compose-jb/tutorials/Mouse_Events/README.md

# Getting Started with Compose for Desktop

## What is covered

In this tutorial we will see how to install mouse event listeners on components
in Compose for Desktop.

## Mouse event listeners

### Click listeners

Click listeners are available in both Compose on Android and Compose for Desktop,
so code like this will work on both platforms:

```kotlin
import androidx.compose.desktop.Window
import androidx.compose.foundation.Text
import androidx.compose.foundation.clickable
import androidx.compose.foundation.layout.*
import androidx.compose.runtime.mutableStateOf
import androidx.compose.runtime.remember
import androidx.compose.ui.Alignment
import androidx.compose.ui.Modifier
import androidx.compose.ui.unit.IntSize
import androidx.compose.ui.unit.sp

fun main() = Window(title = "Compose for Desktop", size = IntSize(400, 400)) {
    var count = 0
    Box(alignment = Alignment.Center, modifier = Modifier.fillMaxWidth()) {
        var text = remember { mutableStateOf("Click me!") }
        Text(
                text = text.value,
                fontSize = 50.sp,
                modifier = Modifier
                        .clickable(
                            onClick = {
                                text.value = "Click! ${count++}"
                            },
                            onDoubleClick = {
                                text.value = "Double click! ${count++}"
                            },
                            onLongClick = {
                                text.value = "Long click! ${count++}"
                            }
                        )
                        .align(Alignment.Center)
        )
    }
}
```

![Application running](mouse_click.gif)

### Mouse move listeners

As typically mouse and other positional pointers are only available on desktop platforms,
the following code will only work with Compose for Desktop.
Let's create a window and install a pointer move filter on it that changes the background
color according to the mouse pointer position:
```kotlin
import androidx.compose.desktop.Window
import androidx.compose.foundation.background
import androidx.compose.foundation.layout.*
import androidx.compose.runtime.mutableStateOf
import androidx.compose.runtime.remember
import androidx.compose.ui.Alignment
import androidx.compose.ui.Modifier
import androidx.compose.ui.graphics.Color
import androidx.compose.ui.input.pointer.pointerMoveFilter
import androidx.compose.ui.unit.IntSize

fun main() = Window(title = "Compose for Desktop", size = IntSize(400, 400)) {
    var color = remember { mutableStateOf(Color(0, 0, 0)) }
    Box(
            modifier = Modifier
                    .wrapContentSize(Alignment.Center)
                    .fillMaxSize()
                    .background(color = color.value)
                    .pointerMoveFilter(
                            onMove = {
                                color.value = Color(it.x.toInt() % 256, it.y.toInt() % 256, 0)
                                false
                            }
                    )
    )
}
```

![Application running](mouse_move.gif)

### Mouse enter listeners

Compose for Desktop also supports pointer enter and exit handlers, like this:
```kotlin
import androidx.compose.desktop.Window
import androidx.compose.foundation.Text
import androidx.compose.foundation.background
import androidx.compose.foundation.layout.*
import androidx.compose.runtime.mutableStateOf
import androidx.compose.runtime.remember
import androidx.compose.ui.Modifier
import androidx.compose.ui.graphics.Color
import androidx.compose.ui.input.pointer.pointerMoveFilter
import androidx.compose.ui.text.font.FontStyle
import androidx.compose.ui.unit.IntSize
import androidx.compose.ui.unit.dp
import androidx.compose.ui.unit.sp

fun main() = Window(title = "Compose for Desktop", size = IntSize(400, 400)) {
    Column(verticalArrangement = Arrangement.spacedBy(10.dp)) {
        repeat(10) { index ->
            var active = remember { mutableStateOf(false) }
            Text(
                    modifier = Modifier
                            .fillMaxWidth()
                            .background(color = if (active.value) Color.Green else Color.White)
                            .pointerMoveFilter(
                                    onEnter = {
                                        active.value = true
                                        false
                                    },
                                    onExit = {
                                        active.value = false
                                        false
                                    }
                            ),
                    fontSize = 30.sp,
                    fontStyle = if (active.value) FontStyle.Italic else FontStyle.Normal,
                    text = "Item $index"
                )
        }
    }
}
```
![Application running](mouse_enter.gif)