Feature/Design System Shadow

designsystem/src/main/java/com/apeun/gidaechi/designsystem/component/modifier/ShadowModifier.kt

@@ -0,0 +1,105 @@
+package com.apeun.gidaechi.designsystem.component.modifier
+
+import android.graphics.BlurMaskFilter
+import android.graphics.Color.toArgb
+import androidx.compose.foundation.background
+import androidx.compose.foundation.layout.Box
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.Spacer
+import androidx.compose.foundation.layout.fillMaxSize
+import androidx.compose.foundation.layout.height
+import androidx.compose.foundation.layout.size
+import androidx.compose.runtime.Composable
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.draw.drawBehind
+import androidx.compose.ui.graphics.Color
+import androidx.compose.ui.graphics.Paint
+import androidx.compose.ui.graphics.drawscope.drawIntoCanvas
+import androidx.compose.ui.graphics.toArgb
+import androidx.compose.ui.tooling.preview.Preview
+import androidx.compose.ui.unit.Dp
+import androidx.compose.ui.unit.dp
+import com.apeun.gidaechi.designsystem.theme.SeugiTheme
+import com.apeun.gidaechi.designsystem.theme.White
+
+sealed class DropShadowType(
+    val blur: Dp,
+    val offsetY: Dp,
+    val color: Color,
+) {
+    data object Ev1 : DropShadowType(9.dp, 3.dp, Color(0x08000000))
+    data object Ev2 : DropShadowType(12.dp, 4.dp, Color(0x0F000000))
+    data object Ev3 : DropShadowType(18.dp, 6.dp, Color(0x14000000))
+}
+
+/**
+ * Seugi DropShadow
+ *
+ * @param type: the size of the shadow according to the design system.
+ * @param modifier: the Modifier to be applied to this drop shadow
+ */
+fun Modifier.dropShadow(type: DropShadowType, modifier: Modifier = Modifier) = then(
+    modifier.drawBehind {
+        drawIntoCanvas { canvas ->
+            type.run {
+                val paint = Paint()
+                val frameworkPaint = paint.asFrameworkPaint()
+                val spreadPixel = 0f
+                val leftPixel = (0f - spreadPixel) + 0f // offsetX
+                val topPixel = (0f - spreadPixel) + type.offsetY.toPx()
+                val rightPixel = size.width + spreadPixel
+                val bottomPixel = size.height + spreadPixel
+
+                frameworkPaint.color = type.color.toArgb()
+
+                if (type.blur != 0.dp) {
+                    frameworkPaint.maskFilter = BlurMaskFilter(
+                        type.blur.toPx(),
+                        BlurMaskFilter.Blur.NORMAL,
+                    )
+                }
+
+                canvas.drawRoundRect(
+                    left = leftPixel,
+                    top = topPixel,
+                    right = rightPixel,
+                    bottom = bottomPixel,
+                    radiusX = 0f,
+                    radiusY = 0f,
+                    paint = paint,
+                )
+            }
+        }
+    },
+)
+
+@Composable
+@Preview(showBackground = true)
+private fun ShadowModifierPreview() {
+    SeugiTheme {
+        Column(
+            modifier = Modifier.fillMaxSize(),
+        ) {
+            Box(
+                modifier = Modifier
+                    .size(50.dp)
+                    .dropShadow(DropShadowType.Ev1)
+                    .background(White),
+            )
+            Spacer(modifier = Modifier.height(30.dp))
+            Box(
+                modifier = Modifier
+                    .size(50.dp)
+                    .dropShadow(DropShadowType.Ev2)
+                    .background(White),
+            )
+            Spacer(modifier = Modifier.height(30.dp))
+            Box(
+                modifier = Modifier
+                    .size(50.dp)
+                    .dropShadow(DropShadowType.Ev3)
+                    .background(White),
+            )
+        }
+    }
+}