Join the python modules `gpu` and `_gpu` into one.

Maybe it's still early to set the new drawing api for python.
But joining these two modules is an initial step.

```
>>> gpu.
        matrix
        select
        types
```
```
>>> gpu.types.GPU
                 Batch(
                 OffScreen(
                 VertBuf(
                 VertFormat(
```
The creation of a new offscreen object is now done by the `GPUOffscreen.__new__` method.

Reviewers: campbellbarton, dfelinto

Reviewed By: campbellbarton, dfelinto

Tags: #bf_blender_2.8

Differential Revision: https://developer.blender.org/D3667

1 files changed, 230 insertions, 0 deletions

diff --git a/source/blender/python/gpu/gpu_py_vertex_format.c b/source/blender/python/gpu/gpu_py_vertex_format.c
new file mode 100644
index 00000000000..96ca4003dc9
--- /dev/null
+++ b/source/blender/python/gpu/gpu_py_vertex_format.c
@@ -0,0 +1,230 @@
+/*
+ * ***** BEGIN GPL LICENSE BLOCK *****
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ *
+ * ***** END GPL LICENSE BLOCK *****
+ */
+
+/** \file blender/python/gpu/gpu_py_vertex_format.c
+ *  \ingroup bpygpu
+ *
+ * - Use ``bpygpu_`` for local API.
+ * - Use ``BPyGPU`` for public API.
+ */
+
+#include <Python.h>
+
+#include "BLI_math.h"
+
+#include "MEM_guardedalloc.h"
+
+#include "../generic/py_capi_utils.h"
+#include "../generic/python_utildefines.h"
+
+#include "gpu_py_vertex_format.h" /* own include */
+
+#ifdef __BIG_ENDIAN__
+   /* big endian */
+#  define MAKE_ID2(c, d)  ((c) << 8 | (d))
+#  define MAKE_ID3(a, b, c) ( (int)(a) << 24 | (int)(b) << 16 | (c) << 8 )
+#  define MAKE_ID4(a, b, c, d) ( (int)(a) << 24 | (int)(b) << 16 | (c) << 8 | (d) )
+#else
+   /* little endian  */
+#  define MAKE_ID2(c, d)  ((d) << 8 | (c))
+#  define MAKE_ID3(a, b, c) ( (int)(c) << 16 | (b) << 8 | (a) )
+#  define MAKE_ID4(a, b, c, d) ( (int)(d) << 24 | (int)(c) << 16 | (b) << 8 | (a) )
+#endif
+
+/* -------------------------------------------------------------------- */
+
+/** \name Enum Conversion
+ *
+ * Use with PyArg_ParseTuple's "O&" formatting.
+ * \{ */
+
+static int bpygpu_ParseVertCompType(PyObject *o, void *p)
+{
+	Py_ssize_t comp_type_id_len;
+	const char *comp_type_id = _PyUnicode_AsStringAndSize(o, &comp_type_id_len);
+	if (comp_type_id == NULL) {
+		PyErr_Format(PyExc_ValueError,
+		             "expected a string, got %s",
+		             Py_TYPE(o)->tp_name);
+		return 0;
+	}
+
+	GPUVertCompType comp_type;
+	if (comp_type_id_len == 2) {
+		switch (*((ushort *)comp_type_id)) {
+			case MAKE_ID2('I', '8'): { comp_type = GPU_COMP_I8; goto success; }
+			case MAKE_ID2('U', '8'): { comp_type = GPU_COMP_U8; goto success; }
+		}
+	}
+	else if (comp_type_id_len == 3) {
+		switch (*((uint *)comp_type_id)) {
+			case MAKE_ID3('I', '1', '6'): { comp_type = GPU_COMP_I16; goto success; }
+			case MAKE_ID3('U', '1', '6'): { comp_type = GPU_COMP_U16; goto success; }
+			case MAKE_ID3('I', '3', '2'): { comp_type = GPU_COMP_I32; goto success; }
+			case MAKE_ID3('U', '3', '2'): { comp_type = GPU_COMP_U32; goto success; }
+			case MAKE_ID3('F', '3', '2'): { comp_type = GPU_COMP_F32; goto success; }
+			case MAKE_ID3('I', '1', '0'): { comp_type = GPU_COMP_I10; goto success; }
+		}
+	}
+
+	PyErr_Format(PyExc_ValueError,
+	             "unknown type literal: '%s'",
+	             comp_type_id);
+	return 0;
+
+success:
+	*((GPUVertCompType *)p) = comp_type;
