Reinforce bitmap reconfiguration on Android

* java/org/gnu/emacs/EmacsView.java (EmacsView) <unswapped>: New
field in which to record whether the back buffer has received
contents beyond those present at the last buffer swap.
<dimensionsLock>: Delete field.
(onAttachedToWindow, onLayout, handleDirtyBitmap)
(prepareForLayout): Rather, synchronize window dimensions with
the view.
(getCanvas, getBitmap): Do not reconfigure the back buffer
bitmap if such outstanding data exists.
(postSwapBuffers): New function.
(swapBuffers): If such outstanding data exists and the back
bufferis pending reconfiguration, recreate the back buffer and
report exposure.

* src/androidterm.c (handle_one_android_event): Fix indentation.

1 files changed, 93 insertions, 68 deletions

diff --git a/java/org/gnu/emacs/EmacsView.java b/java/org/gnu/emacs/EmacsView.java
index 78d1ef785da..2ea54217837 100644
--- a/java/org/gnu/emacs/EmacsView.java
+++ b/java/org/gnu/emacs/EmacsView.java
@@ -88,15 +88,15 @@ public final class EmacsView extends ViewGroup
   /* Whether or not a popup is active.  */
   private boolean popupActive;
 
+  /* Whether the back buffer has been updated since the last swap.  */
+  private boolean unswapped;
+
   /* The current context menu.  */
   private EmacsContextMenu contextMenu;
 
   /* The last measured width and height.  */
   private int measuredWidth, measuredHeight;
 
-  /* Object acting as a lock for those values.  */
-  private Object dimensionsLock;
-
   /* The serial of the last clip rectangle change.  */
   private long lastClipSerial;
 
@@ -153,9 +153,6 @@ public final class EmacsView extends ViewGroup
 
     /* Add this view as its own global layout listener.  */
     getViewTreeObserver ().addOnGlobalLayoutListener (this);
-
-    /* Create an object used as a lock.  */
-    this.dimensionsLock = new Object ();
   }
 
   private void
@@ -164,12 +161,9 @@ public final class EmacsView extends ViewGroup
     Bitmap oldBitmap;
     int measuredWidth, measuredHeight;
 
-    synchronized (dimensionsLock)
-      {
-        /* Load measuredWidth and measuredHeight.  */
-        measuredWidth = this.measuredWidth;
-        measuredHeight = this.measuredHeight;
-      }
+    /* Load measuredWidth and measuredHeight.  */
+    measuredWidth = this.measuredWidth;
+    measuredHeight = this.measuredHeight;
 
     if (measuredWidth == 0 || measuredHeight == 0)
       return;
@@ -231,8 +225,14 @@ public final class EmacsView extends ViewGroup
   public synchronized Bitmap
   getBitmap ()
   {
-    if (bitmapDirty || bitmap == null)
+    /* Never alter the bitmap if modifications have been received that
+       are still to be copied to the front buffer, as this indicates
+       that redisplay is in the process of copying matrix contents to
+       the glass, and such events as generally prompt a complete
+       regeneration of the frame's contents might not be processed.  */
+    if (!unswapped && (bitmapDirty || bitmap == null))
       handleDirtyBitmap ();
+    unswapped = true;
 
     return bitmap;
   }
@@ -242,11 +242,12 @@ public final class EmacsView extends ViewGroup
   {
     int i;
 
-    if (bitmapDirty || bitmap == null)
+    if (!unswapped && (bitmapDirty || bitmap == null))
       handleDirtyBitmap ();
 
     if (canvas == null)
       return null;
+    unswapped = true;
 
     /* Update clip rectangles if necessary.  */
     if (gc.clipRectID != lastClipSerial)
@@ -266,14 +267,11 @@ public final class EmacsView extends ViewGroup
     return canvas;
   }
 
-  public void
+  public synchronized void
   prepareForLayout (int wantedWidth, int wantedHeight)
   {
-    synchronized (dimensionsLock)
-      {
-        measuredWidth = wantedWidth;
-        measuredHeight = wantedWidth;
-      }
+    measuredWidth = wantedWidth;
+    measuredHeight = wantedWidth;
   }
 
   @Override
@@ -329,8 +327,8 @@ public final class EmacsView extends ViewGroup
   }
 
   /* Note that the monitor lock for the window must never be held from
-     within the lock for the view, because the window also locks the
-     other way around.  */
+     within that for the view, because the window acquires locks in the
+     opposite direction.  */
 
   @Override
   protected void
@@ -346,7 +344,7 @@ public final class EmacsView extends ViewGroup
     count = getChildCount ();
     needExpose = false;
 
-    synchronized (dimensionsLock)
+    synchronized (this)
       {
         /* Load measuredWidth and measuredHeight.  */
         oldMeasuredWidth = measuredWidth;
@@ -355,48 +353,48 @@ public final class EmacsView extends ViewGroup
         /* Set measuredWidth and measuredHeight.  */
         measuredWidth = right - left;
         measuredHeight = bottom - top;
-      }
 
-    /* If oldMeasuredHeight or oldMeasuredWidth are wrong, set changed
-       to true as well.  */
+        /* If oldMeasuredHeight or oldMeasuredWidth are wrong, set
+           changed to true as well.  */
 
