fansiterm

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 Go to latest Published: May 10, 2024 License: GPL-2.0 Imports: 19 Imported by: 0

README

Fansiterm Screenshot

FANSITERM

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Fake (virtual) ANSI TERMinal.

Fansiterm is a golang package for implementing a partially compatible ANSI terminal, rendered to an image.Image (really, a golang.org/x/image/draw.Image). This is suitable for the graphical backend of a virtual terminal emulator.

The intent is for implementing a terminal on micro controllers connected to graphical displays. This provides an easy way to make a TUI for the micro controller and take advantage of packages like github.com/charmbracelet/bubbletea or for making a simple dumb terminal-type device.

Overview

The (*fansiterm.Device) object implements io.Writer. (*fansiterm.Device).Render implements image.Draw. To push data (text) to the terminal, you simply call Write() against the Device object.

The text isn't buffered anywhere, if you need the text or want to implement more advanced features like scrolling, that's up to whatever is writing to (*fansiterm).Device. Incomplete escape sequences will be bufferred and it's possible to "hang" the terminal by sending an incomplete sequence and then overloading the system memory. This is inline with how actual physical dumb terminals of yore worked.

If you want to push your own graphics or other operations, you can draw directly to the (*fansiterm.Device).Render object as well, as it implements draw.Image.

If Device is initialized with a nil image buffer, it allocates its own buffer. Otherwise, you can pass a draw.Image object (like what the driver for an OLED or TFT screen provides you) to it and any Write()s to the (*fansiterm.Device) will be immediately rendered to the backing screen. Whether the screen buffers image data and needs to be manually blitted is screen driver dependant.

For use with microcontrollers, you'll want to pass it the pseudo-buffer provided by the screen driver, as chances are your MCU does not have enough ram for a single frame buffer--in addition to the memory used for all the tiles and the rest of the program.

Features

  • Cursor styles: Block, Beam, Underscore
  • Bell is supported: a callback is provided for when the terminal receives a \a (bell character). So you could trigger a beep via a speaker and PWM or blink an LED or blink the backlight, etc.
  • Standard cursor manipulation supported.
  • Regular, Bold, and "italic" Font (italics are reasonably faked by rotating individual tiles)
  • Underline, Double Underline, Strikethrough
  • Several "TileSets" come built-in: inconsolata, Fira Code Nerd Mono, x3270, julia mono, and fansi
  • Tool to generate additional tilesets from TTF fonts is included: look in tiles/ and tiles/gentileset/
  • Custom Tile loading for alternate character set (shift-out character set, commonly used for line-drawing/pseudo graphics)
  • Tiles are rendered using an 8-bit Alpha mask, allowing for clean blending and anti-aliased rendering of glyphs.
  • 4-bit (with extended codes for bright / high intensity) color; 256-Color; True Color (24 bit).

Non-Features

The main purpose of this package is for use on rather low-power microcontrollers, so some standard features for terminal emulators are not implemented.

  • Blinking text and blink cursors
    • this would require a some kind of timer-callback. As it is, fansiterm is only using CPU when bytes are being written to it.
  • Resizable Text
    • Right now, the pre-rendered inconsolata.Regular8x16 and inconsolata.Bold8x16 are used.
    • It's possible to use basicfont.Regular7x13, but you have to give up bold support.
  • Hardware acceleration. Fansiterm remains aganostic of what it's rendering to and thus can't take advantage of any double-buffers or hardware-cursors on its own. Backwards compatible PRs to improve hardware support / hardware acceleration are very much welcome.

TODO

  • General Clean Up (Device struct is a bit of a mess) Always more to be done, but I'm relatively happy with things now.
  • Package documentation
    • Reviewing the package documentation now shows me I have far too much exported. A major to do is only have things exported if they actually need to be exported.
  • Test on real hardware
  • 1-bit color/rendering support for very-very-constrained systems
  • More configurable font / better font configuration Now using a purpose-built Tile system.
    • Better, user-oriented font config system: The means are in place, now just have to make it easy to use.
  • Optimize drawing/rendering routines This has been greatly improved.
    • Add in hardware accel / filling rectangle support (some hardware can fill rectangles more efficiently than the equivalent single-pixel-pushing)
  • Standardize / settle upon an API
    • Limit your interactions to the io.Write() interface.
  • Modify gentileset utility to only dump specific ranges--currently any of the "Nerd" fonts included (Fira, x3270, and julia) use too much RAM to actually load onto an RP2040.

