|
|
              
MapCircleThe MapCircle element displays a geographic circle on a Map. More... Inherits Item This type was introduced in Qt Location 5.0. Properties
Detailed DescriptionThe MapCircle element displays a geographic circle on a Map, which consists of all points that are within a set distance from one central point. Depending on map projection, a geographic circle may not always be a perfect circle on the screen: for instance, in the Mercator projection, circles become ovoid in shape as they near the poles. To display a perfect screen circle around a point, use a MapQuickItem containing a relevant QML element instead. By default, the circle is displayed as a 1 pixel black border with no fill. To change its appearance, use the color, border.color and border.width properties. Internally, a MapCircle is implemented as a many-sided polygon. To calculate the radius points it uses a spherical model of the Earth, similar to the atDistanceAndAzimuth method of the QML Coordinate element. These two things can occasionally have implications for the accuracy of the circle's shape, depending on position and map projection. PerformanceMapCircle performance is almost equivalent to that of a MapPolygon with 125 vertices. There is a small amount of additional overhead with respect to calculating the vertices first. Like the other map objects, MapCircle is normally drawn without a smooth appearance. Setting the opacity property will force the object to be blended, which decreases performance considerably depending on the graphics hardware in use. Example UsageThe following snippet shows a map containing a MapCircle, centered at the coordinate (-27, 153) with a radius of 5km. The circle is filled in green, with a 3 pixel black border. Map {
MapCircle {
center: Coordinate { latitude: -27; longitude: 153.0 }
radius: 5000.0
color: 'green'
border.width: 3
}
}
Property DocumentationThese properties hold the width and color used to draw the border of the circle. The width is in pixels and is independent of the zoom level of the map. The default values correspond to a black border with a width of 1 pixel. For no line, use a width of 0 or a transparent color. This property holds the central point about which the circle is defined. See also radius. This property holds the fill color of the circle when drawn. For no fill, use a transparent color. This property holds the opacity of the item. Opacity is specified as a number between 0 (fully transparent) and 1 (fully opaque). The default is 1. If an item's opacity is set to 0, the item will no longer receive mouse events. Similarly, setting the visible property to false stops mouse events. This property holds the radius of the circle, in meters on the ground. See also center. |
