How to Add Text Using Paths Drawing

Is there a way to add text using Paths Drawing

With MKOverlayPathView, I think the easiest way to add text is to override drawMapRect:zoomScale:inContext: and put the path and text drawing there (and do nothing in or don't implement createPath).

But if you're going to use drawMapRect anyway, you might want to just switch to subclassing a plain MKOverlayView instead of MKOverlayPathView.

With an MKOverlayView, override the drawMapRect:zoomScale:inContext: method and draw the circle using CGContextAddArc (or CGContextAddEllipseInRect or CGPathAddArc).

You can draw the text using drawAtPoint in this method which will have the required context.

For example:

-(void)drawMapRect:(MKMapRect)mapRect zoomScale:(MKZoomScale)zoomScale inContext:(CGContextRef)context
{
    //calculate CG values from circle coordinate and radius...
    CLLocationCoordinate2D center = circle_overlay_center_coordinate_here;

    CGPoint centerPoint = 
        [self pointForMapPoint:MKMapPointForCoordinate(center)];

    CGFloat radius = MKMapPointsPerMeterAtLatitude(center.latitude) * 
                         circle_overlay_radius_here;

    CGFloat roadWidth = MKRoadWidthAtZoomScale(zoomScale);

    //draw the circle...
    CGContextSetStrokeColorWithColor(context, [UIColor blueColor].CGColor);
    CGContextSetFillColorWithColor(context, [[UIColor blueColor] colorWithAlphaComponent:0.2].CGColor);
    CGContextSetLineWidth(context, roadWidth);
    CGContextAddArc(context, centerPoint.x, centerPoint.y, radius, 0, 2 * M_PI, true);
    CGContextDrawPath(context, kCGPathFillStroke);

    //draw the text...
    NSString *text = @"Hello";
    UIGraphicsPushContext(context);
    [[UIColor redColor] set];
    [text drawAtPoint:centerPoint 
             withFont:[UIFont systemFontOfSize:(5.0 * roadWidth)]];
    UIGraphicsPopContext();
}

In relation to a comment in another answer...

When the center coordinate or radius (or whatever) of the associated MKOverlay changes, you can make the MKOverlayView "move" by calling setNeedsDisplayInMapRect: on it (instead of removing and adding the overlay again). (When using a MKOverlayPathView, you can call invalidatePath instead.)

When calling setNeedsDisplayInMapRect:, you can pass the boundingMapRect of the overlay for the map rect parameter.

In the LocationReminders sample app from WWDC 2010, the overlay view uses KVO to observe changes to the associated MKOverlay and makes itself move whenever it detects a change to the circle's properties but you could monitor the changes in other ways and call setNeedsDisplayInMapRect: explicitly from outside the overlay view.

_{(In a comment on another answer I did mention using MKOverlayPathView and that is how the LocationReminders app implements a moving circle overlay view. But I should have mentioned how you can also use MKOverlayView to draw a circle. Sorry about that.)}

Add text to the path

Is it possible to add text to the current path, e.g. for clipping?

The simple answer is no, text paths are not exposed to us through canvas context so we cannot use them for things such as clipping.

The only way is either to:

Use composite mode to "punch" a hole for the text. Works much in the same way as clipping but is related to mattes more than paths.
Extract the text paths from fonts as polygons manually and use that with line, Bezier etc. A library that can help extract font paths could be opentype.js.

How can I draw text on a path in Jetpack Compose?

We use nativeCanvas to draw a text using Path in Compose, like how we do normally in Custom Views.

Ex:

@Composable
fun ArcTextExample() {
    val paint = Paint().asFrameworkPaint()
    Canvas(modifier = Modifier.fillMaxSize()) {
        paint.apply {
            isAntiAlias = true
            textSize = 24f
            typeface = Typeface.create(Typeface.DEFAULT, Typeface.BOLD)
        }

        drawIntoCanvas {
            val path = Path()
            path.addArc(RectF(0f, 100f, 200f, 300f), 270f, 180f)
            it.nativeCanvas.drawTextOnPath("Hello World Example", path, 0f, 0f, paint)
        }
    }
}

