Adds feature to discard all the changes on the map

modules/core/history.js

@@ -15,7 +15,7 @@ import {
 
 
 export function coreHistory(context) {
-    var dispatch = d3_dispatch('reset', 'change', 'merge', 'restore', 'undone', 'redone', 'storage_error');
+    var dispatch = d3_dispatch('reset', 'change', 'merge', 'restore', 'undone', 'redone', 'storage_error','discarded');
     var lock = utilSessionMutex('lock');
 
     // restorable if iD not open in another window/tab and a saved history exists in localStorage
@@ -197,6 +197,18 @@ export function coreHistory(context) {
             return change(previous);
         },
 
+        discard: function() {
+            d3_select(document).interrupt('history.perform');
+
+            var previousStack = _stack[_index];
+            var previous = previousStack.graph;
+
+            // Discards changes by reverting to the initial state of the map
+            _index = 0;
+            dispatch.call('discarded', this, _stack[_index], previousStack);
+            return change(previous);
+        },
+
 
         // Back to the previous annotated state or _index = 0.
         undo: function() {

modules/ui/intro/helper.js

@@ -107,6 +107,7 @@ export function helpHtml(id, replacements) {
 
         // reference localized UI labels directly so that they'll always match
         save: t.html('save.title'),
+        discard: t.html('discard.title'),
         undo: t.html('undo.title'),
         redo: t.html('redo.title'),
         upload: t.html('commit.save'),

modules/ui/tools/index.js

@@ -1,5 +1,6 @@
 export * from './modes';
 export * from './notes';
 export * from './save';
+export * from './discard';
 export * from './sidebar_toggle';
 export * from './undo_redo';

modules/ui/tools/undo_redo.js

@@ -44,7 +44,6 @@ export function uiToolUndoRedo(context) {
         return context.mode() && context.mode().id !== 'save' && context.map().editableDataEnabled(true /* ignore min zoom */);
     }
 
-
     tool.render = function(selection) {
         var tooltipBehavior = uiTooltip()
             .placement('bottom')
@@ -60,6 +59,9 @@ export function uiToolUndoRedo(context) {
 
         var lastPointerUpType;
 
+        var longPressTimer;
+        var longPressFlag = false;
+
         var buttons = selection.selectAll('button')
             .data(commands)
             .enter()
@@ -69,21 +71,32 @@ export function uiToolUndoRedo(context) {
                 // `pointerup` is always called before `click`
                 lastPointerUpType = d3_event.pointerType;
             })
-            .on('click', function(d3_event, d) {
+            .on('mousedown', function(d3_event, d) {
                 d3_event.preventDefault();
+                if(d.id === 'undo'){
+                    //logic to check for long-press of undo button
+                    longPressTimer = setTimeout(function() {
+                        longPressFlag = true;
+                        context.history().discard();                        
+                    }, 1000);
+                }
 
+            })
+            .on('mouseup', function(d3_event, d) {
                 var annotation = d.annotation();
-
-                if (editable() && annotation) {
+                
+                if (editable() && annotation && !longPressFlag) {                 
                     d.action();
                 }
-
+                longPressFlag = false ;
+                clearTimeout(longPressTimer);
+
                 if (editable() && (
                     lastPointerUpType === 'touch' ||
                     lastPointerUpType === 'pen')
                 ) {
                     // there are no tooltips for touch interactions so flash feedback instead
-
+    
                     var label = annotation ?
                         t.append(d.id + '.tooltip', { action: annotation }) :
                         t.append(d.id + '.nothing');

modules/ui/top_toolbar.js

@@ -3,7 +3,7 @@ import {
 } from 'd3-selection';
 
 import _debounce from 'lodash-es/debounce';
-import { uiToolDrawModes, uiToolNotes, uiToolSave, uiToolSidebarToggle, uiToolUndoRedo } from './tools';
+import { uiToolDrawModes, uiToolNotes, uiToolSave, uiToolSidebarToggle, uiToolUndoRedo, uiToolDiscard } from './tools';
 
 
 export function uiTopToolbar(context) {
@@ -12,7 +12,8 @@ export function uiTopToolbar(context) {
         modes = uiToolDrawModes(context),
         notes = uiToolNotes(context),
         undoRedo = uiToolUndoRedo(context),
-        save = uiToolSave(context);
+        save = uiToolSave(context),
+        discard = uiToolDiscard(context);
 
     function notesEnabled() {
         var noteLayer = context.layers().layer('notes');