html: extend GwtGL20 instead of emulating it

vtm-gdx-html/src/org/oscim/gdx/client/GwtGLAdapter.java

@@ -0,0 +1,53 @@
+package org.oscim.gdx.client;
+
+import java.nio.Buffer;
+import java.nio.IntBuffer;
+
+import org.oscim.backend.GL20;
+
+import com.badlogic.gdx.backends.gwt.GwtGL20;
+import com.badlogic.gdx.graphics.Pixmap;
+import com.google.gwt.typedarrays.client.Uint8ArrayNative;
+import com.google.gwt.webgl.client.WebGLRenderingContext;
+
+public class GwtGLAdapter extends GwtGL20 implements GL20 {
+
+	protected final WebGLRenderingContext gl;
+
+	public GwtGLAdapter(WebGLRenderingContext gl) {
+		super(gl);
+		gl.pixelStorei(WebGLRenderingContext.UNPACK_PREMULTIPLY_ALPHA_WEBGL, 1);
+		this.gl = gl;
+	}
+
+	@Override
+	public void glGetShaderSource(int shader, int bufsize, Buffer length, String source) {
+
+	}
+
+	@Override
+	public void glTexImage2D(int target, int level, int internalformat, int width, int height,
+	        int border, int format, int type,
+	        Buffer pixels) {
+		Pixmap pixmap = Pixmap.pixmaps.get(((IntBuffer) pixels).get(0));
+		if (pixmap != null) {
+			// Gdx.app.log("GwtGL20", "load texture "+ target + " "+ width + " " + height + " " + type + " " + format);
+			gl.texImage2D(target, level, internalformat, format, type, pixmap.getCanvasElement());
+		} else if (format == GL20.GL_ALPHA) {
+			// Gdx.app.log("GwtGL20", "load byte texture " + width + " " + height + " " + type + " " + format);
+			int tmp[] = new int[(width * height) >> 2];
+			((IntBuffer) pixels).get(tmp);
+
+			Uint8ArrayNative v = com.google.gwt.typedarrays.client.Uint8ArrayNative.create(width
+			        * height);
+
+			for (int i = 0, n = (width * height) >> 2; i < n; i++) {
+				v.set(i * 4 + 3, (tmp[i] >> 24) & 0xff);
+				v.set(i * 4 + 2, (tmp[i] >> 16) & 0xff);
+				v.set(i * 4 + 1, (tmp[i] >> 8) & 0xff);
+				v.set(i * 4 + 0, (tmp[i]) & 0xff);
+			}
+			gl.texImage2D(target, level, internalformat, width, height, 0, format, type, v);
+		}
+	}
+}