#region PDFsharp - A .NET library for processing PDF
//
// Authors:
//   Stefan Lange
//
// Copyright (c) 2005-2016 empira Software GmbH, Cologne Area (Germany)
//
// http://www.PdfSharp.com
// http://sourceforge.net/projects/pdfsharp
//
// Permission is hereby granted, free of charge, to any person obtaining a
// copy of this software and associated documentation files (the "Software"),
// to deal in the Software without restriction, including without limitation
// the rights to use, copy, modify, merge, publish, distribute, sublicense,
// and/or sell copies of the Software, and to permit persons to whom the
// Software is furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included
// in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
// THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER 
// DEALINGS IN THE SOFTWARE.
#endregion

namespace PdfSharpCore.Drawing
{
    // In GDI+ the functions Save/Restore, BeginContainer/EndContainer, Transform, SetClip and ResetClip
    // can be combined in any order. E.g. you can set a clip region, save the graphics state, empty the
    // clip region and draw without clipping. Then you can restore to the previous clip region. With PDF
    // this behavior is hard to implement. To solve this problem I first an automaton that keeps track
    // of all clipping paths and the current transformation when the clip path was set. The automation
    // manages a PDF graphics state stack to calculate the desired bahaviour. It also takes into consideration
    // not to multiply with inverse matrixes when the user sets a new transformation matrix.
    // After the design works on pager I decided not to implement it because it is much to large-scale.
    // Instead I lay down some rules how to use the XGraphics class.
    //
    // * Before you set a transformation matrix save the graphics state (Save) or begin a new container
    //   (BeginContainer).
    // 
    // * Instead of resetting the transformation matrix, call Restore or EndContainer. If you reset the
    //   transformation, in PDF must be multiplied with the inverse matrix. That leads to round off errors
    //   because in PDF file only 3 digits are used and Acrobat internally uses fixed point numbers (until
    //   versioin 6 or 7 I think).
    //
    // * When no clip path is defined, you can set or intersect a new path.
    //
    // * When a clip path is already defined, you can always intersect with a new one (wich leads in general
    //   to a smaller clip region).
    //
    // * When a clip path is already defined, you can only reset it to the empty region (ResetClip) when
    //   the graphics state stack is at the same position as it had when the clip path was defined. Otherwise
    //   an error occurs.
    //
    // Keeping these rules leads to easy to read code and best results in PDF output.

    /// <summary>
    /// Represents the internal state of an XGraphics object.
    /// Used when the state is saved and restored.
    /// </summary>
    internal class InternalGraphicsState
    {
        public InternalGraphicsState(XGraphics gfx)
        {
            _gfx = gfx;
        }

        public InternalGraphicsState(XGraphics gfx, XGraphicsState state)
        {
            _gfx = gfx;
            State = state;
            State.InternalState = this;
        }

        public InternalGraphicsState(XGraphics gfx, XGraphicsContainer container)
        {
            _gfx = gfx;
            container.InternalState = this;
        }

        /// <summary>
        /// Gets or sets the current transformation matrix.
        /// </summary>
        public XMatrix Transform
        {
            get { return _transform; }
            set { _transform = value; }
        }
        XMatrix _transform;

        /// <summary>
        /// Called after this instanced was pushed on the internal graphics stack.
        /// </summary>
        public void Pushed()
        {
        }

        /// <summary>
        /// Called after this instanced was popped from the internal graphics stack.
        /// </summary>
        public void Popped()
        {
            Invalid = true;
        }

        public bool Invalid;

        readonly XGraphics _gfx;

        internal XGraphicsState State;
    }
}