Fix for TAVRIDA-T-5

src/jvmMain/kotlin/centre/sciprog/maps/compose/MapViewJvm.kt

@@ -1,23 +1,20 @@
 package centre.sciprog.maps.compose
 
 import androidx.compose.foundation.Canvas
-import androidx.compose.foundation.gestures.detectDragGestures
+import androidx.compose.foundation.gestures.drag
+import androidx.compose.foundation.gestures.forEachGesture
 import androidx.compose.foundation.layout.fillMaxSize
 import androidx.compose.runtime.*
 import androidx.compose.ui.ExperimentalComposeUiApi
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.geometry.Offset
+import androidx.compose.ui.geometry.Rect
 import androidx.compose.ui.graphics.Color
-import androidx.compose.ui.graphics.drawscope.DrawScope
+import androidx.compose.ui.graphics.PathEffect
-import androidx.compose.ui.graphics.drawscope.clipRect
+import androidx.compose.ui.graphics.drawscope.*
-import androidx.compose.ui.graphics.drawscope.drawIntoCanvas
-import androidx.compose.ui.graphics.drawscope.translate
 import androidx.compose.ui.graphics.nativeCanvas
 import androidx.compose.ui.graphics.toArgb
-import androidx.compose.ui.input.pointer.PointerEventType
+import androidx.compose.ui.input.pointer.*
-import androidx.compose.ui.input.pointer.PointerInputChange
-import androidx.compose.ui.input.pointer.onPointerEvent
-import androidx.compose.ui.input.pointer.pointerInput
 import androidx.compose.ui.unit.*
 import centre.sciprog.maps.*
 import mu.KotlinLogging
@@ -25,8 +22,8 @@ import org.jetbrains.skia.Font
 import org.jetbrains.skia.Paint
 import kotlin.math.ceil
 import kotlin.math.floor
+import kotlin.math.log2
 import kotlin.math.pow
-import kotlin.math.roundToInt
 
 
 private fun Color.toPaint(): Paint = Paint().apply {
@@ -39,6 +36,7 @@ private val logger = KotlinLogging.logger("MapView")
 /**
  * A component that renders map and provides basic map manipulation capabilities
  */
+@OptIn(ExperimentalComposeUiApi::class)
 @Composable
 actual fun MapView(
     initialViewPoint: MapViewPoint,
@@ -73,20 +71,62 @@ actual fun MapView(
      */
     fun DpOffset.toGeodetic() = WebMercatorProjection.toGeodetic(toMercator())
 
-    @OptIn(ExperimentalComposeUiApi::class)
+    // Selection rectangle. If null - no selection
-    val canvasModifier = modifier.onPointerEvent(PointerEventType.Press) {
+    var selectRect by remember { mutableStateOf<Rect?>(null) }
-        val (xPos, yPos) = it.changes.first().position
+
-        onClick(DpOffset(xPos.toDp(), yPos.toDp()).toGeodetic())
+    val canvasModifier = modifier.pointerInput(Unit) {
+        forEachGesture {
+            awaitPointerEventScope {
+                val event: PointerEvent = awaitPointerEvent()
+                event.changes.forEach { change ->
+                    if (event.buttons.isPrimaryPressed) {
+                        //Evaluating selection frame
+                        if (event.keyboardModifiers.isShiftPressed) {
+                            selectRect = Rect(change.position, change.position)
+                            drag(change.id) { dragChange ->
+                                selectRect?.let { rect ->
+                                    val offset = dragChange.position
+                                    selectRect = Rect(
+                                        kotlin.math.min(offset.x, rect.left),
+                                        kotlin.math.min(offset.y, rect.top),
+                                        kotlin.math.max(offset.x, rect.right),
+                                        kotlin.math.max(offset.y, rect.bottom)
+                                    )
+                                }
+                            }
+                            selectRect?.let { rect ->
+                                val (centerX, centerY) = rect.center
+                                val centerGmc = DpOffset(centerX.toDp(), centerY.toDp()).toGeodetic()
+
+                                val horizontalZoom: Float = log2(canvasSize.width.toPx() / rect.width)
+                                val verticalZoom: Float = log2(canvasSize.height.toPx() / rect.height)
+
+
+                                viewPoint = MapViewPoint(centerGmc, viewPoint.zoom + kotlin.math.min(verticalZoom, horizontalZoom))
+                                selectRect = null
+                            }
+                        } else {
+                            val dragStart = change.position
+                            val dpPos = DpOffset(dragStart.x.toDp(), dragStart.y.toDp())
+                            onClick(dpPos.toGeodetic())
+                            drag(change.id) { dragChange ->
+                                val dragAmount = dragChange.position - dragChange.previousPosition
+                                viewPoint = viewPoint.move(
+                                    -dragAmount.x.toDp().value / tileScale,
+                                    +dragAmount.y.toDp().value / tileScale
+                                )
+                            }
+                        }
+                    }
+                }
+            }
+        }
     }.onPointerEvent(PointerEventType.Scroll) {
         val change = it.changes.first()
         val (xPos, yPos) = change.position
         //compute invariant point of translation
         val invariant = DpOffset(xPos.toDp(), yPos.toDp()).toGeodetic()
         viewPoint = viewPoint.zoom(-change.scrollDelta.y.toDouble() * config.zoomSpeed, invariant)
-    }.pointerInput(Unit) {
-        detectDragGestures { _: PointerInputChange, dragAmount: Offset ->
-            viewPoint = viewPoint.move(-dragAmount.x.toDp().value / tileScale, +dragAmount.y.toDp().value / tileScale)
-        }
     }.fillMaxSize()
 
 
@@ -189,5 +229,17 @@ actual fun MapView(
                 drawFeature(zoom, feature)
             }
         }
+        selectRect?.let { rect ->
+            drawRect(
+                color = Color.Blue,
+                topLeft = rect.topLeft,
+                size = rect.size,
+                alpha = 0.5f,
+                style = Stroke(
+                    width = 2f,
+                    pathEffect = PathEffect.dashPathEffect(floatArrayOf(10f, 10f), 0f)
+                )
+            )
+        }
     }
 }