Handle cursor area with custom writer (#17)

Author: lammel

README.md

@@ -0,0 +1,66 @@
+package main
+
+import (
+	"fmt"
+	"time"
+
+	"atomicgo.dev/cursor"
+)
+
+func main() {
+	fmt.Println("Cursor area movement demo")
+	fmt.Println("--------------------------")
+
+	area := cursor.NewArea()
+	content := `Start content with some rows
+	1. Row1
+	2. Row2
+	---
+	`
+	area.Update(content)
+
+	time.Sleep(1 * time.Second)
+	area.Up(2)
+	area.Move(3, 0)
+	fmt.Print("Replaced row 2")
+
+	time.Sleep(1 * time.Second)
+	area.StartOfLine()
+	area.Move(8, -1)
+	fmt.Print("3. Appended row")
+
+	time.Sleep(1 * time.Second)
+	area.Update(content + "(restored content after move)")
+
+	time.Sleep(1 * time.Second)
+	area.Up(6)
+	fmt.Print("<<< AFTER Up(6)")
+	time.Sleep(1 * time.Second)
+	area.Update(content + "(restored content after cursor up out of bounds)")
+
+	time.Sleep(1 * time.Second)
+	area.Down(6)
+	fmt.Print("<<< AFTER Down(6)")
+	time.Sleep(1 * time.Second)
+	area.Update(content + "(restored content after cursor down out of bounds)")
+
+	time.Sleep(1 * time.Second)
+	area.Top()
+	fmt.Print("<<< AFTER Top()")
+	time.Sleep(1 * time.Second)
+	area.Update(content + "(restored content after cursor top)")
+
+	time.Sleep(1 * time.Second)
+	area.Bottom()
+	fmt.Print("<<< AFTER Bottom()")
+	time.Sleep(1 * time.Second)
+	area.Update(content + "(restored content after cursor bottom)")
+
+	time.Sleep(1 * time.Second)
+	area.Update("")
+	time.Sleep(1 * time.Second)
+	area.Update(content + "(restored content after empty line)")
+
+	time.Sleep(1 * time.Second)
+	fmt.Println("\n--- DONE")
+}

_examples/area/movement/main.go

@@ -0,0 +1,66 @@
+package main
+
+import (
+	"fmt"
+	"math/rand"
+	"time"
+
+	"atomicgo.dev/cursor"
+)
+
+func main() {
+	fmt.Println("Multiline cursor area demo")
+	fmt.Println("--------------------------")
+
+	area := cursor.NewArea()
+	header := "This is a multiline demo\nwith 2 lines:\n"
+	area.Update(header)
+	content := header
+	for i := 1; i < 6; i++ {
+		if i%2 == 0 {
+			content += fmt.Sprintf(" + %d\n", i)
+		} else {
+			content += fmt.Sprintf(" - line: %d", i)
+		}
+		time.Sleep(1 * time.Second)
+		area.Update(content)
+	}
+
+	time.Sleep(1 * time.Second)
+	area.Update("Test varying area sizes now")
+	time.Sleep(500 * time.Millisecond)
+	area.Update(buildContent(1, 2))
+	time.Sleep(500 * time.Millisecond)
+	area.Update(buildContent(2, 9))
+	time.Sleep(500 * time.Millisecond)
+	area.Update(buildContent(3, 5))
+	time.Sleep(500 * time.Millisecond)
+	area.Update(buildContent(4, 0))
+	time.Sleep(500 * time.Millisecond)
+	area.Update(buildContent(5, 6))
+	time.Sleep(500 * time.Millisecond)
+	area.Update(buildContent(6, 1))
+	time.Sleep(500 * time.Millisecond)
+	area.Update(buildContent(7, 3))
+
+	time.Sleep(1 * time.Second)
+	fmt.Println("\n--- DONE")
+}
+
+func buildContent(idx int, n int) string {
+	content := fmt.Sprintf(">>> START OF CONTENT %d/%d <<<\n", idx, n)
+	for i := 0; i < n; i++ {
+		for i := 0; i < 5; i++ {
+			content += words[rand.Intn(len(words))] + " "
+		}
+		content += "\n"
+	}
+
+	return content
+}
+
+var words = []string{
+	"ball", "summer", "hint", "mountain", "island", "onion", "world",
+	"run", "hit", "fly", "swim", "crawl", "build", "dive", "jump",
+	"crazy", "funny", "strange", "yellow", "red", "blue", "green", "white",
+}

