Tab Bar: fix 0ea4408 (#3414)

imgui_widgets.cpp

@@ -7253,7 +7253,7 @@ static void ImGui::TabBarLayout(ImGuiTabBar* tab_bar)
     // Actual layout in host window (we don't do it in BeginTabBar() so as not to waste an extra frame)
     ImGuiWindow* window = g.CurrentWindow;
     window->DC.CursorPos = tab_bar->BarRect.Min;
-    ItemSize(tab_bar->BarRect.GetSize(), tab_bar->FramePadding.y);
+    ItemSize(ImVec2(tab_bar->WidthAllTabs, tab_bar->BarRect.GetHeight()), tab_bar->FramePadding.y);
     window->DC.IdealMaxPos.x = ImMax(window->DC.IdealMaxPos.x, tab_bar->BarRect.Min.x + tab_bar->WidthAllTabsIdeal);
 }