Adjust viewport center when in trackpad input mode.

remoting/android/java/src/org/chromium/chromoting/DesktopCanvas.java

Index: remoting/android/java/src/org/chromium/chromoting/DesktopCanvas.java
diff --git a/remoting/android/java/src/org/chromium/chromoting/DesktopCanvas.java b/remoting/android/java/src/org/chromium/chromoting/DesktopCanvas.java
index 778c395267e875f75548e8ff8aa6acc33aa484e0..2cc913d79301d30d85f9fbd142c61015f4d8371d 100644
--- a/remoting/android/java/src/org/chromium/chromoting/DesktopCanvas.java
+++ b/remoting/android/java/src/org/chromium/chromoting/DesktopCanvas.java
@@ -58,6 +58,18 @@ public class DesktopCanvas {
      */
     private RectF mVisibleImagePadding = new RectF();
 
+    /**
+     * Tracks whether to adjust the viewport to account for System UI. If false, the viewport
+     * center is the center of the screen.  If true, then System UI offsets will be used to
+     * adjust the position of the viewport to ensure the cursor is visible.
+     */
+    private boolean mAdjustViewportForSystemUi = false;
+
+    /**
+    * Represents the amount of space, in pixels, to adjust the cursor center along the y-axis.
+    */
+    private float mCursorOffsetScreenY = 0.0f;
+
     public DesktopCanvas(RenderStub renderStub, RenderData renderData) {
         mRenderStub = renderStub;
         mRenderData = renderData;
@@ -122,13 +134,35 @@ public class DesktopCanvas {
      */
     public void setSystemUiOffsetValues(int left, int top, int right, int bottom) {
         mSystemUiScreenSize.set(left, top, right, bottom);
+
+        if (mAdjustViewportForSystemUi) {
+            // Adjust the cursor position to ensure it's visible when large System UI (defined as
+            // 1/3 or more of the total screen size) is displayed.  This is typically the Soft
+            // Keyboard. Without this change, it is difficult for users to enter text into edit
+            // controls which are located bottom of the screen and may not be able to view their
+            // cursor at all.
+            if (bottom > (mRenderData.screenHeight / 3)) {
+                // Center the cursor within the viewable area (not obscured by System UI).
+                mCursorOffsetScreenY = (((float) mRenderData.screenHeight - bottom) / 2.0f);
+            } else {
+                mCursorOffsetScreenY = 0.0f;
+            }
+
+            // Apply the cursor offset.
+            setCursorPosition(mCursorPosition.x, mCursorPosition.y);
+        }
     }
 
     /** Called to indicate that no System UI is visible. */
     public void clearSystemUiOffsets() {
+        mCursorOffsetScreenY = 0.0f;
         mSystemUiScreenSize.setEmpty();
     }
 
+    public void adjustViewportForSystemUi(boolean adjustViewportForSystemUi) {
+        mAdjustViewportForSystemUi = adjustViewportForSystemUi;
+    }
+
     /** Resizes the image by zooming it such that the image is displayed without borders. */
     public void resizeImageToFitScreen() {
         // Protect against being called before the image has been initialized.
@@ -220,9 +254,10 @@ public class DesktopCanvas {
         mRenderData.transform.mapPoints(viewportPosition);
 
         float viewportTransX = ((float) mRenderData.screenWidth / 2) - viewportPosition[0];
-        float viewportTransY = ((float) mRenderData.screenHeight / 2) - viewportPosition[1];
+        float viewportTransY =
+                ((float) mRenderData.screenHeight / 2) - viewportPosition[1] - mCursorOffsetScreenY;
 
-        // Translate the image so the viewport center is displayed in the middle of the screen.
+        // Translate the image to move the viewport to the expected screen location.
         mRenderData.transform.postTranslate(viewportTransX, viewportTransY);
 
         updateVisibleImagePadding();
@@ -263,9 +298,10 @@ public class DesktopCanvas {
         // the desktop image from 'snapping' back to pre-System UI state.
         RectF systemUiOverlap = getSystemUiOverlap();
         float[] padding = {Math.max(mVisibleImagePadding.left, systemUiOverlap.left),
-                Math.max(mVisibleImagePadding.top, systemUiOverlap.top),
+                Math.max(mVisibleImagePadding.top + mCursorOffsetScreenY, systemUiOverlap.top),
                 Math.max(mVisibleImagePadding.right, systemUiOverlap.right),
-                Math.max(mVisibleImagePadding.bottom, systemUiOverlap.bottom)};
+                Math.max(mVisibleImagePadding.bottom - mCursorOffsetScreenY,
+                        systemUiOverlap.bottom)};
         Matrix screenToImage = new Matrix();
         mRenderData.transform.invert(screenToImage);
         screenToImage.mapVectors(padding);
@@ -325,9 +361,10 @@ public class DesktopCanvas {
         // Note: Ignore negative padding (clamp to 0) since that means no overlap exists.
         PointF letterboxPadding = getLetterboxPadding();
         return new RectF(Math.max(mSystemUiScreenSize.left - letterboxPadding.x, 0.0f),
-                Math.max(mSystemUiScreenSize.top - letterboxPadding.y, 0.0f),
+                Math.max(mSystemUiScreenSize.top - letterboxPadding.y + mCursorOffsetScreenY, 0.0f),
                 Math.max(mSystemUiScreenSize.right - letterboxPadding.x, 0.0f),
-                Math.max(mSystemUiScreenSize.bottom - letterboxPadding.y, 0.0f));
+                Math.max(mSystemUiScreenSize.bottom - letterboxPadding.y - mCursorOffsetScreenY,
+                        0.0f));
     }
 
     /**