+	return 1;
+}
+
+static int bpygpu_ParseVertFetchMode(PyObject *o, void *p)
+{
+	Py_ssize_t mode_id_len;
+	const char *mode_id = _PyUnicode_AsStringAndSize(o, &mode_id_len);
+	if (mode_id == NULL) {
+		PyErr_Format(PyExc_ValueError,
+		             "expected a string, got %s",
+		             Py_TYPE(o)->tp_name);
+		return 0;
+	}
+#define MATCH_ID(id) \
+	if (mode_id_len == strlen(STRINGIFY(id))) { \
+		if (STREQ(mode_id, STRINGIFY(id))) { \
+			mode = GPU_FETCH_##id; \
+			goto success; \
+		} \
+	} ((void)0)
+
+	GPUVertFetchMode mode;
+	MATCH_ID(FLOAT);
+	MATCH_ID(INT);
+	MATCH_ID(INT_TO_FLOAT_UNIT);
+	MATCH_ID(INT_TO_FLOAT);
+#undef MATCH_ID
+	PyErr_Format(PyExc_ValueError,
+	             "unknown type literal: '%s'",
+	             mode_id);
+	return 0;
+
+success:
+	(*(GPUVertFetchMode *)p) = mode;
+	return 1;
+}
+
+/** \} */
+
+
+/* -------------------------------------------------------------------- */
+
+/** \name VertFormat Type
+ * \{ */
+
+static PyObject *bpygpu_VertFormat_new(PyTypeObject *UNUSED(type), PyObject *args, PyObject *kwds)
+{
+	if (PyTuple_GET_SIZE(args) || (kwds && PyDict_Size(kwds))) {
+		PyErr_SetString(PyExc_TypeError,
+		                "VertFormat(): takes no arguments");
+		return NULL;
+	}
+
+	BPyGPUVertFormat *ret = (BPyGPUVertFormat *)BPyGPUVertFormat_CreatePyObject(NULL);
+
+	return (PyObject *)ret;
+}
+
+PyDoc_STRVAR(bpygpu_VertFormat_attr_add_doc,
+"TODO"
+);
+static PyObject *bpygpu_VertFormat_attr_add(BPyGPUVertFormat *self, PyObject *args, PyObject *kwds)
+{
+	static const char *kwlist[] = {"id", "comp_type", "len", "fetch_mode", NULL};
+
+	struct {
+		const char *id;
+		GPUVertCompType comp_type;
+		uint len;
+		GPUVertFetchMode fetch_mode;
+	} params;
+
+	if (self->fmt.attr_len == GPU_VERT_ATTR_MAX_LEN) {
+		PyErr_SetString(PyExc_ValueError, "Maxumum attr reached " STRINGIFY(GPU_VERT_ATTR_MAX_LEN));
+		return NULL;
+	}
+
+	if (!PyArg_ParseTupleAndKeywords(
+	        args, kwds, "$sO&IO&:attr_add", (char **)kwlist,
+	        &params.id,
+	        bpygpu_ParseVertCompType, &params.comp_type,
+	        &params.len,
+	        bpygpu_ParseVertFetchMode, &params.fetch_mode))
+	{
+		return NULL;
+	}
+
+	uint attr_id = GPU_vertformat_attr_add(&self->fmt, params.id, params.comp_type, params.len, params.fetch_mode);
+	return PyLong_FromLong(attr_id);
+}
+
+static struct PyMethodDef bpygpu_VertFormat_methods[] = {
+	{"attr_add", (PyCFunction)bpygpu_VertFormat_attr_add,
+	 METH_VARARGS | METH_KEYWORDS, bpygpu_VertFormat_attr_add_doc},
+	{NULL, NULL, 0, NULL}
+};
+
+
+static void bpygpu_VertFormat_dealloc(BPyGPUVertFormat *self)
+{
+	Py_TYPE(self)->tp_free(self);
+}
+
+PyTypeObject BPyGPUVertFormat_Type = {
+	PyVarObject_HEAD_INIT(NULL, 0)
+	.tp_name = "GPUVertFormat",
+	.tp_basicsize = sizeof(BPyGPUVertFormat),
+	.tp_dealloc = (destructor)bpygpu_VertFormat_dealloc,
+	.tp_flags = Py_TPFLAGS_DEFAULT,
+	.tp_methods = bpygpu_VertFormat_methods,
+	.tp_new = bpygpu_VertFormat_new,
+};
+
+/** \} */
+
+
+/* -------------------------------------------------------------------- */
+
+/** \name Public API
+ * \{ */
+
+PyObject *BPyGPUVertFormat_CreatePyObject(GPUVertFormat *fmt)
+{
+	BPyGPUVertFormat *self;
+
+	self = PyObject_New(BPyGPUVertFormat, &BPyGPUVertFormat_Type);
+	if (fmt) {
+		self->fmt = *fmt;
+	}
+	else {
+		memset(&self->fmt, 0, sizeof(self->fmt));
+	}
+
+	return (PyObject *)self;
+}
+
+/** \} */