Docking: Fixed rendering of outer decoration happening on non-visible docked window (#2623, #2109). Revealed by 0770449. We are actually better than before now, as previously those would get unnecessarily get rendered into a hidden draw list.

imgui.cpp

@@ -6181,24 +6181,29 @@ bool ImGui::Begin(const char* name, bool* p_open, ImGuiWindowFlags flags)
                 window->DrawList->AddRectFilled(bb.Min, bb.Max, GetColorU32(ImGuiCol_NavWindowingHighlight, g.NavWindowingHighlightAlpha * 0.25f), g.Style.WindowRounding);
         }
 
+        const bool is_undocked_or_docked_visible = !window->DockIsActive || window->DockTabIsVisible;
+
         // Since 1.71, child window can render their decoration (bg color, border, scrollbars, etc.) within their parent to save a draw call.
         // When using overlapping child windows, this will break the assumption that child z-order is mapped to submission order.
         // We disable this when the parent window has zero vertices, which is a common pattern leading to laying out multiple overlapping child.
         // We also disabled this when we have dimming overlay behind this specific one child.
         // FIXME: More code may rely on explicit sorting of overlapping child window and would need to disable this somehow. Please get in contact if you are affected.
-        bool render_decorations_in_parent = false;
-        if ((flags & ImGuiWindowFlags_ChildWindow) && !(flags & ImGuiWindowFlags_Popup) && !window_is_child_tooltip)
-            if (window->DrawList->CmdBuffer.back().ElemCount == 0 && parent_window->DrawList->VtxBuffer.Size > 0)
-                render_decorations_in_parent = true;
-        if (render_decorations_in_parent)
-            window->DrawList = parent_window->DrawList;
-        
-        const ImGuiWindow* window_to_highlight = g.NavWindowingTarget ? g.NavWindowingTarget : g.NavWindow;
-        const bool title_bar_is_highlight = want_focus || (window_to_highlight && (window->RootWindowForTitleBarHighlight == window_to_highlight->RootWindowForTitleBarHighlight || (window->DockNode && window->DockNode == window_to_highlight->DockNode)));
-        RenderWindowDecorations(window, title_bar_rect, title_bar_is_highlight, handle_borders_and_resize_grips, resize_grip_count, resize_grip_col, resize_grip_draw_size);
+        if (is_undocked_or_docked_visible)
+        {
+            bool render_decorations_in_parent = false;
+            if ((flags & ImGuiWindowFlags_ChildWindow) && !(flags & ImGuiWindowFlags_Popup) && !window_is_child_tooltip)
+                if (window->DrawList->CmdBuffer.back().ElemCount == 0 && parent_window->DrawList->VtxBuffer.Size > 0)
+                    render_decorations_in_parent = true;
+            if (render_decorations_in_parent)
+                window->DrawList = parent_window->DrawList;
 
-        if (render_decorations_in_parent)
-            window->DrawList = &window->DrawListInst;
+            const ImGuiWindow* window_to_highlight = g.NavWindowingTarget ? g.NavWindowingTarget : g.NavWindow;
+            const bool title_bar_is_highlight = want_focus || (window_to_highlight && (window->RootWindowForTitleBarHighlight == window_to_highlight->RootWindowForTitleBarHighlight || (window->DockNode && window->DockNode == window_to_highlight->DockNode)));
+            RenderWindowDecorations(window, title_bar_rect, title_bar_is_highlight, handle_borders_and_resize_grips, resize_grip_count, resize_grip_col, resize_grip_draw_size);
+
+            if (render_decorations_in_parent)
+                window->DrawList = &window->DrawListInst;
+        }
 
         // Draw navigation selection/windowing rectangle border
         if (g.NavWindowingTargetAnim == window)