Update Adding Python Bindings

John McCardle 2026-02-07 23:47:56 +00:00
commit d65242a074

@ -1,379 +1,379 @@
# Adding Python Bindings
Step-by-step guide for exposing C++ functionality to Python in McRogueFace.
## Prerequisites
- Understanding of [[Python-Binding-Layer]] system architecture
- Familiarity with C++ class or function to expose
- McRogueFace builds from project root with `make`
## Quick Reference
**Related Systems:** [[Python-Binding-Layer]], [[UI-Component-Hierarchy]]
**Key Files:**
- `src/McRFPy_API.cpp` - Module definition and type registration
- `src/McRFPy_Doc.h` - Documentation macros (MCRF_METHOD, MCRF_PROPERTY, etc.)
- `src/PyObjectUtils.h` - Helper utilities
- Individual `src/Py*.cpp` files - Type bindings
---
## Workflow 1: Adding a Property to Existing Class
### Step 1: Add to PyGetSetDef Array
Find the class's `getsetters` array:
```cpp
PyGetSetDef UISprite::getsetters[] = {
// Existing properties...
// Add new property with doc macro
{"rotation", (getter)UISprite::get_rotation, (setter)UISprite::set_rotation,
MCRF_PROPERTY(rotation,
"Sprite rotation angle in degrees. Range: 0-360."
), NULL},
{NULL} // Sentinel - always last!
};
```
### Step 2: Implement Getter Function
```cpp
PyObject* UISprite::get_rotation(PyUISpriteObject* self, void* closure) {
if (!self->data) {
PyErr_SetString(PyExc_RuntimeError, "UISprite data is null");
return NULL;
}
return PyFloat_FromDouble(self->data->rotation);
}
```
### Step 3: Implement Setter Function
```cpp
int UISprite::set_rotation(PyUISpriteObject* self, PyObject* value, void* closure) {
if (!self->data) {
PyErr_SetString(PyExc_RuntimeError, "UISprite data is null");
return -1;
}
if (!PyFloat_Check(value) && !PyLong_Check(value)) {
PyErr_SetString(PyExc_TypeError, "rotation must be a number");
return -1;
}
double rotation = PyFloat_AsDouble(value);
if (rotation < 0 || rotation > 360) {
PyErr_SetString(PyExc_ValueError, "rotation must be 0-360");
return -1;
}
self->data->rotation = rotation;
return 0;
}
```
### Step 4: Rebuild and Test
```bash
# From project root
make clean && make
cd build
./mcrogueface --headless -c "
import mcrfpy, sys
s = mcrfpy.Sprite(x=0, y=0, sprite_index=0)
s.rotation = 45
assert s.rotation == 45
print('PASS')
sys.exit(0)
"
```
---
## Workflow 2: Adding a Method to Existing Class
### Step 1: Add to PyMethodDef Array
```cpp
PyMethodDef UIGrid::methods[] = {
// Existing methods...
{"fill_walkable", (PyCFunction)UIGrid::fill_walkable, METH_VARARGS | METH_KEYWORDS,
MCRF_METHOD(Grid, fill_walkable,
MCRF_SIG("(walkable: bool)", "None"),
MCRF_DESC("Set walkable property for all cells."),
MCRF_ARGS_START
MCRF_ARG("walkable", "Whether cells should be walkable")
)},
{NULL} // Sentinel
};
```
### Step 2: Implement Method
```cpp
PyObject* UIGrid::fill_walkable(PyUIGridObject* self, PyObject* args, PyObject* kwds) {
if (!self->data) {
PyErr_SetString(PyExc_RuntimeError, "Grid data is null");
return NULL;
}
int walkable;
static char* kwlist[] = {"walkable", NULL};
if (!PyArg_ParseTupleAndKeywords(args, kwds, "p", kwlist, &walkable)) {
return NULL;
}
for (int x = 0; x < self->data->grid_x; x++) {
for (int y = 0; y < self->data->grid_y; y++) {
self->data->at(x, y).walkable = walkable;
}
}
Py_RETURN_NONE;
}
```
### Step 3: Test
```python
import mcrfpy
import sys
grid = mcrfpy.Grid(grid_size=(10, 10), pos=(0, 0), size=(160, 160))
grid.fill_walkable(True)
assert grid.at(5, 5).walkable == True
print("PASS")
sys.exit(0)
```
---
## Workflow 3: Creating New Python Type
### Step 1: Define Type Structure
In new header file (e.g., `src/PyMyType.h`):
```cpp
typedef struct {
PyObject_HEAD