Note:
we should use android.graphics.Path

And the result will be like:

enter image description here

Properly draw text using GraphicsPath

Seems you are providing wrong measure for font size in the first place and then adding extra thickness to the brush. Try this instead:

using (GraphicsPath path = new GraphicsPath())
{
    path.AddString(
        text,                         
        _fontStyle.FontFamily,      
        (int)_fontStyle.Style,      
        e.Graphics.DpiY * fontSize / 72f,       // em size
        new Point(0, 0),                       // location where to draw text
        string_format);          

    e.Graphics.SmoothingMode = SmoothingMode.AntiAlias;
    e.Graphics.CompositingQuality = CompositingQuality.HighQuality;
    e.Graphics.CompositingMode = CompositingMode.SourceOver;
    e.Graphics.DrawPath(new Pen(Color.Red), path);
}

Drawing a path with subtracted text using Core Graphics

Here's some code I ran and tested that will work for you. See the inline comments for details:

Update: I've removed the manualYOffset: parameter. It now does a calculation to center the text vertically in the circle. Enjoy!

- (void)drawRect:(CGRect)rect {
    // Make sure the UIView's background is set to clear either in code or in a storyboard/nib

    CGContextRef context = UIGraphicsGetCurrentContext();

    [[UIColor whiteColor] setFill];
    CGContextAddArc(context, CGRectGetMidX(rect), CGRectGetMidY(rect), CGRectGetWidth(rect)/2, 0, 2*M_PI, YES);
    CGContextFillPath(context);

    // Manual offset may need to be adjusted depending on the length of the text
    [self drawSubtractedText:@"Foo" inRect:rect inContext:context];
}

- (void)drawSubtractedText:(NSString *)text inRect:(CGRect)rect inContext:(CGContextRef)context {
    // Save context state to not affect other drawing operations
    CGContextSaveGState(context);

    // Magic blend mode
    CGContextSetBlendMode(context, kCGBlendModeDestinationOut);

    // This seemingly random value adjusts the text
    // vertically so that it is centered in the circle.
    CGFloat Y_OFFSET = -2 * (float)[text length] + 5;

    // Context translation for label
    CGFloat LABEL_SIDE = CGRectGetWidth(rect);
    CGContextTranslateCTM(context, 0, CGRectGetHeight(rect)/2-LABEL_SIDE/2+Y_OFFSET);

    // Label to center and adjust font automatically
    UILabel *label = [[UILabel alloc] initWithFrame:CGRectMake(0, 0, LABEL_SIDE, LABEL_SIDE)];
    label.font = [UIFont boldSystemFontOfSize:120];
    label.adjustsFontSizeToFitWidth = YES;
    label.text = text;
    label.textAlignment = NSTextAlignmentCenter;
    label.backgroundColor = [UIColor clearColor];
    [label.layer drawInContext:context];

    // Restore the state of other drawing operations
    CGContextRestoreGState(context);
}

Here's the result (you can change the background to anything and you'll still be able to see through the text):

Result

Add text label to drawn shape

In your drawRect implementation you can draw the coordinates of the view with something like:

("\(frame.origin.x), \(frame.origin.y)" as NSString).drawAtPoint(.zero, withAttributes: [
    NSFontAttributeName: UIFont.systemFontOfSize(14),
    NSForegroundColorAttributeName: UIColor.blackColor()
    ])

Which simply creates a string of the coordinates, casts it to an NSString and then calls the drawAtPoint method to draw it in the view's context.

You can of course change .zero to any CGPoint depending on where you want to draw the string and can edit the attributes as desired.

To make sure that this gets updated when the user pans around you will want to also add:

self.setNeedsDisplay()

to the bottom of your didPan method.

Hope this helps :)

Draw text around QPainterPath efficiently

There is no built-in method to draw a text following a path.

But, if QPainter is not efficient enough, you can gain some perfs by building a new path with your text and by drawing after your loop (you will not use QPainter::save() and QPainter::restore() in a loop):

void paintEvent(QPaintEvent* event)
    {
        QString text = "Short text";
        text = text.repeated(1000); // Check with a very long text
        QPainterPath rawPath;
        rawPath.addEllipse(QRect(0, 0, 200, 200));

        QPainterPath path;

        double const step = 1.0 / double(text.length());
        double percent = 0.0;
        for(QChar const& c: text)
        {
            double angle = rawPath.angleAtPercent(percent);
            QPointF point = rawPath.pointAtPercent(percent);

            QTransform mat;
            mat.rotate(-angle);
            QPainterPath p2;
            p2.addText(0, 0, font(), c);
            p2 = mat.map(p2);
            path.addPath(p2.translated(point));
            percent += step;
        }

        QPainter painter(this);
        painter.drawPath(path.translated(100, 100));
    }