Work around more problems with Bitmaps

* java/org/gnu/emacs/EmacsNative.java (EmacsNative): New
function `blitRect'.
* java/org/gnu/emacs/EmacsSurfaceView.java (EmacsSurfaceView):
Use it on Android 8.x.
* src/android.c (blitRect): Implement new function.

2 files changed, 39 insertions, 4 deletions

diff --git a/java/org/gnu/emacs/EmacsNative.java b/java/org/gnu/emacs/EmacsNative.java
index e699dda9ad4..56c03ee38dc 100644
--- a/java/org/gnu/emacs/EmacsNative.java
+++ b/java/org/gnu/emacs/EmacsNative.java
@@ -20,6 +20,9 @@ along with GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.  */
 package org.gnu.emacs;
 
 import android.content.res.AssetManager;
+
+import android.graphics.Bitmap;
+
 import android.view.inputmethod.ExtractedText;
 import android.view.inputmethod.ExtractedTextRequest;
 
@@ -216,6 +219,13 @@ public final class EmacsNative
      failure.  */
   public static native int[] getSelection (short window);
 
+
+  /* Graphics functions used as a replacement for potentially buggy
+     Android APIs.  */
+
+  public static native void blitRect (Bitmap src, Bitmap dest, int x1,
+                                      int y1, int x2, int y2);
+
   static
   {
     /* Older versions of Android cannot link correctly with shared
diff --git a/java/org/gnu/emacs/EmacsSurfaceView.java b/java/org/gnu/emacs/EmacsSurfaceView.java
index e0411f7f8b3..0deb930c2c2 100644
--- a/java/org/gnu/emacs/EmacsSurfaceView.java
+++ b/java/org/gnu/emacs/EmacsSurfaceView.java
@@ -57,11 +57,36 @@ public final class EmacsSurfaceView extends View
   private void
   copyToFrontBuffer (Bitmap bitmap, Rect damageRect)
   {
-    if (damageRect != null)
-      bitmapCanvas.drawBitmap (bitmap, damageRect, damageRect,
-                               bitmapPaint);
+    EmacsService.checkEmacsThread ();
+
+    if (Build.VERSION.SDK_INT != Build.VERSION_CODES.O
+        && Build.VERSION.SDK_INT != Build.VERSION_CODES.O_MR1)
+      {
+        /* If `drawBitmap' can safely be used while a bitmap is locked
+           by another thread, continue here... */
+
+        if (damageRect != null)
+          bitmapCanvas.drawBitmap (bitmap, damageRect, damageRect,
+                                   bitmapPaint);
+        else
+          bitmapCanvas.drawBitmap (bitmap, 0f, 0f, bitmapPaint);
+      }
     else
-      bitmapCanvas.drawBitmap (bitmap, 0f, 0f, bitmapPaint);
+      {
+        /* But if it can not, as on Android 8.0 and 8.1, then use a
+           replacement function.  */
+
+        if (damageRect != null)
+          EmacsNative.blitRect (bitmap, frontBuffer,
+                                damageRect.left,
+                                damageRect.top,
+                                damageRect.right,
+                                damageRect.bottom);
+        else
+          EmacsNative.blitRect (bitmap, frontBuffer, 0, 0,
+                                bitmap.getWidth (),
+                                bitmap.getHeight ());
+      }
   }
 
   private void