[#19258] [patch] Adding drawing capabilities to BGE Python

patch from Mitchell Stokes (moguri)

simple use case
 scene.post_draw = [pyOpenGLFunc]

this only needs to be set once, then the funcion runs each redraw.

note, this patch also changes how python scripts run (not modules): Dont clear the namespace after running a script, since functions still use the namespace, BGE API is now better when dealing with stale data.

made some changes to this patch.
- assigning a list didnt decrement the existing list.
- initialize as NULL rather then a blank list
- dont use string comparisons for the callbacks, pass the python list to use instead.
- dont check the list items are callable. python will display an error if they are not.
- use python list macros that dont do any type checking sine blender does this when assigning the list

---- from tracker, edited since an updated patch changes some things.
Here is a patch to be able to draw to the screen with BGE Python. This will be very handy for GUI stuff. This patch
works by having the user register a callback in the scene. Two options are available KX_Scene.pre_draw
and KX_Scene.post_draw. The difference between these is when Python draws to the screen (before or after the BGE).
Each can take a list of functions. Here is an example that draws a blue semi-transparent

1 files changed, 84 insertions, 0 deletions

diff --git a/source/gameengine/Ketsji/KX_Scene.cpp b/source/gameengine/Ketsji/KX_Scene.cpp
index 655c8eedaae..c018dcd387f 100644
--- a/source/gameengine/Ketsji/KX_Scene.cpp
+++ b/source/gameengine/Ketsji/KX_Scene.cpp
@@ -211,6 +211,8 @@ KX_Scene::KX_Scene(class SCA_IInputDevice* keyboarddevice,
 	
 #ifndef DISABLE_PYTHON
 	m_attr_dict = PyDict_New(); /* new ref */
+	m_draw_call_pre = NULL;
+	m_draw_call_post = NULL;
 #endif
 }
 
@@ -264,6 +266,9 @@ KX_Scene::~KX_Scene()
 #ifndef DISABLE_PYTHON
 	PyDict_Clear(m_attr_dict);
 	Py_DECREF(m_attr_dict);
+
+	Py_XDECREF(m_draw_call_pre);
+	Py_XDECREF(m_draw_call_post);
 #endif
 }
 
@@ -401,6 +406,28 @@ bool KX_Scene::IsClearingZBuffer()
 	return m_isclearingZbuffer;
 }
 
+void KX_Scene::RunDrawingCallbacks(PyObject* cb_list)
+{
+	int len;
+
+	if (cb_list && (len=PyList_GET_SIZE(cb_list)))
+	{
+		PyObject* func;
+		PyObject* ret;
+
+		// Iterate the list and run the callbacks
+		for (int pos=0; pos < len; pos++)
+		{
+			func= PyList_GET_ITEM(cb_list, pos);
+			ret= PyObject_CallObject(func, NULL);
+			if (ret==NULL) {
+				PyErr_Print();
+				PyErr_Clear();
+			}
+		}
+	}
+}
+
 void KX_Scene::EnableZBufferClearing(bool isclearingZbuffer)
 {
 	m_isclearingZbuffer = isclearingZbuffer;
@@ -1997,6 +2024,61 @@ int KX_Scene::pyattr_set_active_camera(void *self_v, const KX_PYATTRIBUTE_DEF *a
 	return PY_SET_ATTR_SUCCESS;
 }
 
+PyObject* KX_Scene::pyattr_get_drawing_callback_pre(void *self_v, const KX_PYATTRIBUTE_DEF *attrdef)
+{
+	KX_Scene* self = static_cast<KX_Scene*>(self_v);
+
+	if(self->m_draw_call_pre==NULL)
+		self->m_draw_call_pre= PyList_New(0);
+	else
+		Py_INCREF(self->m_draw_call_pre);
+	return self->m_draw_call_pre;
+}
+
+PyObject* KX_Scene::pyattr_get_drawing_callback_post(void *self_v, const KX_PYATTRIBUTE_DEF *attrdef)
+{
+	KX_Scene* self = static_cast<KX_Scene*>(self_v);
+
+	if(self->m_draw_call_post==NULL)
+		self->m_draw_call_post= PyList_New(0);
+	else
+		Py_INCREF(self->m_draw_call_post);
+	return self->m_draw_call_post;
+}
+
+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);
+
+	if (!PyList_CheckExact(value))
+	{
+		PyErr_SetString(PyExc_ValueError, "Expected a list");
+		return PY_SET_ATTR_FAIL;
+	}
+	Py_XDECREF(self->m_draw_call_pre);
+
+	Py_INCREF(value);
+	self->m_draw_call_pre = value;
+
+	return PY_SET_ATTR_SUCCESS;
+}
+
+int KX_Scene::pyattr_set_drawing_callback_post(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_call_post);
+
+	Py_INCREF(value);
+	self->m_draw_call_post = value;
+
+	return PY_SET_ATTR_SUCCESS;
+}
 
 PyAttributeDef KX_Scene::Attributes[] = {
 	KX_PYATTRIBUTE_RO_FUNCTION("name",				KX_Scene, pyattr_get_name),
@@ -2005,6 +2087,8 @@ PyAttributeDef KX_Scene::Attributes[] = {
 	KX_PYATTRIBUTE_RO_FUNCTION("cameras",			KX_Scene, pyattr_get_cameras),
 	KX_PYATTRIBUTE_RO_FUNCTION("lights",			KX_Scene, pyattr_get_lights),
 	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_BOOL_RO("suspended",				KX_Scene, m_suspend),
 	KX_PYATTRIBUTE_BOOL_RO("activity_culling",		KX_Scene, m_activity_culling),
 	KX_PYATTRIBUTE_FLOAT_RW("activity_culling_radius", 0.5f, FLT_MAX, KX_Scene, m_activity_box_radius),