Merge pull request #109100 from aaronfranke/range-snap

Fix snapping logic in Range

doc/classes/Range.xml

@@ -64,7 +64,7 @@
 		</member>
 		<member name="size_flags_vertical" type="int" setter="set_v_size_flags" getter="get_v_size_flags" overrides="Control" enum="Control.SizeFlags" is_bitfield="true" default="0" />
 		<member name="step" type="float" setter="set_step" getter="get_step" default="0.01">
-			If greater than 0, [member value] will always be rounded to a multiple of this property's value. If [member rounded] is also [code]true[/code], [member value] will first be rounded to a multiple of this property's value, then rounded to the nearest integer.
+			If greater than 0, [member value] will always be rounded to a multiple of this property's value above [member min_value]. For example, if [member min_value] is [code]0.1[/code] and step is 0.2, then [member value] is limited to [code]0.1[/code], [code]0.3[/code], [code]0.5[/code], and so on. If [member rounded] is also [code]true[/code], [member value] will first be rounded to a multiple of this property's value, then rounded to the nearest integer.
 		</member>
 		<member name="value" type="float" setter="set_value" getter="get_value" default="0.0">
 			Range's current value. Changing this property (even via code) will trigger [signal value_changed] signal. Use [method set_value_no_signal] if you want to avoid it.

scene/gui/range.cpp

@@ -30,6 +30,28 @@
 
 #include "range.h"
 
+#include "thirdparty/misc/r128.h"
+
+double Range::_snapped_r128(double p_value, double p_step) {
+	if (p_step != 0) {
+		// All these lines are the equivalent of: p_value = Math::floor(p_value / p_step + 0.5) * p_step;
+		// Convert to String to force rounding to a decimal value (not a binary one).
+		String step_str = String::num(p_step);
+		String value_str = String::num(p_value);
+		R128 step_r128;
+		R128 value_r128;
+		const R128 half_r128 = R128(0.5);
+		r128FromString(&step_r128, step_str.ascii().get_data(), nullptr);
+		r128FromString(&value_r128, value_str.ascii().get_data(), nullptr);
+		r128Div(&value_r128, &value_r128, &step_r128);
+		r128Add(&value_r128, &value_r128, &half_r128);
+		r128Floor(&value_r128, &value_r128);
+		r128Mul(&value_r128, &value_r128, &step_r128);
+		p_value = value_r128;
+	}
+	return p_value;
+}
+
 PackedStringArray Range::get_configuration_warnings() const {
 	PackedStringArray warnings = Control::get_configuration_warnings();
 
@@ -140,7 +162,8 @@ void Range::_set_value_no_signal(double p_val) {
 
 double Range::_calc_value(double p_val, double p_step) const {
 	if (p_step > 0) {
-		p_val = Math::round((p_val - shared->min) / p_step) * p_step + shared->min;
+		// Subtract min to support cases like min = 0.1, step = 0.2, snaps to 0.1, 0.3, 0.5, etc.
+		p_val = _snapped_r128(p_val - shared->min, p_step) + shared->min;
 	}
 
 	if (_rounded_values) {

scene/gui/range.h

@@ -62,6 +62,7 @@ class Range : public Control {
 	void _set_value_no_signal(double p_val);
 
 protected:
+	static double _snapped_r128(double p_value, double p_step);
 	double _calc_value(double p_val, double p_step) const;
 	virtual void _value_changed(double p_value);
 	void _notify_shared_value_changed() { shared->emit_value_changed(); }