Tables: fixed right-clicking right-most section (past right-most column) from highlighting right-most column.

docs/CHANGELOG.txt

@@ -103,6 +103,7 @@ Other changes:
 - Tables: Fixed bottom-most and right-most outer border offset by one. (#6765, #3752) [@v-ein]
 - Tables: Fixed top-most outer border being drawn with both TableBorderLight and TableBorderStrong
   in some situations, causing the earlier to be visible underneath when alpha is not 1.0f.
+- Tables: fixed right-clicking right-most section (past right-most column) from highlighting a column.
 - TabBar: Fixed position of unsaved document marker (ImGuiTabItemFlags_UnsavedDocument) which was
   accidentally offset in 1.89.9. (#6862) [@alektron]
 - Fonts: 'float size_pixels' passed to AddFontXXX() functions is now rounded to lowest integer.

imgui.h

@@ -507,7 +507,7 @@ namespace ImGui
     // - Most widgets return true when the value has been changed or when pressed/selected
     // - You may also use one of the many IsItemXXX functions (e.g. IsItemActive, IsItemHovered, etc.) to query widget state.
     IMGUI_API bool          Button(const char* label, const ImVec2& size = ImVec2(0, 0));   // button
-    IMGUI_API bool          SmallButton(const char* label);                                 // button with FramePadding=(0,0) to easily embed within text
+    IMGUI_API bool          SmallButton(const char* label);                                 // button with (FramePadding.y == 0) to easily embed within text
     IMGUI_API bool          InvisibleButton(const char* str_id, const ImVec2& size, ImGuiButtonFlags flags = 0); // flexible button behavior without the visuals, frequently useful to build custom behaviors using the public api (along with IsItemActive, IsItemHovered, etc.)
     IMGUI_API bool          ArrowButton(const char* str_id, ImGuiDir dir);                  // square button with an arrow shape
     IMGUI_API bool          Checkbox(const char* label, bool* v);

imgui_tables.cpp

@@ -2919,9 +2919,9 @@ void ImGui::TableHeadersRow()
         TableUpdateLayout(table);
 
     // Open row
-    const float row_y1 = GetCursorScreenPos().y;
     const float row_height = TableGetHeaderRowHeight();
     TableNextRow(ImGuiTableRowFlags_Headers, row_height);
+    const float row_y1 = GetCursorScreenPos().y;
     if (table->HostSkipItems) // Merely an optimization, you may skip in your own code.
         return;
 
@@ -2943,7 +2943,7 @@ void ImGui::TableHeadersRow()
     ImVec2 mouse_pos = ImGui::GetMousePos();
     if (IsMouseReleased(1) && TableGetHoveredColumn() == columns_count)
         if (mouse_pos.y >= row_y1 && mouse_pos.y < row_y1 + row_height)
-            TableOpenContextMenu(-1); // Will open a non-column-specific popup.
+            TableOpenContextMenu(columns_count); // Will open a non-column-specific popup.
 }
 
 // Emit a column header (text + optional sort order)