Windows: BgClickFlags inherited by default + missing info in Changelog. Amend 40f9e4e. (#899, #3071, #5044, #3379)

Author: ocornut

docs/CHANGELOG.txt

@@ -50,6 +50,9 @@ Other Changes:
 - Tables: Angled headers: fixed an auto-resize feedback loop that could
   affect tables with empty non-resizing columns using angled headers, making
   them typically flicker back and forth between +0 and +1 pixels.
+- Windows: io.ConfigWindowsMoveFromTitleBarOnly is latched during Begin(),
+  effectively allowing to change the value on a per-window basis (although
+  there is a better internal mechanism for it).
 - Disabled: fixed a bug when a previously enabled item that got nav focus
   and then turns disabled could still be activated using keyboard. (#9036)
 - InputText: when buffer is not resizable, trying to paste contents that

imgui.cpp

@@ -7949,7 +7949,7 @@ bool ImGui::Begin(const char* name, bool* p_open, ImGuiWindowFlags flags)
         // Set default BgClickFlags
         // This is set at the end of this function, so UpdateManualResize()/ClampWindowPos() may use last-frame value if overriden by user code.
         // FIXME: The general intent is that we will later expose config options to default to enable scrolling + select scrolling mouse button.
-        window->BgClickFlags = g.IO.ConfigWindowsMoveFromTitleBarOnly ? ImGuiWindowBgClickFlags_None : ImGuiWindowBgClickFlags_Move;
+        window->BgClickFlags = (flags & ImGuiWindowFlags_ChildWindow) ? parent_window->BgClickFlags : (g.IO.ConfigWindowsMoveFromTitleBarOnly ? ImGuiWindowBgClickFlags_None : ImGuiWindowBgClickFlags_Move);
 
         // We fill last item data based on Title Bar/Tab, in order for IsItemHovered() and IsItemActive() to be usable after Begin().
         // This is useful to allow creating context menus on title bar only, etc.