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/* Communication module for Android terminals. -*- c-file-style: "GNU" -*-
Copyright (C) 2023-2024 Free Software Foundation, Inc.
This file is part of GNU Emacs.
GNU Emacs is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or (at
your option) any later version.
GNU Emacs is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with GNU Emacs. If not, see <https://www.gnu.org/licenses/>. */
package org.gnu.emacs;
import android.view.View;
import android.os.Build;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Rect;
import android.graphics.Paint;
import java.lang.ref.WeakReference;
/* This originally extended SurfaceView. However, doing so proved to
be too slow, and Android's surface view keeps up to three of its
own back buffers, which use too much memory (up to 96 MB for a
single frame.) */
public final class EmacsSurfaceView extends View
{
private static final String TAG = "EmacsSurfaceView";
/* The complete buffer contents at the time of the last draw. */
private Bitmap frontBuffer;
/* Whether frontBuffer has been updated since the last call to
`onDraw'. */
private boolean bitmapChanged;
/* Canvas representing the front buffer. */
private Canvas bitmapCanvas;
/* Reference to the last bitmap copied to the front buffer. */
private WeakReference<Bitmap> bitmap;
/* Paint objects used on the main and UI threads, respectively. */
private static final Paint bitmapPaint, uiThreadPaint;
static
{
/* Create two different Paint objects; one is used on the main
thread for buffer swaps, while the other is used from the UI
thread in `onDraw'. This is necessary because Paint objects
are not thread-safe, even if their uses are interlocked. */
bitmapPaint = new Paint ();
uiThreadPaint = new Paint ();
};
public
EmacsSurfaceView (EmacsView view)
{
super (view.getContext ());
this.bitmap = new WeakReference<Bitmap> (null);
}
private void
copyToFrontBuffer (Bitmap bitmap, Rect damageRect)
{
EmacsService.checkEmacsThread ();
if (Build.VERSION.SDK_INT != Build.VERSION_CODES.O
&& Build.VERSION.SDK_INT != Build.VERSION_CODES.O_MR1
&& Build.VERSION.SDK_INT != Build.VERSION_CODES.N_MR1
&& Build.VERSION.SDK_INT != Build.VERSION_CODES.N)
{
/* 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
{
/* But if it can not, as on Android 7.0 through 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 ());
}
/* See the large comment inside `onDraw'. */
bitmapChanged = true;
}
private void
reconfigureFrontBuffer (Bitmap bitmap)
{
/* First, remove the old front buffer. */
if (frontBuffer != null)
{
frontBuffer.recycle ();
frontBuffer = null;
bitmapCanvas = null;
}
this.bitmap = new WeakReference<Bitmap> (bitmap);
/* Next, create the new front buffer if necessary. */
if (bitmap != null && frontBuffer == null)
{
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O)
frontBuffer = Bitmap.createBitmap (bitmap.getWidth (),
bitmap.getHeight (),
Bitmap.Config.ARGB_8888,
false);
else
frontBuffer = Bitmap.createBitmap (bitmap.getWidth (),
bitmap.getHeight (),
Bitmap.Config.ARGB_8888);
bitmapCanvas = new Canvas (frontBuffer);
/* And copy over the bitmap contents. */
copyToFrontBuffer (bitmap, null);
}
else if (bitmap != null)
/* Just copy over the bitmap contents. */
copyToFrontBuffer (bitmap, null);
}
public synchronized void
setBitmap (Bitmap bitmap, Rect damageRect)
{
if (bitmap != this.bitmap.get ())
reconfigureFrontBuffer (bitmap);
else if (bitmap != null)
copyToFrontBuffer (bitmap, damageRect);
if (bitmap != null)
{
/* In newer versions of Android, the invalid rectangle is
supposedly internally calculated by the system. How that
is done is unknown, but calling `invalidateRect' is now
deprecated.
Fortunately, nobody has deprecated the version of
`postInvalidate' that accepts a dirty rectangle. */
if (damageRect != null)
postInvalidate (damageRect.left, damageRect.top,
damageRect.right, damageRect.bottom);
else
postInvalidate ();
}
}
@Override
public synchronized void
onDraw (Canvas canvas)
{
/* Paint the view's bitmap; the bitmap might be recycled right
now. */
if (frontBuffer != null)
{
/* The first time the bitmap is drawn after a buffer swap,
mark its contents as having changed. This increments the
``generation ID'' used by Android to avoid uploading buffer
textures for unchanged bitmaps.
When a buffer swap takes place, the bitmap is initially
updated from the Emacs thread, resulting in the generation
ID being increased. If the render thread is texturizing
the bitmap while the swap takes place, it might record the
generation ID after the update for a texture containing the
contents of the bitmap prior to the swap, leaving the
texture tied to the bitmap partially updated.
Android never calls `onDraw' if the render thread is still
processing the bitmap. Update the generation ID here to
ensure that a new texture will be uploaded if the bitmap
has changed.
Uploading the bitmap contents to the GPU uses an excessive
amount of memory, as the entire bitmap is placed into the
graphics command queue, but this memory is actually shared
among all other applications and reclaimed by the system
when necessary. */
if (bitmapChanged)
{
EmacsNative.notifyPixelsChanged (frontBuffer);
bitmapChanged = false;
}
canvas.drawBitmap (frontBuffer, 0f, 0f, uiThreadPaint);
}
}
};
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