Plot shrank or expanded when activating or deactivating legend keys

Basically, when I double-clicked on the legend keys to activate or deactive them, the plot shrank or expanded. I posted the issue on StackOverflow and the user mnist found that it was the empty string that caused the problem.

Here is the reprex

p <- ggplot(mpg, aes(x = displ, y = hwy, color = factor(cyl), shape = class)) +
geom_point(size = 3) +
    scale_color_manual(values = c("4" = "#abd9e9",
                                  "5" = "#2c7bb6",
                                  "6" = "#ff7f00",
                                  "8" = "#d7191c")) +
    scale_shape_manual(values = c(2, 5, 16, 17, 18, 19, 25)) +
    guides(color = guide_legend(title = "Cyl", order = 1),
           shape = guide_legend(title = "", order = 2)) +
    theme_classic(base_size = 16)
p

ggplotly(p) %>%
    layout(xaxis = list(autorange = "reversed",
                        tickvals = c(2, 3, 5, 6),                        
                        ticktext = c("2", "", "5", "6"))) 

首先使用 ggplotly 运行提供的 R reprex，并复现双击图例键时绘图大小发生变化的情况。跟踪图例激活期间如何处理空的图例标题或标签，然后验证切换这些键不再改变绘图尺寸。