vtkTextRenderer.h

/*=========================================================================

  Program:   Visualization Toolkit
  Module:    vtkTextRenderer.h

  Copyright (c) Ken Martin, Will Schroeder, Bill Lorensen
  All rights reserved.
  See Copyright.txt or http://www.kitware.com/Copyright.htm for details.

     This software is distributed WITHOUT ANY WARRANTY; without even
     the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
     PURPOSE.  See the above copyright notice for more information.

=========================================================================*/

/**
 * @class   vtkTextRenderer
 * @brief   Interface for generating images and path data from
 * string data, using multiple backends.
 *
 *
 * vtkTextRenderer produces images, bounding boxes, and vtkPath
 * objects that represent text. The advantage of using this class is to easily
 * integrate mathematical expressions into renderings by automatically switching
 * between FreeType and MathText backends. If the input string contains at least
 * two "$" symbols separated by text, the MathText backend will be used. If
 * the string does not meet this criteria, or if no MathText implementation is
 * available, the faster FreeType rendering facilities are used. Literal $
 * symbols can be used by escaping them with backslashes, "\$" (or "\\$" if the
 * string is set programatically).
 *
 * For example, "Acceleration ($\\frac{m}{s^2}$)" will use MathText, but
 * "\\$500, \\$100" will use FreeType.
 *
 * By default, the backend is set to Detect, which determines the backend based
 * on the contents of the string. This can be changed by setting the
 * DefaultBackend ivar.
 *
 * Note that this class is abstract -- link to the vtkRenderingFreetype module
 * to get the default implementation.
*/

#ifndef vtkTextRenderer_h
#define vtkTextRenderer_h

#include "vtkRenderingCoreModule.h" // For export macro
#include "vtkObject.h"
#include "vtkTuple.h"  // For metrics struct
#include "vtkVector.h" // For metrics struct

class vtkImageData;
class vtkPath;
class vtkStdString;
class vtkUnicodeString;
class vtkTextProperty;

namespace vtksys {
class RegularExpression;
}

class VTKRENDERINGCORE_EXPORT vtkTextRendererCleanup
{
public:
  vtkTextRendererCleanup();
  ~vtkTextRendererCleanup();

private:
  vtkTextRendererCleanup(const vtkTextRendererCleanup& other) VTK_DELETE_FUNCTION;
  vtkTextRendererCleanup& operator=(const vtkTextRendererCleanup& rhs) VTK_DELETE_FUNCTION;
};

class VTKRENDERINGCORE_EXPORT vtkTextRenderer: public vtkObject
{
public:
  struct Metrics
  {
    /**
     * Construct a Metrics object with all members initialized to 0.
     */
    Metrics()
      : BoundingBox(0),
        TopLeft(0), TopRight(0), BottomLeft(0), BottomRight(0)
    {
    }

    /**
     * The axis-aligned bounding box of the rendered text and background, in
     * pixels. The origin of the bounding box is the anchor point of the data
     * when considering justification. Layout is { xMin, xMax, yMin, yMax }.
     */
    vtkTuple<int, 4> BoundingBox;

    //@{
    /**
     * The corners of the rendered text (or background, if applicable), in pixels.
     * Uses the same origin as BoundingBox.
     */
    vtkVector2i TopLeft;
    vtkVector2i TopRight;
    vtkVector2i BottomLeft;
    vtkVector2i BottomRight;
  };
    //@}

  vtkTypeMacro(vtkTextRenderer, vtkObject)
  virtual void PrintSelf(ostream &os, vtkIndent indent);

  /**
   * This is a singleton pattern New. There will be only ONE reference
   * to a vtkTextRenderer subclass object per process. Clients that
   * call this method must use Delete() on the object so that reference
   * counting will work. The single instance will be unreferenced when
   * the program exits. You should just use the static GetInstance() method
   * anyway to get the singleton. This method may return NULL if the object
   * factory cannot find an override.
   */
  static vtkTextRenderer *New();

  /**
   * Return the singleton instance with no reference counting. May return NULL
   * if the object factory cannot find an override.
   */
  static vtkTextRenderer* GetInstance();

  /**
   * Available backends. FreeType and MathText are provided in the default
   * implementation of this interface. Enum values less than 16 are reserved.
   * Custom overrides should define other backends starting at 16.
   */
  enum Backend
  {
    Default = -1,
    Detect = 0,
    FreeType,
    MathText,

