splitview: support snapSize

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

@@ -47,6 +47,7 @@ export interface IView {
 	readonly maximumSize: number;
 	readonly onDidChange: Event<number | undefined>;
 	readonly priority?: LayoutPriority;
+	readonly snapSize?: number;
 	layout(size: number, orientation: Orientation): void;
 }
 
@@ -351,7 +352,7 @@ export class SplitView extends Disposable {
 		} else {
 			for (let i = 0; i < this.viewItems.length; i++) {
 				const item = this.viewItems[i];
-				item.size = clamp(Math.round(this.proportions[i] * size), item.view.minimumSize, item.view.maximumSize);
+				item.size = SplitView.clamp(item, Math.round(this.proportions[i] * size));
 			}
 		}
 
@@ -443,7 +444,7 @@ export class SplitView extends Disposable {
 		}
 
 		size = typeof size === 'number' ? size : item.size;
-		size = clamp(size, item.view.minimumSize, item.view.maximumSize);
+		size = SplitView.clamp(item, size);
 
 		if (this.inverseAltBehavior && index > 0) {
 			// In this case, we want the view to grow or shrink both sides equally
@@ -550,27 +551,29 @@ export class SplitView extends Disposable {
 		const downItems = downIndexes.map(i => this.viewItems[i]);
 		const downSizes = downIndexes.map(i => sizes[i]);
 
-		const minDeltaUp = upIndexes.reduce((r, i) => r + (this.viewItems[i].view.minimumSize - sizes[i]), 0);
+		const minDeltaUp = upIndexes.reduce((r, i) => r + ((typeof this.viewItems[i].view.snapSize === 'number' ? 0 : this.viewItems[i].view.minimumSize) - sizes[i]), 0);
 		const maxDeltaUp = upIndexes.reduce((r, i) => r + (this.viewItems[i].view.maximumSize - sizes[i]), 0);
-		const maxDeltaDown = downIndexes.length === 0 ? Number.POSITIVE_INFINITY : downIndexes.reduce((r, i) => r + (sizes[i] - this.viewItems[i].view.minimumSize), 0);
+		const maxDeltaDown = downIndexes.length === 0 ? Number.POSITIVE_INFINITY : downIndexes.reduce((r, i) => r + (sizes[i] - (typeof this.viewItems[i].view.snapSize === 'number' ? 0 : this.viewItems[i].view.minimumSize)), 0);
 		const minDeltaDown = downIndexes.length === 0 ? Number.NEGATIVE_INFINITY : downIndexes.reduce((r, i) => r + (sizes[i] - this.viewItems[i].view.maximumSize), 0);
 		const minDelta = Math.max(minDeltaUp, minDeltaDown, overloadMinDelta);
 		const maxDelta = Math.min(maxDeltaDown, maxDeltaUp, overloadMaxDelta);
 
-		delta = clamp(delta, minDelta, maxDelta);
+		const tentativeDelta = clamp(delta, minDelta, maxDelta);
+		let actualDelta = 0;
 
-		for (let i = 0, deltaUp = delta; i < upItems.length; i++) {
+		for (let i = 0, deltaUp = tentativeDelta; i < upItems.length; i++) {
 			const item = upItems[i];
-			const size = clamp(upSizes[i] + deltaUp, item.view.minimumSize, item.view.maximumSize);
+			const size = SplitView.clamp(item, upSizes[i] + deltaUp/* , upIndexes[i] === index */);
 			const viewDelta = size - upSizes[i];
 
+			actualDelta += viewDelta;
 			deltaUp -= viewDelta;
 			item.size = size;
 		}
 
-		for (let i = 0, deltaDown = delta; i < downItems.length; i++) {
+		for (let i = 0, deltaDown = actualDelta; i < downItems.length; i++) {
 			const item = downItems[i];
-			const size = clamp(downSizes[i] - deltaDown, item.view.minimumSize, item.view.maximumSize);
+			const size = SplitView.clamp(item, downSizes[i] - deltaDown);
 			const viewDelta = size - downSizes[i];
 
 			deltaDown += viewDelta;
@@ -580,13 +583,24 @@ export class SplitView extends Disposable {
 		return delta;
 	}
 
+	private static clamp(item: IViewItem, size: number): number {
+		const result = clamp(size, item.view.minimumSize, item.view.maximumSize);
+
+		if (typeof item.view.snapSize !== 'number' || size >= item.view.minimumSize) {
+			return result;
+		}
+
+		const snapSize = Math.min(item.view.snapSize, item.view.minimumSize);
+		return size < snapSize ? 0 : item.view.minimumSize;
+	}
+
 	private distributeEmptySpace(): void {
 		let contentSize = this.viewItems.reduce((r, i) => r + i.size, 0);
 		let emptyDelta = this.size - contentSize;
 
 		for (let i = this.viewItems.length - 1; emptyDelta !== 0 && i >= 0; i--) {
 			const item = this.viewItems[i];
-			const size = clamp(item.size + emptyDelta, item.view.minimumSize, item.view.maximumSize);
+			const size = SplitView.clamp(item, item.size + emptyDelta);
 			const viewDelta = size - item.size;
 
 			emptyDelta -= viewDelta;