Fixed vertical scrollbar top coordinates when using thick borders on windows with no title bar and no menu bar. (#9366)

docs/CHANGELOG.txt

@@ -74,6 +74,9 @@ Other Changes:
     user to tell us ImGuiSelectionUserData are indices)
   - Box-Select, Tables: fixed an issue when calling `BeginMultiSelect()` in a table
     before layout has been locked (first row or headers row submitted). (#8250)
+- Style:
+  - Fixed vertical scrollbar top coordinates when using thick borders on windows
+    with no title bar and no menu bar. (#9366)
 - Fonts:
   - imgui_freetype: add FreeType headers & compiled version in 'About Dear ImGui' details.
   - Assert when using MergeMode with an explicit size over a target font with an implicit

imgui_widgets.cpp

@@ -977,7 +977,7 @@ ImRect ImGui::GetWindowScrollbarRect(ImGuiWindow* window, ImGuiAxis axis)
     const float scrollbar_size = window->ScrollbarSizes[axis ^ 1]; // (ScrollbarSizes.x = width of Y scrollbar; ScrollbarSizes.y = height of X scrollbar)
     IM_ASSERT(scrollbar_size >= 0.0f);
     const float border_size = IM_ROUND(window->WindowBorderSize * 0.5f);
-    const float border_top = (window->Flags & ImGuiWindowFlags_MenuBar) ? IM_ROUND(g.Style.FrameBorderSize * 0.5f) : 0.0f;
+    const float border_top = (window->Flags & ImGuiWindowFlags_MenuBar) ? IM_ROUND(g.Style.FrameBorderSize * 0.5f) : (window->Flags & ImGuiWindowFlags_NoTitleBar) ? border_size : 0;
     if (axis == ImGuiAxis_X)
         return ImRect(inner_rect.Min.x + border_size, ImMax(outer_rect.Min.y + border_size, outer_rect.Max.y - border_size - scrollbar_size), inner_rect.Max.x - border_size, outer_rect.Max.y - border_size);
     else