    UserBackend = 16
  };

  //@{
  /**
   * The backend to use when none is specified. Default: Detect
   */
  vtkSetMacro(DefaultBackend, int)
  vtkGetMacro(DefaultBackend, int)
  //@}

  //@{
  /**
   * Determine the appropriate back end needed to render the given string.
   */
  virtual int DetectBackend(const vtkStdString &str);
  virtual int DetectBackend(const vtkUnicodeString &str);
  //@}

  /**
   * Test for availability of various backends
   */
  virtual bool FreeTypeIsSupported() { return false; }
  virtual bool MathTextIsSupported() { return false; }

  //@{
  /**
   * Given a text property and a string, get the bounding box {xmin, xmax,
   * ymin, ymax} of the rendered string in pixels. The origin of the bounding
   * box is the anchor point described by the horizontal and vertical
   * justification text property variables.
   * Return true on success, false otherwise.
   */
  bool GetBoundingBox(vtkTextProperty *tprop, const vtkStdString &str,
                      int bbox[4], int dpi, int backend = Default)
  {
    return this->GetBoundingBoxInternal(tprop, str, bbox, dpi, backend);
  }
  bool GetBoundingBox(vtkTextProperty *tprop, const vtkUnicodeString &str,
                      int bbox[4], int dpi, int backend = Default)
  {
    return this->GetBoundingBoxInternal(tprop, str, bbox, dpi, backend);
  }
  //@}


  //@{
  /**
   * Given a text property and a string, get some metrics for the rendered
   * string.
   * Return true on success, false otherwise.
   */
  bool GetMetrics(vtkTextProperty *tprop, const vtkStdString &str,
                  Metrics &metrics, int dpi, int backend = Default)
  {
    return this->GetMetricsInternal(tprop, str, metrics, dpi, backend);
  }
  bool GetMetrics(vtkTextProperty *tprop, const vtkUnicodeString &str,
                  Metrics &metrics, int dpi, int backend = Default)
  {
    return this->GetMetricsInternal(tprop, str, metrics, dpi, backend);
  }
  //@}

  //@{
  /**
   * Given a text property and a string, this function initializes the
   * vtkImageData *data and renders it in a vtkImageData.
   * Return true on success, false otherwise. If using the overload that
   * specifies "textDims", the array will be overwritten with the pixel width
   * and height defining a tight bounding box around the text in the image,
   * starting from the upper-right corner. This is used when rendering for a
   * texture on graphics hardware that requires texture image dimensions to be
   * a power of two; textDims can be used to determine the texture coordinates
   * needed to cleanly fit the text on the target.
   * The origin of the image's extents is aligned with the anchor point
   * described by the text property's vertical and horizontal justification
   * options.
   */
  bool RenderString(vtkTextProperty *tprop, const vtkStdString &str,
                    vtkImageData *data, int textDims[2], int dpi,
                    int backend = Default)
  {
    return this->RenderStringInternal(tprop, str, data, textDims, dpi, backend);
  }
  bool RenderString(vtkTextProperty *tprop, const vtkUnicodeString &str,
                    vtkImageData *data, int textDims[2], int dpi,
                    int backend = Default)
  {
    return this->RenderStringInternal(tprop, str, data, textDims, dpi, backend);
  }
  //@}

  //@{
  /**
   * This function returns the font size (in points) and sets the size in @a
   * tprop that is required to fit the string in the target rectangle. The
   * computed font size will be set in @a tprop as well. If an error occurs,
   * this function will return -1.
   */
  int GetConstrainedFontSize(const vtkStdString &str, vtkTextProperty *tprop,
                             int targetWidth, int targetHeight, int dpi,
                             int backend = Default)
  {
    return this->GetConstrainedFontSizeInternal(str, tprop, targetWidth,
                                                targetHeight, dpi, backend);
  }
  int GetConstrainedFontSize(const vtkUnicodeString &str, vtkTextProperty *tprop,
                             int targetWidth, int targetHeight, int dpi,
                             int backend = Default)
  {
    return this->GetConstrainedFontSizeInternal(str, tprop, targetWidth,
                                                targetHeight, dpi, backend);
  }
  //@}

