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..52aa6ca7121d5d11c7efc9b82c3a27f2285d8ccd 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 +134,33 @@ public class DesktopCanvas {
      */
     public void setSystemUiOffsetValues(int left, int top, int right, int bottom) {
         mSystemUiScreenSize.set(left, top, right, bottom);
+
+        // Adjust the cursor position to ensure it visible when large System UI (defined as 1/3 or

[Lambros, 2016/10/05 01:35:54]

s/it/it is/

[joedow, 2016/10/05 16:12:26]

Done.

+        // 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 (mAdjustViewportForSystemUi && bottom > (mRenderData.screenHeight / 3)) {
+            // Center the cursor within the viewable area (not obscurred by System UI).

[Lambros, 2016/10/05 01:35:54]

obscured

[joedow, 2016/10/05 16:12:26]

Done.

+            mCursorOffsetScreenY = (((float) mRenderData.screenHeight - bottom) / 2.0f);
+        } else {
+            mCursorOffsetScreenY = 0.0f;
+        }
+
+        if (mAdjustViewportForSystemUi) {
+            setCursorPosition(mCursorPosition.x, mCursorPosition.y);

[Lambros, 2016/10/05 01:35:54]

This feels suspect. Why do you need this call only conditionally?

[joedow, 2016/10/05 16:12:26]

It only affects the case where the cursor offset changes.  It's basically an
optimization for Touch mode.  I'll add a comment.

+        }
     }
 
     /** 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.
@@ -220,7 +252,8 @@ 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.

[Lambros, 2016/10/05 01:35:54]

I guess "middle of the screen" is no longer accurate?

[joedow, 2016/10/05 16:12:26]

That's true, this comment should be updated.

         mRenderData.transform.postTranslate(viewportTransX, viewportTransY);
@@ -263,9 +296,10 @@ 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 +359,10 @@ 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));
     }
 
     /**