Introduction

Is Filled controls whether a shape is filled in or if it is drawn using stroke - another word for outline. By default this is true, but it can be unchecked to make a shape draw its outline.

Stroke Width

Stroke Width controls the thickness of the stroke (outline). Increasing the value makes the stroke thicker.

Stroke, Gradient, and Dropshadow

If a Skia standard element has its Is Filled unchecked, this affects the rendering of gradients and dropshadows.

Gradients only fill the solid parts of a shape, so if a shape has Is Filled set to false, the hollow center of the shape does not show gradient color.

Dropshadows respect the opaque part of the shape, so changing Is Filled also affects the dropshadow.

Introduction

Has Dropshadow controls whether a dropshadow is drawn below an element. By default this value is false.

The following image shows two RoundedRectangles. The left with Has Dropshadow unchecked, the right with Has Dropshadow checked.

Note that if an instance has a dropshadow, the dropshadow renders outside of the bounds of the instance.

Dropshadows draw as part of the object, so if multiple objects stack, their dropshadows also stack.

Dropshadow Offset X and Y

Dropshadow Offset X and Y control the position of the dropshadow relative to the main body of the instance. By default this value is 3 pixels below (Dropshadow Offset Y of positive 3).

This value can be changed to offset the dropshadow in any direction increasing a sense of height for the element.

Dropshadow Blur X and Y

Dropshadow Blur X and Y control how much to blur the dropshadow on the X and Y axes, respectively. A value of 0 creates a sharp shadow, while a larger value increases blur. Note that the X and Y values can be adjusted independently.

Dropshadow Alpha

Dropshadow Alpha controls the transparency of a dropshadow. A fully-opaque dropshadow has an alpha of 255. This value can be modified to decrease or increase the dropshadow's opacity.

Dropshadow Red, Green, and Blue

Dropshadow Red, Green, and Blue can be used to adjust the dropshadow color. Usually dropshadows are pure black with their transparency adjusted by Dropshadow Alpha, but they can also include other colors if needed.

Introduction

Sweep Angle defines the angle that the arc covers. This is a signed value, with positive values going counterclockwise.

The following shows an arc with a positive Sweep Angle of 135 degrees.

Changing the Sweep Angle changes the length of the arc. If the value is negative, then the Sweep Angle increases the size clockwise.

A sweep angle of 360 creates an arc that extends to a full circle. Values greater than 360 appear the same as if Sweep Angle is set to 360.

Introduction

Thickness controls the width of the arc line in pixels. This value can be increased to make the line arc thicker.

Thickness can be increased to create a wedge.

Note that Thickness can be increased to any value including values larger than the radius of the arc. Large values can result in the arc rendering past its center point creating a bowtie shape.

Other undesirable rendering effects can happen with large thicknesses when working with arcs which have one size (width or height) larger than the other, as shown in the following image:

Introduction

Arcs are curved lines with variable thickness. Arcs can also be used to draw wedges if the line thickness is large enough.

Arc dimensions

Arcs draw inside their bounds, with the edge of the arc touching the bounding rectangle. The thickness of the arc remains consisntent regardless of the bound width and height.

The following shows an arc with a Sweep Angle of 270 degrees, being resized in the Editor tab.

Introduction

The Use Gradient property controls whether a Skia Standard Element uses gradient values if true or a solid color if false.

By default this value is false.

If this value is set to true, then additional properties appear for controlling the gradient.

Red1 and 2, Green1 and 2, Blue1 and 2

Gradients create a smooth interpolation of color from the first set of values (Red1, Green1, Blue1) to the second set of values (Red2, Green2, Blue2).

Changing these values adjusts the gradient start and end colors.

Gradient X1 and 2, Gradient Y1 and 2

The gradient values appear at their respective values at the points specified by Gradient X1, Gradient Y1, Gradient X2, and Gradient Y2. For example the gradient points could be visualized as shown in the following image:

Changing the Gradient X or Y values changes the start and end points for the gradient.

Gradient X1 and X2 Units, Gradient Y1 and Y2 Units

Gradient values use Units similar to X Units and Y Units. By default, gradient values are relative to the top-left of the element. Since the gradient values are not affected by size, changing the size of the element does not affect the gradient.

The gradient X and Y units can be changed. Each value can be set independently. For example, the X2 and Y2 units can be adjusted to be relative to the bottom-right corner of the instance. The following shows a RoundedRectangle with the Gradient X2 and Y2 values 100 pixels up and to the left of the bottom-right corner. If the RoundedRectangle is resized, then the gradient adjusts in response.

