Text alignment logic is backwards for non-special-cases

[prestidigitator-mt]

Describe the bug
Renderer (e.g. Renderer.PlaceHorizontal and Renderer.PlaceVertical) places text using inverse of correct padding for any positions other than 0 (left/top), 1 (right/bottom), and 0.5 (due to symmetry)

Setup
Please complete the following information along with version numbers, if applicable.

• OS: Arch Linux
• Shell: bash
• Terminal Emulator: konsole
• Terminal Multiplexer: tmux
• Locale: en_US.UTF-8
• Versions: 0.9.1 and (at time of submission) the latest commit on master
• Go Version: go version go1.21.1 linux/amd64

To Reproduce
Steps to reproduce the behavior:

1. In a new directory, save the given source code as lg_test.go
2. Run go mod init lgtest
3. Run go get github.com/charmbracelet/[email protected] (or, at time-of-submission, go get github.com/charmbracelet/lipgloss@master)
4. Run go test .
5. Notice that test cases 2 and 5 of both tests fail. This is due to the left, right, top, and bottom placement being special-cased, while all positions in between use logic which is exactly backwards for calculating the padding (e.g.

   lipgloss/position.go

   Lines 83 to 85 in b0605d3

   	split := int(math.Round(float64(totalGap) * pos.value()))
   	left := totalGap - split
   	right := totalGap - left

   ).

Source Code

package main

import (
    "testing"

    "github.com/charmbracelet/lipgloss"
)


type blackhole struct{}
func (bh blackhole) Write(b []byte) (int, error) { return len(b), nil }


func TestPlaceHorizontal(t *testing.T) {
    testCases := []struct{
        w   int
        s   string
        pos lipgloss.Position
        exp string
    }{
        {w: 10, s: "Hello", pos: lipgloss.Left,  exp: "Hello     "},
        {w: 10, s: "Hello", pos: 0,              exp: "Hello     "},
        {w: 10, s: "Hello", pos: 0.000000001,    exp: "Hello     "},
        {w: 10, s: "Hello", pos: lipgloss.Right, exp: "     Hello"},
        {w: 10, s: "Hello", pos: 1,              exp: "     Hello"},
        {w: 10, s: "Hello", pos: 0.999999999,    exp: "     Hello"},
    }

    for tci, tc := range testCases {
        r := lipgloss.NewRenderer(blackhole{})

        act := r.PlaceHorizontal(tc.w, tc.pos, tc.s)
        exp := tc.exp

        if exp != act {
            t.Errorf("tc #%d: expected %q, got %q", tci, exp, act)
        }
    }
}

func TestPlaceVertical(t *testing.T) {
    testCases := []struct{
        h   int
        s   string
        pos lipgloss.Position
        exp string
    }{
        {h: 3, s: "Hello", pos: lipgloss.Top,    exp: "Hello\n     \n     "},
        {h: 3, s: "Hello", pos: 0,               exp: "Hello\n     \n     "},
        {h: 3, s: "Hello", pos: 0.000000001,     exp: "Hello\n     \n     "},
        {h: 3, s: "Hello", pos: lipgloss.Bottom, exp: "     \n     \nHello"},
        {h: 3, s: "Hello", pos: 1,               exp: "     \n     \nHello"},
        {h: 3, s: "Hello", pos: 0.999999999,     exp: "     \n     \nHello"},
    }

    for tci, tc := range testCases {
        r := lipgloss.NewRenderer(blackhole{})

        act := r.PlaceVertical(tc.h, tc.pos, tc.s)
        exp := tc.exp

        if exp != act {
            t.Errorf("tc #%d: expected %q, got %q", tci, exp, act)
        }
    }
}

Expected behavior

All tests pass.

Screenshots

--- FAIL: TestPlaceHorizontal (0.00s)
    lg_test.go:36: tc #2: expected "Hello     ", got "     Hello"
    lg_test.go:36: tc #5: expected "     Hello", got "Hello     "
--- FAIL: TestPlaceVertical (0.00s)
    lg_test.go:63: tc #2: expected "Hello\n     \n     ", got "     \n     \nHello"
    lg_test.go:63: tc #5: expected "     \n     \nHello", got "Hello\n     \n     "
FAIL
FAIL	lg-test	0.002s
FAIL

Additional context