Set sizes are fractions

[OvermindDL1]

Is your feature request related to a problem? Please describe.

Many areas take in something like impl Into<Vec2>, but this only allows setting a hard (logical) pixel size, which is limited because it can't work based on the viewable area, percentage, etc...

Describe the solution you'd like

It would be most convenient if the arguments that took a size took an enum instead, perhaps with a few useful heads like:

enum Size {
	LogicalPixel(float, float),     // Logical pixels...
	DevicePixel(float, float),      // Device pixels...
	ScreenPercentage(float, float), // 0.0 to 1.0 for the size of the overall screen dimensions
	ParentPercentage(float, float), // 0.0 to 1.0 for the available size the parent is offering it
	SelfPercantage(float, float),   // Multiplier of the 'preferred' size (so (2.0, 2.0) of a label
	                                // would double it's default size in each dimension)
}

Describe alternatives you've considered

Only real alternative that I see currently is calculating everything manually at every location you want to do something other than logical pixels, or reimplementing all the widgets and areas/panels.

[emilk]

I'm not convinced this is an improvement. The current system has the benefit of being simple: there is only one unit and one coordinate system. Going away from this will open up a can of complexity

• DevicePixel - I see no reason to want to say "this button should be this many physical pixels wide so that it looks different on different on different displays". Seems like an invitation to portability problems
• ScreenPercentage/ParentPercentage: Is Size::ScreenPercentage(0.2, 0.5) really better than vec2(0.2, 0.5) * screen_size ?
• ParentPercentage: what parent? the immediate one? and what size? it's current, or its maximum?

I think I need some concrete user stories to be convinced of this.

PS: You are also confusing percentages (0%-100%) with fractions (0-1)

[emilk]

Note that for Grid we do want some way to set a row/column size as a fraction of parent (see for instance #176 (comment))

[emilk]

Most of this can now be accomplished with egui_extras::Strip (#963), so I'm gonna close this.