Initial patterm project

internal/app/screen_renderer.go

@@ -0,0 +1,86 @@
+package app
+
+import (
+	"fmt"
+	"strings"
+
+	"github.com/harrybrwn/patterm/internal/vt"
+)
+
+func renderScreenSnapshot(text string, cursor vt.CursorState, layout terminalLayout) []byte {
+	lines := strings.Split(strings.ReplaceAll(text, "\r\n", "\n"), "\n")
+	cols := int(layout.childCols())
+	rows := int(layout.childRows())
+
+	var b strings.Builder
+	b.WriteString("\x1b[?25l")
+	for r := 0; r < rows; r++ {
+		line := ""
+		if r < len(lines) {
+			line = truncateCells(lines[r], cols)
+		}
+		fmt.Fprintf(&b, "\x1b[%d;%dH%s", int(layout.mainTop)+r, int(layout.mainLeft), padRight(line, cols))
+	}
+
+	if cursor.Visible {
+		row := int(layout.mainTop) + int(cursor.Row)
+		col := int(layout.mainLeft) + int(cursor.Col)
+		if row < int(layout.mainTop) {
+			row = int(layout.mainTop)
+		}
+		maxRow := int(layout.mainTop) + rows - 1
+		if row > maxRow {
+			row = maxRow
+		}
+		if col < int(layout.mainLeft) {
+			col = int(layout.mainLeft)
+		}
+		maxCol := int(layout.mainLeft) + cols - 1
+		if col > maxCol {
+			col = maxCol
+		}
+		fmt.Fprintf(&b, "\x1b[?25h\x1b[%d;%dH", row, col)
+	}
+	return []byte(b.String())
+}
+
+func renderCursor(cursor vt.CursorState, layout terminalLayout) []byte {
+	cols := int(layout.childCols())
+	rows := int(layout.childRows())
+	row := int(layout.mainTop) + int(cursor.Row)
+	col := int(layout.mainLeft) + int(cursor.Col)
+	if row < int(layout.mainTop) {
+		row = int(layout.mainTop)
+	}
+	maxRow := int(layout.mainTop) + rows - 1
+	if row > maxRow {
+		row = maxRow
+	}
+	if col < int(layout.mainLeft) {
+		col = int(layout.mainLeft)
+	}
+	maxCol := int(layout.mainLeft) + cols - 1
+	if col > maxCol {
+		col = maxCol
+	}
+	return []byte(fmt.Sprintf("\x1b[?25h\x1b[%d;%dH", row, col))
+}
+
+func truncateCells(s string, width int) string {
+	if width <= 0 {
+		return ""
+	}
+	if visibleLen(s) <= width {
+		return s
+	}
+	var b strings.Builder
+	n := 0
+	for _, r := range s {
+		if n >= width {
+			break
+		}
+		b.WriteRune(r)
+		n++
+	}
+	return b.String()
+}