Future

I want to keep a very stripped down, barebones version of fansiterm that will work on very resource constrained microcontrollers. However, I'm very open to having a more featureful v2 that is suitable for using as a backend for something as full blown as desktop terminal emulator.

Screenshot

Fansiterm Screenshot

The screenshot demonstrates:

  • FANSITERM is colored using inverted VGA color ( SGR CSI34;7m ) and is also bold (SGR CSI1m).
  • The trademark character (™) is present in inconsolata.Regular8x16 and rendered correctly here.
  • On either end of FANSITERM are custom tiles, defined using 8x16 pixel PNGs, in the fansi TileSet (fansiterm/tiles/fansi) and set to represent the characters '(' and ')' in the alternate chracter set (actived with the SHIFT-OUT byte, 0x0E, and deactived with SHIFT-IN byte, 0x0F).
  • Custom rounded-endcap tiles are used to surround 433 MHz and KHz, also via alternate chracter set (and mapped to '{' and '}').
  • The distance between 'Freq:' and '443 MHz' and 'Bandwidth:' and '005 KHz' are managed via tab characters.
  • The gradient bar is implemented using 24-bit True Color and an on-the-fly generated gradient tile.
  • Finally, the cursor is a block style cursor. All cursor shapes are implemented by inverting the colors they land over top.
  • This is a 240x135 pixel. While 240 is evenly divisible by 8, 135 is not divisible by 16. The terminal is automatically centered. (It is a TODO item to add customizable offset).

See Also

I found out about this when nearly done with this project:

https://github.com/tinygo-org/tinyterm

Same basic idea--tinyterm is a (tiny)go implementation of a terminal. Tinyterm is meant to be a minimal implementation to aid in troubleshooting projects. Fansiterm is meant to be the main interface / visual subsystem.

Tinyterm is specifically for tinygo, but fansiterm will work anywhere regular go will.

Documentation

Index

Constants

This section is empty.

Variables

View Source 
var (
	// These Colors are for the 4-bit ANSI colors
	// Since they're exported, they can be overridden.
	// It would be convient to have a pallet, but given
	// TrueColor support, why bother?
	ColorBlack         = NewOpaqueColor(0, 0, 0)
	ColorBrightBlack   = NewOpaqueColor(85, 85, 85)
	ColorRed           = NewOpaqueColor(127, 0, 0)
	ColorBrightRed     = NewOpaqueColor(255, 0, 0)
	ColorGreen         = NewOpaqueColor(0, 170, 0)
	ColorBrightGreen   = NewOpaqueColor(85, 255, 85)
	ColorYellow        = NewOpaqueColor(170, 85, 0)
	ColorBrightYellow  = NewOpaqueColor(255, 255, 85)
	ColorBlue          = NewOpaqueColor(0, 0, 170)
	ColorBrightBlue    = NewOpaqueColor(85, 85, 255)
	ColorMagenta       = NewOpaqueColor(170, 0, 170)
	ColorBrightMagenta = NewOpaqueColor(255, 85, 255)
	ColorCyan          = NewOpaqueColor(0, 170, 170)
	ColorBrightCyan    = NewOpaqueColor(85, 255, 255)
	// Okay, I deviated from VGA colors here. VGA "white" is way too gray.
	ColorWhite = NewOpaqueColor(240, 240, 240)
	// ColorWhite       = NewOpaqueColor(170, 170, 170)
	ColorBrightWhite = NewOpaqueColor(255, 255, 255)
)
View Source 
var (
	// CursorBlock, CursorBeam, and CursorUnderscore are the 3 cursor display options.
	CursorBlock      = blockRect
	CursorBeam       = beamRect
	CursorUnderscore = underscoreRect
)
View Source 
var AttrDefault = Attr{
	Fg: ColorWhite,
	Bg: ColorBlack,
}
View Source 
var Colors256 = [256]Color{}/* 256 elements not displayed */

Colors256 defines the default set of 256 Colors

View Source 
var ConfigDefault = Config{
	TabSize: 8,
}

Functions

This section is empty.

