Simplifying StyleSheet implementations

[TimUntersberger]

Right now any StyleSheet has a list of functions without a default implementation. Implementing a StyleSheet is really annoying, because you have to override all of the functions and not just the thing you want to change.

I recently wanted to just change the border_radius of a text_input and I had to write the following code.

impl StyleSheet for Styles {
    fn active(&self) -> Style {
        Style {
            border_radius: 0,
            ..Style::default()
        }
    }

    fn focused(&self) -> Style {
        Style {
            border_color: Color::from_rgb(0.5, 0.5, 0.5),
            ..self.active()
        }
    }

    fn placeholder_color(&self) -> Color {
        Color::from_rgb(0.7, 0.7, 0.7)
    }

    fn value_color(&self) -> Color {
        Color::from_rgb(0.3, 0.3, 0.3)
    }

    fn selection_color(&self) -> Color {
        Color::from_rgb(0.8, 0.8, 1.0)
    }
}

As you can see I mostly just copied your sourcecode.

If StyleSheets would have these default styles as default implementation like this:

trait StyleSheet {
    fn active(&self) -> Style {
        Style {
            background: Background::Color(Color::WHITE),
            border_radius: 0,
            border_width: 1.0,
            border_color: Color::from_rgb(0.7, 0.7, 0.7),
        }
    }

    fn focused(&self) -> Style {
        Style {
            border_color: Color::from_rgb(0.5, 0.5, 0.5),
            ..self.active()
        }
    }

    fn placeholder_color(&self) -> Color {
        Color::from_rgb(0.7, 0.7, 0.7)
    }

    fn value_color(&self) -> Color {
        Color::from_rgb(0.3, 0.3, 0.3)
    }

    fn selection_color(&self) -> Color {
        Color::from_rgb(0.8, 0.8, 1.0)
    }
}

Implementing StyleSheets would be way more easy. Changing the border_radius would now only require the following code:

impl StyleSheet for Styles {
    fn active(&self) -> Style {
        Style {
            border_radius: 0,
            ..Style::default()
        }
    }
}

Is there a reason why StyleSheets are implemented like this right now?

[hecrj]

I think it's a good idea.

Is there a reason why StyleSheets are implemented like this right now?

No particular reason. In fact, the button::StyleSheet trait already does it.

If anyone wants to give this a shot, feel free!

[TimUntersberger]

I will open a PR for this later this week.

[TimUntersberger]

How would you want to do default styles which can be extended?

What if any function that returns a Style receives the default style as argument?

[13r0ck]

I don't think that is how button::Stylesheet does it. I'm not against different techniques though, why do you think that that would be better?

[TimUntersberger]

I'm not against different techniques though, why do you think that that would be better?

If you are talking about my previous comment then because I don't know how to override the active style of a button for example without having to set each field.

Example:

impl button::StyleSheet for Style {
  fn active(&self) -> button::Style {
    // here I have to create the whole button::Style struct which requires me to know about the default values
  }
}

After thinking about this some more I discovered that button::Default exists. Maybe making the Default styles accessible to the users would we a solution?

Example:

impl button::StyleSheet for Style {
  fn active(&self) -> button::Style {
    let mut style = button::DefaultStyle.active(); // renamed to DefaultStyle for clarity
    // do something with style
    style
  }
}

[13r0ck]

Maybe this is something that could be solved with code generation?
Like from your first comment, you are basically setting what you want, then copying and pasting the rest from iced's source. Which code generation could totally do

Something like?

#[derive(Styles)]
impl StyleSheet for Styles {
    fn active(&self) -> Style {
        Style {
            border_radius: 0,
            ..Style::default()
        }
    }
}

[TimUntersberger]

I created a draft PR which prototypes the idea I mentioned above using a button.

[13r0ck]

@hecrj I think thi should be closed because of #1362, as #781 was for the same reason.