From c3aa97010788c2890709bb05859ed0db05d9b29c Mon Sep 17 00:00:00 2001
From: Beka Westberg <bwestberg@google.com>
Date: Fri, 28 Jul 2023 08:35:29 -0700
Subject: [PATCH] feat: add the ability to toggle scrollbar visibility (#7314)

---
 core/scrollbar.ts      | 18 +++++++++++++++---
 core/scrollbar_pair.ts | 10 ++++++++++
 2 files changed, 25 insertions(+), 3 deletions(-)

diff --git a/core/scrollbar.ts b/core/scrollbar.ts
index 2a7984a72..b1209c5f4 100644
--- a/core/scrollbar.ts
+++ b/core/scrollbar.ts
@@ -657,13 +657,25 @@ export class Scrollbar {
    * @param visible True if visible.
    */
   setVisible(visible: boolean) {
-    const visibilityChanged = visible !== this.isVisible();
-
     // Ideally this would also apply to scrollbar pairs, but that's a bigger
-    // headache (due to interactions with the corner square).
+    // headache (due to interactions with the corner square), and the fact
+    // that telling the pair to resize itself would cause circular dependencies.
     if (this.pair) {
       throw Error('Unable to toggle visibility of paired scrollbars.');
     }
+    this.setVisibleInternal(visible);
+  }
+
+  /**
+   * Set whether the scrollbar is visible. Bypasses checking whether this
+   * scrollbar is part of a pair so that it can be toggled by the scrollbar
+   * pair.
+   *
+   * @param visible True if visible.
+   * @internal
+   */
+  setVisibleInternal(visible: boolean) {
+    const visibilityChanged = visible !== this.isVisible();
     this.isHandleVisible = visible;
     if (visibilityChanged) {
       this.updateDisplay_();
diff --git a/core/scrollbar_pair.ts b/core/scrollbar_pair.ts
index 5b8ede4e7..8bb2b3d3a 100644
--- a/core/scrollbar_pair.ts
+++ b/core/scrollbar_pair.ts
@@ -306,6 +306,16 @@ export class ScrollbarPair {
     return isVisible;
   }
 
+  /**
+   * Sets the visibility of any existing scrollbars.
+   *
+   * @param visible True if visible.
+   */
+  setVisible(visible: boolean) {
+    if (this.hScroll) this.hScroll.setVisibleInternal(visible);
+    if (this.vScroll) this.vScroll.setVisibleInternal(visible);
+  }
+
   /**
    * Recalculates the scrollbars' locations within their path and length.
    * This should be called when the contents of the workspace have changed.