Long legend with horizontal orientation got truncated when converting ggplot object using ggplotly but it's fine when using plot_ly

Hi all, as a work-around approah to display a very long multi-column legend, I tried to use the layout(legend = list(orientation = "h")).

Here is the data_frame I was working with:

When I first built a ggplot object and then used ggplotly to convert it, I got this:
p <- ggplot(df, aes_string("cluster", "mCH", fill="cluster"))
p <- p + geom_boxplot() + scale_fill_manual(values = colors2, name="Cluster") + theme_bw() + ggtitle("someGene")
p.ggplotly <- p %>% ggplotly(tooltip = c("cluster", "mCH", "density")) %>% layout(legend = list(orientation = "h"))
p.ggplotly

The legend had only one row and it just got out of the margin... But when I did a similar thing using plot_ly the legend was fine:

p.plotly <- plot_ly(df,x=~cluster, y=~mCH,type="box", color=~cluster, colors=colors2) %>% layout(legend=list(orientation = "h"))
p.plotly

And I thought this is somehow control by the layout, so I tried copying the layout from p.plotly to p.ggplotly:
p.ggplotly.bak <- p.ggplotly
p.ggplotly$x$layout <- p.plotly$x$layout
But the legend was still truncated...
p.ggplotly

However if I did it the other way around, I got a something like this:
p.plotly$x$layout <- p.ggplotly.bak$x$layout
p.plotly

The legend was displayed correctly with multiple rows(even though the position was not right, but I know how to adjust for that).

I'm not sure if this is because the ggplotly and plot_ly is inherently different, or there're other options that can controll this behavior (or this is just a bug?). Any idea? I somehow prefer to use ggplotly...

FYI, ggplot2 version is 2.2.1 and plotly version is 4.5.6.9000. Thanks!

使用报告中的 ggplot2 和 plotly R 示例复现该问题，将 ggplotly 转换与等效的 plot_ly 图表以及水平图例布局进行比较。跟踪转换和渲染行为，以确定 ggplotly 图例被截断的原因，然后验证较长的图例可以跨多行显示，同时不会破坏报告中所述的绘图行为。