Gradient X and Y values can exist outside of the visual space of the instance, and even outside of its bounds. The following image shows an Arc with a gradient which is defined below the visual part of the arc. Notice that the Gradient Y values are both 0 PixelsFromBottom.

Gradient Type

Gradient Type controls whether the gradient is linear or radial. Radial gradients place the center of the radial gradient at X1,Y1 and the edge of the radial gradient at X2, Y2.

Introduction

ColoredCircle are round shapes which can be filled in or drawn as an outline. Unlike the non-Skia Circle element, ColoredCircles can be filled in and provide more options for customizing their appearance.

ColoredCircles support Skia properties such as Has Dropshadow, Is Filled, and Use Gradient. For more information and examples, see the Skia Standard Element General Properties pages.

Introduction

Start Angle defines the angle of the starting point of the arc. This value is measured in degrees, with a value of 0 pointing to the right. The value increases counterclockwise. the Start Angle and Sweep Angle values combine to determine the range of angles covered by the Arc.

The following image shows the an Arc with a Start Angle of 0. The red lines and text are not part of the arc and are added to the screen shot to show the location of the Start Angle.

Changing the Start Angle moves one side of the arc. The arc appears to rotate if the Start Angle is changed gradually.

Start Angle defines the starting point of the arc. A value of 270 degrees and a value of -90 place the starting point of the arc in the same location. Values larger than 360 result in the value looping. These values, although normally not needed, can be used to create spinning animatoins.

Introduction

The Canvas element creates an instance of a SKCanvas which can be accessed in code to perform custom rendering. The contents of the Canvas cannot be modified in Gum. Since it is a Gum object, it does provide all of the variables for positioning, sizing but the rendering must be performed in custom code.

Since the Canvas cannot perform any rendering in Gum, it appears as an empty container.

Introduction

LottieAnimation instances can render animations in the Lottie format. Lottie files are animated files, usually with vector art, which serve as an alternative to gifs. Since they are often vector art, Lottie files can be resized without pixelation.

Lottie files can be downloaded from various sites or created in application such as Adobe After Effects. If you are interested in testing out Lottie animations, you may want to check lottiefiles.com for sample Lottie files.

The following shows a Lottie animation playing in Gum. Source file: https://lottiefiles.com/free-animation/city-skyline-HFnJYQZLPP

Source File

The Source File variable controls the lottie animation displayed. This value can be set and changed just like source files on other elements such as a .png on a Sprite.

Lottie Width and Height

Width and Height values can be set on a Lottie file just like any other Gum element. Unlike rasterized objects such as Sprites, LottieAnimations use Vector art so they can be resized and still retain crisp edges and details.

LottieAnimations are still rasterized in Gum, so they display pixels when the view is zoomed in, especially if the LottieAnimation has a small Width or Height.

Introduction

The Corner Radius variable controls the radius of each of the four corners on a rounded rectangle. A value of 0 results in a sharp corner. Increasing this value makes the corners more rounded.

Introduction

Svgs can display .svg files. Since these files are vector art, they can be resized without pixelation.

The following is an Svg instance displaying the FlatRedBall logo. Source SVG: https://github.com/flatredball/FlatRedBallMedia/blob/master/FlatRedBall%20Logos/frb-logo-main.svg

Source File

The Source File variable controls the lottie animation displayed. This value can be set and changed just like source files on other elements such as a .png on a Sprite.

Svg Width and Height

Width and Height values can be set on an Svg file just any other Gum element. Unlike rasterized objects such as Sprites, Svgs use Vector art so they can be resized and still retain crisp edges and details.

Svgs are still rasterized in Gum, so they display pixels when the view is zoomed in, especially if the Svg has a small Width or Height.

Maintain File Aspect Ratio Width and Height

Svgs support the Maintain File Aspect Ratio Width and Maintain File Aspect Ratio Height units. For more information, see the Width Units and Height Units page.

Introduction

Skia standard elements are a collection of elements which use SkiaSharp for rendering. Skia standard elements provide additional types of visuals supported by Gum, but not all runtimes support Skia standard elements.

Skia adds advanced vector graphics support for shapes such as Arc, ColoredCircle, and RoundedRectangle. Skia also adds support for vector file formats such as SVG and Lottie.

Enabling Skia Standard Elements

Skia standard elements must be explicitly added to gum projects. To add Skia standard elements Select Plugins -> Add Skia Standard Elements.

After clicking this option, Gum adds new standard elements.

Once these Skia standard elements are added, they can be added to Screens and Components just like any other standard element.

Introduction

RoundedRectangle is similar to a ColoredRectangle with the added functionality of supporting rounded corners.