• A layer is a virtual construct that can hold graphical elements.
• Multi-layering is the combining of layers into a single images.
• It creates the illusion that all those elements are parts of the same scene.

• In this scheme, the graphics library combines the elements from multiple source layers into a single frame.
• This requires CPU processing power and bus bandwidth, which can become significant for large resolution layers.

• Integrated display controllers such as the GLCD and the LCDC supports multiple hardware overlays.
• Each overlay has its own frame buffer.
• The graphics library renders to each overlay frame buffer depending on the draw requirement.
• The display controller composites the overlays into a single frame.
• It becomes a form of hardware graphics acceleration.
• Dynamic content with minimal load on the CPU, and no GPU needed.

IMPORTANT NOTE: Multi-layering in MPLAB® Harmony Graphics relies on display controllers with hardware overlay support. For software-based multi-layering, the recommendation is to use a single layer in the Screen Designer window. The panel widget can be used as the virtual layer construct.

• Hardware Overlays are supported in Legato and Composer using Layers.

NOTE: If you have a hard time viewing this image, right-click and open the image in a new tab to enlarge it.

• Here is a visualization of what goes on behind the scenes.

IMPORTANT NOTE: Multi-layering in MPLAB® Harmony Graphics relies on display controllers with hardware overlay support. For software-based multi-layering, the recommendation is to use a single layer in the Screen Designer window. The panel widget can be used as the virtual layer construct.

(This is an example from Legato Dashboard)

IMPORTANT NOTE: Multi-layering in MPLAB® Harmony Graphics relies on display controllers with hardware overlay support. For software-based multi-layering, the recommendation is to use a single layer in the Screen Designer window. The panel widget can be used as the virtual layer construct.

(This is an example from Legato Video Player)

IMPORTANT NOTE: Multi-layering in MPLAB® Harmony Graphics relies on display controllers with hardware overlay support. For software-based multi-layering, the recommendation is to use a single layer in the Screen Designer window. The panel widget can be used as the virtual layer construct.

IMPORTANT NOTE: Multi-layering in MPLAB® Harmony Graphics relies on display controllers with hardware overlay support. For software-based multi-layering, the recommendation is to use a single layer in the Screen Designer window. The panel widget can be used as the virtual layer construct.

• Pre-rotated needle images are stored in DDR/SDRAM
• Upper layers are used to display the needles
• To start the animation, the layer start address is set to the location of the images in DDR/SDRAM
• The GLCD/LCDC layer position is also adjusted to show the needles at the correct location on the screen

(This is an example from Legato Dashboard)

IMPORTANT NOTE: Multi-layering in MPLAB® Harmony Graphics relies on display controllers with hardware overlay support. For software-based multi-layering, the recommendation is to use a single layer in the Screen Designer window. The panel widget can be used as the virtual layer construct.

• Create an oversized Layer in MPLAB® Harmony Graphics Composer
  • Add all the menu widgets to the layer
  • Only widgets that will slide should be in this layer
• Set the display controller x-stride using the display controller PLIB
• To move the layer to the left, add the x-offset position (in bytes) of the menu to the start address of the frame buffer in the display controller
• Fast and smooth motion can be achieved with very little CPU usage and without a GPU

It is best practice to set all the screens in your design with the maximum number of layers needed for any one screen. For example, if you need three layers in screen 1 and only one layer in screen 2, please enable all three layers in screen 2 as well. You can add a clear panel widget to the layers that are unused.