From ceacdc4d5a7bed88b4d9d239de2d65c840a8c011 Mon Sep 17 00:00:00 2001
From: Simon Hong <shong@brave.com>
Date: Fri, 5 Dec 2025 09:31:37 +0900
Subject: [PATCH] Don't add additional padding when vertical tab is hidden
 completely (#32657)

Resolves brave/brave-browser#51056

Set 0 as vertical tab's minimum width when hidden completely.
BraveBrowserViewLayout will not consider vertical tab when calculating contents view's margin as it's hidden.

TEST=VerticalTabStripHideCompletelyTest.GetMinimumWidth
---
 browser/ui/views/frame/brave_browser_view_layout.cc         | 6 +++++-
 .../frame/vertical_tabs/vertical_tab_strip_browsertest.cc   | 6 +++---
 .../frame/vertical_tabs/vertical_tab_strip_region_view.cc   | 4 +++-
 3 files changed, 11 insertions(+), 5 deletions(-)

diff --git a/browser/ui/views/frame/brave_browser_view_layout.cc b/browser/ui/views/frame/brave_browser_view_layout.cc
index 532858a394d..2350b4c9fc6 100644
--- a/browser/ui/views/frame/brave_browser_view_layout.cc
+++ b/browser/ui/views/frame/brave_browser_view_layout.cc
@@ -320,8 +320,10 @@ void BraveBrowserViewLayout::UpdateContentsContainerInsets(
   // Due to vertical tab's padding(tabs::kMarginForVerticalTabContainers), we
   // can see some space between vertical tab and contents. However, If we don't
   // have margin from contents, vertical tab side contents shadow isn't visible.
-  // So, having half or margin from vertical tab and half from contents.
+  // So, having half of margin from vertical tab and half from contents.
   if (browser() && tabs::utils::ShouldShowVerticalTabs(browser()) &&
+      (vertical_tab_strip_host_ &&
+       vertical_tab_strip_host_->GetPreferredSize().width() != 0) &&
       !IsFullscreenForBrowser()) {
     const int margin_with_vertical_tab =
         browser()
@@ -463,6 +465,8 @@ gfx::Insets BraveBrowserViewLayout::AdjustInsetsConsideringFrameBorder(
     const gfx::Insets& insets) {
   BrowserView* browser_view = BrowserView::GetBrowserViewForBrowser(browser());
   if (!browser() || !tabs::utils::ShouldShowVerticalTabs(browser()) ||
+      (vertical_tab_strip_host_ &&
+       vertical_tab_strip_host_->GetPreferredSize().width() == 0) ||
       (browser_view && browser_view->IsFullscreen())) {
     return insets;
   }
diff --git a/browser/ui/views/frame/vertical_tabs/vertical_tab_strip_browsertest.cc b/browser/ui/views/frame/vertical_tabs/vertical_tab_strip_browsertest.cc
index 0fdc9a97f82..a476f6d5fda 100644
--- a/browser/ui/views/frame/vertical_tabs/vertical_tab_strip_browsertest.cc
+++ b/browser/ui/views/frame/vertical_tabs/vertical_tab_strip_browsertest.cc
@@ -1209,9 +1209,9 @@ IN_PROC_BROWSER_TEST_F(VerticalTabStripHideCompletelyTest, GetMinimumWidth) {
   ASSERT_EQ(BraveVerticalTabStripRegionView::State::kCollapsed,
             region_view->state());
 
-  // The minimum width of the region view should be 4px, which is narrower than
-  // it used to be.
-  EXPECT_EQ(4, region_view->GetMinimumSize().width());
+  // The minimum width of the region view should be 0px as it's hidden
+  // completely when collapsed.
+  EXPECT_EQ(0, region_view->GetMinimumSize().width());
 
   // When the preference is disabled, the minimum width should be back to
   // 41px(w/o rounded corners) or 38px(with rounded corners) due to region
diff --git a/browser/ui/views/frame/vertical_tabs/vertical_tab_strip_region_view.cc b/browser/ui/views/frame/vertical_tabs/vertical_tab_strip_region_view.cc
index c07feadcd70..0da34021510 100644
--- a/browser/ui/views/frame/vertical_tabs/vertical_tab_strip_region_view.cc
+++ b/browser/ui/views/frame/vertical_tabs/vertical_tab_strip_region_view.cc
@@ -775,7 +775,9 @@ gfx::Size BraveVerticalTabStripRegionView::CalculatePreferredSize(
 }
 
 gfx::Size BraveVerticalTabStripRegionView::GetMinimumSize() const {
-  if (IsFloatingEnabledForBrowserFullscreen()) {
+  if (IsFloatingEnabledForBrowserFullscreen() ||
+      ((tabs::utils::ShouldHideVerticalTabsCompletelyWhenCollapsed(browser_) &&
+        state_ != State::kExpanded))) {
     // Vertical tab strip always overlaps the contents area.
     return {};
   }