layout/generic/nsILineIterator.h

   1 /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* This Source Code Form is subject to the terms of the Mozilla Public
   3  * License, v. 2.0. If a copy of the MPL was not distributed with this
   4  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   5 #ifndef nsILineIterator_h___
   6 #define nsILineIterator_h___
   7
   8 #include "nscore.h"
   9 #include "nsCoord.h"
  10
  11 class nsIFrame;
  12 struct nsRect;
  13
  14 // Line Flags (see GetLine below)
  15
  16 // This bit is set when the line is wrapping up a block frame. When
  17 // clear, it means that the line contains inline elements.
  18 #define NS_LINE_FLAG_IS_BLOCK           0x1
  19
  20 // This bit is set when the line ends in some sort of break.
  21 #define NS_LINE_FLAG_ENDS_IN_BREAK      0x4
  22
  23 /**
  24  * Line iterator API.
  25  *
  26  * Lines are numbered from 0 to N, where 0 is the top line and N is
  27  * the bottom line.
  28  *
  29  * Obtain this interface from frames via nsIFrame::GetLineIterator.
  30  * When you are finished using the iterator, call DisposeLineIterator()
  31  * to destroy the iterator if appropriate.
  32  */
  33 class nsILineIterator
  34 {
  35 protected:
  36   ~nsILineIterator() { }
  37
  38 public:
  39   virtual void DisposeLineIterator() = 0;
  40
  41   /**
  42    * The number of lines in the block
  43    */
  44   virtual int32_t GetNumLines() = 0;
  45
  46   /**
  47    * The prevailing direction of lines.
  48    *
  49    * @return true if the CSS direction property for the block is
  50    *         "rtl", otherwise false
  51    */
  52   virtual bool GetDirection() = 0;
  53
  54   // Return structural information about a line. aFirstFrameOnLine is
  55   // the first frame on the line and aNumFramesOnLine is the number of
  56   // frames that are on the line. If the line-number is invalid then
  57   // aFirstFrameOnLine will be nullptr and aNumFramesOnLine will be
  58   // zero.
  59   //
  60   // For valid line numbers, aLineBounds is set to the bounding box of
  61   // the line (which is based on the in-flow position of the frames on
  62   // the line; if a frame was moved because of relative positioning
  63   // then its coordinates may be outside the line bounds).
  64   //
  65   // In addition, aLineFlags will contain flag information about the
  66   // line.
  67   NS_IMETHOD GetLine(int32_t aLineNumber,
  68                      nsIFrame** aFirstFrameOnLine,
  69                      int32_t* aNumFramesOnLine,
  70                      nsRect& aLineBounds,
  71                      uint32_t* aLineFlags) = 0;
  72
  73   /**
  74    * Given a frame that's a child of the block, find which line its on
  75    * and return that line index, as long as it's at least as big as
  76    * aStartLine.  Returns -1 if the frame cannot be found on lines
  77    * starting with aStartLine.
  78    */
  79   virtual int32_t FindLineContaining(nsIFrame* aFrame,
  80                                      int32_t aStartLine = 0) = 0;
  81
  82   // Given a line number and an X coordinate, find the frame on the
  83   // line that is nearest to the X coordinate. The
  84   // aXIsBeforeFirstFrame and aXIsAfterLastFrame flags are updated
  85   // appropriately.
  86   NS_IMETHOD FindFrameAt(int32_t aLineNumber,
  87                          nscoord aX,
  88                          nsIFrame** aFrameFound,
  89                          bool* aXIsBeforeFirstFrame,
  90                          bool* aXIsAfterLastFrame) = 0;
  91
  92   // Give the line iterator implementor a chance todo something more complicated than
  93   // nsIFrame::GetNextSibling()
  94   NS_IMETHOD GetNextSiblingOnLine(nsIFrame*& aFrame, int32_t aLineNumber) = 0;
  95
  96 #ifdef IBMBIDI
  97   // Check whether visual and logical order of frames within a line are identical.
  98   //  If not, return the first and last visual frames
  99   NS_IMETHOD CheckLineOrder(int32_t                  aLine,
 100                             bool                     *aIsReordered,
 101                             nsIFrame                 **aFirstVisual,
 102                             nsIFrame                 **aLastVisual) = 0;
 103 #endif
 104 };
 105
 106 class nsAutoLineIterator
 107 {
 108 public:
 109   nsAutoLineIterator() : mRawPtr(nullptr) { }
 110   nsAutoLineIterator(nsILineIterator *i) : mRawPtr(i) { }
 111
 112   ~nsAutoLineIterator() {
 113     if (mRawPtr)
 114       mRawPtr->DisposeLineIterator();
 115   }
 116
 117   operator nsILineIterator*() { return mRawPtr; }
 118   nsILineIterator* operator->() { return mRawPtr; }
 119
 120   nsILineIterator* operator=(nsILineIterator* i) {
 121     if (i == mRawPtr)
 122       return i;
 123
 124     if (mRawPtr)
 125       mRawPtr->DisposeLineIterator();
 126
 127     mRawPtr = i;
 128     return i;
 129   }
 130
 131 private:
 132   nsILineIterator* mRawPtr;
 133 };
 134
 135 #endif /* nsILineIterator_h___ */