Fix rendering of multi-line selection when only top row is visible

Fixes #3069

addons/xterm-addon-webgl/src/RectangleRenderer.ts

@@ -196,7 +196,7 @@ export class RectangleRenderer {
     } else {
       // Draw first row
       const startCol = model.viewportStartRow === model.viewportCappedStartRow ? model.startCol : 0;
-      const startRowEndCol = model.viewportCappedStartRow === model.viewportCappedEndRow ? model.endCol : terminal.cols;
+      const startRowEndCol = model.viewportCappedStartRow === model.viewportEndRow ? model.endCol : terminal.cols;
       this._addRectangleFloat(
         this._vertices.selection,
         0,

src/browser/renderer/SelectionRenderLayer.ts

@@ -88,7 +88,7 @@ export class SelectionRenderLayer extends BaseRenderLayer {
     } else {
       // Draw first row
       const startCol = viewportStartRow === viewportCappedStartRow ? start[0] : 0;
-      const startRowEndCol = viewportCappedStartRow === viewportCappedEndRow ? end[0] : this._bufferService.cols;
+      const startRowEndCol = viewportCappedStartRow === viewportEndRow ? end[0] : this._bufferService.cols;
       this._fillCells(startCol, viewportCappedStartRow, startRowEndCol - startCol, 1);
 
       // Draw middle rows

src/browser/renderer/dom/DomRenderer.ts

@@ -306,7 +306,7 @@ export class DomRenderer extends Disposable implements IRenderer {
     } else {
       // Draw first row
       const startCol = viewportStartRow === viewportCappedStartRow ? start[0] : 0;
-      const endCol = viewportCappedStartRow === viewportCappedEndRow ? end[0] : this._bufferService.cols;
+      const endCol = viewportCappedStartRow === viewportEndRow ? end[0] : this._bufferService.cols;
       documentFragment.appendChild(this._createSelectionElement(viewportCappedStartRow, startCol, endCol));
       // Draw middle rows
       const middleRowsCount = viewportCappedEndRow - viewportCappedStartRow - 1;