[patch] Stop ValueSlider reporting a change on held frames that move nothing

ImGui.Widgets/ValueSlider.cs

@@ -259,7 +259,10 @@
 
 		private static bool SetValue(ref double value, double target, double min, double max, bool isInteger)
 		{
-			double next = Math.Clamp(isInteger ? Math.Round(target, MidpointRounding.AwayFromZero) : target, min, max);
+			// The value is stored as a float or an int, so it is compared as one: a drag held as a double
+			// that a float cannot hold exactly would otherwise read as a fresh change on every held frame.
+			double stored = isInteger ? Math.Round(target, MidpointRounding.AwayFromZero) : (float)target;
+			double next = Math.Clamp(stored, min, max);
 			if (IsSameValue(next, value))
 			{
 				return false;
@@ -282,7 +285,7 @@
 			ImDrawListPtr drawList = ImGui.GetWindowDrawList();
 			ImGuiStylePtr style = ImGui.GetStyle();
 			float rounding = style.FrameRounding;
 			ImGuiCol background = held ? ImGuiCol.FrameBgActive : hovered ? ImGuiCol.FrameBgHovered : ImGuiCol.FrameBg;
 			drawList.AddRectFilled(frame.Min, frame.Max, ImGui.GetColorU32(background), rounding);
 
 			(float start, float end) = ValueSliderState.FillSpan(value, min, max, options.Fill, options.Logarithmic, spec.Epsilon);

tests/ImGui.Widgets.UITests/ValueSliderTests.cs

@@ -344,6 +344,42 @@ public void ValueSlider_APrefixIsDrawnButNotTyped()
 		Assert.AreEqual(30f, value, "A typed value with the prefix in front was not read.");
 	}
 
+	[TestMethod]
+	public void ValueSlider_AHeldPointerThatStopsReportsNoChange()
+	{
+		// 0..1 over 200 px, so a 7 px drag lands on 0.035, which a float cannot hold exactly.
+		float fraction = 0.5f;
+		int changes = 0;
+		Start(() =>
+		{
+			ImGui.PushItemWidth(FrameWidth);
+			if (ImGuiWidgets.ValueSlider(Label, ref fraction, 0f, 1f))
+			{
+				changes++;
+			}
+
+			ImGui.PopItemWidth();
+		});
+
+		Rectangle rect = RectOf(Label);
+		float x = rect.MinX + (FrameWidth / 2f);
+		float y = rect.MinY + (rect.Height / 2f);
+		Harness.Mouse.MoveTo(x, y);
+		Step();
+		HarnessMouse.Down(0);
+		Step();
+		Harness.Mouse.MoveTo(x + 7f, y);
+		Step(2);
+
+		Assert.AreNotEqual(0.5f, fraction, "The drag did not move the value.");
+		changes = 0;
+		Step(5);
+		HarnessMouse.Up(0);
+		Step();
+
+		Assert.AreEqual(0, changes, "The slider reported a change on frames the held pointer did not move.");
+	}
+
 	[TestMethod]
 	public void ValueSlider_ReportsTheFrameItChangedOn()
 	{