john
/
McRogueFace
1
0
Fork 0
Code Issues 46 Pull Requests Projects 1 Releases Wiki Activity

Add "Adding-Python-Bindings"

John McCardle 2025-10-25 21:01:17 +00:00
parent b8af2bd821
commit dd7a569928
1 changed files with 435 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

435
Adding-Python-Bindings.-.md Normal file

@ -0,0 +1,435 @@
# 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 `PYTHON_BINDING_PATTERNS.md` (repository root)
- C++ class or function to expose
## Quick Reference
**Related Systems:** [[Python-Binding-Layer]], [[UI-Component-Hierarchy]]
**Key Files:**
- `src/McRFPy_API.cpp` - Module-level functions
- `src/PyObjectUtils.h` - Helper utilities
- Individual `src/UI*.cpp` files - Type bindings
**Documentation Format:** See CLAUDE.md "Inline C++ Documentation Format"
---
## Workflow 1: Adding a Property to Existing Class
### Step 1: Add to PyGetSetDef Array
Find the class's `getsetters` array (e.g., `PyUISprite::getsetters`):
```cpp
PyGetSetDef PyUISprite::getsetters[] = {
// Existing properties...
// Add new property
{"rotation", (getter)PyUISprite::get_rotation, (setter)PyUISprite::set_rotation,
"Sprite rotation angle in degrees. Range: 0-360.", NULL},
{NULL} // Sentinel - always last!
};
```
### Step 2: Implement Getter Function
```cpp
PyObject* PyUISprite::get_rotation(PyUISprite* 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 PyUISprite::set_rotation(PyUISprite* 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; // Success
}
```
### Step 4: Add Documentation
Update the docstring in PyGetSetDef:
```cpp
{"rotation", (getter)PyUISprite::get_rotation, (setter)PyUISprite::set_rotation,
"Sprite rotation angle in degrees.\n\n"
"Range: 0-360 degrees. 0 is upright, increases clockwise.\n\n"
"Example:\n"
" sprite.rotation = 90 # Rotate 90 degrees clockwise\n\n"
"Note:\n"
" Rotation is applied during rendering, not to position.",
NULL},
```
### Step 5: Rebuild and Test
```bash
make clean && make
cd build
./mcrogueface --exec test_rotation.py
```
---
## Workflow 2: Adding a Method to Existing Class
### Step 1: Add to PyMethodDef Array
Find the class's `methods` array:
```cpp
PyMethodDef PyUIGrid::methods[] = {
// Existing methods...
{"fill_rect", (PyCFunction)PyUIGrid::fill_rect, METH_VARARGS | METH_KEYWORDS,
"fill_rect(x: int, y: int, w: int, h: int, tile: int) -> None\n\n"
"Fill rectangular area with tile index.\n\n"
"Args:\n"
" x: Top-left X coordinate\n"
" y: Top-left Y coordinate\n"
" w: Width in tiles\n"
" h: Height in tiles\n"
" tile: Tile sprite index\n\n"
"Example:\n"
" grid.fill_rect(5, 5, 10, 10, 42) # Fill 10x10 area with tile 42"},
{NULL} // Sentinel
};
```
### Step 2: Implement Method Function
```cpp
PyObject* PyUIGrid::fill_rect(PyUIGrid* self, PyObject* args, PyObject* kwds) {
if (!self->data) {
PyErr_SetString(PyExc_RuntimeError, "Grid data is null");
return NULL;
}
int x, y, w, h, tile;
static char* kwlist[] = {"x", "y", "w", "h", "tile", NULL};
if (!PyArg_ParseTupleAndKeywords(args, kwds, "iiiii", kwlist,
&x, &y, &w, &h, &tile)) {
return NULL; // PyArg functions set error automatically
}
// Bounds checking
if (x < 0 || y < 0 || x + w > self->data->grid_x || y + h > self->data->grid_y) {
PyErr_SetString(PyExc_ValueError, "Rectangle out of grid bounds");
return NULL;
}
// Fill the rectangle
for (int dx = 0; dx < w; dx++) {
for (int dy = 0; dy < h; dy++) {
self->data->at(x + dx, y + dy).tilesprite = tile;
}
}
Py_RETURN_NONE;
}
```
### Step 3: Test
```python
import mcrfpy
grid = mcrfpy.Grid(50, 50, 16, 16)
grid.texture = mcrfpy.createTexture("tiles.png")
# Test new method
grid.fill_rect(10, 10, 5, 5, 42)
# Verify
assert grid.at((10, 10)).tilesprite == 42
print("Test passed!")
```
---
## Workflow 3: Creating New Python Type
### Step 1: Define Python Type Structure
In new header file (e.g., `src/UIButton.h`):
```cpp
// Python object wrapper
typedef struct {
PyObject_HEAD
std::shared_ptr<UIButton> data;
} PyUIButtonObject;
// Python type object
class PyUIButton {
public:
static PyTypeObject Type;
static PyGetSetDef getsetters[];
static PyMethodDef methods[];
// Lifecycle
static PyObject* pynew(PyTypeObject* type, PyObject* args, PyObject* kwds);
static int pyinit(PyUIButtonObject* self, PyObject* args, PyObject* kwds);
static void dealloc(PyUIButtonObject* self);
// Properties
