Reduce the effect of noise on power flow direction visualisation

We visualise the direction of power flow with an icon and a colour
e.g. feed-in icon with green colour gauge, versus grid-draw icon
     with blue colour gauge.

This commit ensures that we don't flicker between feed-in and
grid-draw visualisation if the value is actually zero and the
readings are just noise, by requiring that the feed-in value
exceeds a certain threshold before we recognise it.

(Note that this will not prevent flickering if feed-in amount
happens to hover around -0.5, but this is much less likely.)

Also, this aligns the expectation of the user with the value shown
e.g. -0.4 Watts will be shown as 0 W due to zero-digit-precision,
and so the user does not expect to see any feed-in at this value.

Contributes to #1328

components/AcInputDirectionIcon.qml

@@ -9,11 +9,15 @@ import Victron.VenusOS
 
 // When ESS feedback to grid is enabled, show an arrow indicating the flow direction.
 CP.ColorImage {
+	property real activeInputPower: (!Global.acInputs.activeInput || !Global.acInputs.activeInput.power) ? 0
+			: Global.acInputs.activeInput.power <= -0.5 ? Global.acInputs.activeInput.power
+			: Global.acInputs.activeInput.power >= 0.5 ? Global.acInputs.activeInput.power
+			: 0 // clamp to zero any values close to zero (assume it's noise) to avoid UI flicker.
 	visible: Global.systemSettings.essFeedbackToGridEnabled && Global.acInputs.activeInput
-	source: !!Global.acInputs.activeInput
-			? (Global.acInputs.activeInput.power < 0 ? "qrc:/images/icon_to_grid.svg" : "qrc:/images/icon_from_grid.svg")
-			: ""
-	color: !Global.acInputs.activeInput || (Global.acInputs.activeInput.power || 0) === 0 ? Theme.color_background_disabled
-			: Global.acInputs.activeInput.power < 0 ? Theme.color_green
+	source: !Global.acInputs.activeInput ? ""
+			: activeInputPower < 0 ? "qrc:/images/icon_to_grid.svg"
+			: "qrc:/images/icon_from_grid.svg"
+	color: (!Global.acInputs.activeInput || activeInputPower === 0) ? Theme.color_background_disabled
+			: activeInputPower < 0 ? Theme.color_green
 			: Theme.color_blue
 }

components/SideMultiGauge.qml

@@ -48,7 +48,7 @@ Item {
 			id: gaugeDelegate
 
 			readonly property bool feedingToGrid: root.inputMode
-					&& (model.power || 0) < 0
+					&& (model.power || 0) <= -0.5 // ignore noise values (negative close to zero)
 
 			width: Theme.geometry_briefPage_edgeGauge_width
 			height: root.height

components/ThreePhaseBarGauge.qml

@@ -66,7 +66,7 @@ Flow {
 				height: parent.height
 				sourceComponent: Global.isGxDevice ? cheapGauge : prettyGauge
 				readonly property bool feedingToGrid: root.inputMode
-						&& (model.power || 0) < 0
+						&& (model.power || 0) <= -0.5 // ignore noise values (negative close to zero)
 			}
 
 			Component {

components/ThreePhaseDisplay.qml

@@ -34,7 +34,7 @@ Flow {
 		delegate: Item {
 			id: phaseDelegate
 
-			readonly property bool feedingToGrid: root.inputMode && (model.power || 0) < 0
+			readonly property bool feedingToGrid: root.inputMode && (model.power || 0) <= -0.5 // ignore noise values (negative close to zero)
 			readonly property int valueStatus: feedingToGrid ? Theme.Ok
 					: root.phaseModelProperty ? Theme.getValueStatus(valueRange.valueAsRatio * 100, root.valueType)
 					: Theme.Ok