std::shared_ptr<MyType> data;
} PyMyTypeObject;
namespace mcrfpydef {
static PyTypeObject PyMyTypeType = {
.tp_name = "mcrfpy.MyType",
.tp_basicsize = sizeof(PyMyTypeObject),
// ... filled in during init
};
}
class PyMyType {
public:
static PyGetSetDef getsetters[];
static PyMethodDef methods[];
static int init(PyMyTypeObject* self, PyObject* args, PyObject* kwds);
static PyObject* pynew(PyTypeObject* type, PyObject* args, PyObject* kwds);
static void dealloc(PyMyTypeObject* self);
};
```
### Step 2: Implement (in `src/PyMyType.cpp`)
```cpp
#include "PyMyType.h"
#include "McRFPy_Doc.h"
int PyMyType::init(PyMyTypeObject* self, PyObject* args, PyObject* kwds) {
// Parse arguments, initialize self->data
self->data = std::make_shared<MyType>();
return 0;
}
PyObject* PyMyType::pynew(PyTypeObject* type, PyObject* args, PyObject* kwds) {
auto* self = (PyMyTypeObject*)type->tp_alloc(type, 0);
if (self) self->data = nullptr;
return (PyObject*)self;
}
void PyMyType::dealloc(PyMyTypeObject* self) {
self->data.reset();
Py_TYPE(self)->tp_free((PyObject*)self);
}
PyGetSetDef PyMyType::getsetters[] = {
{"name", (getter)get_name, (setter)set_name,
MCRF_PROPERTY(name, "Object name."), NULL},
{NULL}
};
PyMethodDef PyMyType::methods[] = {
{NULL}
};
```
### Step 3: Register in Module
In `src/McRFPy_API.cpp`:
```cpp
#include "PyMyType.h"
// In the exported_types or internal_types array:
static PyTypeObject* exported_types[] = {
// ... existing types ...
&mcrfpydef::PyMyTypeType,
};
// Before PyType_Ready calls:
mcrfpydef::PyMyTypeType.tp_methods = PyMyType::methods;
mcrfpydef::PyMyTypeType.tp_getset = PyMyType::getsetters;
mcrfpydef::PyMyTypeType.tp_init = (initproc)PyMyType::init;
mcrfpydef::PyMyTypeType.tp_new = PyMyType::pynew;
mcrfpydef::PyMyTypeType.tp_dealloc = (destructor)PyMyType::dealloc;
```
CMake auto-discovers new `.cpp` files via GLOB_RECURSE, so no CMakeLists.txt changes needed.
---
## Documentation Macros
Use macros from `src/McRFPy_Doc.h` for all Python-facing documentation:
| Macro | Purpose |
|-------|---------|
| `MCRF_METHOD(cls, name, ...)` | Method docstring |
| `MCRF_PROPERTY(name, desc)` | Property docstring |
| `MCRF_SIG(params, ret)` | Method signature |
| `MCRF_DESC(text)` | Description paragraph |
| `MCRF_ARGS_START` | Begin arguments section |
| `MCRF_ARG(name, desc)` | Individual argument |
| `MCRF_RETURNS(text)` | Return value description |
| `MCRF_RAISES(exc, cond)` | Exception documentation |
| `MCRF_NOTE(text)` | Important notes |
| `MCRF_LINK(path, text)` | External documentation link |
---
## Testing Your Bindings
### Direct Execution Test
```python
import mcrfpy
import sys
# Test property
s = mcrfpy.Sprite(x=0, y=0, sprite_index=0)
s.rotation = 45
assert s.rotation == 45
# Test method
grid = mcrfpy.Grid(grid_size=(10, 10), pos=(0, 0), size=(160, 160))
grid.fill_walkable(True)
assert grid.at(5, 5).walkable == True
print("PASS")
sys.exit(0)
```
### Run
```bash
cd build
./mcrogueface --headless --exec ../tests/unit/my_binding_test.py
```
---
## Regenerating Documentation
After adding bindings:
```bash
# From project root
make
# Generate all docs (recommended)
./tools/generate_all_docs.sh
# Or individually:
cd build
./mcrogueface --headless --exec ../tools/generate_dynamic_docs.py
./mcrogueface --headless --exec ../tools/generate_stubs_v2.py
```
---
## Common Pitfalls
### Pitfall 1: Forgetting NULL Sentinel
```cpp
// WRONG - missing sentinel causes crash
PyGetSetDef getsetters[] = {
{"x", get_x, set_x, "X position", NULL}
};
// CORRECT
PyGetSetDef getsetters[] = {
{"x", get_x, set_x, "X position", NULL},
{NULL} // Must have this!
