sash: increase sash corner area

src/vs/base/browser/ui/sash/sash.css

@@ -54,8 +54,8 @@
 .monaco-sash:not(.disabled).orthogonal-start::before,
 .monaco-sash:not(.disabled).orthogonal-end::after {
 	content: ' ';
-	height: 4px;
-	width: 4px;
+	height: 8px;
+	width: 8px;
 	z-index: 100;
 	display: block;
 	cursor: all-scroll;
@@ -63,19 +63,23 @@
 }
 
 .monaco-sash.orthogonal-start.vertical::before {
-	top: -2px;
+	left: -2px;
+	top: -4px;
 }
 
 .monaco-sash.orthogonal-end.vertical::after {
-	bottom: -2px;
+	left: -2px;
+	bottom: -4px;
 }
 
 .monaco-sash.orthogonal-start.horizontal::before {
-	left: -2px;
+	top: -2px;
+	left: -4px;
 }
 
 .monaco-sash.orthogonal-end.horizontal::after {
-	right: -2px;
+	top: -2px;
+	right: -4px;
 }
 
 .monaco-sash.disabled {

src/vs/base/browser/ui/sash/sash.ts

@@ -179,15 +179,15 @@ export class Sash {
 			let orthogonalSash: Sash | undefined;
 
 			if (this.orientation === Orientation.VERTICAL) {
-				if (e.offsetY <= 2) {
+				if (e.offsetY <= 4) {
 					orthogonalSash = this.orthogonalStartSash;
-				} else if (e.offsetY >= this.el.clientHeight - 2) {
+				} else if (e.offsetY >= this.el.clientHeight - 4) {
 					orthogonalSash = this.orthogonalEndSash;
 				}
 			} else {
-				if (e.offsetX <= 2) {
+				if (e.offsetX <= 4) {
 					orthogonalSash = this.orthogonalStartSash;
-				} else if (e.offsetX >= this.el.clientWidth - 2) {
+				} else if (e.offsetX >= this.el.clientWidth - 4) {
 					orthogonalSash = this.orthogonalEndSash;
 				}
 			}