static_cast<KX_Scene*>(self_v);
@@ -2433,6 +2445,22 @@ int KX_Scene::pyattr_set_drawing_callback_post(void *self_v, const KX_PYATTRIBUT
 	return PY_SET_ATTR_SUCCESS;
 }
 
+int KX_Scene::pyattr_set_drawing_setup_callback_pre(void *self_v, const KX_PYATTRIBUTE_DEF *attrdef, PyObject *value)
+{
+	KX_Scene* self = static_cast<KX_Scene*>(self_v);
+
+	if (!PyList_CheckExact(value)) {
+		PyErr_SetString(PyExc_ValueError, "Expected a list");
+		return PY_SET_ATTR_FAIL;
+	}
+
+	Py_XDECREF(self->m_draw_setup_call_pre);
+	Py_INCREF(value);
+
+	self->m_draw_setup_call_pre = value;
+	return PY_SET_ATTR_SUCCESS;
+}
+
 PyObject *KX_Scene::pyattr_get_gravity(void *self_v, const KX_PYATTRIBUTE_DEF *attrdef)
 {
 	KX_Scene* self = static_cast<KX_Scene*>(self_v);
@@ -2462,6 +2490,7 @@ PyAttributeDef KX_Scene::Attributes[] = {
 	KX_PYATTRIBUTE_RW_FUNCTION("active_camera",		KX_Scene, pyattr_get_active_camera, pyattr_set_active_camera),
 	KX_PYATTRIBUTE_RW_FUNCTION("pre_draw",			KX_Scene, pyattr_get_drawing_callback_pre, pyattr_set_drawing_callback_pre),
 	KX_PYATTRIBUTE_RW_FUNCTION("post_draw",			KX_Scene, pyattr_get_drawing_callback_post, pyattr_set_drawing_callback_post),
+	KX_PYATTRIBUTE_RW_FUNCTION("pre_draw_setup",	KX_Scene, pyattr_get_drawing_setup_callback_pre, pyattr_set_drawing_setup_callback_pre),
 	KX_PYATTRIBUTE_RW_FUNCTION("gravity",			KX_Scene, pyattr_get_gravity, pyattr_set_gravity),
 	KX_PYATTRIBUTE_BOOL_RO("suspended",				KX_Scene, m_suspend),
 	KX_PYATTRIBUTE_BOOL_RO("activity_culling",		KX_Scene, m_activity_culling),