Types

type Attr 

type Attr struct {
	Bold            bool
	Underline       bool
	DoubleUnderline bool
	Strike          bool
	Blink           bool
	Reversed        bool
	Italic          bool
	Fg              Color
	Bg              Color
}

type Color 

type Color struct {
	// contains filtered or unexported fields
}

Color both implements color.Color and image.Image. image.Image needs a color.Model, so for convenience's sake, Color also implements color.Model so it can simply have ColorModel() return itself. The main purpose of Color is so there is no need to instantiate an image.Unform everytime we need to draw something in a particular color.

func NewColor 

func NewColor(r, g, b, a uint8) Color

NewColor returns a new Color.

func NewOpaqueColor 

func NewOpaqueColor(r, g, b uint8) Color

NewOpaqueColor returns a Color that has a fully opaque alpha value.

func (Color) At 

func (c Color) At(int, int) color.Color

At implements image.Image

func (Color) Bounds 

func (c Color) Bounds() image.Rectangle

Bounds implements image.Image

func (Color) ColorModel 

func (c Color) ColorModel() color.Model

ColorModel implements image.Image

func (Color) Convert 

func (c Color) Convert(c2 color.Color) color.Color

Convert (fake) implements color.Model.

func (Color) RGBA 

func (c Color) RGBA() (r, g, b, a uint32)

RGBA implements color.Color

type Colorizer 

type Colorizer func() color.RGBA

the tinygo.org/x/drivers/pixel package has a somewhat incompatible color interface with the color.Color interface. This type definition and it's associated function allows a pixel.Color's RGBA method to be cast so that it implements the color.Color interface. Example: pixelColor := pixel.NewColor[pixel.RGB888](127,127,127) drawImage.Set(xPos,yPos, Colorizer(pixelColor.RGBA))

func (Colorizer) RGBA 

func (c Colorizer) RGBA() (r, g, b, a uint32)

type Config 

type Config struct {
	TabSize     int
	CursorStyle int
	CursorBlink bool
}

type Cursor 

type Cursor struct {
	// contains filtered or unexported fields
}

Cursor is used to track the cursor.

type Device 

type Device struct {
	// BellFunc is called if it is non-null and the terminal would
	// display a bell character
	// TODO: Implement affirmative beep (default) and negative acknowledge beep
	// Negative acknowledge is produced when \a is sent while in SHIFT-OUT mode.
	// Affirmative: C-G (quarter notes?)
	// NAK: C♭ (whole note?)
	BellFunc func()

	// Config species the runtime configurable features of fansiterm.
	Config Config

	// Render collects together all the graphical rendering fields.
	Render Render

	// Miscellaneous properties, like "Window Title"
	Properties map[Property]string

	// Output specifies the program attached to the terminal. This should be the
	// same interface that the input mechanism (whatever that may be) uses to write
	// to the program. On POSIX systems, this would be equivalent to Stdin.
	// Default is io.Discard. Setting to nil will cause Escape Sequences that
	// write a response to panic.
	Output io.Writer

	sync.Mutex
	// contains filtered or unexported fields
}

Device implements a virtual terminal. It supports being io.Write()n to. It handles the cursor and processing of sequences.

func New 

func New(cols, rows int, buf draw.Image) *Device

New returns an initialized *Device. If buf is nil, an internal buffer is used. Otherwise if you specify a hardware backed draw.Image, writes to Device will immediately be written to the backing hardware--whether this is instaneous or buffered is up to the device and the device driver.

func NewAtResolution 

func NewAtResolution(x, y int, buf draw.Image) *Device

NewAtResolution is like New, but rather than specifying the columns and rows, you specify the desired resolution. The maximum rows and cols will be determined automatically and the terminal rendered in the center. Fansiterm will only ever update / work on the rectangle it has claimed. If you want to use an existing backing buffer and position that, use NewWithBuf and use xform.SubImage() to locate the terminal.

