Docking: Amend b16f738 fixed dimming of docked window + removed thin …

…highlight around windows (never worked on docked window, not viewports friendly, hard to move to EndFrame) (#2700, #2539, #2522)

imgui.cpp

@@ -6730,16 +6730,12 @@ bool ImGui::Begin(const char* name, bool* p_open, ImGuiWindowFlags flags)
         if (dim_bg_for_modal || dim_bg_for_window_list)
         {
             const ImU32 dim_bg_col = GetColorU32(dim_bg_for_modal ? ImGuiCol_ModalWindowDimBg : ImGuiCol_NavWindowingDimBg, g.DimBgRatio);
+            ImDrawList* bg_draw_list = window->DockIsActive ? window->DockNode->HostWindow->DrawList : window->DrawList;
+            if (window->DockIsActive || (flags & ImGuiWindowFlags_DockNodeHost))
+                window->DrawList->ChannelsSetCurrent(0);
             window->DrawList->AddRectFilled(viewport_rect.Min, viewport_rect.Max, dim_bg_col);
-        }
-
-        // Draw navigation selection/windowing rectangle background
-        if (dim_bg_for_window_list && window == g.NavWindowingTargetAnim)
-        {
-            ImRect bb = window->Rect();
-            bb.Expand(g.FontSize);
-            if (!bb.Contains(viewport_rect)) // Avoid drawing if the window covers all the viewport anyway
-                window->DrawList->AddRectFilled(bb.Min, bb.Max, GetColorU32(ImGuiCol_NavWindowingHighlight, g.NavWindowingHighlightAlpha * 0.25f), g.Style.WindowRounding);
+            if (window->DockIsActive || (flags & ImGuiWindowFlags_DockNodeHost))
+                window->DrawList->ChannelsSetCurrent(1);
         }
 
         // Child windows can render their decoration (bg color, border, scrollbars, etc.) within their parent to save a draw call (since 1.71)