distance measurer

app/src/main/java/com/mirenkov/ktheightmap/MapCanvas.kt

@@ -49,6 +49,7 @@ fun MapCanvas(
     var pointLat by rememberSaveable { viewModel.rememberedPointLat }
     var pointLon by rememberSaveable { viewModel.rememberedPointLon }
     var invokeHeightCalc by remember { mutableStateOf(false) }
+    val startTargetMeters = 64 * 1000 * 1000
     Canvas(
         modifier = modifier.fillMaxSize()
             .pointerInput(Unit) {
@@ -93,6 +94,10 @@ fun MapCanvas(
             }
         }
 
+        val targetMeters = startTargetMeters shr level
+        val targetPixels = (targetMeters).toFloat() / SphereMercator.scaledMetersPerPixel(level)
+        val measurerHeight = 24F
+
         val centerTileX = (1 + (offsetX + halvedX) / TILE_SIZE).toDouble()
         val centerTileY = (1 + (offsetY + halvedY) / TILE_SIZE).toDouble()
 
@@ -239,19 +244,31 @@ fun MapCanvas(
         }
 
         // Cursor path
-        val path = Path()
+        val cursorPath = Path()
-        path.moveTo(halvedX - crossRadius, halvedY)
+        with(cursorPath) {
-        path.lineTo(halvedX + crossRadius, halvedY)
+            moveTo(halvedX - crossRadius, halvedY)
-        path.moveTo(halvedX, halvedY - crossRadius)
+            lineTo(halvedX + crossRadius, halvedY)
-        path.lineTo(halvedX, halvedY + crossRadius)
+            moveTo(halvedX, halvedY - crossRadius)
-        path.close()
+            lineTo(halvedX, halvedY + crossRadius)
+            close()
+        }
 
         // Cursor
         drawPath(
-            path,
+            cursorPath,
             Color.White,
             style = Stroke(width = 6F)
         )
+        // Height under cursor
+        drawText(
+            textMeasurer = textMeasurer,
+            text = buildAnnotatedString {
+                withStyle(SpanStyle(color = Color.White)) {
+                    append("${KhmParser.getHeight(lon, lat, ctx)}m")
+                }
+            },
+            topLeft = Offset(halvedX + crossRadius, halvedY + crossRadius)
+        )
 
         // Info box
         drawRect(
@@ -277,15 +294,41 @@ fun MapCanvas(
             topLeft = latLonOffset
         )
 
-        // Height under cursor
+        // Distance measurer path
+        val measurerPath = Path()
+        with(measurerPath) {
+            moveTo((halvedX - targetPixels).toFloat(), 8F)
+            relativeLineTo(0F, measurerHeight)
+            relativeMoveTo(targetPixels.toFloat() * 2F, 0F)
+            relativeLineTo(0F, -measurerHeight)
+            relativeMoveTo(0F, measurerHeight / 2F)
+            relativeLineTo(-2F * targetPixels.toFloat(), 0F)
+            close()
+        }
+
+        // Distance measurer
+        drawPath(
+            measurerPath,
+            Color.White,
+            style = Stroke(width = 6F)
+        )
+
+        // Distance measurer text
         drawText(
             textMeasurer = textMeasurer,
             text = buildAnnotatedString {
+                withStyle(ParagraphStyle(textAlign = TextAlign.Center)) {
                     withStyle(SpanStyle(color = Color.White)) {
-                    append("${KhmParser.getHeight(lon, lat, ctx)}m")
+                        val text = if (targetMeters >= 100000)
+                            "${targetMeters / 1000}km"
+                        else
+                            "${targetMeters}m"
+                        append(text)
+                    }
                 }
             },
-            topLeft = Offset(halvedX + crossRadius, halvedY + crossRadius)
+            topLeft = Offset(targetPixels.toFloat() * 2F, measurerHeight),
+            size = Size(targetPixels.toFloat() * 2F, 48F)
         )
     }
 }