-    if (right - left != oldMeasuredWidth
-        || bottom - top != oldMeasuredHeight)
-      changed = true;
+        if (right - left != oldMeasuredWidth
+            || bottom - top != oldMeasuredHeight)
+          changed = true;
 
-    /* Dirty the back buffer if the layout change resulted in the view
-       being resized.  */
-
-    if (changed)
-      {
-        /* Expose the window upon a change in the view's size that
-           prompts the creation of a new bitmap.  */
-        explicitlyDirtyBitmap ();
-        needExpose = true;
+        /* Dirty the back buffer if the layout change resulted in the view
+           being resized.  */
 
-        /* This might return NULL if this view is not attached.  */
-        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.R)
+        if (changed)
           {
-            /* If a toplevel view is focused and isCurrentlyTextEditor
-               is enabled when the IME is hidden, clear
-               isCurrentlyTextEditor so it isn't shown again if the
-               user dismisses Emacs before returning.  */
-            rootWindowInsets = getRootWindowInsets ();
-
-            if (isCurrentlyTextEditor
-                && rootWindowInsets != null
-                && isAttachedToWindow
-                && !rootWindowInsets.isVisible (WindowInsets.Type.ime ())
-                /* N.B. that the keyboard is dismissed during gesture
-                   navigation under Android 30, but the system is
-                   quite temperamental regarding whether the window is
-                   focused at that point.  Ideally
-                   isCurrentlyTextEditor shouldn't be reset in that
-                   case, but detecting that situation appears to be
-                   impossible.  Sigh.  */
-                && (window == EmacsActivity.focusedWindow
-                    && hasWindowFocus ()))
-              isCurrentlyTextEditor = false;
+            /* Expose the window upon a change in the view's size that
+               prompts the creation of a new bitmap.  */
+            bitmapDirty = needExpose = true;
+
+            /* This might return NULL if this view is not attached.  */
+            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.R)
+              {
+                /* If a toplevel view is focused and
+                   isCurrentlyTextEditor is enabled when the IME is
+                   hidden, clear isCurrentlyTextEditor so it isn't shown
+                   again if the user dismisses Emacs before
+                   returning.  */
+                rootWindowInsets = getRootWindowInsets ();
+
+                if (isCurrentlyTextEditor
+                    && rootWindowInsets != null
+                    && isAttachedToWindow
+                    && !rootWindowInsets.isVisible (WindowInsets.Type.ime ())
+                    /* N.B. that the keyboard is dismissed during
+                       gesture navigation under Android 30, but the
+                       system is quite temperamental regarding whether
+                       the window is focused at that point.  Ideally
+                       isCurrentlyTextEditor shouldn't be reset in that
+                       case, but detecting that situation appears to be
+                       impossible.  Sigh.  */
+                    && (window == EmacsActivity.focusedWindow
+                        && hasWindowFocus ()))
+                  isCurrentlyTextEditor = false;
+              }
           }
       }
 
@@ -449,6 +447,33 @@ public final class EmacsView extends ViewGroup
     damageRegion.op (left, top, right, bottom, Region.Op.UNION);
   }
 
+  /* Complete deferred reconfiguration of the front buffer after a
+     buffer swap completes, and generate Expose events for the same.  */
+
+  private void
+  postSwapBuffers ()
+  {
+    if (!unswapped)
+      return;
+
+    unswapped = false;
+
+    /* If the bitmap is dirty, reconfigure the bitmap and
+       generate an Expose event to produce its contents.  */
+
+    if ((bitmapDirty || bitmap == null)
+        /* Do not generate Expose events if handleDirtyBitmap will
+           not create a valid bitmap, or the consequent buffer swap
+           will produce another event, ad infinitum.  */
+        && isAttachedToWindow && measuredWidth != 0
+        && measuredHeight != 0)
+      {
+        handleDirtyBitmap ();
+        EmacsNative.sendExpose (this.window.handle, 0, 0,
+                                measuredWidth, measuredHeight);
+      }
+  }
+
   /* This method is called from both the UI thread and the Emacs
      thread.  */
 
@@ -467,7 +492,10 @@ public final class EmacsView extends ViewGroup
     /* Now see if there is a damage region.  */
 
     if (damageRegion.isEmpty ())
-      return;
+      {
+        postSwapBuffers ();
+        return;
+      }
 
     /* And extract and clear the damage region.  */
 
@@ -479,6 +507,7 @@ public final class EmacsView extends ViewGroup
         /* Transfer the bitmap to the surface view, then invalidate
            it.  */
         surfaceView.setBitmap (bitmap, damageRect);
+        postSwapBuffers ();
       }
   }
 
@@ -758,13 +787,9 @@ public final class EmacsView extends ViewGroup
        was called.  */
     bitmapDirty = true;
 
-    synchronized (dimensionsLock)
-      {
-        /* Now expose the view contents again.  */
-        EmacsNative.sendExpose (this.window.handle, 0, 0,
-                                measuredWidth, measuredHeight);
-      }
-
+    /* Now expose the view contents again.  */
+    EmacsNative.sendExpose (this.window.handle, 0, 0,
+                            measuredWidth, measuredHeight);
     super.onAttachedToWindow ();
   }