[LOOP1992] Do not allow a value of -0 on the y-axis (dosing chart) (#272)

* do not allow a value of -0 on the y-axis

* avoid -0 even when padding is not needed

Author: nhamming

LoopUI/Charts/DoseChart.swift

@@ -65,8 +65,14 @@ public extension DoseChart {
 
         let points = generateDosePoints(startDate: startDate)
 
-        let yAxisValues = ChartAxisValuesStaticGenerator.generateYAxisValuesWithChartPoints(points.basal + points.bolus + doseDisplayRangePoints, minSegmentCount: 2, maxSegmentCount: 3, multiple: log(2) / 2, axisValueGenerator: { ChartAxisValueDoubleLog(screenLocDouble: $0, formatter: integerFormatter, labelSettings: axisLabelSettings) }, addPaddingSegmentIfEdge: true)
-
+        let yAxisValues = ChartAxisValuesStaticGenerator.generateYAxisValuesUsingLinearSegmentStep(
+            chartPoints: points.basal + points.bolus + doseDisplayRangePoints,
+            minSegmentCount: 2,
+            maxSegmentCount: 3,
+            multiple: log(2) / 2,
+            axisValueGenerator: { ChartAxisValueDoubleLog(screenLocDouble: $0, formatter: integerFormatter, labelSettings: axisLabelSettings) },
+            addPaddingSegmentIfEdge: true)
+        
         let yAxisModel = ChartAxisModel(axisValues: yAxisValues, lineColor: colors.axisLine, labelSpaceReservationMode: .fixed(labelsWidthY))
 
         let coordsSpace = ChartCoordsSpaceLeftBottomSingleAxis(chartSettings: chartSettings, chartFrame: frame, xModel: xAxisModel, yModel: yAxisModel)

LoopUI/Extensions/ChartAxisValuesStaticGenerator.swift

@@ -40,8 +40,14 @@ extension ChartAxisValuesStaticGenerator {
 
             /// If there should be a padding segment added when a scalar value falls on the first or last axis value, adjust the first and last axis values
             if firstValue =~ first && addPaddingSegmentIfEdge {
+               firstValue = firstValue - segmentSize
+            }
+            
+            // do not allow a value of -0 on the axis
+            while firstValue < 0 && firstValue.rounded() == -0 {
                 firstValue = firstValue - segmentSize
             }
+            
             if lastValue =~ last && addPaddingSegmentIfEdge {
                 lastValue = lastValue + segmentSize
             }