Scrollbar: fixed miscalculation of vertical scrollbar visibility when required solely by the presence of an horizontal scrollbar. (#1574)

Initially fixed by 2d9d7a10c, and broken back by a0994d74c2 (v1.71, wow).

docs/CHANGELOG.txt

@@ -47,6 +47,8 @@ Other changes:
   responsible for honoring io.ConfigWindowsMoveFromTitleBarOnly. (#7576, #899)
 - Scrollbar: made scrolling logic more standard: clicking above or below the
   grab scrolls by one page, holding mouse button repeats scrolling. (#7328, #150)
+- Scrollbar: fixed miscalculation of vertical scrollbar visibility when required
+  solely by the presence of an horizontal scrollbar. (#1574)
 - Combo: simplified Combo() API uses a list clipper (due to its api it wasn't
   previously trivial before we added clipper.IncludeItemByIndex() function).
 - Disabled: nested tooltips or other non-child window within a BeginDisabled()

imgui.cpp

@@ -6926,7 +6926,7 @@ bool ImGui::Begin(const char* name, bool* p_open, ImGuiWindowFlags flags)
             window->ScrollbarY = (flags & ImGuiWindowFlags_AlwaysVerticalScrollbar) || ((needed_size_from_last_frame.y > size_y_for_scrollbars) && !(flags & ImGuiWindowFlags_NoScrollbar));
             window->ScrollbarX = (flags & ImGuiWindowFlags_AlwaysHorizontalScrollbar) || ((needed_size_from_last_frame.x > size_x_for_scrollbars - (window->ScrollbarY ? style.ScrollbarSize : 0.0f)) && !(flags & ImGuiWindowFlags_NoScrollbar) && (flags & ImGuiWindowFlags_HorizontalScrollbar));
             if (window->ScrollbarX && !window->ScrollbarY)
-                window->ScrollbarY = (needed_size_from_last_frame.y > size_y_for_scrollbars) && !(flags & ImGuiWindowFlags_NoScrollbar);
+                window->ScrollbarY = (needed_size_from_last_frame.y > size_y_for_scrollbars - style.ScrollbarSize) && !(flags & ImGuiWindowFlags_NoScrollbar);
             window->ScrollbarSizes = ImVec2(window->ScrollbarY ? style.ScrollbarSize : 0.0f, window->ScrollbarX ? style.ScrollbarSize : 0.0f);
 
             // Amend the partially filled window->DecorationXXX values.

imgui.h

@@ -28,7 +28,7 @@
 // Library Version
 // (Integer encoded as XYYZZ for use in #if preprocessor conditionals, e.g. '#if IMGUI_VERSION_NUM >= 12345')
 #define IMGUI_VERSION       "1.90.8 WIP"
-#define IMGUI_VERSION_NUM   19073
+#define IMGUI_VERSION_NUM   19074
 #define IMGUI_HAS_TABLE
 
 /*