Merge changes Icd3e0c93,I8932e80c into main

* changes:
  TopologyScale: limit vertical padding
  TopologyScale values for scaling the topology pane

src/com/android/settings/connecteddevice/display/DisplayTopology.kt

@@ -19,9 +19,118 @@ package com.android.settings.connecteddevice.display
 import com.android.settings.R
 
 import android.content.Context
+import android.graphics.Point
+import android.graphics.PointF
+import android.graphics.RectF
 
 import androidx.preference.Preference
 
+import java.util.Locale
+
+import kotlin.math.max
+import kotlin.math.min
+
+/**
+ * Contains the parameters needed for transforming global display coordinates to and from topology
+ * pane coordinates. This is necessary for implementing an interactive display topology pane. The
+ * pane allows dragging and dropping display blocks into place to define the topology. Conversion to
+ * pane coordinates is necessary when rendering the original topology. Conversion in the other
+ * direction, to display coordinates, is necessary for resolve a drag position to display space.
+ *
+ * The topology pane coordinates are integral and represent the relative position from the upper-
+ * left corner of the pane. It uses a scale optimized for showing all displays with minimal or no
+ * scrolling. The display coordinates are floating point and the origin can be in any position. In
+ * practice the origin will be the upper-left coordinate of the primary display.
+ */
+class TopologyScale(paneWidth : Int, displaysPos : Collection<RectF>) {
+    /** Scale of block sizes to real-world display sizes. Should be less than 1. */
+    val blockRatio : Float
+
+    /** Height of topology pane needed to allow all display blocks to appear with some padding. */
+    val paneHeight : Int
+
+    /** Pane's X view coordinate that corresponds with topology's X=0 coordinate. */
+    val originPaneX : Int
+
+    /** Pane's Y view coordinate that corresponds with topology's Y=0 coordinate. */
+    val originPaneY : Int
+
+    init {
+        val displayBounds = RectF(
+                Float.MAX_VALUE, Float.MAX_VALUE, Float.MIN_VALUE, Float.MIN_VALUE)
+        var smallestDisplayDim = Float.MAX_VALUE
+        var biggestDisplayHeight = Float.MIN_VALUE
+
+        // displayBounds is the smallest rect encompassing all displays, in display space.
+        // smallestDisplayDim is the size of the smallest display edge, in display space.
+        for (pos in displaysPos) {
+            displayBounds.union(pos)
+            smallestDisplayDim = minOf(smallestDisplayDim, pos.height(), pos.width())
+            biggestDisplayHeight = max(biggestDisplayHeight, pos.height())
+        }
+
+        // Set height according to the width and the aspect ratio of the display bounds.
+        // 0.05 is a reasonable limit to the size of display blocks. It appears to match the
+        // ratio used in the ChromeOS topology editor. It prevents blocks from being too large,
+        // which would make dragging and dropping awkward.
+        val rawBlockRatio = min(0.05, paneWidth.toDouble() * 0.6 / displayBounds.width())
+
+        // If the `ratio` is set too low because one of the displays will have an edge less than
+        // 48dp long, increase it such that the smallest edge is that long. This may override the
+        // 0.05 limit since it is more important than it.
+        blockRatio = max(48.0 / smallestDisplayDim, rawBlockRatio).toFloat()
+
+        // Essentially, we just set the pane height based on the pre-determined pane width and the
+        // aspect ratio of the display bounds. But we may need to increase it slightly to achieve
+        // 20% padding above and below the display bounds - this is where the 0.6 comes from.
+        val rawPaneHeight = max(
+                paneWidth.toDouble() / displayBounds.width() * displayBounds.height(),
+                displayBounds.height() * blockRatio / 0.6)
+
+        // It is easy for the aspect ratio to result in an excessively tall pane, since the width is
+        // pre-determined and may be considerably wider than necessary. So we prevent the height
+        // from growing too large here, by limiting vertical padding to the size of the tallest
+        // display. This improves results for very tall display bounds.
+        paneHeight = min(
+                rawPaneHeight.toInt(),
+                (blockRatio * (displayBounds.height() + biggestDisplayHeight * 2f)).toInt())
+
+        // Set originPaneXY (the location of 0,0 in display space in the pane's coordinate system)
+        // such that the display bounds rect is centered in the pane.
+        // It is unlikely that either of these coordinates will be negative since blockRatio has
+        // been chosen to allow 20% padding around each side of the display blocks. However, the
+        // a11y requirement applied above (48.0 / smallestDisplayDim) may cause the blocks to not
+        // fit. This should be rare in practice, and can be worked around by moving the settings UI
+        // to a larger display.
+        val blockMostLeft = (paneWidth - displayBounds.width() * blockRatio) / 2
+        val blockMostTop = (paneHeight - displayBounds.height() * blockRatio) / 2
+
+        originPaneX = (blockMostLeft - displayBounds.left * blockRatio).toInt()
+        originPaneY = (blockMostTop - displayBounds.top * blockRatio).toInt()
+    }
+
+    /** Transforms coordinates in view pane space to display space. */
+    fun paneToDisplayCoor(panePos : Point) : PointF {
+        return PointF(
+                (panePos.x - originPaneX).toFloat() / blockRatio,
+                (panePos.y - originPaneY).toFloat() / blockRatio)
+    }
+
+    /** Transforms coordinates in display space to view pane space. */
+    fun displayToPaneCoor(displayPos : PointF) : Point {
+        return Point(
+                (displayPos.x * blockRatio).toInt() + originPaneX,
+                (displayPos.y * blockRatio).toInt() + originPaneY)
+    }
+
+    override fun toString() : String {
+        return String.format(
+                Locale.ROOT,
+                "{TopoScale blockRatio=%f originPaneXY=%d,%d paneHeight=%d}",
+                blockRatio, originPaneX, originPaneY, paneHeight)
+    }
+}
+
 const val PREFERENCE_KEY = "display_topology_preference"
 
 /**