message: Combo: Arrow button isn't displayed over frame color, so color is consistent with other button + the button doesn't have inner rounding.
diff: @@ -10596,8 +10596,9 @@ bool ImGui::BeginCombo(const char* label, const char* preview_value, ImGuiComboF
  const float arrow_size = GetFrameHeight();
  const ImRect value_bb(frame_bb.Min, frame_bb.Max - ImVec2(arrow_size, 0.0f));
  RenderNavHighlight(frame_bb, id);
  - RenderFrame(frame_bb.Min, frame_bb.Max, GetColorU32(ImGuiCol_FrameBg), true, style.FrameRounding);
  - RenderFrame(ImVec2(frame_bb.Max.x-arrow_size, frame_bb.Min.y), frame_bb.Max, GetColorU32(popup_open || hovered ? ImGuiCol_ButtonHovered : ImGuiCol_Button), true, style.FrameRounding); // FIXME-ROUNDING
  + window->DrawList->AddRectFilled(frame_bb.Min, ImVec2(frame_bb.Max.x - arrow_size, frame_bb.Max.y), GetColorU32(ImGuiCol_FrameBg), style.FrameRounding, ImDrawCornerFlags_Left);
  + window->DrawList->AddRectFilled(ImVec2(frame_bb.Max.x - arrow_size, frame_bb.Min.y), frame_bb.Max, GetColorU32(popup_open || hovered ? ImGuiCol_ButtonHovered : ImGuiCol_Button), style.FrameRounding, (w <= arrow_size) ? ImDrawCornerFlags_All : ImDrawCornerFlags_Right);
  + RenderFrameBorder(frame_bb.Min, frame_bb.Max, style.FrameRounding);
  RenderArrow(ImVec2(frame_bb.Max.x - arrow_size + style.FramePadding.y, frame_bb.Min.y + style.FramePadding.y), ImGuiDir_Down);
  if (preview_value != NULL)
  RenderTextClipped(frame_bb.Min + style.FramePadding, value_bb.Max, preview_value, NULL, NULL, ImVec2(0.0f,0.0f));
  