Proposal: Use integers for FontStyle

[joachimschmidt557]

Currently, FontStyle is represented as a (possibly packed after #5) struct of bools.

I think using integer types and bitwise operations, we could achieve better and possibly faster functionality. Consider the following simplified example:

const FontStyle = u3;

const default: FontStyle = 0b000;
const bold: FontStyle = 0b001;
const dim: FontStyle = 0b010;
const italic: FontStyle = 0b100;

Combining font styles can be done with bitwise or; checking for a style can be done with bitwise and.

cc @data-man

[data-man]

I think bitwise operations will decrease output's performance.

[joachimschmidt557]

@data-man That may be right for checking a specific field of the FontStyle, i.e. checking whether font_style.bold == true. When using integers, we have an additional overhead of one bitwise operation in addition to the comparison.

But for other purposes, this has increased performance:

• checking if multiple fields are set
• checking for equality (includes checking isDefault)
• checking if a given font style has at least the attributes of another font style (no attributes were removed)

All operations are turned into O(1) operations instead of O(n) where n is the number of fields.

[data-man]

When using integers, we have an additional overhead of one bitwise operation in addition to the comparison.

And for convenience, some helpers will be needed: isBold/setBold, etc.

[joachimschmidt557]

@data-man Yes, that would aid the usability of FontStyle if it would be represented as an integer. But those will be small functions which will be almost-surely inlined in a release build, so the overhead of an additional function call won't be there, only the overhead of the bitwise operation then.

I'll leave this proposal open until some benchmarks have been integrated into the library. From then on, we can test the performance of checking attributes/setting attributes/checking equality/subset of attributes/etc. And from these results, we can then proceed to select the appropriate representation of FontStyle

[data-man]

@joachimschmidt557
I think helpers for RGB type are more important. Maybe in new module.
Rust's rgb24 as example.

[joachimschmidt557]

@data-man If you want, feel free to implement that.

[data-man]

pub const FontStyle = packed struct {
...
const Self = @This();
...
pub fn asUInt(self: Self) u11 {
    return @bitCast(u11, self);
}
...

?

[joachimschmidt557]

@data-man Yup, don't know why this hasn't occurred to me yet. This means we can get the best of both worlds. I guess we can close this issue now.