combo-breaker

Introduction: Text layout for Compose to flow text around arbitrary shapes.
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combo-breaker combo-breaker-material3 Android build status

Composable widget for Jetpack Compose that allows to flow text around arbitrary shapes over multiple columns. The TextFlow composable behaves as a Box layout and will automatically flow the text content around its children.

Features

  • Multi-column layout
  • Styled strings (AnnotatedString)
  • Default rectangular shapes
  • Arbitrary shapes (any Path)
  • Justification
  • Hyphenation
  • Compatible with API 29+

Design Systems

Combo Breaker provides two levels of APIs depending on what design system you use:

  • BasicTextFlow from the dev.romainguy:combo-breaker artifact, which works with any design system
  • TextFlow from the dev.romainguy:combo-breaker-material3 artifact, which works with Material3

Choose BasicTextFlow if you do not have or do not want a dependency on androidx.compose.material3:material3.

Examples

The following code defines two images to flow text around:

TextFlow(
    SampleText,
    style = TextStyle(fontSize = 14.sp),
    columns = 2
) {
    Image(
        bitmap = letterT.asImageBitmap(),
        contentDescription = "",
        modifier = Modifier
            .flowShape(FlowType.OutsideEnd)
    )

    Image(
        bitmap = badgeBitmap.asImageBitmap(),
        contentDescription = "",
        modifier = Modifier
            .align(Alignment.Center)
            .flowShape(margin = 6.dp)
    )
}

Flow around rectangular shapes

Any child of TextFlow allows text to flow around a rectangular shape of the same dimensions of the child. The flowShape modifier is used to control where text flows around the shape (to the right/end of the T) and around both the left and right sides of the landscape photo (default behavior). In addition, you can define a margin around the shape.

The flowShape modifier also lets you specify a specific shape instead of a default rectangle. This can be done by passing a Path or a lambda that returns a Path. The lambda alternative is useful when you need to create a Path based on the dimensions of the TextFlow or the dimensions of its child.

Here is an example of a TextFlow using non-rectangular shapes:

val microphoneShape = microphoneBitmap.toPath(alphaThreshold = 0.5f).asComposePath()
val badgeShape = badgeShape.toPath(alphaThreshold = 0.5f).asComposePath()

TextFlow(
    SampleText,
    style = TextStyle(fontSize = 14.sp),
    columns = 2
) {
    Image(
        bitmap = microphoneBitmap.asImageBitmap(),
        contentDescription = "",
        modifier = Modifier
            .offset { Offset(-microphoneBitmap.width / 4.5f, 0.0f).round() }
            .flowShape(FlowType.OutsideEnd, 6.dp, microphoneShape)
    )

    Image(
        bitmap = badgeBitmap.asImageBitmap(),
        contentDescription = "",
        modifier = Modifier
            .align(Alignment.Center)
            .flowShape(FlowType.Outside, 6.dp, badgeShape)
    )
}

The non-rectangular Path shape is created using the extension Bitmap.toPath from the pathway library. Using that API, a shape can be extracted from a bitmap and used as the flow shape for the desired child:

Flow around non-rectangular shapes

TextFlow supports multiple text styles and lets you control justification and hyphenation. In the example below, both justification and hyphenation are enabled:

Justification and hyphenation

You can also specify multiple shapes for any given element by using the flowShapes modifiers instead of flowShape. flowShapes accepts/returns list of paths instead of a single path. For instance, with pathway you can easily extract a list of paths from a Bitmap by using Bitmap.toPaths() instead of Bitmap.toPath().

val heartsShapes = heartsBitmap.toPaths().map { it.asComposePath() }

TextFlow(
    SampleText,
    style = TextStyle(fontSize = 12.sp),
    columns = 2
) {
    Image(
        bitmap = heartsBitmap.asImageBitmap(),
        contentDescription = "",
        modifier = Modifier
            .align(Alignment.Center)
            .flowShapes(FlowType.Outside, 4.dp, heartsShapes)
    )
}

This creates many shapes around which the text can flow:

Multiple shapes per element

Maven

repositories {
    // ...
    mavenCentral()
}

dependencies {
    // Use this library and BasicTextFlow() if you don't want a dependency on material3
    implementation 'dev.romainguy:combo-breaker:0.8.0'

    // Use this library and TextFlow() if you use material3
    implementation 'dev.romainguy:combo-breaker-material3:0.8.0'
}

Roadmap

  • Backport to earlier API levels.
  • Lines containing styles of different line heights can lead to improper flow around certain shapes.
  • More comprehensive TextFlowLayoutResult.
  • Add support to ellipsize the last line when the entire text cannot fit in the layout area.
  • Add support for text-relative placement of flow shapes.
  • Implement margins support without relying on Path.op which can be excessively expensive with complex paths.
  • BiDi text hasn't been tested yet, and probably doesn't work properly (RTL layouts are however supported for the placement of flow shapes and the handling of columns).
  • Improve performance of contours extraction from an image (could be multi-threaded for instance).
  • Investigate an alternative and simpler way to handle placement around shapes (beam cast instead of the purely geometric approach that currently requires a lot of intersection work).
  • Support flowing text inside shapes.

License

Please see LICENSE.

Attribution

The render of the microphone was made possible thanks to RCA 44-BX Microphone by Tom Seddon, licensed under Creative Commons Attribution.

Sample text taken from the Wikipedia Hyphen article.

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