Add ability to specify color and font of axis tick labels for each axis

[TommiKabelitz]

This allows specifying the color and font (through FontId) of the tick labels for each axis on a plot

All feedback and criticism of the API and implementation are much appreciated. I will note, to ensure that the fading of the tick label color is respected, I did the following

let text_color = if let Some(color) = self.hints.tick_label_color {
    color.gamma_multiply(strength.sqrt())
} else {
    super::color_from_strength(ui, strength)
};

and I don't love the duplication of the gamma_multiply, I just didn't want to touch the color_from_strength function without the all clear.

• Closes Add ability to specify the color of the axis tick labels #154
• I have followed the instructions in the PR template

[bircni]

import egui::FontId directly

[bircni]

import egui::Color32 directly

[bircni]

whats the default?
maybe set it to a default which we already use

[bircni]

else use Default::default()

[TommiKabelitz]

Currently the default is whatever is in ui.visuals().text_color() when the plot is actually rendered because this function

/// Determine a color from a 0-1 strength value.
pub fn color_from_strength(ui: &Ui, strength: f32) -> Color32 {
    let base_color = ui.visuals().text_color();
    base_color.gamma_multiply(strength.sqrt())
}

is called to determine the color when the plot is shown.

I am still just calling this function when color is None so the behavior is not changing. I could potentially move the default to the instantiation of AxisHints, but that would change the behavior in cases where ui.visuals().text_color() is changed between creation of the axes and showing the plot.

[bircni]

works for me

[bircni]

this comment is not necessary for this func

[bircni]

this comment is not necessary for this func

[bircni]

2x clones?
Is there something else possible?

[TommiKabelitz]

I could be mistaken, but I don't think so. Cloning FontId is pretty cheap as it is just an f32 and the FontFamily enum which is an Arc.

I think you need to clone in both cases as layout_no_wrap expects an owned FontId. When the font has not been specified we use the global one so you need to clone. When it is specified, you have to clone as we only have a reference to self and so cannot move it out of the shared reference.

The implications of changing layout_no_wrap to accept an owned value look to be significant at a glance.