Drawing stuff

borealis uses nanovg (nvg) to draw stuff on screen. Look at the nvg documentation to know what you can do with borealis!

Transparency

Every view has an alpha attribute which corresponds to their transparency multiplied by the one of their parent. It means that a hidden BoxLayout will have all its children hidden as well.

The View class has helper methods to easily apply that transparency system to nanovg colors:

• The a method takes an NVGColor, applies the view transparency and returns a new color
• The RGB and RGBf methods families allow to create new colors from RGB(A) with the transparency already applied (wrappers around nvgRGB functions)

Drawing text

Built-in fonts are stored in the FontStash instance of Application, as nanovg font IDs (to be used with nvgFontFaceId). The stash instance is given as parameter of the draw() method of each view.

Some views like Label allow to change the font used for drawing, but you need to load them yourself using Application::loadFont or Application::loadFontFromMemory first.

There are currently three fonts in the stash:

• material: the Material Icons font
• sharedSymbols: the Switch shared symbols font (only available on HOS)
• regular: all of the above merged with the regular text font (shared font on HOS, InterUI on PC)

nanovg allows merging fonts (called font "fallbacks"), and this is what is happening with the regular font. That allows you to use the shared symbols and material seamlessly when drawing text using the regular font.

When drawing using the regular font, each glyph is looked up in the following order:

1. Regular text font
2. Shared symbols font
3. Material Icons font

Unfortunately some glyphs are common for both Material Icons and shared symbols fonts. We decided to give priority to the shared symbols font since it contains fewer glyphs than Material Icons. You can use the material font if you want to access all glyphs from Material Icons.