Center text vertically

[hiworld75018]

When using big fonts, I noticed that text is not actually vertically centered.
Adding this in DrawUtils.drawText() makes it work:

if let font = attributes?[NSFontAttributeName] as? UIFont {
point.y -= font.lineHeight / 2
}

[liuxuan30]

could you specify which font size are you using, also is it axis label text or value text? A screenshot is even better.

[hiworld75018]

In case there is a single value, I use the chartView.noDataText field to display it, using font size 36 (with chartView.data == nil).

[liuxuan30]

a single value, but using no data text? Confused. Can you post a screenshot?

[hiworld75018]

You may try this code, to display the "single" value converted into a string that will sit in the middle of the "chart":

UIFontDescriptor* bodyDescriptor = [UIFontDescriptor preferredFontDescriptorWithTextStyle:UIFontTextStyleBody];
UIFont* font = [UIFont fontWithDescriptor:bodyDescriptor size:36.]; // some BIG size

PieChartView* chartView = [[PieChartView alloc] initWithFrame:CGRectMake(0, 0, 300, 200)];

chartView.infoTextColor = [UIColor redColor];
chartView.infoFont = font;

chartView.noDataText = @"99%"; // the "single" value is converted into text here

// Remove the chart legend + label "description"
chartView.legend.enabled = NO;
chartView.descriptionText = @"";

[liuxuan30]

if your "single value" means noDataText, on my side I see it like below:
The 99% seems a little bit lower than the center. Is this what are you trying to say?

[liuxuan30]

OK I checked the code:

    public class func drawText(context context: CGContext, text: String, var point: CGPoint, align: NSTextAlignment, attributes: [String : AnyObject]?)
    {
        if (align == .Center)
        {
            point.x -= text.sizeWithAttributes(attributes).width / 2.0
        }

It seems it just tried to center x but no y. I will file a PR later.

[hiworld75018]

I think I've got a better way to fix it:

In ChartViewBase.drawRect(rect), use lineHeight to center vertically before calling ChartUtils.drawText()

CGContextSaveGState(context)
let lineHeight = infoFont.lineHeight
ChartUtils.drawText(..., point: CGPoint(x: frame.width / 2.0, y: frame.height / 2.0 - lineHeight / 2.0), ...)
if (noDataTextDescription != nil && (noDataTextDescription!).characters.count > 0)
{
...
ChartUtils.drawText(..., point: CGPoint(x: frame.width / 2.0, y: frame.height / 2.0 - lineHeight / 2.0 + textOffset), ...)
...
}

I noticed the same in PieChartRenderer.drawValues(context)

// y -= lineHeight
if (drawXVals && drawYVals)
{
y -= lineHeight
...
}
else if (drawXVals && !drawYVals)
{
y -= lineHeight / 2
...
}
else if (!drawXVals && drawYVals)
{
y -= lineHeight / 2
...
}

[liuxuan30]

You could file a PR for this. Mine is closed since I don't see the big picture and don't have much time for details right now. Hope you can fix them all from my PR. There are two texts for no data case. We need adjust them all.

[danielgindi]

Modifying drawText is the wrong approach and will make all text drawing in axises incorrect.
Fix coming...