};
```
### Pitfall 2: Type Preservation in Collections
When returning from collections, use `RET_PY_INSTANCE`:
```cpp
// WRONG - returns base UIDrawable wrapper
return generic_wrap(item->data);
// CORRECT - preserves derived type (Frame, Caption, etc.)
RET_PY_INSTANCE(item->data);
```
### Pitfall 3: Missing Error Checks
```cpp
// WRONG - no type check
double value = PyFloat_AsDouble(obj);
// CORRECT
if (!PyFloat_Check(obj) && !PyLong_Check(obj)) {
PyErr_SetString(PyExc_TypeError, "Expected number");
return NULL;
}
double value = PyFloat_AsDouble(obj);
```
### Pitfall 4: Not Setting tp_methods/tp_getset Before PyType_Ready
```cpp
// WRONG - setting after PyType_Ready has no effect
PyType_Ready(&MyType);
MyType.tp_methods = methods;
// CORRECT - set before PyType_Ready
MyType.tp_methods = methods;
MyType.tp_getset = getsetters;
PyType_Ready(&MyType);
```
---
## Related Documentation
- [[Python-Binding-Layer]] - System architecture
- [[UI-Component-Hierarchy]] - Classes exposed to Python
- `src/McRFPy_Doc.h` - Documentation macro reference
# Adding Python Bindings
Step-by-step guide for exposing C++ functionality to Python in McRogueFace.
## Prerequisites
- Understanding of [[Python-Binding-Layer]] system architecture
- Familiarity with C++ class or function to expose
- McRogueFace builds from project root with `make`
## Quick Reference
**Related Systems:** [[Python-Binding-Layer]], [[UI-Component-Hierarchy]]
**Key Files:**
- `src/McRFPy_API.cpp` - Module definition and type registration
- `src/McRFPy_Doc.h` - Documentation macros (MCRF_METHOD, MCRF_PROPERTY, etc.)
- `src/PyObjectUtils.h` - Helper utilities
- Individual `src/Py*.cpp` files - Type bindings
---
## Workflow 1: Adding a Property to Existing Class
### Step 1: Add to PyGetSetDef Array
Find the class's `getsetters` array:
```cpp
PyGetSetDef UISprite::getsetters[] = {
// Existing properties...
// Add new property with doc macro
{"rotation", (getter)UISprite::get_rotation, (setter)UISprite::set_rotation,
MCRF_PROPERTY(rotation,
"Sprite rotation angle in degrees. Range: 0-360."
), NULL},
{NULL} // Sentinel - always last!
};
```
### Step 2: Implement Getter Function
```cpp
PyObject* UISprite::get_rotation(PyUISpriteObject* self, void* closure) {
if (!self->data) {
PyErr_SetString(PyExc_RuntimeError, "UISprite data is null");
return NULL;
}
return PyFloat_FromDouble(self->data->rotation);
}
```
### Step 3: Implement Setter Function
```cpp
int UISprite::set_rotation(PyUISpriteObject* self, PyObject* value, void* closure) {
if (!self->data) {
PyErr_SetString(PyExc_RuntimeError, "UISprite data is null");
return -1;
}
if (!PyFloat_Check(value) && !PyLong_Check(value)) {
PyErr_SetString(PyExc_TypeError, "rotation must be a number");
return -1;
}
double rotation = PyFloat_AsDouble(value);
if (rotation < 0 || rotation > 360) {
PyErr_SetString(PyExc_ValueError, "rotation must be 0-360");
return -1;
}
self->data->rotation = rotation;
return 0;
}
```
### Step 4: Rebuild and Test
```bash
# From project root
make clean && make
cd build
./mcrogueface --headless -c "
import mcrfpy, sys
s = mcrfpy.Sprite(x=0, y=0, sprite_index=0)
s.rotation = 45
assert s.rotation == 45
print('PASS')
sys.exit(0)
"
```
---
## Workflow 2: Adding a Method to Existing Class
### Step 1: Add to PyMethodDef Array
```cpp
PyMethodDef UIGrid::methods[] = {
// Existing methods...