static PyObject* get_text(PyUIButtonObject* self, void* closure);
static int set_text(PyUIButtonObject* self, PyObject* value, void* closure);
// ... more properties
};
```
### Step 2: Implement Type Object
In `src/UIButton.cpp`:
```cpp
PyTypeObject PyUIButton::Type = {
PyVarObject_HEAD_INIT(NULL, 0)
.tp_name = "mcrfpy.Button",
.tp_basicsize = sizeof(PyUIButtonObject),
.tp_dealloc = (destructor)PyUIButton::dealloc,
.tp_flags = Py_TPFLAGS_DEFAULT,
.tp_doc = "Button UI element with click handling",
.tp_methods = PyUIButton::methods,
.tp_getset = PyUIButton::getsetters,
.tp_new = PyUIButton::pynew,
.tp_init = (initproc)PyUIButton::pyinit,
};
```
### Step 3: Register in Module
In `src/McRFPy_API.cpp::PyInit_mcrfpy()`:
```cpp
// After other type registrations
if (PyType_Ready(&PyUIButton::Type) < 0) {
return NULL;
}
Py_INCREF(&PyUIButton::Type);
if (PyModule_AddObject(m, "Button", (PyObject*)&PyUIButton::Type) < 0) {
Py_DECREF(&PyUIButton::Type);
Py_DECREF(m);
return NULL;
}
```
### Step 4: Implement Constructor
```cpp
PyObject* PyUIButton::pynew(PyTypeObject* type, PyObject* args, PyObject* kwds) {
PyUIButtonObject* self = (PyUIButtonObject*)type->tp_alloc(type, 0);
if (self != NULL) {
self->data = nullptr; // Initialize in __init__
}
return (PyObject*)self;
}
int PyUIButton::pyinit(PyUIButtonObject* self, PyObject* args, PyObject* kwds) {
int x = 0, y = 0, w = 100, h = 30;
const char* text = "";
static char* kwlist[] = {"x", "y", "w", "h", "text", NULL};
if (!PyArg_ParseTupleAndKeywords(args, kwds, "|iiiis", kwlist,
&x, &y, &w, &h, &text)) {
return -1;
}
self->data = std::make_shared<UIButton>(x, y, w, h, text);
return 0;
}
```
---
## Common Patterns & Helpers
### PyArgHelpers for Position/Size
Use standardized helpers for tuple support:
```cpp
#include "PyArgHelpers.h"
// Accept (x, y) tuple OR separate x, y args
int x, y;
if (!PyArgParseTuple_IntIntHelper(args, kwds, x, y, "position", "x", "y")) {
return -1;
}
```
**See:** `src/PyArgHelpers.h` for complete helper reference
### Closure Parameter Encoding
For UIDrawable-derived types:
```cpp
// Encode type and member index
(void*)((intptr_t)PyObjectsEnum::BUTTON << 8 | BUTTON_MEMBER_TEXT)
```
**See:** `PYTHON_BINDING_PATTERNS.md` for complete encoding scheme
### Error Handling
**Always check for NULL:**
```cpp
if (!self->data) {
PyErr_SetString(PyExc_RuntimeError, "Object data is null");
return NULL; // Or -1 for setters
}
```
**Set descriptive errors:**
```cpp
PyErr_Format(PyExc_ValueError, "Index %d out of range (0-%d)", idx, max_idx);
```
---
## Testing Your Bindings
### Manual Testing
```python
#!/usr/bin/env python3
import mcrfpy
# Test property
sprite = mcrfpy.Sprite("test.png", 0, 0)
sprite.rotation = 45
assert sprite.rotation == 45
# Test method
grid = mcrfpy.Grid(10, 10, 16, 16)
grid.fill_rect(0, 0, 5, 5, 42)
assert grid.at((0, 0)).tilesprite == 42
print("All tests passed!")
```
### Automated Testing
Create test in `tests/test_new_binding.py`:
```python
import mcrfpy
import sys
def test_binding():
# Your tests here
pass
if __name__ == "__main__":
try:
test_binding()
print("PASS")
sys.exit(0)
except Exception as e:
print(f"FAIL: {e}")
sys.exit(1)
```
Run: `./build/mcrogueface --headless --exec tests/test_new_binding.py`
---
## Common Pitfalls
### Pitfall 1: Forgetting NULL Sentinel
```cpp
// WRONG - missing sentinel
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 - loses derived type
return (PyObject*)item->data.get();
// CORRECT - preserves type
RET_PY_INSTANCE(item->data);
```
### Pitfall 3: Missing Error Checks
```cpp
// WRONG - no error check
double value = PyFloat_AsDouble(obj);
// CORRECT
if (!PyFloat_Check(obj)) {
PyErr_SetString(PyExc_TypeError, "Expected float");
return NULL;
}
double value = PyFloat_AsDouble(obj);
```
---
## Related Documentation
- [[Python-Binding-Layer]] - System architecture
- `PYTHON_BINDING_PATTERNS.md` - Complete pattern reference
- CLAUDE.md - Inline documentation format
- [Python C API Reference](https://docs.python.org/3/c-api/)
## Next Steps
After adding bindings:
1. Rebuild: `make clean && make`
2. Test manually
3. Add automated test in `tests/`
4. Regenerate stub files: `./build/mcrogueface --exec tools/generate_stubs.py`
5. Update API docs: `./build/mcrogueface --exec tools/generate_dynamic_docs.py`
6. Document in wiki if new system