Documentation
¶
Overview ¶
Package text implements efficient text drawing for the Pixel library.
Index ¶
- Variables
- func RangeTable(table *unicode.RangeTable) []rune
- type Atlas
- func (a *Atlas) Ascent() float64
- func (a *Atlas) Contains(r rune) bool
- func (a *Atlas) Descent() float64
- func (a *Atlas) DrawRune(prevR, r rune, dot pixel.Vec) (rect, frame, bounds pixel.Rect, newDot pixel.Vec)
- func (a *Atlas) Glyph(r rune) Glyph
- func (a *Atlas) Kern(r0, r1 rune) float64
- func (a *Atlas) LineHeight() float64
- func (a *Atlas) Picture() pixel.Picture
- type Glyph
- type Text
- func (txt *Text) Atlas() *Atlas
- func (txt *Text) Bounds() pixel.Rect
- func (txt *Text) BoundsOf(s string) pixel.Rect
- func (txt *Text) Clear()
- func (txt *Text) Draw(t pixel.Target, matrix pixel.Matrix)
- func (txt *Text) DrawColorMask(t pixel.Target, matrix pixel.Matrix, mask color.Color)
- func (txt *Text) Write(p []byte) (n int, err error)
- func (txt *Text) WriteByte(c byte) error
- func (txt *Text) WriteRune(r rune) (n int, err error)
- func (txt *Text) WriteString(s string) (n int, err error)
Constants ¶
This section is empty.
Variables ¶
var ASCII []rune
ASCII is a set of all ASCII runes. These runes are codepoints from 32 to 127 inclusive.
Functions ¶
func RangeTable ¶
func RangeTable(table *unicode.RangeTable) []rune
RangeTable takes a *unicode.RangeTable and generates a set of runes contained within that RangeTable.
Types ¶
type Atlas ¶
type Atlas struct {
// contains filtered or unexported fields
}
Atlas is a set of pre-drawn glyphs of a fixed set of runes. This allows for efficient text drawing.
func NewAtlas ¶
NewAtlas creates a new Atlas containing glyphs of the union of the given sets of runes (plus unicode.ReplacementChar) from the given font face.
Creating an Atlas is rather expensive, do not create a new Atlas each frame.
Do not destroy or close the font.Face after creating the Atlas. Atlas still uses it.
func (*Atlas) DrawRune ¶
func (a *Atlas) DrawRune(prevR, r rune, dot pixel.Vec) (rect, frame, bounds pixel.Rect, newDot pixel.Vec)
DrawRune returns parameters necessary for drawing a rune glyph.
Rect is a rectangle where the glyph should be positioned. Frame is the glyph frame inside the Atlas's Picture. NewDot is the new position of the dot.
func (*Atlas) Kern ¶
Kern returns the kerning distance between runes r0 and r1. Positive distance means that the glyphs should be further apart.
func (*Atlas) LineHeight ¶
LineHeight returns the recommended vertical distance between two lines of text.
type Text ¶
type Text struct {
// Orig specifies the text origin, usually the top-left dot position. Dot is always aligned
// to Orig when writing newlines.
Orig pixel.Vec
// Dot is the position where the next character will be written. Dot is automatically moved
// when writing to a Text object, but you can also manipulate it manually
Dot pixel.Vec
// Color is the color of the text that is to be written. Defaults to white.
Color color.Color
// LineHeight is the vertical distance between two lines of text.
//
// Example:
// txt.LineHeight = 1.5 * txt.Atlas().LineHeight()
LineHeight float64
// TabWidth is the horizontal tab width. Tab characters will align to the multiples of this
// width.
//
// Example:
// txt.TabWidth = 8 * txt.Atlas().Glyph(' ').Advance
TabWidth float64
// contains filtered or unexported fields
}
Text allows for effiecient and convenient text drawing.
To create a Text object, use the New constructor:
txt := text.New(pixel.ZV, text.NewAtlas(face, text.ASCII))
As suggested by the constructor, a Text object is always associated with one font face and a fixed set of runes. For example, the Text we created above can draw text using the font face contained in the face variable and is capable of drawing ASCII characters.
Here we create a Text object which can draw ASCII and Katakana characters:
txt := text.New(0, text.NewAtlas(face, text.ASCII, text.RangeTable(unicode.Katakana)))
Similarly to IMDraw, Text functions as a buffer. It implements io.Writer interface, so writing text to it is really simple:
fmt.Print(txt, "Hello, world!")
Newlines, tabs and carriage returns are supported.
Finally, if we want the written text to show up on some other Target, we can draw it:
txt.Draw(target)
Text exports two important fields: Orig and Dot. Dot is the position where the next character will be written. Dot is automatically moved when writing to a Text object, but you can also manipulate it manually. Orig specifies the text origin, usually the top-left dot position. Dot is always aligned to Orig when writing newlines.
To reset the Dot to the Orig, just assign it:
txt.Dot = txt.Orig
func New ¶
New creates a new Text capable of drawing runes contained in the provided Atlas. Orig and Dot will be initially set to orig.
Here we create a Text capable of drawing ASCII characters using the Go Regular font.
ttf, err := truetype.Parse(goregular.TTF)
if err != nil {
panic(err)
}
face := truetype.NewFace(ttf, &truetype.Options{
Size: 14,
})
txt := text.New(orig, text.NewAtlas(face, text.ASCII))
func (*Text) Atlas ¶
Atlas returns the underlying Text's Atlas containing all of the pre-drawn glyphs. The Atlas is also useful for getting values such as the recommended line height.
func (*Text) Bounds ¶
Bounds returns the bounding box of the text currently written to the Text excluding whitespace.
If the Text is empty, a zero rectangle is returned.
func (*Text) BoundsOf ¶
BoundsOf returns the bounding box of s if it was to be written to the Text right now.
func (*Text) Draw ¶
Draw draws all text written to the Text to the provided Target. The text is transformed by the provided Matrix.
This method is equivalent to calling DrawColorMask with nil color mask.
If there's a lot of text written to the Text, changing a matrix or a color mask often might hurt performance. Consider using your Target's SetMatrix or SetColorMask methods if available.
func (*Text) DrawColorMask ¶
DrawColorMask draws all text written to the Text to the provided Target. The text is transformed by the provided Matrix and masked by the provided color mask.
If there's a lot of text written to the Text, changing a matrix or a color mask often might hurt performance. Consider using your Target's SetMatrix or SetColorMask methods if available.
func (*Text) Write ¶
Write writes a slice of bytes to the Text. This method never fails, always returns len(p), nil.
func (*Text) WriteByte ¶
WriteByte writes a byte to the Text. This method never fails, always returns nil.
Writing a multi-byte rune byte-by-byte is perfectly supported.
Source Files