_examples/area/multiline/main.go

@@ -0,0 +1,32 @@
+package main
+
+import (
+	"fmt"
+	"time"
+
+	"atomicgo.dev/cursor"
+)
+
+func main() {
+	fmt.Println("Single line cursor area demo")
+	fmt.Println("----------------------------")
+
+	area := cursor.NewArea()
+
+	header := "This is a singleline without newline"
+	area.Update(header)
+	for i := 1; i < 6; i++ {
+		time.Sleep(1 * time.Second)
+		area.Update(fmt.Sprintf("%s: %d", header, i))
+	}
+
+	header = "This is a singleline with newline"
+	area.Update(header + "\n")
+	for i := 1; i < 6; i++ {
+		time.Sleep(1 * time.Second)
+		area.Update(fmt.Sprintf("%s: %d\n", header, i))
+	}
+
+	time.Sleep(1 * time.Second)
+	fmt.Println("\n--- DONE")
+}

_examples/area/singleline/main.go

@@ -1,67 +1,164 @@
 package cursor
 
 import (
-	"fmt"
 	"os"
-	"runtime"
 	"strings"
 )
 
 // Area displays content which can be updated on the fly.
 // You can use this to create live output, charts, dropdowns, etc.
 type Area struct {
-	height int
-	writer Writer
+	height     int
+	writer     Writer
+	cursor     *Cursor
+	cursorPosY int
 }
 
 // NewArea returns a new Area.
 func NewArea() Area {
 	return Area{
-		writer: os.Stdout,
-		height: 0,
+		height:     0,
+		writer:     os.Stdout,
+		cursor:     cursor,
+		cursorPosY: 0,
 	}
 }
 
-// WithWriter sets a custom writer for the Area.
+// WithWriter sets the custom writer.
 func (area Area) WithWriter(writer Writer) Area {
 	area.writer = writer
+	area.cursor = area.cursor.WithWriter(writer)
 
 	return area
 }
 
 // Clear clears the content of the Area.
 func (area *Area) Clear() {
-	Bottom()
+	// Initialize writer if not done yet
+	if area.writer == nil {
+		area.writer = os.Stdout
+	}
 
 	if area.height > 0 {
-		ClearLinesUp(area.height)
+		area.Bottom()
+		area.ClearLinesUp(area.height)
+		area.StartOfLine()
+	} else {
+		area.StartOfLine()
+		area.cursor.ClearLine()
 	}
 }
 
-// Update overwrites the content of the Area.
+// Update overwrites the content of the Area and adjusts its height based on content.
 func (area *Area) Update(content string) {
-	oldWriter := target
-
-	SetTarget(area.writer) // Temporary set the target to the Area's writer so we can use the cursor functions
 	area.Clear()
+	area.writeArea(content)
+	area.cursorPosY = 0
+	area.height = strings.Count(content, "\n")
+}
 
