Kotlin Jetpack Compose one sided stroke

In order to add a border to any side of a UI component
in Jetpack Compose, you can extend the Modifier class with
your own custom border functions that simply draw a custom line.

Here's how you can achieve this:

**For the top border:**

fun Modifier.topBorder(strokeWidth: Dp, color: Color) = composed(
    factory = {
        val density = LocalDensity.current    
        val strokeWidthPx = density.run { strokeWidth.toPx() }

        Modifier.drawBehind {
            val width = size.width
            val strokeWidthHalf = strokeWidthPx / 2

            drawLine(
                color = color,
                start = Offset(x = 0f, y = strokeWidthHalf),
                end = Offset(x = width, y = strokeWidthHalf),
                strokeWidth = strokeWidthPx
            )
        }
    }
)

**For the bottom border:**

fun Modifier.bottomBorder(strokeWidth: Dp, color: Color) = composed(
    factory = {
        val density = LocalDensity.current    
        val strokeWidthPx = density.run { strokeWidth.toPx() }

        Modifier.drawBehind {
            val width = size.width
            val height = size.height - strokeWidthPx / 2

            drawLine(
                color = color,
                start = Offset(x = 0f, y = height),
                end = Offset(x = width , y = height),
                strokeWidth = strokeWidthPx
            )
        }
    }
)

**For the left border:**

fun Modifier.leftBorder(strokeWidth: Dp, color: Color) = composed(
    factory = {
        val density = LocalDensity.current    
        val strokeWidthPx = density.run { strokeWidth.toPx() }

        Modifier.drawBehind {
            val height = size.height
            val strokeWidthHalf = strokeWidthPx / 2

            drawLine(
                color = color,
                start = Offset(x = strokeWidthHalf, y = 0f),
                end = Offset(x = strokeWidthHalf, y = height),
                strokeWidth = strokeWidthPx
            )
        }
    }
)

**For the right border:**

fun Modifier.rightBorder(strokeWidth: Dp, color: Color) = composed(
    factory = {
        val density = LocalDensity.current    
        val strokeWidthPx = density.run { strokeWidth.toPx() }

        Modifier.drawBehind {
            val width = size.width - strokeWidthPx / 2
            val height = size.height

            drawLine(
                color = color,
                start = Offset(x = width, y = 0f),
                end = Offset(x = width, y = height),
                strokeWidth = strokeWidthPx
            )
        }
    }
)

With these extension functions, you can easily add a border
to any side of your UI component by just appending the function
to the component's modifier. For example:

Text(
    text = "Hello, World!",
    modifier = Modifier.rightBorder(2.dp, Color.Black)
)

This will draw a black border with a thickness of 2.dp on the right side of the text.
Kotlin相关代码片段
