add GradientOffset for rotating gradients by 45 degrees

Author: SmartToolFactory

extendedcolors/src/main/java/com/smarttoolfactory/extendedcolors/GradientOffset.kt

@@ -0,0 +1,85 @@
+package com.smarttoolfactory.extendedcolors
+
+import androidx.compose.ui.geometry.Offset
+
+/**
+ *
+ * Get a [GradientOffset] that rotate a gradient clockwise with specified angle in degrees.
+ * Default value for [GradientOffset] is [GradientAngle.CW0] which is 0 degrees
+ * that returns a horizontal gradient.
+ *
+ * Get start and end offsets that are limited between [0f, Float.POSITIVE_INFINITY] in x and
+ * y axes wrapped in [GradientOffset].
+ * Infinity is converted to Composable width on x axis, height on y axis in shader.
+ *
+ * Default angle for [Brush.linearGradient] when no offset is 0 degrees in Compose ,
+ * [Brush.verticalGradient]  is [Brush.linearGradient] with 90 degrees.
+ *
+ * ```
+ *  0 degrees
+ *  start = Offset(0f,0f),
+ *  end = Offset(Float.POSITIVE_INFINITY,0f)
+ *
+ * 45 degrees
+ * start = Offset(0f, Float.POSITIVE_INFINITY),
+ * end = Offset(Float.POSITIVE_INFINITY, 0f)
+ *
+ * 90 degrees
+ * start = Offset(0f, Float.POSITIVE_INFINITY),
+ * end = Offset.Zero
+ *
+ * 135 degrees
+ * start = Offset.Infinity,
+ * end = Offset.Zero
+ *
+ * 180 degrees
+ * start = Offset(Float.POSITIVE_INFINITY, 0f),
+ * end = Offset.Zero,
+ *
+ * ```
+ */
+fun GradientOffset(angle: GradientAngle = GradientAngle.CW0): GradientOffset {
+    return when (angle) {
+        GradientAngle.CW45 -> GradientOffset(
+            start = Offset.Zero,
+            end = Offset.Infinite
+        )
+        GradientAngle.CW90 -> GradientOffset(
+            start = Offset.Zero,
+            end = Offset(0f, Float.POSITIVE_INFINITY)
+        )
+        GradientAngle.CW135 -> GradientOffset(
+            start = Offset(Float.POSITIVE_INFINITY, 0f),
+            end = Offset(0f, Float.POSITIVE_INFINITY)
+        )
+        GradientAngle.CW180 -> GradientOffset(
+            start = Offset(Float.POSITIVE_INFINITY, 0f),
+            end = Offset.Zero,
+        )
+        GradientAngle.CW225 -> GradientOffset(
+            start = Offset.Infinite,
+            end = Offset.Zero
+        )
+        GradientAngle.CW270 -> GradientOffset(
+            start = Offset(0f, Float.POSITIVE_INFINITY),
+            end = Offset.Zero
+        )
+        GradientAngle.CW315 -> GradientOffset(
+            start = Offset(0f, Float.POSITIVE_INFINITY),
+            end = Offset(Float.POSITIVE_INFINITY, 0f)
+        )
+        else -> GradientOffset(
+            start = Offset.Zero,
+            end = Offset(Float.POSITIVE_INFINITY, 0f)
+        )
+    }
+}
+
+/**
+ * Offset for [Brush.linearGradient] to rotate gradient depending on [start] and [end] offsets.
+ */
+data class GradientOffset(val start: Offset, val end: Offset)
+
+enum class GradientAngle {
+    CW0, CW45, CW90, CW135, CW180, CW225, CW270, CW315
+}