{"fill_walkable", (PyCFunction)UIGrid::fill_walkable, METH_VARARGS | METH_KEYWORDS,
MCRF_METHOD(Grid, fill_walkable,
MCRF_SIG("(walkable: bool)", "None"),
MCRF_DESC("Set walkable property for all cells."),
MCRF_ARGS_START
MCRF_ARG("walkable", "Whether cells should be walkable")
)},
{NULL} // Sentinel
};
```
### Step 2: Implement Method
```cpp
PyObject* UIGrid::fill_walkable(PyUIGridObject* self, PyObject* args, PyObject* kwds) {
if (!self->data) {
PyErr_SetString(PyExc_RuntimeError, "Grid data is null");
return NULL;
}
int walkable;
static char* kwlist[] = {"walkable", NULL};
if (!PyArg_ParseTupleAndKeywords(args, kwds, "p", kwlist, &walkable)) {
return NULL;
}
for (int x = 0; x < self->data->grid_x; x++) {
for (int y = 0; y < self->data->grid_y; y++) {
self->data->at(x, y).walkable = walkable;
}
}
Py_RETURN_NONE;
}
```
### Step 3: Test
```python
import mcrfpy
import sys
grid = mcrfpy.Grid(grid_size=(10, 10), pos=(0, 0), size=(160, 160))
grid.fill_walkable(True)
assert grid.at(5, 5).walkable == True
print("PASS")
sys.exit(0)
```
---
## Workflow 3: Creating New Python Type
### Step 1: Define Type Structure
In new header file (e.g., `src/PyMyType.h`):
```cpp
typedef struct {
PyObject_HEAD
std::shared_ptr<MyType> data;
} PyMyTypeObject;
namespace mcrfpydef {
static PyTypeObject PyMyTypeType = {
.tp_name = "mcrfpy.MyType",
.tp_basicsize = sizeof(PyMyTypeObject),
// ... filled in during init
};
}
class PyMyType {
public:
static PyGetSetDef getsetters[];
static PyMethodDef methods[];
static int init(PyMyTypeObject* self, PyObject* args, PyObject* kwds);
static PyObject* pynew(PyTypeObject* type, PyObject* args, PyObject* kwds);
static void dealloc(PyMyTypeObject* self);
};
```
### Step 2: Implement (in `src/PyMyType.cpp`)
```cpp
#include "PyMyType.h"
#include "McRFPy_Doc.h"
int PyMyType::init(PyMyTypeObject* self, PyObject* args, PyObject* kwds) {
// Parse arguments, initialize self->data
self->data = std::make_shared<MyType>();
return 0;
}
PyObject* PyMyType::pynew(PyTypeObject* type, PyObject* args, PyObject* kwds) {
auto* self = (PyMyTypeObject*)type->tp_alloc(type, 0);
if (self) self->data = nullptr;
return (PyObject*)self;
}
void PyMyType::dealloc(PyMyTypeObject* self) {
self->data.reset();
Py_TYPE(self)->tp_free((PyObject*)self);
}
PyGetSetDef PyMyType::getsetters[] = {
{"name", (getter)get_name, (setter)set_name,
MCRF_PROPERTY(name, "Object name."), NULL},
{NULL}
};
PyMethodDef PyMyType::methods[] = {
{NULL}
};
```
### Step 3: Register in Module
In `src/McRFPy_API.cpp`:
```cpp
#include "PyMyType.h"
// In the exported_types or internal_types array:
static PyTypeObject* exported_types[] = {
// ... existing types ...
