package org.eclipse.swt.internal.qt.graphics;

/**

 * Buffer provides a storage for GraphicsContext commands. If GraphicsContext is bound to

 * Buffer all subsequental draw commands are recorded within the buffer and can be replayed 

 * later by processing it with GraphicsContext.render()-method.

 * 

 * The main benefit of buffer is the possibility to render to it outside paint callbacks, 

 * i.e. when the actual rendering target cannot be bound. Usage of buffer may also improve 

 * performance.

 * 

 */

public final class NativeCommandBuffer {

	/**

	 * Native peer handle

	 */

	int handle = 0;

	/**

	 * State of native peer

	 */

	boolean disposed;

	/**

	 * Constructor

	 * @throws OutOfMemoryError If native buffer creation fails

	 */

	public NativeCommandBuffer() {

		Utils.validateUiThread();

		handle = OS.buffer_init();

		if (handle == 0) {

			throw new OutOfMemoryError("Native buffer creation failed");

		}

	}

	/**

	 * Disposes this buffer and cleans all related native resources

	 */

	public void dispose() {

		if (!disposed) {

			OS.buffer_dispose(handle);

			handle = 0;

			disposed = true;

		}

	}

    /**

     * Gets the rectangle where draw operations have affected,

     * i.e. the invalid rectangle.

     *

     * Values are stored in rect array as follows: 

     * <ul>

     * <li>rect[0] - the x coordinate of rect</li>

     * <li>rect[1] - the y coordinate of rect

     * <li>rect[2] - the width of rect

     * <li>rect[3] - the height of rect

     * </ul>

     * 

     * @param rect Integer array where the rect data is populated, size must be atleast 4

     * @throws NullPointerException if rect is null

     * @throws IllegalArgumentException if rect.length < 4

     * @throws IllegalStateException if the buffer has already been disposed

	 */

	public void getInvalidRect(int[] rect) {

		checkState();

		if(rect == null) {

			throw new NullPointerException("rect is null");

		}

		if(rect.length < 4) {

			throw new IllegalArgumentException("rect array size is < 4");

		}

		OS.buffer_getInvalidRect(handle, rect);

	}

    /**

     * Gets the state of this Buffer, i.e. is it disposed or not. 

     * 

     * @return true if this instanace has been disposed, otherwise false

     */

	public boolean isDisposed() {

		return disposed;

	}

    /**

     * private method for checking the state of this instance.

     * @throws IllegalStateException If this instance is already disposed 

     */

    private void checkState() {

    	Utils.validateUiThread();

        if (disposed) {

            throw new IllegalStateException("Buffer already disposed");

        }

    }

}