Clamp Caption numeric setters to prevent UBSan float->uint UB

The `outline` and `font_size` property setters (and the matching kwargs
in __init__) passed a raw float straight into SFML's setOutlineThickness
and setCharacterSize. setCharacterSize takes unsigned int, so any
negative or out-of-range float produced undefined behavior — UBSan's
"value outside the representable range" report.

Clamp before the cast. Negative outline is also nonsensical, so it's
clamped to 0 for consistency (not UB, but wrong).

Fuzz corpus crash
tests/fuzz/crashes/property_types-crash-1f7141d732736d04b99d20261abd766194246ea6
now runs cleanly.

closes #309

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/UICaption.cpp

@@ -209,11 +209,18 @@ int UICaption::set_float_member(PyUICaptionObject* self, PyObject* value, void*
         self->data->markCompositeDirty(); // #289: position change invalidates parent cache
     }
     else if (member_ptr == 4) { //outline
+        // #309: negative outline thickness is nonsensical; clamp to 0
+        if (val < 0.0f) val = 0.0f;
         self->data->text.setOutlineThickness(val);
         self->data->markDirty(); // #289: content change invalidates own + parent cache
     }
     else if (member_ptr == 5) { // character size
-        self->data->text.setCharacterSize(val);
+        // #309: SFML setCharacterSize takes unsigned int; casting a negative or
+        // out-of-range float is UB. Clamp to a safe range before the cast.
+        // Upper bound is a practical cap well below UINT_MAX to keep SFML sane.
+        if (val < 0.0f) val = 0.0f;
+        else if (val > 65535.0f) val = 65535.0f;
+        self->data->text.setCharacterSize(static_cast<unsigned int>(val));
         self->data->markDirty(); // #289: content change invalidates own + parent cache
     }
     return 0;
@@ -503,6 +510,8 @@ int UICaption::init(PyUICaptionObject* self, PyObject* args, PyObject* kwds)
     self->data = std::make_shared<UICaption>();
     self->data->position = sf::Vector2f(x, y);
     self->data->text.setPosition(self->data->position);
+    // #309: clamp outline to non-negative
+    if (outline < 0.0f) outline = 0.0f;
     self->data->text.setOutlineThickness(outline);
 
     // Set the font
@@ -516,6 +525,9 @@ int UICaption::init(PyUICaptionObject* self, PyObject* args, PyObject* kwds)
     }
 
     // Set character size
+    // #309: clamp before casting to unsigned int to avoid UB on out-of-range floats
+    if (font_size < 0.0f) font_size = 0.0f;
+    else if (font_size > 65535.0f) font_size = 65535.0f;
     self->data->text.setCharacterSize(static_cast<unsigned int>(font_size));
     
     // Set text

tests/regression/issue_309_caption_numeric_setter_test.py

@@ -0,0 +1,64 @@
+"""Regression test for issue #309.
+
+Caption numeric setters (outline, font_size) previously cast raw floats to
+unsigned int without clamping. Feeding a negative or out-of-range value
+triggered UBSan under the fuzz harness (fuzz_property_types).
+
+This test exercises the patched paths with values that would previously be UB:
+- negative outline
+- negative font_size
+- extremely large font_size (beyond UINT_MAX)
+
+Also exercises the constructor path which had the same bug.
+"""
+
+import mcrfpy
+import sys
+
+
+def main():
+    # Setter path: create a Caption then poke the values
+    c = mcrfpy.Caption(text="x", pos=(0, 0))
+
+    # Negative outline: used to be UB via setOutlineThickness -> sane now
+    c.outline = -5.0
+    # Post-clamp: the value exposed is the raw float (getter returns float),
+    # but the UB path is gone. Just assert no crash and no Python exception.
+    _ = c.outline
+
+    # Very large outline: float stays a float, not UB, but make sure it doesn't explode
+    c.outline = 1e9
+    _ = c.outline
+
+    # Negative font_size: this was the UBSan trigger (-992.065 in the original crash)
+    c.font_size = -992.065
+    _ = c.font_size  # must not crash
+
+    # Font size above UINT_MAX: would cast to huge unsigned, now clamped
+    c.font_size = 1e20
+    _ = c.font_size
+
+    # Constructor path: kwargs with pathological values
+    c2 = mcrfpy.Caption(text="y", pos=(10, 10), outline=-3.0, font_size=-17.5)
+    # Accessing properties must not crash
+    _ = c2.outline
+    _ = c2.font_size
+
+    c3 = mcrfpy.Caption(text="z", pos=(20, 20), font_size=1e15)
+    _ = c3.font_size
+
+    # Type errors should still be raised for non-numeric input
+    try:
+        c.font_size = "not a number"
+    except TypeError:
+        pass
+    else:
+        print("FAIL: font_size should reject strings")
+        sys.exit(1)
+
+    print("PASS")
+    sys.exit(0)
+
+
+if __name__ == "__main__":
+    main()