Separator: clarified setting the ImGuiSeparatorFlags_SpanAllColumns flag. (#759)

Technically a no-op.

imgui.h

@@ -826,7 +826,7 @@ namespace ImGui
     IMGUI_API bool                  BeginDragDropTarget();                                                          // call after submitting an item that may receive a payload. If this returns true, you can call AcceptDragDropPayload() + EndDragDropTarget()
     IMGUI_API const ImGuiPayload*   AcceptDragDropPayload(const char* type, ImGuiDragDropFlags flags = 0);          // accept contents of a given type. If ImGuiDragDropFlags_AcceptBeforeDelivery is set you can peek into the payload before the mouse button is released.
     IMGUI_API void                  EndDragDropTarget();                                                            // only call EndDragDropTarget() if BeginDragDropTarget() returns true!
-    IMGUI_API const ImGuiPayload*   GetDragDropPayload();                                                           // peek directly into the current payload from anywhere. may return NULL. use ImGuiPayload::IsDataType() to test for the payload type.
+    IMGUI_API const ImGuiPayload*   GetDragDropPayload();                                                           // peek directly into the current payload from anywhere. returns NULL when drag and drop is finished or inactive. use ImGuiPayload::IsDataType() to test for the payload type.
 
     // Disabling [BETA API]
     // - Disable all user interactions and dim items visuals (applying style.DisabledAlpha over current colors)

imgui_internal.h

@@ -720,7 +720,6 @@ struct ImChunkStream
     int     offset_from_ptr(const T* p) { IM_ASSERT(p >= begin() && p < end()); const ptrdiff_t off = (const char*)p - Buf.Data; return (int)off; }
     T*      ptr_from_offset(int off)    { IM_ASSERT(off >= 4 && off < Buf.Size); return (T*)(void*)(Buf.Data + off); }
     void    swap(ImChunkStream<T>& rhs) { rhs.Buf.swap(Buf); }
-
 };
 
 // Helper: ImGuiTextIndex<>

imgui_widgets.cpp

@@ -1467,7 +1467,11 @@ void ImGui::Separator()
     // Those flags should eventually be configurable by the user
     // FIXME: We cannot g.Style.SeparatorTextBorderSize for thickness as it relates to SeparatorText() which is a decorated separator, not defaulting to 1.0f.
     ImGuiSeparatorFlags flags = (window->DC.LayoutType == ImGuiLayoutType_Horizontal) ? ImGuiSeparatorFlags_Vertical : ImGuiSeparatorFlags_Horizontal;
-    flags |= ImGuiSeparatorFlags_SpanAllColumns; // NB: this only applies to legacy Columns() api as they relied on Separator() a lot.
+
+    // Only applies to legacy Columns() api as they relied on Separator() a lot.
+    if (window->DC.CurrentColumns)
+        flags |= ImGuiSeparatorFlags_SpanAllColumns;
+
     SeparatorEx(flags, 1.0f);
 }