  //@{
  /**
   * Given a text property and a string, this function populates the vtkPath
   * path with the outline of the rendered string. The origin of the path
   * coordinates is aligned with the anchor point described by the text
   * property's horizontal and vertical justification options.
   * Return true on success, false otherwise.
   */
  bool StringToPath(vtkTextProperty *tprop, const vtkStdString &str,
                    vtkPath *path, int dpi, int backend = Default)
  {
    return this->StringToPathInternal(tprop, str, path, dpi, backend);
  }
  bool StringToPath(vtkTextProperty *tprop, const vtkUnicodeString &str,
                    vtkPath *path, int dpi, int backend = Default)
  {
    return this->StringToPathInternal(tprop, str, path, dpi, backend);
  }
  //@}

  /**
   * Set to true if the graphics implmentation requires texture image dimensions
   * to be a power of two. Default is true, but this member will be set
   * appropriately by vtkOpenGLRenderWindow::OpenGLInitContext when GL is
   * inited.
   */
  void SetScaleToPowerOfTwo(bool scale)
  {
    this->SetScaleToPowerOfTwoInternal(scale);
  }

  friend class vtkTextRendererCleanup;

protected:
  vtkTextRenderer();
  ~vtkTextRenderer();

  //@{
  /**
   * Virtual methods for concrete implementations of the public methods.
   */
  virtual bool GetBoundingBoxInternal(vtkTextProperty *tprop,
                                      const vtkStdString &str,
                                      int bbox[4], int dpi, int backend) = 0;
  virtual bool GetBoundingBoxInternal(vtkTextProperty *tprop,
                                      const vtkUnicodeString &str,
                                      int bbox[4], int dpi, int backend) = 0;
  virtual bool GetMetricsInternal(vtkTextProperty *tprop,
                                  const vtkStdString &str,
                                  Metrics &metrics, int dpi, int backend) = 0;
  virtual bool GetMetricsInternal(vtkTextProperty *tprop,
                                  const vtkUnicodeString &str,
                                  Metrics &metrics, int dpi, int backend) = 0;
  virtual bool RenderStringInternal(vtkTextProperty *tprop,
                                    const vtkStdString &str,
                                    vtkImageData *data, int textDims[2],
                                    int dpi, int backend) = 0;
  virtual bool RenderStringInternal(vtkTextProperty *tprop,
                                    const vtkUnicodeString &str,
                                    vtkImageData *data, int textDims[2],
                                    int dpi, int backend) = 0;
  virtual int GetConstrainedFontSizeInternal(const vtkStdString &str,
                                             vtkTextProperty *tprop,
                                             int targetWidth, int targetHeight,
                                             int dpi, int backend) = 0;
  virtual int GetConstrainedFontSizeInternal(const vtkUnicodeString &str,
                                             vtkTextProperty *tprop,
                                             int targetWidth, int targetHeight,
                                             int dpi, int backend) = 0;
  virtual bool StringToPathInternal(vtkTextProperty *tprop,
                                    const vtkStdString &str, vtkPath *path,
                                    int dpi, int backend) = 0;
  virtual bool StringToPathInternal(vtkTextProperty *tprop,
                                    const vtkUnicodeString &str, vtkPath *path,
                                    int dpi, int backend) = 0;
  virtual void SetScaleToPowerOfTwoInternal(bool scale) = 0;
  //@}

  /**
   * Set the singleton instance. Call Delete() on the supplied
   * instance after setting it to fix the reference count.
   */
  static void SetInstance(vtkTextRenderer *instance);

  //@{
  /**
   * The singleton instance and the singleton cleanup instance.
   */
  static vtkTextRenderer *Instance;
  static vtkTextRendererCleanup Cleanup;
  //@}

  vtksys::RegularExpression *MathTextRegExp;
  vtksys::RegularExpression *MathTextRegExp2;

  //@{
  /**
   * Replace all instances of "\$" with "$".
   */
  virtual void CleanUpFreeTypeEscapes(vtkStdString &str);
  virtual void CleanUpFreeTypeEscapes(vtkUnicodeString &str);
  //@}

  /**
   * The backend to use when none is specified. Default: Detect
   */
  int DefaultBackend;

private:
  vtkTextRenderer(const vtkTextRenderer &) VTK_DELETE_FUNCTION;
  void operator=(const vtkTextRenderer &) VTK_DELETE_FUNCTION;
};

#endif //vtkTextRenderer_h