fix overscan issue and enable linkifier on partial shown matches

src/Buffer.test.ts

@@ -3,7 +3,7 @@
  * @license MIT
  */
 
-import { assert } from 'chai';
+import { assert, expect } from 'chai';
 import { ITerminal } from './Types';
 import { Buffer, DEFAULT_ATTR, CHAR_DATA_CHAR_INDEX } from './Buffer';
 import { CircularList } from './common/CircularList';
@@ -514,4 +514,35 @@ describe('Buffer', () => {
       }
     });
   });
+  describe('BufferStringIterator', function(): void {
+    it('iterator does not ovrflow buffer limits', function(): void {
+      const terminal = new TestTerminal({rows: 5, cols: 10, scrollback: 5});
+      const data = [
+        'aaaaaaaaaa',
+        'aaaaaaaaa\n',
+        'aaaaaaaaaa',
+        'aaaaaaaaa\n',
+        'aaaaaaaaaa',
+        'aaaaaaaaaa',
+        'aaaaaaaaaa',
+        'aaaaaaaaa\n',
+        'aaaaaaaaaa',
+        'aaaaaaaaaa'
+      ];
+      terminal.writeSync(data.join(''));
+      // brute force test with insane values
+      expect(() => {
+        for (let overscan = 0; overscan < 20; ++overscan) {
+          for (let start = -10; start < 20; ++start) {
+            for (let end = -10; end < 20; ++end) {
+              const it = terminal.buffer.iterator(false, start, end, overscan, overscan);
+              while (it.hasNext()) {
+                it.next();
+              }
+            }
+          }
+        }
+      }).to.not.throw();
+    });
+  });
 });

src/Buffer.ts

@@ -371,8 +371,8 @@ export class Buffer implements IBuffer {
     this.markers.splice(this.markers.indexOf(marker), 1);
   }
 
-  public iterator(trimRight: boolean, startIndex?: number, endIndex?: number): IBufferStringIterator {
-    return new BufferStringIterator(this, trimRight, startIndex, endIndex);
+  public iterator(trimRight: boolean, startIndex?: number, endIndex?: number, startOverscan?: number, endOverscan?: number): IBufferStringIterator {
+    return new BufferStringIterator(this, trimRight, startIndex, endIndex, startOverscan, endOverscan);
   }
 }
 
@@ -401,15 +401,35 @@ export class Marker extends EventEmitter implements IMarker {
   }
 }
 
+/**
+ * Iterator to get unwrapped content strings from the buffer.
+ * The iterator returns at least the string data between the borders
+ * `startIndex` and `endIndex` (exclusive) and will expand the lines
+ * by `startOverscan` to the top and by `endOverscan` to the bottom,
+ * if no new line was found in between.
+ * It will never read/return string data beyond `startIndex - startOverscan`
+ * or `endIndex + endOverscan`. Therefore the first and last line might be truncated.
+ * It is possible to always get the full string for the first and last line as well
+ * by setting the overscan values to the actual buffer length. This not recommended
+ * since it might return the whole buffer within a single string in a worst case scenario.
+ */
 export class BufferStringIterator implements IBufferStringIterator {
   private _current: number;
 
   constructor (
     private _buffer: IBuffer,
     private _trimRight: boolean,
     private _startIndex: number = 0,
-    private _endIndex: number = _buffer.lines.length
+    private _endIndex: number = _buffer.lines.length,
+    private _startOverscan: number = 0,
+    private _endOverscan: number = 0
   ) {
+    if (this._startIndex < 0) {
+      this._startIndex = 0;
+    }
+    if (this._endIndex > this._buffer.lines.length) {
+      this._endIndex = this._buffer.lines.length;
+    }
     this._current = this._startIndex;
   }
 
