Special handling of one key mini-keyboard to mitigate visual flicker

Use pre-computed width and height of mini keyboard if
 * Popup key preview is enabled
 * The mini keyboard has only one key
 * Pre-computed width and height are specified

Bug: 5248783
Change-Id: I53475698e87d5bd67d36e63323c25a9e9f18fbb1

2 files changed, 23 insertions, 6 deletions

diff --git a/java/src/com/android/inputmethod/keyboard/KeyboardView.java b/java/src/com/android/inputmethod/keyboard/KeyboardView.java
index 6af4123c9..6492c00fa 100644
--- a/java/src/com/android/inputmethod/keyboard/KeyboardView.java
+++ b/java/src/com/android/inputmethod/keyboard/KeyboardView.java
@@ -100,7 +100,7 @@ public class KeyboardView extends View implements PointerTracker.DrawingProxy {
 
     // Key preview
     private final int mKeyPreviewLayoutId;
-    private final KeyPreviewDrawParams mKeyPreviewDrawParams;
+    protected final KeyPreviewDrawParams mKeyPreviewDrawParams;
     private boolean mShowKeyPreviewPopup = true;
     private final int mDelayBeforePreview;
     private int mDelayAfterPreview;
@@ -284,11 +284,13 @@ public class KeyboardView extends View implements PointerTracker.DrawingProxy {
         }
     }
 
-    private static class KeyPreviewDrawParams {
+    protected static class KeyPreviewDrawParams {
         // XML attributes.
         public final Drawable mPreviewBackground;
         public final Drawable mPreviewLeftBackground;
         public final Drawable mPreviewRightBackground;
+        public final int mPreviewBackgroundWidth;
+        public final int mPreviewBackgroundHeight;
         public final int mPreviewTextColor;
         public final int mPreviewOffset;
         public final int mPreviewHeight;
@@ -312,6 +314,10 @@ public class KeyboardView extends View implements PointerTracker.DrawingProxy {
             setAlpha(mPreviewBackground, PREVIEW_ALPHA);
             setAlpha(mPreviewLeftBackground, PREVIEW_ALPHA);
             setAlpha(mPreviewRightBackground, PREVIEW_ALPHA);
+            mPreviewBackgroundWidth = a.getDimensionPixelSize(
+                    R.styleable.KeyboardView_keyPreviewBackgroundWidth, 0);
+            mPreviewBackgroundHeight = a.getDimensionPixelSize(
+                    R.styleable.KeyboardView_keyPreviewBackgroundHeight, 0);
             mPreviewOffset = a.getDimensionPixelOffset(
                     R.styleable.KeyboardView_keyPreviewOffset, 0);
             mPreviewHeight = a.getDimensionPixelSize(
diff --git a/java/src/com/android/inputmethod/keyboard/MiniKeyboard.java b/java/src/com/android/inputmethod/keyboard/MiniKeyboard.java
index d4b35a556..ac9290bfd 100644
--- a/java/src/com/android/inputmethod/keyboard/MiniKeyboard.java
+++ b/java/src/com/android/inputmethod/keyboard/MiniKeyboard.java
@@ -215,10 +215,21 @@ public class MiniKeyboard extends Keyboard {
             mParams.mIsRtlKeyboard = parentKeyboard.mIsRtlKeyboard;
             mMoreKeys = parentKey.mMoreKeys;
 
-            final int keyWidth = getMaxKeyWidth(view, mMoreKeys, mParams.mDefaultKeyWidth);
-            mParams.setParameters(mMoreKeys.length, parentKey.mMaxMoreKeysColumn,
-                    keyWidth, parentKeyboard.mMostCommonKeyHeight, parentKey.mX
-                            + (mParams.mDefaultKeyWidth - keyWidth) / 2, view.getMeasuredWidth());
+            final int previewWidth = view.mKeyPreviewDrawParams.mPreviewBackgroundWidth;
+            final int previewHeight = view.mKeyPreviewDrawParams.mPreviewBackgroundHeight;
+            final int width, height;
+            // Use pre-computed width and height if these values are available and mini keyboard
+            // has only one key to mitigate visual flicker between key preview and mini keyboard.
+            if (view.isKeyPreviewPopupEnabled() && mMoreKeys.length == 1 && previewWidth > 0
+                    && previewHeight > 0) {
+                width = previewWidth;
+                height = previewHeight + mParams.mVerticalGap;
+            } else {
+                width = getMaxKeyWidth(view, parentKey.mMoreKeys, mParams.mDefaultKeyWidth);
+                height = parentKeyboard.mMostCommonKeyHeight;
+            }
+            mParams.setParameters(mMoreKeys.length, parentKey.mMaxMoreKeysColumn, width, height,
+                    parentKey.mX + (mParams.mDefaultKeyWidth - width) / 2, view.getMeasuredWidth());
         }
 
         private static int getMaxKeyWidth(KeyboardView view, CharSequence[] moreKeys,