From d6307b2718d6f3a1e40ffd0fce5f2e564cdd4e49 Mon Sep 17 00:00:00 2001
From: Zachary Yedidia <zyedidia@gmail.com>
Date: Sat, 4 Jun 2016 16:25:11 -0400
Subject: [PATCH] Proper support for double width characters

Fixes #99
---
 cmd/micro/cursor.go | 19 +++++++------------
 cmd/micro/util.go   | 24 ++++++++++++++++++++++++
 cmd/micro/view.go   | 11 +++++++++++
 3 files changed, 42 insertions(+), 12 deletions(-)

diff --git a/cmd/micro/cursor.go b/cmd/micro/cursor.go
index a2ca8b44..19f36dfc 100644
--- a/cmd/micro/cursor.go
+++ b/cmd/micro/cursor.go
@@ -1,9 +1,5 @@
 package main
 
-import (
-	"strings"
-)
-
 // FromCharPos converts from a character position to an x, y position
 func FromCharPos(loc int, buf *Buffer) (int, int) {
 	return FromCharPosStart(0, 0, 0, loc, buf)
@@ -357,13 +353,13 @@ func (c *Cursor) GetCharPosInLine(lineNum, visualPos int) int {
 	// Get the tab size
 	tabSize := int(settings["tabsize"].(float64))
 	// This is the visual line -- every \t replaced with the correct number of spaces
-	visualLine := strings.Replace(c.buf.Lines[lineNum], "\t", "\t"+Spaces(tabSize-1), -1)
-	if visualPos > Count(visualLine) {
-		visualPos = Count(visualLine)
+	visualLineLen := StringWidth(c.buf.Lines[lineNum])
+	if visualPos > visualLineLen {
+		visualPos = visualLineLen
 	}
-	numTabs := NumOccurences(visualLine[:visualPos], '\t')
-	if visualPos >= (tabSize-1)*numTabs {
-		return visualPos - (tabSize-1)*numTabs
+	width := WidthOfLargeRunes(c.buf.Lines[lineNum])
+	if visualPos >= width {
+		return visualPos - width
 	}
 	return visualPos / tabSize
 }
@@ -371,8 +367,7 @@ func (c *Cursor) GetCharPosInLine(lineNum, visualPos int) int {
 // GetVisualX returns the x value of the cursor in visual spaces
 func (c *Cursor) GetVisualX() int {
 	runes := []rune(c.buf.Lines[c.Y])
-	tabSize := int(settings["tabsize"].(float64))
-	return c.X + NumOccurences(string(runes[:c.X]), '\t')*(tabSize-1)
+	return StringWidth(string(runes[:c.X]))
 }
 
 // Relocate makes sure that the cursor is inside the bounds of the buffer
diff --git a/cmd/micro/util.go b/cmd/micro/util.go
index 02dacf38..46da66da 100644
--- a/cmd/micro/util.go
+++ b/cmd/micro/util.go
@@ -7,6 +7,8 @@ import (
 	"strings"
 	"time"
 	"unicode/utf8"
+
+	"github.com/mattn/go-runewidth"
 )
 
 // Util.go is a collection of utility functions that are used throughout
@@ -138,6 +140,28 @@ func GetModTime(path string) (time.Time, bool) {
 	return info.ModTime(), true
 }
 
+func StringWidth(str string) int {
+	sw := runewidth.StringWidth(str)
+	sw += NumOccurences(str, '\t') * (int(settings["tabsize"].(float64)) - 1)
+	return sw
+}
+
+func WidthOfLargeRunes(str string) int {
+	count := 0
+	for _, ch := range str {
+		var w int
+		if ch == '\t' {
+			w = int(settings["tabsize"].(float64))
+		} else {
+			w = runewidth.RuneWidth(ch)
+		}
+		if w > 1 {
+			count += (w - 1)
+		}
+	}
+	return count
+}
+
 func runePos(p int, str string) int {
 	return utf8.RuneCountInString(str[:p])
 }
diff --git a/cmd/micro/view.go b/cmd/micro/view.go
index cd2fc324..0940acc9 100644
--- a/cmd/micro/view.go
+++ b/cmd/micro/view.go
@@ -7,6 +7,7 @@ import (
 	"strings"
 	"time"
 
+	"github.com/mattn/go-runewidth"
 	"github.com/zyedidia/tcell"
 )
 
@@ -601,6 +602,16 @@ func (v *View) DisplayView() {
 						screen.SetContent(x-v.leftCol, lineN, ' ', nil, lineStyle)
 					}
 				}
+			} else if runewidth.RuneWidth(ch) > 1 {
+				if x-v.leftCol >= v.lineNumOffset {
+					screen.SetContent(x-v.leftCol, lineN, ch, nil, lineStyle)
+				}
+				for i := 0; i < runewidth.RuneWidth(ch)-1; i++ {
+					x++
+					if x-v.leftCol >= v.lineNumOffset {
+						screen.SetContent(x-v.leftCol, lineN, ' ', nil, lineStyle)
+					}
+				}
 			} else {
 				if x-v.leftCol >= v.lineNumOffset {
 					screen.SetContent(x-v.leftCol, lineN, ch, nil, lineStyle)