The Mosaic class Views::FillGradientPath implements a graphical object specialized to display polygons from provided path data filled by a linear or radial gradient. A single path can be composed of line segments, Bézier curves and elliptical arcs. Several paths can be combined together in order to describe complex shapes. The gradient can contain multiple color stops. This so-called Filled Gradient Path view can be used to compose the appearance of a GUI component, in particular to display pie charts, histograms, polygons, circles, etc. The following screenshot demonstrates few examples of how Filled Gradient Path views appear in the canvas area of Composer (and accordingly on the screen in your target device):

The following sections are intended to provide you an introduction and useful tips of how to work with the Filled Gradient Path view. For the complete reference please see the documentation of the Views::FillGradientPath class.

To add a new Filled Gradient Path view just at the design time of a GUI component do following:

As long as the Filled Gradient Path view is selected you can inspect and modify its properties conveniently in the Inspector window as demonstrated with the property Bounds in the screenshot below. Please note, for better overview the below screenshot has been made with Inspector window being configured to sort the properties by categories:

Once added, you can freely move the Filled Gradient Path view, or you simply grab one of its corners and resize it in this way. You can control the position and the size of the view also by directly modifying its property Bounds. If you want the Filled Gradient Path view to appear behind other views you can reorder it explicitly.

In order to display a graphical shape in the Filled Gradient Path view, you have to provide the corresponding path information. You can consider the path as a list of connected straight line segments (so-called edges) describing precisely the outline of the shape intended to be to displayed. Depending on the application case the path may consist of few or even hundreds of edges. In this manner you describe primitive (e.g. triangles) or even complex shapes (e.g. circles, rings, Bézier curves or polygons).

To provide the path information you use a Path Data object. Usually you will add such object to your component, you will implement code to fill this object with your particular path information (the lines, arcs, Bézier curves, etc.) and finally you will assign the so prepared object to the property Path of the affected Filled Gradient Path view. With the Inspector Assistant you can conveniently select the right object when you edit the initialization expression for the property Path. For example:

As soon as you have connected the both, the information provided in the Path Data object appears within the Filled Gradient Path view. If desired, you can assign the same Path Data object to several Filled Gradient Path views (and Stroked Gradient Path views). If during the runtime of the application, the content of the Path Data object changes, all associated views are updated automatically.

In particular cases, when the desired shape is an ellipse, ring, pie segment, circle segment, etc. you can use the more convenient Arc Path Data object. With this object you don't need to implement any code to prepare the path data. Instead, you simply configure the properties of the Arc Path Data object determining so e.g. the desired radiuses of the ellipse, its start and end angles, and so far.

In order to display a graphical shape in the Filled Gradient Path view, you have to provide the gradient information. You can consider the gradient as a list of color stops. The color values between the color stops are interpolated. Depending on the application case the gradient may consist of two or more color stops, whereby the maximum number of color stops is limited to 256. Additionally, the gradient stores information describing its start/end coordinates or the radius in case of a radial gradient.

To provide the gradient information you use a Linear Gradient or Radial Gradient object. Usually you will add such object to your component, implement code to configure this object with your particular gradient information (color stops, start/end coordinates, radius, etc.) and finally you will assign the so prepared object to the property Gradient of the affected Filled Gradient Path view. With the Inspector Assistant you can conveniently select the right object when you edit the initialization expression for the property Gradient. For example:

As soon as you have connected the both, the information provided in the gradient is used by the Filled Gradient Path view. If desired, you can assign the same Gradient object to several Filled Gradient Path views (and Stroked Gradient Path views). If during the runtime of the application, the content of the Gradient object changes, all associated views are updated automatically.

Per default, the coordinates provided in the associated path object are displayed relative to the top-left corner of the Filled Gradient Path view. This corner corresponds thus to the origin of the path own coordinate system (0,0). By modifying the property Offset you can specify other position within the area of the view where to map the origin of this coordinate system. In other words, changing the property Offset causes the displayed shape to be moved within the Filled Gradient Path view.

Lets assume, the associated path object describes a circle with its center lying at the origin of the path own coordinate system (0,0). Depending on how the property Offset is configured, the circle appears at different positions within the Filled Gradient Path view as demonstrated in the following screenshot. For visualization purpose, the black cross indicates the center of the path coordinate system and the thin blue frames are borders of the respective Filled Gradient Path views. Please note, parts of a shape lying outside of the view area are clipped and not visible:

Originally the positive Y-axis of the path coordinate system points downwards, which corresponds to how other positions or coordinates are treated in Embedded Wizard. By initializing the property FlipY with the value true, the Filled Gradient Path view mirrors vertically the path coordinate system resulting in the Y-axis pointing upwards, which is more natural for mathematical application cases. The shape described by the path appears accordingly mirrored. Furthermore, with this alternation the effect of the property Offset changes, so that it specifies the position where to map the origin of the path coordinate system relative to the bottom-left corner of the view. The following screenshot demonstrates this effect:

With the property FillRule you specify the algorithm which is used by the Filled Gradient Path view during the rasterization process to determine what area of the provided path should appear filled and what area should remain empty. This is in particular essential in case of a complex path, which intersects itself or a path composed of several nested sub-paths. Following are the possible fill rules:

Fill rule	Description
EvenOdd	Fills the path areas alternately depending on the nesting level of the enclosed path segments. An area is considered as filled if the number of path segments between a point lying inside the area and any point outside the entire shape is odd. If the number of path segments is even, the area is not filled.
NonZero	Fills the path areas depending on the nesting level of the enclosed path segments and their winding direction. An area is considered as filled when counting the path segments between a point lying inside the area and any point outside the entire shape the resulting value is not zero, whereby paths with positive winding direction increment the value while paths with negative winding decrement it. If the counter value is 0 (zero), the area is not filled.

The following figures demonstrate the effect of the both fill rules. Please note the small arrows indicating the winding direction of the particular path segment:

The Filled Gradient Path view rasterizes the shape per default with enabled anti-aliasing. This produces the best possible results. If not desired, with the property Quality you can disable this mode. For this purpose initialize Quality with the value false. The following figure demonstrates the results depending on the current setting of the property:

Embedded Wizard own implementation to rasterize vector graphics calculates with 4x anti-aliasing, which means that every pixel is divided in 4 sub-pixel vertically and 4 sub-pixel horizontally. If the vector graphic is rasterized by using target own graphics subsystem (e.g. GPU), the resulting anti-aliasing depends on the implementation of this subsystem. In particular cases (e.g. in case of the WebGL Platform Package) the anti-aliasing can't be deactivated.

The visibility of the Filled Gradient Path view is determined primarily by the property Visible. It is also affected by the provided Path Data and the Gradient object specified for the view.