-	lines := strings.Split(content, "\n")
-	fmt.Fprintln(area.writer, strings.Repeat("\n", len(lines)-1)) // This appends space if the terminal is at the bottom
-	Up(len(lines))
-	SetTarget(oldWriter) // Reset the target to the old writer
-
-	// Workaround for buggy behavior on Windows
-	if runtime.GOOS == "windows" {
-		for _, line := range lines {
-			fmt.Fprint(area.writer, line)
-			StartOfLineDown(1)
+// Up moves the cursor of the area up one line.
+func (area *Area) Up(n int) {
+	if n > 0 {
+		if area.cursorPosY+n > area.height {
+			n = area.height - area.cursorPosY
 		}
-	} else {
-		for _, line := range lines {
-			fmt.Fprintln(area.writer, line)
+
+		area.cursor.Up(n)
+		area.cursorPosY += n
+	}
+}
+
+// Down moves the cursor of the area down one line.
+func (area *Area) Down(n int) {
+	if n > 0 {
+		if area.cursorPosY-n < 0 {
+			n = area.height - area.cursorPosY
 		}
+
+		area.cursor.Down(n)
+		area.cursorPosY -= n
+	}
+}
+
+// Bottom moves the cursor to the bottom of the terminal.
+// This is done by calculating how many lines were moved by Up and Down.
+func (area *Area) Bottom() {
+	if area.cursorPosY > 0 {
+		area.Down(area.cursorPosY)
+		area.cursorPosY = 0
+	}
+}
+
+// Top moves the cursor to the top of the area.
+// This is done by calculating how many lines were moved by Up and Down.
+func (area *Area) Top() {
+	if area.cursorPosY < area.height {
+		area.Up(area.height - area.cursorPosY)
+		area.cursorPosY = area.height
 	}
+}
+
+// StartOfLine moves the cursor to the start of the current line.
+func (area *Area) StartOfLine() {
+	area.cursor.HorizontalAbsolute(0)
+}
 
-	height = 0
-	area.height = len(strings.Split(content, "\n"))
+// StartOfLineDown moves the cursor down by n lines, then moves to cursor to the start of the line.
+func (area *Area) StartOfLineDown(n int) {
+	area.Down(n)
+	area.StartOfLine()
+}
+
+// StartOfLineUp moves the cursor up by n lines, then moves to cursor to the start of the line.
+func (area *Area) StartOfLineUp(n int) {
+	area.Up(n)
+	area.StartOfLine()
+}
+
+// UpAndClear moves the cursor up by n lines, then clears the line.
+func (area *Area) UpAndClear(n int) {
+	area.Up(n)
+	area.cursor.ClearLine()
+}
+
+// DownAndClear moves the cursor down by n lines, then clears the line.
+func (area *Area) DownAndClear(n int) {
+	area.Down(n)
+	area.cursor.ClearLine()
+}
+
+// Move moves the cursor relative by x and y.
+func (area *Area) Move(x, y int) {
+	if x > 0 {
+		area.cursor.Right(x)
+	} else if x < 0 {
+		area.cursor.Left(-x)
+	}
+
+	if y > 0 {
+		area.Up(y)
+	} else if y < 0 {
+		area.Down(-y)
+	}
+}
+
+// ClearLinesUp clears n lines upwards from the current position and moves the cursor.
+func (area *Area) ClearLinesUp(n int) {
+	area.StartOfLine()
+	area.cursor.ClearLine()
+
+	for i := 0; i < n; i++ {
+		area.UpAndClear(1)
+	}
+}
+
+// ClearLinesDown clears n lines downwards from the current position and moves the cursor.
+func (area *Area) ClearLinesDown(n int) {
+	area.StartOfLine()
+	area.cursor.ClearLine()
+
+	for i := 0; i < n; i++ {
+		area.DownAndClear(1)
+	}
 }

area.go

@@ -0,0 +1,13 @@
+//go:build !windows
+// +build !windows
+
+package cursor
+
+import (
+	"fmt"
+)
+
+// Update overwrites the content of the Area and adjusts its height based on content.
+func (area *Area) writeArea(content string) {
+	fmt.Fprint(area.writer, content)
+}

area_other.go

@@ -0,0 +1,21 @@
+//go:build windows
+// +build windows
+
+package cursor
+
+import (
+	"fmt"
+)
+
+// writeArea is a helper for platform dependant output.
+// For Windows newlines '\n' in the content are replaced by '\r\n'
+func (area *Area) writeArea(content string) {
+	last := ' '
+	for _, r := range content {
+		if r == '\n' && last != '\r' {
+			fmt.Fprint(area.writer, "\r\n")
+			continue
+		}
+		fmt.Fprint(area.writer, string(r))
+	}
+}