gfx/src/nsTransform2D.h

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
   3 /* This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 #ifndef nsTransform2D_h___
   8 #define nsTransform2D_h___
   9
  10 #include "nsCoord.h"
  11
  12 class nsTransform2D {
  13  private:
  14   /**
  15    * This represents the following matrix (note that the order of row/column
  16    * indices is opposite to usual notation)
  17    *
  18    *      / m00   0   m20  \
  19    * M =  |  0   m11  m21  |
  20    *      \  0    0    1   /
  21    *
  22    * Transformation of a coordinate (x, y) is obtained by setting
  23    * v = (x, y, 1)^T and evaluating  M . v
  24    **/
  25
  26   float m00, m11, m20, m21;
  27
  28  public:
  29   nsTransform2D(void) {
  30     m20 = m21 = 0.0f;
  31     m00 = m11 = 1.0f;
  32   }
  33
  34   ~nsTransform2D(void) = default;
  35
  36   /**
  37    * set this transform to a translation
  38    *
  39    * @param      tx, x translation
  40    * @param      ty, y translation
  41    **/
  42
  43   void SetToTranslate(float tx, float ty) {
  44     m00 = m11 = 1.0f;
  45     m20 = tx;
  46     m21 = ty;
  47   }
  48
  49   /**
  50    * get the translation portion of this transform
  51    *
  52    * @param      pt, Point to return translation values in
  53    **/
  54
  55   void GetTranslationCoord(nscoord* ptX, nscoord* ptY) const {
  56     *ptX = NSToCoordRound(m20);
  57     *ptY = NSToCoordRound(m21);
  58   }
  59
  60   /**
  61    * apply matrix to vector
  62    *
  63    * @param    pt Point to transform
  64    **/
  65
  66   void TransformCoord(nscoord* ptX, nscoord* ptY) const;
  67
  68   /**
  69    * apply matrix to rect
  70    *
  71    * @param    rect Rect to transform
  72    **/
  73
  74   void TransformCoord(nscoord* aX, nscoord* aY, nscoord* aWidth,
  75                       nscoord* aHeight) const;
  76
  77   /**
  78    * add a scale to a Transform via x, y pair
  79    *
  80    * @param    ptX x value to add as x scale
  81    * @param    ptY y value to add as y scale
  82    **/
  83
  84   void AddScale(float ptX, float ptY) {
  85     m00 *= ptX;
  86     m11 *= ptY;
  87   }
  88
  89   /**
  90    * Set the scale (overriding any previous calls to AddScale, but leaving
  91    * any existing translation).
  92    *
  93    * @param    ptX x value to add as x scale
  94    * @param    ptY y value to add as y scale
  95    **/
  96
  97   void SetScale(float ptX, float ptY) {
  98     m00 = ptX;
  99     m11 = ptY;
 100   }
 101 };
 102
 103 #endif