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Fix callback/timer GC: prevent premature destruction of Python callbacks

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closes #251

Two related bugs where Python garbage collection destroyed callbacks
that were still needed by live C++ objects:

1. **Drawable callbacks (all 8 types)**: tp_dealloc unconditionally called
   click_unregister() etc., destroying callbacks even when the C++ object
   was still alive in a parent's children vector. Fixed by guarding with
   shared_ptr::use_count() <= 1 — only unregister when the Python wrapper
   is the last owner.

2. **Timer GC prevention**: Active timers now hold a Py_INCREF'd reference
   to their Python wrapper (Timer::py_wrapper), preventing GC while the
   timer is registered in the engine. Released on stop(), one-shot fire,
   or destruction. mcrfpy.Timer("name", cb, 100) now works without storing
   the return value.

Also includes audio synth demo UI fixes: button click handling (don't set
on_click on Caption children), single-column slider layout, improved
Animalese contrast.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
This commit is contained in:
John McCardle 2026-02-19 20:53:50 -05:00
commit 9718153709
15 changed files with 740 additions and 231 deletions
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4
src/UIGrid.h
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@ -269,8 +269,8 @@ namespace mcrfpydef {
if (obj->weakreflist != NULL) {
PyObject_ClearWeakRefs(self);
}
// Clear Python references to break cycles
if (obj->data) {
// Only unregister callbacks if we're the last owner (#251)
if (obj->data && obj->data.use_count() <= 1) {
obj->data->click_unregister();
obj->data->on_enter_unregister();
obj->data->on_exit_unregister();