Improve performance for very long lines

cmd/micro/cursor.go

@@ -331,6 +331,7 @@ func (c *Cursor) GetVisualX() int {
 	runes := []rune(c.buf.Line(c.Y))
 	tabSize := int(c.buf.Settings["tabsize"].(float64))
 	return StringWidth(string(runes[:c.X]), tabSize)
+	// return c.Loc.X
 }
 
 // Relocate makes sure that the cursor is inside the bounds of the buffer

cmd/micro/util.go

@@ -294,3 +294,17 @@ func JoinCommandArgs(args ...string) string {
 
 	return buf.String()
 }
+
+func Sub(str string, start, end int) string {
+	len := Count(str)
+	if len > start && len > end {
+		return str[start:end]
+	}
+	if len > start && len < end {
+		return str[start:]
+	}
+	if len < start {
+		return str
+	}
+	return ""
+}

cmd/micro/view.go

@@ -690,8 +690,14 @@ func (v *View) DisplayView() {
 		}
 
 		// Now we actually draw the line
-		colN := 0
-		for _, ch := range line {
+		colN := v.leftCol
+		screenX += v.leftCol
+		charNum = Loc{v.leftCol, charNum.Y}
+		for _, ch := range Sub(line, v.leftCol, v.leftCol+v.width) {
+			if screenX-v.leftCol > v.x+v.width {
+				break
+			}
+
 			lineStyle := defStyle
 
 			if v.Buf.Settings["syntax"].(bool) {