Distance between chart legend and the horizontal bar chart is to big in case of rotated labels

[SvenMuc]

I rechecked the issue with Charts 3.0.1. The behavior is the same. See images below.

chart.xAxis.labelRotationAngle       = -90.0           // rotate label
chart.xAxis.centerAxisLabelsEnabled  = true

chart.xAxis.centerAxisLabelsEnabled  = true

See also my old issue #1360

[SvenMuc]

I tried to investigate the HorizontalBarChartView.calculateOffsets() function. The offset results depend strongly on xAxis label rotation. The calculateOffset() is called 4 times. As you can see, the offsetBottom parameter strongly depends on the xAxis.labelRotationAngle. It increases with a higher rotation angle.

For me it looks like a bug in the calculateLegendOffsetsfunction (see debugging results below). I'll investigate this topics this evening.

chart.xAxis.labelRotationAngle = 0.0

calculateLegendOffsets: offsetTop: 0.0   offsetRight: 0.0  offsetBottom: 29.93359375  offsetLeft: 0.0
Before Extra Offset: offsetTop: 0.0   offsetRight: 0.0  offsetBottom: 41.8671875  offsetLeft: 70.0
After Extra Offset:  offsetTop: 0.0   offsetRight: 0.0  offsetBottom: 41.8671875  offsetLeft: 70.0
restrainViewPort:    offsetTop: 10.0   offsetRight: 10.0  offsetBottom: 41.8671875  offsetLeft: 70.0

chart.xAxis.labelRotationAngle = -45.0

calculateLegendOffsets: offsetTop: 0.0   offsetRight: 0.0  offsetBottom: 63.93359375  offsetLeft: 0.0
Before Extra Offset: offsetTop: 0.0   offsetRight: 0.0  offsetBottom: 75.8671875  offsetLeft: 63.0
After Extra Offset:  offsetTop: 0.0   offsetRight: 0.0  offsetBottom: 75.8671875  offsetLeft: 63.0
restrainViewPort:    offsetTop: 10.0   offsetRight: 10.0  offsetBottom: 75.8671875  offsetLeft: 63.0

chart.xAxis.labelRotationAngle = -90.0

calculateLegendOffsets: offsetTop: 0.0   offsetRight: 0.0  offsetBottom: 69.93359375  offsetLeft: 0.0
Before Extra Offset: offsetTop: 0.0   offsetRight: 0.0  offsetBottom: 81.8671875  offsetLeft: 29.0
After Extra Offset:  offsetTop: 0.0   offsetRight: 0.0  offsetBottom: 81.8671875  offsetLeft: 29.0
restrainViewPort:    offsetTop: 10.0   offsetRight: 10.0  offsetBottom: 81.8671875  offsetLeft: 29.0

[SvenMuc]

I think the root cause can be found in the function calculateLegendOffsetsin BarLineChartViewBase. The switch case .bottom calculates the offsetBottom value by adding the xAxis_labelRotatedHeightwhich in case of an horizontal bar chart the left axis. The correct distance can be calculated by using the label height of the right axis (rightAxis.getRequiredHeightSpace()).

Is there a way to find out if we have a horizontal or vertical chart?

What's the difference between _legend.orientationand _legend.verticalAlignment in the switch cases?

BarLineChartViewBase.calculateLegendOffsets()

          case .horizontal:
                
                print("calculateLegendOffsets->horizontal")
                
                switch _legend.verticalAlignment
                {
                case .top:
                    offsetTop += min(_legend.neededHeight, _viewPortHandler.chartHeight * _legend.maxSizePercent) + _legend.yOffset
                    if xAxis.isEnabled && xAxis.isDrawLabelsEnabled
                    {
                        offsetTop += xAxis.labelRotatedHeight
                        print("calculateLegendOffsets(horizontal,top): offsetTop: \(xAxis.labelRotatedHeight)")
                    }
                    
                case .bottom:
                    offsetBottom += min(_legend.neededHeight, _viewPortHandler.chartHeight * _legend.maxSizePercent) + _legend.yOffset
                    if xAxis.isEnabled && xAxis.isDrawLabelsEnabled
                    {
                        offsetBottom += xAxis.labelRotatedHeight
                        print("calculateLegendOffsets(horizontal,bottom): offsetBottom: \(xAxis.labelRotatedHeight)")
                    }

[SvenMuc]

One possible solution can be the following (case .bottom:):

if rightAxis.isEnabled && rightAxis.isDrawLabelsEnabled
{
    offsetBottom += rightAxis.getRequiredHeightSpace()
}

By this modification I get the correct offset values for a horizontal chart.

calculateLegendOffsets: offsetTop: 0.0   offsetRight: 0.0  offsetBottom: 29.8671875  offsetLeft: 0.0
Before Extra Offset:    offsetTop: 0.0   offsetRight: 0.0  offsetBottom: 41.80078125  offsetLeft: 29.0
After Extra Offset:     offsetTop: 0.0   offsetRight: 0.0  offsetBottom: 41.80078125  offsetLeft: 29.0
restrainViewPort:       offsetTop: 10.0   offsetRight: 10.0  offsetBottom: 41.80078125  offsetLeft: 29.0

But how do I detect the horizontal chart view in BarLineChartViewBase.calculateLegendOffsets()?

Interim solution:

              case .bottom:
                    offsetBottom += min(_legend.neededHeight, _viewPortHandler.chartHeight * _legend.maxSizePercent) + _legend.yOffset

                    if _xAxisRenderer.isKind(of: XAxisRendererHorizontalBarChart.self) {
                        if rightAxis.isEnabled && rightAxis.isDrawLabelsEnabled
                        {
                            offsetBottom += rightAxis.getRequiredHeightSpace()
                            print("calculateLegendOffsets(horizintal,bottom): offsetBottom: \(rightAxis.getRequiredHeightSpace())")
                        }
                    } else {
                        if xAxis.isEnabled && xAxis.isDrawLabelsEnabled
                        {
                            offsetBottom += xAxis.labelRotatedHeight
                            print("calculateLegendOffsets(horizintal,bottom): offsetBottom: \(xAxis.labelRotatedHeight)")
                        }
                    }

[liuxuan30]

Thanks @SvenMuc ! Seems you did a lot of work. Mind to file a PR to fix?

[SvenMuc]

I can do so. But I don't like my solution (see above) very much. Is there a better way to identify whether the xAxis is really the xAxis or the rightAxis @liuxuan30 ?

[liuxuan30]

I saw some code like let didUserDrag = (self is HorizontalBarChartView) to know whether it's horizontal or vertical bar chart.
Also, not sure why you ask 'better way' to identify xAxis is really the xAxis or the rightAxis. Just using the Class.self can know which class it is. But I wonder this seems not an answer to your question.

[SvenMuc]

Filed pull request #2214