Horizontally adjacent plots separated by larger margin in v0.23.0

[ryanavella]

Describe the bug
When switching from egui::plot (v0.22.0) to egui_plot (v0.23.0), horizontally adjacent plots are now separated by an awkwardly large margin.

To Reproduce

This is an attempt to produce a MRE from my own code, it might be further reducible. For v0.23.0, replace egui::plot with egui_plot

use eframe::egui::{self};
use egui::plot::{Line, Plot, PlotPoints};

fn main() {
    let _ = eframe::run_native("", Default::default(), Box::new(|_cc| Box::new(Foo)));
}
struct Foo;

impl eframe::App for Foo {
    fn update(&mut self, ctx: &egui::Context, _frame: &mut eframe::Frame) {
        egui::CentralPanel::default().show(ctx, |ui| {
            const SIZE: f32 = 200.0;

            let v = vec![[0.0, 0.0], [1.0, 1.0]];

            ui.horizontal(|ui| {
                Plot::new(0).height(SIZE).width(SIZE).show(ui, |ui| {
                    ui.line(Line::new(PlotPoints::from(v.clone())));
                });
                Plot::new(1).height(SIZE).width(SIZE).show(ui, |ui| {
                    ui.line(Line::new(PlotPoints::from(v)));
                });
            });
        });
    }
}

Expected behavior

Probably the old behavior from v0.22.0?

Screenshots

v0.22.0

v0.23.0

Desktop (please complete the following information):

• OS: Windows 10
• Browser: Chrome
• Version: v0.23.0

[YgorSouza]

As the axes are now outside the plot viewbox, the widget has to reserve some room for them. This is controlled by the y_axis_width or the custom_y_axes methods.

The code actually has a little diagram explaining how it works.

https://github.com/emilk/egui/blob/2bc2fb9c393bbbfc4832a35af1c100bc4ea48719/crates/egui_plot/src/lib.rs#L767-L788

There doesn't seem to be any way to restore the previous behavior with the axes inside the plot, though (I could be wrong about that, as I haven't kept up with this development and there is a lot of code to read through).

[ryanavella]

Nice catch! I was quickly comparing 0.22.0 and 0.23.0 side-by-side and didn't notice any API differences, but I totally missed the addition of the new methods Plot::y_axis_width and Plot::custom_y_axes.

Applying .y_axis_width(1) gets me 90% of the way there, but there is one big downside: my plots are dynamically updating so I can't predict with certainty how long the tick labels are. Some tick labels will just be 0 and others might be -1e2, for example.

One solution could be adding new variants to HPlacement for inline labels, though I haven't been following development so I don't know how simple it is to bring back the old behavior. If there was a lot of major refactoring between 0.22.0 and 0.23.0 for example, I could see this being a very non-trivial task.