Use a cache to speed up doc->screen and screen->doc mapping on very long document.

demo/demo.js

@@ -85,7 +85,7 @@ exports.launch = function(env) {
 
     // Make the lorem ipsum text a little bit longer.
     var loreIpsum = document.getElementById("plaintext").innerHTML;
-    for (var i = 0; i < 5; i++) {
+    for (var i = 0; i < 11; i++) {
         loreIpsum += loreIpsum;
     }
     docs.plain = new EditSession(loreIpsum);

lib/ace/edit_session.js

@@ -92,6 +92,7 @@ var EditSession = function(text, mode) {
         doc.on("change", this.onChange.bind(this));
         doc.on("changeStart", this.onChangeStart.bind(this));
         doc.on("changeEnd",   this.onChangeEnd.bind(this));
+        this.on("changeFold", this.onChangeFold.bind(this));
     };
 
     this.getDocument = function() {
@@ -99,13 +100,11 @@ var EditSession = function(text, mode) {
     };
 
     this.onChangeStart = function() {
-        console.log(">>> onChangeStart", this.$docChangeCounter);
         this.$docChangeCounter ++;
     };
 
     this.onChangeEnd = function() {
         this.$docChangeCounter --;
-        console.log("<<< onChangeEnd", this.$docChangeCounter);
         if (this.$docChangeCounter == 0
             && !this.$fromUndo && this.$undoManager)
         {
@@ -127,24 +126,36 @@ var EditSession = function(text, mode) {
         }
     };
 
+    this.onChangeFold = function(e) {
+        var fold = e.data;
+        if (this.$cacheRowData
+            && fold.start.row < this.$cacheRowData.docRow)
+        {
+            this.$cacheRowData = null;
+        }
+    };
+
     this.onChange = function(e) {
         var delta = e.data;
         this.$modified = true;
 
+        if (this.$cacheRowData
+            && delta.range.start.row < this.$cacheRowData.docRow)
+        {
+            this.$cacheRowData = null;
+        }
+
         var removedFolds = this.$updateInternalDataOnChange(e);
         if (!this.$fromUndo && this.$undoManager && !delta.ignore) {
-            console.log("onChange", JSON.stringify(delta));
             this.$deltasDoc.push(delta);
             if (removedFolds && removedFolds.length != 0) {
                 this.$deltasFold.push({
                     action: "removeFolds",
                     folds:  removedFolds
                 });
-                console.log("onChangeFold", removedFolds[0].toString());
             }
         }
 
-
         this.bgTokenizer.start(delta.range.start.row);
         this._dispatchEvent("change", e);
     };
@@ -154,6 +165,7 @@ var EditSession = function(text, mode) {
         this.$deltas = [];
         this.$deltasDoc = [];
         this.$deltasFold = [];
+        this.$cacheRowData = null;
         this.getUndoManager().reset();
     };
 
@@ -1361,6 +1373,17 @@ var EditSession = function(text, mode) {
         return this.screenToDocumentPosition(screenRow, screenColumn).column;
     };
 
+    this.setCacheRow = function(docRow) {
+        // Don't update the cache if the docRow stayed the same.
+        if (this.$cacheRowData && this.$cacheRowData.docRow == docRow) {
+            return;
+        }
+        this.$cacheRowData = {
+            docRow: docRow,
+            screenRow: this.documentToScreenRow(docRow, 0)
+        }
+    }
+
     this.screenToDocumentPosition = function(screenRow, screenColumn) {
         var line;
         var docRow = 0;
@@ -1373,6 +1396,12 @@ var EditSession = function(text, mode) {
         var splits = null;
         var split = 0;
 
+        var cacheRowData = this.$cacheRowData;
+        if (cacheRowData && cacheRowData.screenRow < screenRow) {
+            row = cacheRowData.screenRow ;
+            docRow = cacheRowData.docRow;
+        }
+
         while (row <= screenRow) {
             rowLength = this.getRowLength(docRow);
             if (row + rowLength - 1 >= screenRow) {
@@ -1457,6 +1486,12 @@ var EditSession = function(text, mode) {
         }
 
         var rowEnd, row = 0;
+        var cacheRowData = this.$cacheRowData;
+        if (cacheRowData && cacheRowData.docRow < docRow) {
+            row = cacheRowData.docRow ;
+            screenRow = cacheRowData.screenRow// + this.getRowLength(row);;
+        }
+
         while (row < docRow) {
             rowEnd = this.getRowFoldEnd(row);
             if (rowEnd >= docRow) {

lib/ace/edit_session/folding.js

@@ -329,7 +329,7 @@ function Folding() {
 
         // Notify that fold data has changed.
         this.$modified = true;
-        this._dispatchEvent("changeFold");
+        this._dispatchEvent("changeFold", { data: fold });
 
         return fold;
     };
@@ -387,7 +387,7 @@ function Folding() {
 
         // Notify that fold data has changed.
         this.$modified = true;
-        this._dispatchEvent("changeFold");
+        this._dispatchEvent("changeFold", { data: fold });
     }
 
     this.removeFolds = function(folds) {

lib/ace/virtual_renderer.js

@@ -479,6 +479,8 @@ var VirtualRenderer = function(container, theme) {
         var lineHeight = { lineHeight: this.lineHeight };
         firstRow = session.screenToDocumentRow(firstRow, 0);
 
+        session.setCacheRow(firstRow);
+
         // Check if firstRow is inside of a foldLine. If true, then use the first
         // row of the foldLine.
         var foldLine = session.getFoldLine(firstRow);