TextFieldCursor.kt
/*
* Copyright 2020 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package androidx.compose.foundation.text2
import androidx.compose.animation.core.Animatable
import androidx.compose.animation.core.AnimationSpec
import androidx.compose.animation.core.infiniteRepeatable
import androidx.compose.animation.core.keyframes
import androidx.compose.foundation.ExperimentalFoundationApi
import androidx.compose.runtime.LaunchedEffect
import androidx.compose.runtime.remember
import androidx.compose.ui.Modifier
import androidx.compose.ui.MotionDurationScale
import androidx.compose.ui.composed
import androidx.compose.ui.draw.drawWithContent
import androidx.compose.ui.geometry.Offset
import androidx.compose.ui.geometry.Rect
import androidx.compose.ui.graphics.Brush
import androidx.compose.ui.graphics.SolidColor
import androidx.compose.ui.graphics.isUnspecified
import androidx.compose.ui.unit.dp
import kotlinx.coroutines.withContext
@OptIn(ExperimentalFoundationApi::class)
internal fun Modifier.cursor(
textLayoutState: TextLayoutState,
isFocused: Boolean,
state: TextFieldState,
cursorBrush: Brush,
enabled: Boolean
) = if (enabled) composed {
val cursorAlpha = remember { Animatable(1f) }
val isBrushSpecified = !(cursorBrush is SolidColor && cursorBrush.value.isUnspecified)
val value = state.value
if (isFocused && value.selection.collapsed && isBrushSpecified) {
LaunchedEffect(value.annotatedString, value.selection) {
// Animate the cursor even when animations are disabled by the system.
withContext(FixedMotionDurationScale) {
// ensure that the value is always 1f _this_ frame by calling snapTo
cursorAlpha.snapTo(1f)
// then start the cursor blinking on animation clock (500ms on to start)
cursorAlpha.animateTo(0f, cursorAnimationSpec)
}
}
drawWithContent {
this.drawContent()
val cursorAlphaValue = cursorAlpha.value.coerceIn(0f, 1f)
if (cursorAlphaValue != 0f) {
val cursorRect = textLayoutState.layoutResult?.getCursorRect(value.selection.start)
?: Rect(0f, 0f, 0f, 0f)
val cursorWidth = DefaultCursorThickness.toPx()
val cursorX = (cursorRect.left + cursorWidth / 2)
.coerceAtMost(size.width - cursorWidth / 2)
drawLine(
cursorBrush,
Offset(cursorX, cursorRect.top),
Offset(cursorX, cursorRect.bottom),
alpha = cursorAlphaValue,
strokeWidth = cursorWidth
)
}
}
} else {
Modifier
}
} else this
private val cursorAnimationSpec: AnimationSpec<Float> = infiniteRepeatable(
animation = keyframes {
durationMillis = 1000
1f at 0
1f at 499
0f at 500
0f at 999
}
)
internal val DefaultCursorThickness = 2.dp
private object FixedMotionDurationScale : MotionDurationScale {
override val scaleFactor: Float
get() = 1f
}