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package render
import (
"fmt"
"io"
"strings"
)
type (
trimDir uint8
overlapType uint8
)
const (
ToLeft trimDir = iota
ToRight
None overlapType = iota
Covers
Within
Left
Right
)
type Instruction interface {
// Write writes the instruction to the given io.Writer.
Write(io.Writer)
// Pos returns the x,y position of the instruction.
Pos() (int, int)
// Len returns the length of the instructions content.
Len() int
// Trim removes n characters from one side of the instruction.
Trim(n int, d trimDir) Instruction
// Copy creates a new instruction with the same content and position.
Copy() Instruction
}
func overlap(over, under Instruction) overlapType {
ox, oy := over.Pos()
ux, uy := under.Pos()
os, us := over.Len(), under.Len()
// wrong row:
if oy != uy {
return None
}
// totally covers it
if ox <= ux && ox+os >= ux+us {
return Covers
}
// Overlap on the left:
if ox <= ux && ox+os > ux {
return Left
}
// Overlap on the right:
if ox < ux+us && ox+os >= ux+us {
return Right
}
// centered inside:
if ox > ux && ox+os < ux+us {
return Within
}
// Only other option is not touching
return None
}
// Squash creates new instruction from overlapping instructions.
// Whenever an instruction would be written over another instruction,
// the one under is trimmed to only include the part that is not covered.
// Three cases are possible:
// - The under instruction is completely covered by the over instruction.
// - The under instruction is partially covered on one side
// - The under instruction is covered in the center (splitting it in two)
// No matter what, the over instruction never changes so only variations of
// under needs to be returned.
func squash(over Instruction, under Instruction, ot overlapType) []Instruction {
ox, _ := over.Pos()
ux, _ := under.Pos()
os, us := over.Len(), under.Len()
switch ot {
case Covers:
return []Instruction{}
case Left:
overlap := ox + os - ux
under.Trim(overlap, ToLeft)
return []Instruction{under}
case Right:
overlap := ux + us - ox
under.Trim(overlap, ToRight)
return []Instruction{under}
case Within:
overlapL := ox - ux
overlapR := ux + us - (ox + os)
left := under.Copy().Trim(overlapL, ToLeft)
under.Trim(overlapR, ToRight)
return []Instruction{left, under}
default:
return []Instruction{under}
}
}
func reach(i Instruction) string {
x, y := i.Pos()
return fmt.Sprintf("\033[%d;%dH", y, x)
}
// DrawInstruction is a struct that contains content the renderer
// should draw.
type DrawInstruction struct {
// Content is the string that should be drawn.
Content string
// Pos is the position in the terminal where the content should be drawn.
X int
Y int
// Decorators is a list of ANSI escape codes used to decorate the content.
Decorators []string
}
func (d DrawInstruction) Pos() (int, int) {
return d.X, d.Y
}
func (d DrawInstruction) Len() int {
return len(d.Content)
}
func (d DrawInstruction) Write(w io.Writer) {
msg := reach(d) + strings.Join(d.Decorators, "") + d.Content
io.WriteString(w, msg)
}
func (d DrawInstruction) Trim(n int, from trimDir) Instruction {
// Prevents having to error check for negative values.
if n < 0 {
n = -n
}
// If n is greater than the length of the content, return nil.
if n > len(d.Content) {
return nil
}
switch from {
case ToLeft:
d.Content = d.Content[n:]
d.X += n
case ToRight:
d.Content = d.Content[:len(d.Content)-n]
}
return &d
}
func (d DrawInstruction) Copy() Instruction {
return &DrawInstruction{
Content: d.Content,
X: d.X,
Y: d.Y,
Decorators: d.Decorators,
}
}
// ClearInstruction is a struct that contains content the renderer should
// clear. they usually accompany a DrawInstruction (i.e. clear the space
// behind a moving object) but not always.
type ClearInstruction struct {
// Len is the number of consecutive characters to clear.
Size int
// Pos is the position in the terminal where the content should be cleared.
X int
Y int
}
func (c ClearInstruction) Write(w io.Writer) {
// Erase as many characters as the size of the instruction.
msg := reach(c) + "\033[K" + strings.Repeat(" ", c.Size)
// TODO: maybe implement a way to log stuff like writestring errors
io.WriteString(w, msg)
}
func (c ClearInstruction) Pos() (int, int) {
return c.X, c.Y
}
func (c ClearInstruction) Len() int {
if c.Size < 0 {
return -c.Size
}
return c.Size
}
func (c ClearInstruction) Trim(n int, from trimDir) Instruction {
// Prevents having to error check for negative values.
if n < 0 {
n = -n
}
// If n is greater than the length of the content, return nil.
if n > c.Size {
return nil
}
switch from {
case ToLeft:
c.Size -= n
c.X += n
case ToRight:
c.Size -= n
}
return &c
}
func (c ClearInstruction) Copy() Instruction {
return &ClearInstruction{
Size: c.Size,
X: c.X,
Y: c.Y,
}
}
|
