android/source/src/java/org/mozilla/gecko/gfx/TextLayer.java

   1 /* -*- Mode: Java; c-basic-offset: 4; tab-width: 20; indent-tabs-mode: nil; -*-
   2  * This Source Code Form is subject to the terms of the Mozilla Public
   3  * License, v. 2.0. If a copy of the MPL was not distributed with this
   4  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   5
   6 package org.mozilla.gecko.gfx;
   7
   8 import android.graphics.Bitmap;
   9 import android.graphics.Canvas;
  10 import android.graphics.Color;
  11 import android.graphics.Paint;
  12 import android.graphics.Typeface;
  13
  14 import org.libreoffice.kit.DirectBufferAllocator;
  15
  16 import java.nio.ByteBuffer;
  17
  18 /**
  19  * Draws text on a layer. This is used for the frame rate meter.
  20  */
  21 public class TextLayer extends SingleTileLayer {
  22     private final ByteBuffer mBuffer;   // this buffer is owned by the BufferedCairoImage
  23     private final IntSize mSize;
  24
  25     /*
  26      * This awkward pattern is necessary due to Java's restrictions on when one can call superclass
  27      * constructors.
  28      */
  29     private TextLayer(ByteBuffer buffer, BufferedCairoImage image, IntSize size, String text) {
  30         super(false, image);
  31         mBuffer = buffer;
  32         mSize = size;
  33         renderText(text);
  34     }
  35
  36     public static TextLayer create(IntSize size, String text) {
  37         ByteBuffer buffer = DirectBufferAllocator.allocate(size.width * size.height * 4);
  38         BufferedCairoImage image = new BufferedCairoImage(buffer, size.width, size.height,
  39                                                           CairoImage.FORMAT_ARGB32);
  40         return new TextLayer(buffer, image, size, text);
  41     }
  42
  43     public void setText(String text) {
  44         renderText(text);
  45         invalidate();
  46     }
  47
  48     private void renderText(String text) {
  49         Bitmap bitmap = Bitmap.createBitmap(mSize.width, mSize.height, Bitmap.Config.ARGB_8888);
  50         Canvas canvas = new Canvas(bitmap);
  51
  52         Paint textPaint = new Paint();
  53         textPaint.setAntiAlias(true);
  54         textPaint.setColor(Color.WHITE);
  55         textPaint.setFakeBoldText(true);
  56         textPaint.setTextSize(18.0f);
  57         textPaint.setTypeface(Typeface.DEFAULT_BOLD);
  58         float width = textPaint.measureText(text) + 18.0f;
  59
  60         Paint backgroundPaint = new Paint();
  61         backgroundPaint.setColor(Color.argb(127, 0, 0, 0));
  62         canvas.drawRect(0.0f, 0.0f, width, 18.0f + 6.0f, backgroundPaint);
  63
  64         canvas.drawText(text, 6.0f, 18.0f, textPaint);
  65
  66         bitmap.copyPixelsToBuffer(mBuffer.asIntBuffer());
  67     }
  68 }
  69