Draw Units¶

A "Draw Unit" (lv_draw_unit_t) is any peripheral or system that can render something on the screen. This can be a CPU core, a GPU, a custom rendering library for specific draw tasks, or any entity capable of performing rendering.

LVGL supports several built-in draw units that can be enabled in lv_conf.h.

Software Rendering¶

A highly optimized renderer written in C. Even when no GPU is enabled, software rendering provides a performant, low-footprint, and very capable engine for rendering.

Rendering Features¶

The software renderer is capable of rendering most typical draw tasks, including:

fill rectangles with a color or gradient
rounded rectangles and borders
draw box shadows
blend, rotate, scale, or recolor images
draw labels, even with rotated letters
draw skew lines with perpendicular endings and any thickness
draw arcs with rounded or straight endings
blur an area
draw drop shadows for any shape
anti-alaising for all rendering
and many more

Color Format Support¶

It also supports the most common color formats as source and destination, such as RGB888, XRGB8888, ARGB8888, RGB565, L8, A8, I1, and more.

Multi-Core Rendering¶

In case of a multi-core system, each core can perform software rendering in parallel by setting LV_DRAW_SW_DRAW_UNIT_CNT to greater than 1, and setting LV_USE_OS to something other than LV_OS_NONE.

Assembly Acceleration¶

Software rendering can also use various assembly accelerators, such as:

Arm Neon: available on most Cortex-A cores
Arm Helium: available on Cortex-M55 and M85 cores
Arm-2D: a complete library supporting highly optimized Helium acceleration
RISC-V: uses SIMD instructions on RISC-V cores

These can be enabled in lv_conf.h and typically provide 10-30% faster rendering.

Vector Graphics¶

To render vector graphics (e.g. SVG), LVGL uses a third-party library called ThorVG. It supports most vector rendering features such as:

paths from lines, arcs, and Bézier curves
stroke with dashing and joint settings
fill with color, image, or gradient
and many more

To use it, enable LV_USE_THORVG_INTERNAL and LV_USE_VECTOR_GRAPHIC.

VG-Lite¶

A powerful vector graphics accelerator IP developed by Verisilicon. It is widely used by NXP and other chip vendors to provide hardware-accelerated 2D and vector rendering.

Key Features¶

Hardware-accelerated vector path rendering (lines, arcs, Bézier curves)
Fill and stroke support with solid colors and gradients
Image transformations such as scaling, rotation, and blending
Anti-aliasing for smoother edges
Efficient memory usage optimized for embedded systems
High performance with low CPU utilization

To enable VG-Lite support in LVGL, set LV_USE_DRAW_VG_LITE in lv_conf.h.

NemaGFX¶

NemaGFX is a graphics API and GPU family developed by Think Silicon. It is used in various embedded platforms, including STM32 devices with NeoChrom GPUs and Ambiq MCUs, to provide hardware-accelerated 2D rendering.

In addition to the 2D engine, some platforms also include NemaVG, which provides hardware-accelerated vector graphics rendering.

Key Features¶

Hardware-accelerated 2D rendering (fills, blits, compositing)
Image transformations such as scaling, rotation, and blending
Alpha blending and transparency support
Vector graphics acceleration via NemaVG (paths, fills, strokes)
Optimized for low-power embedded systems
Offloads rendering from the CPU for improved performance

To enable NemaGFX support in LVGL, set LV_USE_DRAW_NEMA_GFX in lv_conf.h.

Dave2D¶

Dave2D is a 2D graphics accelerator developed by TES and widely used on Renesas and Alif MCUs.

In Renesas FSP, the DRW peripheral is provided as a port of D/AVE 2D, which is the driver used by the LVGL Dave2D draw unit.

Key Features¶

Rectangle drawing, including gradients
Image drawing, scaling, and rotation
Letter drawing
Triangle drawing
Line drawing
Background rendering that reduces CPU load during drawing

To enable Dave2D support in LVGL, set LV_USE_DRAW_DAVE2D in lv_conf.h.