Curve: Prevent forcing 1.0 min value to 0.99

The setters are called when the property is first initialized, and before
that its default min and max are 0.0 and 1.0 respectively.

If you configured min_value to 1.0 and max_value to e.g. 3.0, since the
min_value setter can be called before that of max_value (which thus still
defaults to 1.0), the min will be set to 0.99.
Same conflict could happen with a configured max_value of 0 if its setter
is called before that of a valid, negative min value.

2 files changed, 10 insertions, 4 deletions

diff --git a/scene/resources/curve.cpp b/scene/resources/curve.cpp
index 950518aa6e..cb710dde43 100644
--- a/scene/resources/curve.cpp
+++ b/scene/resources/curve.cpp
@@ -51,6 +51,7 @@ Curve::Curve() {
 	_baked_cache_dirty = false;
 	_min_value = 0;
 	_max_value = 1;
+	_minmax_set_once = 0b00;
 }
 
 int Curve::add_point(Vector2 p_pos, real_t left_tangent, real_t right_tangent, TangentMode left_mode, TangentMode right_mode) {
@@ -282,20 +283,24 @@ void Curve::update_auto_tangents(int i) {
 #define MIN_Y_RANGE 0.01
 
 void Curve::set_min_value(float p_min) {
-	if (p_min > _max_value - MIN_Y_RANGE)
+	if (_minmax_set_once & 0b11 && p_min > _max_value - MIN_Y_RANGE) {
 		_min_value = _max_value - MIN_Y_RANGE;
-	else
+	} else {
+		_minmax_set_once |= 0b10; // first bit is "min set"
 		_min_value = p_min;
+	}
 	// Note: min and max are indicative values,
 	// it's still possible that existing points are out of range at this point.
 	emit_signal(SIGNAL_RANGE_CHANGED);
 }
 
 void Curve::set_max_value(float p_max) {
-	if (p_max < _min_value + MIN_Y_RANGE)
+	if (_minmax_set_once & 0b11 && p_max < _min_value + MIN_Y_RANGE) {
 		_max_value = _min_value + MIN_Y_RANGE;
-	else
+	} else {
+		_minmax_set_once |= 0b01; // second bit is "max set"
 		_max_value = p_max;
+	}
 	emit_signal(SIGNAL_RANGE_CHANGED);
 }
 
diff --git a/scene/resources/curve.h b/scene/resources/curve.h
index bb12baca48..b677097e86 100644
--- a/scene/resources/curve.h
+++ b/scene/resources/curve.h
@@ -143,6 +143,7 @@ private:
 	int _bake_resolution;
 	float _min_value;
 	float _max_value;
+	int _minmax_set_once; // Encodes whether min and max have been set a first time, first bit for min and second for max.
 };
 
 VARIANT_ENUM_CAST(Curve::TangentMode)