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https://github.com/taigrr/gopher-os
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616fc6a412
The terminal uses console.Vga as its output device. A proper terminal implementation would be using a console.Console interface as its output. However, at this point we cannot use Go interfaces as the fn pointers in the itables have not been yet initialized. The Go runtime bits that set up the itables need access to a memory allocator, a facility which is not yet provided by the kernel.
119 lines
2.2 KiB
Go
119 lines
2.2 KiB
Go
package tty
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import "github.com/achilleasa/gopher-os/kernel/driver/video/console"
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const (
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defaultFg = console.LightGrey
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defaultBg = console.Black
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)
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// Vt implements a simple terminal that can process LF and CR characters. The
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// terminal uses a console device for its output.
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type Vt struct {
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// Go interfaces will not work before we can get memory allocation working.
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// Till then we need to use concrete types instead.
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cons *console.Vga
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width uint16
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height uint16
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curX uint16
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curY uint16
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curAttr console.Attr
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}
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func (t *Vt) Init(cons *console.Vga) {
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t.cons = cons
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t.width, t.height = cons.Dimensions()
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t.curX = 0
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t.curY = 0
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// Default to lightgrey on black text.
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t.curAttr = makeAttr(defaultFg, defaultBg)
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}
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// Clear clears the terminal.
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func (t *Vt) Clear() {
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t.cons.Lock()
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defer t.cons.Unlock()
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t.clear()
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}
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// Position returns the current cursor position (x, y).
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func (t *Vt) Position() (uint16, uint16) {
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t.cons.Lock()
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defer t.cons.Unlock()
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return t.curX, t.curY
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}
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// SetPosition sets the current cursor position to (x,y).
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func (t *Vt) SetPosition(x, y uint16) {
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t.cons.Lock()
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defer t.cons.Unlock()
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if x >= t.width {
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x = t.width - 1
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}
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if y >= t.height {
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y = t.height - 1
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}
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t.curX, t.curY = x, y
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}
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// Write implements io.Writer.
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func (t *Vt) Write(data []byte) (int, error) {
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t.cons.Lock()
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defer t.cons.Unlock()
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attr := t.curAttr
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for _, b := range data {
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switch b {
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case '\r':
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t.cr()
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case '\n':
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t.cr()
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t.lf()
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default:
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t.cons.Write(b, attr, t.curX, t.curY)
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t.curX++
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if t.curX == t.width {
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t.lf()
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}
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}
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}
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return len(data), nil
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}
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// cls clears the terminal.
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func (t *Vt) clear() {
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t.cons.Clear(0, 0, t.width, t.height)
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}
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// cr resets the x coordinate of the terminal cursor to 0.
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func (t *Vt) cr() {
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t.curX = 0
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}
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// lf advances the y coordinate of the terminal cursor by one line scrolling
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// the terminal contents if the end of the last terminal line is reached.
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func (t *Vt) lf() {
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if t.curY+1 < t.height {
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t.curY++
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return
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}
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t.cons.Scroll(console.Up, 1)
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t.cons.Clear(0, t.height-1, t.width, 1)
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return
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}
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func makeAttr(fg, bg console.Attr) console.Attr {
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return (bg << 4) | (fg & 0xF)
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}
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