gecko/mobile/android/base/gfx/SingleTileLayer.java

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 * License.
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 * The Original Code is Mozilla Android code.
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 * The Initial Developer of the Original Code is Mozilla Foundation.
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 * Contributor(s):
 *   Patrick Walton <pcwalton@mozilla.com>
 *   Arkady Blyakher <rkadyb@mit.edu>
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package org.mozilla.gecko.gfx;

import org.mozilla.gecko.gfx.CairoImage;
import org.mozilla.gecko.gfx.CairoUtils;
import org.mozilla.gecko.gfx.IntSize;
import org.mozilla.gecko.gfx.LayerController;
import org.mozilla.gecko.gfx.TileLayer;
import android.graphics.Rect;
import android.graphics.RectF;
import android.graphics.Region;
import android.graphics.RegionIterator;
import android.opengl.GLES20;
import android.util.Log;
import java.nio.FloatBuffer;
import javax.microedition.khronos.opengles.GL10;

/**
 * Encapsulates the logic needed to draw a single textured tile.
 *
 * TODO: Repeating textures really should be their own type of layer.
 */
public class SingleTileLayer extends TileLayer {
    private static final String LOGTAG = "GeckoSingleTileLayer";

    private Rect mMask;

    public SingleTileLayer(CairoImage image) { this(false, image); }

    public SingleTileLayer(boolean repeat, CairoImage image) {
        super(repeat, image);
    }

    /**
     * Set an area to mask out when rendering.
     */
    public void setMask(Rect aMaskRect) {
        mMask = aMaskRect;
    }

    @Override
    public void draw(RenderContext context) {
        // mTextureIDs may be null here during startup if Layer.java's draw method
        // failed to acquire the transaction lock and call performUpdates.
        if (!initialized())
            return;

        RectF bounds;
        int[] cropRect;
        Rect position = getPosition();
        RectF viewport = context.viewport;

        if (repeats()) {
            bounds = new RectF(0.0f, 0.0f, viewport.width(), viewport.height());
            int width = Math.round(viewport.width());
            int height = Math.round(viewport.height());
            cropRect = new int[] { 0, 0, width, height };
        } else {
            bounds = getBounds(context);
            cropRect = new int[] { 0, 0, position.width(), position.height() };
        }

        Rect intBounds = new Rect();
        bounds.roundOut(intBounds);
        Region maskedBounds = new Region(intBounds);
        if (mMask != null) {
            maskedBounds.op(mMask, Region.Op.DIFFERENCE);
            if (maskedBounds.isEmpty())
                return;
        }

        // XXX Possible optimisation here, form this array so we can draw it in
        //     a single call.
        RegionIterator i = new RegionIterator(maskedBounds);
        for (Rect subRect = new Rect(); i.next(subRect);) {
            // Compensate for rounding errors at the edge of the tile caused by
            // the roundOut above
            RectF subRectF = new RectF(Math.max(bounds.left, (float)subRect.left),
                                       Math.max(bounds.top, (float)subRect.top),
                                       Math.min(bounds.right, (float)subRect.right),
                                       Math.min(bounds.bottom, (float)subRect.bottom));

            float height = subRectF.height();
            float left = subRectF.left - viewport.left;
            float top = viewport.height() - (subRectF.top + height - viewport.top);

            float[] coords = {
                //x, y, z, texture_x, texture_y
                left/viewport.width(), top/viewport.height(), 0,
                cropRect[0]/(float)position.width(), cropRect[1]/(float)position.height(),

                left/viewport.width(), (top+height)/viewport.height(), 0,
                cropRect[0]/(float)position.width(), cropRect[3]/(float)position.height(),

                (left+subRectF.width())/viewport.width(), top/viewport.height(), 0,
                cropRect[2]/(float)position.width(), cropRect[1]/(float)position.height(),

                (left+subRectF.width())/viewport.width(), (top+height)/viewport.height(), 0,
                cropRect[2]/(float)position.width(), cropRect[3]/(float)position.height()
            };

            FloatBuffer coordBuffer = context.coordBuffer;
            int positionHandle = context.positionHandle;
            int textureHandle = context.textureHandle;

            GLES20.glBindTexture(GLES20.GL_TEXTURE_2D, getTextureID());

            // Make sure we are at position zero in the buffer
            coordBuffer.position(0);
            coordBuffer.put(coords);

            // Vertex coordinates are x,y,z starting at position 0 into the buffer.
            coordBuffer.position(0);
            GLES20.glVertexAttribPointer(positionHandle, 3, GLES20.GL_FLOAT, false, 20, coordBuffer);

            // Texture coordinates are texture_x, texture_y starting at position 3 into the buffer.
            coordBuffer.position(3);
            GLES20.glVertexAttribPointer(textureHandle, 2, GLES20.GL_FLOAT, false, 20, coordBuffer);
            GLES20.glDrawArrays(GLES20.GL_TRIANGLE_STRIP, 0, 4);
        }
    }
}