@@ -419,6 +439,16 @@ export class BufferStringIterator implements IBufferStringIterator {
 
   public next(): IBufferStringIteratorResult {
     const range = this._buffer.getWrappedRangeForLine(this._current);
+    // limit search window to overscan value at both borders
+    if (range.first < this._startIndex - this._startOverscan) {
+      range.first = this._startIndex - this._startOverscan;
+    }
+    if (range.last > this._endIndex + this._endOverscan) {
+      range.last = this._endIndex + this._endOverscan;
+    }
+    // limit to current buffer length
+    range.first = Math.max(range.first, 0);
+    range.last = Math.min(range.last, this._buffer.lines.length);
     let result = '';
     for (let i = range.first; i <= range.last; ++i) {
       // TODO: always apply trimRight after fixing #1685

src/Linkifier.ts

@@ -21,6 +21,13 @@ export class Linkifier extends EventEmitter implements ILinkifier {
    */
   protected static readonly TIME_BEFORE_LINKIFY = 200;
 
+  /**
+   * Limit of the unwrapping line expansion (overscan) at the top and bottom
+   * of the actual viewport in ASCII characters.
+   * A limit of 2000 should match most sane urls.
+   */
+  protected static readonly OVERSCAN_CHAR_LIMIT = 2000;
+
   protected _linkMatchers: ILinkMatcher[] = [];
 
   private _mouseZoneManager: IMouseZoneManager;
@@ -92,11 +99,19 @@ export class Linkifier extends EventEmitter implements ILinkifier {
     // Invalidate bad end row values (if a resize happened)
     const absoluteRowIndexEnd = buffer.ydisp + Math.min(this._rowsToLinkify.end, this._terminal.rows) + 1;
 
-    // iterate over the range of unwrapped content strings within start..end (excluding)
-    // _doLinkifyRow gets full unwrapped lines with the start row as buffer offset for every matcher
-    // for wrapped content over several rows the iterator might return rows outside the viewport
-    // we skip those later in _doLinkifyRow
-    const iterator = buffer.iterator(false, absoluteRowIndexStart, absoluteRowIndexEnd);
+    // Iterate over the range of unwrapped content strings within start..end
+    // (excluding).
+    // _doLinkifyRow gets full unwrapped lines with the start row as buffer offset
+    // for every matcher.
+    // The unwrapping is needed to also match content that got wrapped across
+    // several buffer lines. To avoid a worst case szenario where the whole buffer
+    // contains just a single unwrapped string we limit this line expansion beyond
+    // the viewport to +OVERSCAN_CHAR_LIMIT chars (overscan) at top and bottom.
+    // This comes with the tradeoff that matches longer than OVERSCAN_CHAR_LIMIT
+    // chars will not match anymore at the viewport borders.
+    const overscanLineLimit = Math.ceil(Linkifier.OVERSCAN_CHAR_LIMIT / this._terminal.cols);
+    const iterator = this._terminal.buffer.iterator(
+      false, absoluteRowIndexStart, absoluteRowIndexEnd, overscanLineLimit, overscanLineLimit);
     while (iterator.hasNext()) {
       const lineData: IBufferStringIteratorResult = iterator.next();
       for (let i = 0; i < this._linkMatchers.length; i++) {
@@ -208,14 +223,6 @@ export class Linkifier extends EventEmitter implements ILinkifier {
       // get the buffer index as [absolute row, col] for the match
       const bufferIndex = this._terminal.buffer.stringIndexToBufferIndex(rowIndex, stringIndex);
 
-      // skip rows outside of the viewport
-      if (bufferIndex[0] - this._terminal.buffer.ydisp < 0) {
-        continue;
-      }
-      if (bufferIndex[0] - this._terminal.buffer.ydisp > this._terminal.rows) {
-        break;
-      }
-
       const line = this._terminal.buffer.lines.get(bufferIndex[0]);
       const char = line.get(bufferIndex[1]);
       let fg: number | undefined;

src/Types.ts

@@ -296,7 +296,7 @@ export interface IBuffer {
   nextStop(x?: number): number;
   prevStop(x?: number): number;
   stringIndexToBufferIndex(lineIndex: number, stringIndex: number): number[];
-  iterator(trimRight: boolean, startIndex?: number, endIndex?: number): IBufferStringIterator;
+  iterator(trimRight: boolean, startIndex?: number, endIndex?: number, startOverscan?: number, endOverscan?: number): IBufferStringIterator;
 }
 
 export interface IBufferSet extends IEventEmitter {