func NewWithBuf 

func NewWithBuf(buf draw.Image) *Device

NewWithBuf uses buf as its target. NewWithBuf() will panic if called against a nil buf. If using fansiterm with backing hardware, NewWithBuf is likely the way you want to instantiate fansiterm. If you have buf providing an interface to a 240x135 screen, using the default 8x16 tiles, you can have an 40x8 cell terminal, with 7 rows of pixels leftover. If you want to have those extra 7 rows above the rendered terminal, you can do so like this:

term := NewWithBuf(xform.SubImage(buf,image.Rect(0,0,240,128).Add(0,7)))

Note: you can skip the Add() and just define your rectangle as image.Rect(0,7,240,135), but I find supplying the actual dimensions and then adding an offset to be clearer.

func (*Device) Clear 

func (d *Device) Clear(x1, y1, x2, y2 int)

Clear writes a block of current background color in a rectangular shape, specified in units of cells (rows and columns). So (*Device).Clear(0,0, (*Device).cols, (*Device).rows) would clear the whole screen.

func (*Device) ColsRemaining 

func (d *Device) ColsRemaining() int

ColsRemaining returns how many columns are remaining until EOL

func (*Device) HandleCSISequence 

func (d *Device) HandleCSISequence(seq []rune)

func (*Device) HandleEscSequence 

func (d *Device) HandleEscSequence(seq []rune)

HandleEscSequence handles escape sequences. This should be the whole complete sequence. Bounds are not checked so an incomplete sequence will cause a panic.

func (*Device) HandleOSCSequence 

func (d *Device) HandleOSCSequence(seq []rune)

func (*Device) Image 

func (d *Device) Image() image.Image

func (*Device) MoveCursorAbs 

func (d *Device) MoveCursorAbs(x, y int)

func (*Device) MoveCursorRel 

func (d *Device) MoveCursorRel(x, y int)

func (*Device) RenderRunes 

func (d *Device) RenderRunes(sym []rune)

RenderRunes does not do *any* interpretation of escape codes or control characters like \r or \n. It simply renders a slice of runes (as a string) at the cursor position. It is up to the caller of RenderRunes to ensure there's enough space for the runes on the buffer and to process any control sequences.

func (*Device) Scroll 

func (d *Device) Scroll(amount int)

func (*Device) ScrollToCursor 

func (d *Device) ScrollToCursor()

func (*Device) SetCursorStyle 

func (d *Device) SetCursorStyle(style cursorRectFunc)

SetCursorStyle changes the shape of the cursor. Valid options are CursorBlock, CursorBeam, and CursorUnderscore. CursorBlock is the default.

func (*Device) VisualBell 

func (d *Device) VisualBell()

VisualBell inverts the screen for a quarter second.

func (*Device) Write 

func (d *Device) Write(data []byte) (n int, err error)

Write implements io.Write and is the main way to interract with with (*fansiterm).Device. This is essentially writing to the "terminal." Writes are more or less unbuffered with the exception of escape sequences. If a partial escape sequence is written to Device, the beginning will be bufferred and prepended to the next write.

func (*Device) WriteAt 

func (d *Device) WriteAt(p []byte, off int64) (n int, err error)

WriteAt works like calling the save cursor position escape sequence, then the absolute set cursor position escape sequence, writing to the terminal, and then finally restoring cursor position. The offset is just the i'th character on screen. Negative offset values are set to 0, values larger than d.rows * d.cols are set to d.rows*d.cols.

type Property 

type Property int
const (
	PropertyWindowTitle Property = iota
)

type Render 

type Render struct {
	draw.Image

	// Some displays require a flush / blit / sync call
	// this could be called at the end of (*Device).Write().
	DisplayFunc func()
	// contains filtered or unexported fields
}

Source Files

View all Source files

Directories

Path Synopsis
fansi
firacodenerd
inconsolata
juliamono
x3270

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