&mcrfpydef::PyMyTypeType,
};
// Before PyType_Ready calls:
mcrfpydef::PyMyTypeType.tp_methods = PyMyType::methods;
mcrfpydef::PyMyTypeType.tp_getset = PyMyType::getsetters;
mcrfpydef::PyMyTypeType.tp_init = (initproc)PyMyType::init;
mcrfpydef::PyMyTypeType.tp_new = PyMyType::pynew;
mcrfpydef::PyMyTypeType.tp_dealloc = (destructor)PyMyType::dealloc;
```
CMake auto-discovers new `.cpp` files via GLOB_RECURSE, so no CMakeLists.txt changes needed.
---
## Documentation Macros
Use macros from `src/McRFPy_Doc.h` for all Python-facing documentation:
| Macro | Purpose |
|-------|---------|
| `MCRF_METHOD(cls, name, ...)` | Method docstring |
| `MCRF_PROPERTY(name, desc)` | Property docstring |
| `MCRF_SIG(params, ret)` | Method signature |
| `MCRF_DESC(text)` | Description paragraph |
| `MCRF_ARGS_START` | Begin arguments section |
| `MCRF_ARG(name, desc)` | Individual argument |
| `MCRF_RETURNS(text)` | Return value description |
| `MCRF_RAISES(exc, cond)` | Exception documentation |
| `MCRF_NOTE(text)` | Important notes |
| `MCRF_LINK(path, text)` | External documentation link |
---
## Testing Your Bindings
### Direct Execution Test
```python
import mcrfpy
import sys
# Test property
s = mcrfpy.Sprite(x=0, y=0, sprite_index=0)
s.rotation = 45
assert s.rotation == 45
# Test method
grid = mcrfpy.Grid(grid_size=(10, 10), pos=(0, 0), size=(160, 160))
grid.fill_walkable(True)
assert grid.at(5, 5).walkable == True
print("PASS")
sys.exit(0)
```
### Run
```bash
cd build
./mcrogueface --headless --exec ../tests/unit/my_binding_test.py
```
---
## Regenerating Documentation
After adding bindings:
```bash
# From project root
make
# Generate all docs (recommended)
./tools/generate_all_docs.sh
# Or individually:
cd build
./mcrogueface --headless --exec ../tools/generate_dynamic_docs.py
./mcrogueface --headless --exec ../tools/generate_stubs_v2.py
```
---
## Common Pitfalls
### Pitfall 1: Forgetting NULL Sentinel
```cpp
// WRONG - missing sentinel causes crash
PyGetSetDef getsetters[] = {
{"x", get_x, set_x, "X position", NULL}
};
// CORRECT
PyGetSetDef getsetters[] = {
{"x", get_x, set_x, "X position", NULL},
{NULL} // Must have this!
};
```
### Pitfall 2: Type Preservation in Collections
When returning from collections, use `RET_PY_INSTANCE`:
```cpp
// WRONG - returns base UIDrawable wrapper
return generic_wrap(item->data);
// CORRECT - preserves derived type (Frame, Caption, etc.)
RET_PY_INSTANCE(item->data);
```
### Pitfall 3: Missing Error Checks
```cpp
// WRONG - no type check
double value = PyFloat_AsDouble(obj);
// CORRECT
if (!PyFloat_Check(obj) && !PyLong_Check(obj)) {
PyErr_SetString(PyExc_TypeError, "Expected number");
return NULL;
}
double value = PyFloat_AsDouble(obj);
```
### Pitfall 4: Not Setting tp_methods/tp_getset Before PyType_Ready
```cpp
// WRONG - setting after PyType_Ready has no effect
PyType_Ready(&MyType);
MyType.tp_methods = methods;
// CORRECT - set before PyType_Ready
MyType.tp_methods = methods;
MyType.tp_getset = getsetters;
PyType_Ready(&MyType);
```
---
## Related Documentation
- [[Python-Binding-Layer]] - System architecture
- [[UI-Component-Hierarchy]] - Classes exposed to Python
- `src/McRFPy_Doc.h` - Documentation macro reference
- [Python C API Reference](https://docs.python.org/3/c-api/)