How the background source item should be scaled to fill the screen. The value may be one of:

• Background.Strech The source item will not be scaled.
• Background.PreserveAspectWidth The source item will be scaled so its width matches the width of the screen. This may result in no background being rendered in parts of the screen and should only be used in portrait orientations with source images with the same aspect ratio or taller than the screen.
• Background.PreserveAspectSquare The smallest dimension of the sourceItem will be scaled to fit the height of the screen so that the screen is filled in both orientations.

The default value is Background.PreserveAspectSquare

A Material containing the GLSL shaders which will be used to render the background item.

A background must have a valid material set or it will not render anything.

An item which can be tiled by the background material.

The pattern item must be a texture provider item, this can be an Image, a ShaderEffectSource, a FilteredImage, or any other item with layer.enabled: true.

If a material GLSL vertex shader defines a uniform highp mat4 patternMatrix that matrix will be populated with a transform which when multiplied with the screen coordinates will give the texture sampling coordinates to tile the pattern item at 1:1 scale.

To sample the patternItem in a material GLSL fragment shader add the uniform lowp sampler2D patternTexture.

A basic material for a background which includes only a tiled patternItem would look like:

 Material {
     vertexShader: "
         attribute highp vec4 position;

         uniform highp mat4 positionMatrix;
         uniform highp mat4 patternMatrix;

         varying highp vec2 patternCoord;"

         void backgroundMain() {
             gl_Position = positionMatrix * position;
             patternCoord = (patternMatrix * gl_Position).xy;
         }
     "

     fragmentShader: "
         uniform lowp sampler2D patternTexture;

         varying highp vec2 patternCoord;

         void backgroundMain() {
             gl_FragColor = texture2D(patternTexture, patternCoord);
         }
     "
 }
 

The radius of any rounded corners on the backround item.

By default the radius is 0.

See also roundedCorners.

Which corners of the Background item should be rounded. This can be any combination of the following flags:

• Corners.None No corners are rounded.
• Corners.TopLeft The top left corner should be rounded.
• Corners.TopRight The top right corner should be rounded.
• Corners.BottomLeft The bottom left corner should be rounded.
• Corners.BottomRight The bottom right corner should be rounded.
• Corners.All All the corners should be rounded.

The default value is Corners.All, note however that since the default radius is 0 no corners will be rounded by default.

An item which can be displayed fullscreen by the background material.

The source item must be a texture provider item, this can be an Image, a ShaderEffectSource, a FilteredImage, or any other item with layer.enabled: true.

If a material GLSL vertex shader defines a uniform highp mat4 sourceMatrix that matrix will be populated with a transform which when multiplied with the screen coordinates will give the texture sampling coordinates to center the item in the screen and scale it according to the fillMode.

To sample the sourceItem in a material GLSL fragment shader add the uniform lowp sampler2D sourceTexture.

A basic material for a background which includes only a fullscreen sourceItem would look like:

 Material {
     vertexShader: "
         attribute highp vec4 position;

         uniform highp mat4 positionMatrix;
         uniform highp mat4 sourceMatrix;

         varying highp vec2 sourceCoord;"

         void backgroundMain() {
             gl_Position = positionMatrix * position;
             sourceCoord = (sourceMatrix * gl_Position).xy;
         }
     "

     fragmentShader: "
         uniform lowp sampler2D sourceTexture;

         varying highp vec2 sourceCoord;

         void backgroundMain() {
             gl_FragColor = texture2D(sourceTexture, sourceCoord);
         }
     "
 }
 

An item which can be used to apply a rotation transform to a background.

A background item ignores the transforms applied to it directly when rendering, so just like moving an item won't effect the content it draws at any point on the screen rotating and scaling also have no effect. Instead a background can be rotated by having it follow the transforms applied to a reference transformItem.

When a transformItem is rotated the sourceMatrix uniform of the material vertex shader will have the same transform applied so that the sourceItem is rotated to match that item and any other backgrounds with the transformItem. If the vertex shader defines the uniform highp mat4 transformMatrix that will be populated with a transform that follows the transform item indepedently of any additional sourceItem transforms.