Add option for very accurate dirty flag

Set the `fastdirty` option flag to off if you really want accurate
reporting on whether the buffer is modified. This is more resource
intensive but it can be useful for people who don't mind.

Closes #787
Closes #467

cmd/micro/buffer.go

@@ -2,6 +2,7 @@ package main
 
 import (
 	"bytes"
+	"crypto/md5"
 	"encoding/gob"
 	"io"
 	"io/ioutil"
@@ -57,6 +58,9 @@ type Buffer struct {
 	syntaxDef   *highlight.Def
 	highlighter *highlight.Highlighter
 
+	// Hash of the original buffer -- empty if fastdirty is on
+	origHash [16]byte
+
 	// Buffer local settings
 	Settings map[string]interface{}
 }
@@ -174,7 +178,7 @@ func NewBuffer(reader io.Reader, size int64, path string) *Buffer {
 			}
 
 			if b.Settings["saveundo"].(bool) {
-				// We should only use last time's eventhandler if the file wasn't by someone else in the meantime
+				// We should only use last time's eventhandler if the file wasn't modified by someone else in the meantime
 				if b.ModTime == buffer.ModTime {
 					b.EventHandler = buffer.EventHandler
 					b.EventHandler.buf = b
@@ -188,6 +192,10 @@ func NewBuffer(reader io.Reader, size int64, path string) *Buffer {
 		screen.EnableMouse()
 	}
 
+	if !b.Settings["fastdirty"].(bool) {
+		b.origHash = md5.Sum([]byte(b.String()))
+	}
+
 	b.cursors = []*Cursor{&b.Cursor}
 
 	return b
@@ -451,6 +459,13 @@ func (b *Buffer) SaveAsWithSudo(filename string) error {
 	return err
 }
 
+func (b *Buffer) Modified() bool {
+	if b.Settings["fastdirty"].(bool) {
+		return b.IsModified
+	}
+	return b.origHash != md5.Sum([]byte(b.String()))
+}
+
 func (b *Buffer) insert(pos Loc, value []byte) {
 	b.IsModified = true
 	b.LineArray.insert(pos, value)

cmd/micro/settings.go

@@ -1,6 +1,7 @@
 package main
 
 import (
+	"crypto/md5"
 	"encoding/json"
 	"errors"
 	"io/ioutil"
@@ -198,10 +199,13 @@ func DefaultGlobalSettings() map[string]interface{} {
 		"colorscheme":    "default",
 		"cursorline":     true,
 		"eofnewline":     false,
-		"rmtrailingws":   false,
+		"fastdirty":      true,
+		"fileformat":     "unix",
 		"ignorecase":     false,
 		"indentchar":     " ",
 		"infobar":        true,
+		"mouse":          true,
+		"rmtrailingws":   false,
 		"ruler":          true,
 		"savecursor":     false,
 		"saveundo":       false,
@@ -221,8 +225,6 @@ func DefaultGlobalSettings() map[string]interface{} {
 		},
 		"pluginrepos": []string{},
 		"useprimary":  true,
-		"fileformat":  "unix",
-		"mouse":       true,
 	}
 }
 
@@ -236,10 +238,13 @@ func DefaultLocalSettings() map[string]interface{} {
 		"colorcolumn":    float64(0),
 		"cursorline":     true,
 		"eofnewline":     false,
-		"rmtrailingws":   false,
+		"fastdirty":      true,
+		"fileformat":     "unix",
 		"filetype":       "Unknown",
 		"ignorecase":     false,
 		"indentchar":     " ",
+		"mouse":          true,
+		"rmtrailingws":   false,
 		"ruler":          true,
 		"savecursor":     false,
 		"saveundo":       false,
@@ -254,8 +259,6 @@ func DefaultLocalSettings() map[string]interface{} {
 		"tabsize":        float64(4),
 		"tabstospaces":   false,
 		"useprimary":     true,
-		"fileformat":     "unix",
-		"mouse":          true,
 	}
 }
 
@@ -358,6 +361,26 @@ func SetLocalOption(option, value string, view *View) error {
 		return err
 	}
 
+	if option == "fastdirty" {
+		// If it is being turned off, we have to hash every open buffer
+		var empty [16]byte
+		for _, tab := range tabs {
+			for _, v := range tab.views {
+				if !nativeValue.(bool) {
+					if v.Buf.origHash == empty {
+						data, err := ioutil.ReadFile(v.Buf.AbsPath)
+						if err != nil {
+							data = []byte{}
+						}
+						v.Buf.origHash = md5.Sum(data)
+					}
+				} else {
+					v.Buf.IsModified = v.Buf.Modified()
+				}
+			}
+		}
+	}
+
 	buf.Settings[option] = nativeValue
 
 	if option == "statusline" {

cmd/micro/statusline.go

@@ -20,7 +20,7 @@ func (sline *Statusline) Display() {
 	file := sline.view.Buf.GetName()
 
 	// If the buffer is dirty (has been modified) write a little '+'
-	if sline.view.Buf.IsModified {
+	if sline.view.Buf.Modified() {
 		file += " +"
 	}
 

cmd/micro/tab.go

@@ -91,7 +91,7 @@ func TabbarString() (string, map[int]int) {
 		}
 		buf := t.views[t.CurView].Buf
 		str += buf.GetName()
-		if buf.IsModified {
+		if buf.Modified() {
 			str += " +"
 		}
 		if i == curTab {

cmd/micro/view.go

@@ -199,7 +199,7 @@ func (v *View) ScrollDown(n int) {
 // If there are unsaved changes, the user will be asked if the view can be closed
 // causing them to lose the unsaved changes
 func (v *View) CanClose() bool {
-	if v.Type == vtDefault && v.Buf.IsModified {
+	if v.Type == vtDefault && v.Buf.Modified() {
 		var choice bool
 		var canceled bool
 		if v.Buf.Settings["autosave"].(bool) {

runtime/help/options.md

@@ -161,6 +161,22 @@ Here are the options that you can set:
 
     default value: `on`
 
+* `fileformat`: this determines what kind of line endings micro will use for the file. Unix line endings
+   are just `\n` (lf) whereas dos line endings are `\r\n` (crlf). The two possible values for this option
+   are `unix` and `dos`. The fileformat will be automatically detected and displayed on the statusline but
+   this option is useful if you would like to change the line endings or if you are starting a new file.
+
+    default value: `unix`
+
+* `fastdirty`: this determines what kind of algorithm micro uses to determine if a buffer is modified or
+   not. When `fastdirty` is on, micro just uses a boolean `modified` that is set to `true` as soon as the user
+   makes an edit. This is fast, but can be inaccurate. If `fastdirty` is off, then micro will hash the current
+   buffer against a hash of the original file (created when the buffer was loaded). This is more accurate but
+   obviously more resource intensive. This option is only for people who really care about having accurate
+   modified status.
+
+    default value: `on`
+
 ---
 
 Default plugin options:
@@ -179,13 +195,6 @@ Default plugin options:
 
 	default value: `on`
 
-* `fileformat`: this determines what kind of line endings micro will use for the file. Unix line endings
-   are just `\n` (lf) whereas dos line endings are `\r\n` (crlf). The two possible values for this option
-   are `unix` and `dos`. The fileformat will be automatically detected and displayed on the statusline but
-   this option is useful if you would like to change the line endings or if you are starting a new file.
-
-    default value: `unix`
-
 Any option you set in the editor will be saved to the file 
 ~/.config/micro/settings.json so, in effect, your configuration file will be 
 created for you. If you'd like to take your configuration with you to another