NVPR Shaped Text Sample

Category: Visuals

Min PC GPU: Fermi-based (GTX 4xx)

Min Tegra Device: Tegra K1

Description

This sample demonstrates sophisticated text layout using the open source HarfBuzz text shaping engine library to position glyphs for strings of Unicode text.

APIs Used

NV_path_rendering
EXT_direct_state_access

Shared User Interface

The OpenGL samples all share a common app framework and certain user interface elements, centered around the "Tweakbar" panel on the left side of the screen, which lets you interactively control certain variables in each sample.

To show and hide the Tweakbar, simply click or touch the triangular button positioned in the top-left of the view.

Other controls are listed below.

Device	Input	Result
touch	2-Finger Drag	Translate the view
	2-Finger Pinch	Scale the view
mouse	Left-Click Drag	Translate the view
	Right-Click Drag	Scale the view (up:out, down:in)
keyboard	Escape	Quit the application
	Tab	Toggle Tweakbar visibility
gamepad	Start	Toggle Tweakbar visibility

App-Specific Controls

This sample has the following app-specific controls:

keyboard	R	Reset Scene
	F	Toggle Path Fill
	S	Toggle Path Stroke
	, / .	Font Size -/+
gamepad	X	Reset Scene
	Left Shoulder Button	Toggle Path Fill
	Right Shoulder Button	Toggle Path Stroke
	DPAD Left/Right	Font Size -/+

Technical Details

Samples of text in various languages using appropriate scripts are rendered from their resolution-independent outlines. NV_path_rendering does the work of rendering font glyphs of TrueType/OpenType, with HarfBuzz doing glyph positioning and Unicode script shaping, and FreeType2 used to load the underlying metrics for each font.

The sample relies on revision 1.3 of the NV_path_rendering extension that adds support for glyph indexed font usage. In particular, glPathGlyphIndexArrayNVand glPathMemoryGlyphIndexArrayNV.