HikoGUI is a cross platform C++ GUI library.
Manuals
Subsystems
Documentation for the HikoGUI sub-systems can be found in the:
- Module
and - Related Pages tabs.
Features
Box drawing
Most drawing is done through the box-drawing shader. The box-drawing shader can draw an anti-aliased box with:
- a background color mixed from the 4 vertices,
- a border color mixed from the 4 vertices,
- a border width,
- a corner radius for each corner, and
- a clipping rectangle to cut part of the box.
This primitive can be used to draw different shapes, like:
- normal rectangles,
- rounded rectangles,
- slots, and
- circles.
Text drawing
Glyphs are drawn by the GPU using a signed-distance-field shader. This shader is able to render glyphs with subpixel-anti-aliasing without using a post-processing filter.
Glyphs are lazily and asynchronous, added to the texture-atlas when needed. By adding the glyphs as signed distance fields to the texture atlas a glyph needs to be added only once to be usable for displaying at any size.
Performance
HikoGUI is designed for low latency interactive applications.
For this reason, we have the following design considerations:
- Widgets need to be able to animate at 60 fps.
- CPU and GPU usage when drawing at 60 fps need to remain low.
- Monitored data needs to be reflected in the user interface with at most one frame delay.
- During drawing the widget can use predictive algorithms to determine what should be shown to the user at the display time. When for example showing the current time on the display.
The following is used to implement the requirements:
- Use game-like redraw loop running at the current system's frame rate. Immediately reflecting updated data. And caching size-constraining, layout, text-shaping, and other expensive pre-draw operations.
- Partial drawing, widgets will only draw anything that falls within the current scissor rectangle. The scissor rectangle allows the GPU to discard drawing outside it to improve drawing speed.
- All drawing is done by passing vertices to different shaders for GPU accelerated drawing of: rounded-rectangles, pixmap-images and text-glyphs.
