layout/generic/nsILineIterator.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 #ifndef nsILineIterator_h___
   7 #define nsILineIterator_h___
   8
   9 #include "nscore.h"
  10 #include "nsPoint.h"
  11 #include "mozilla/Attributes.h"
  12
  13 class nsIFrame;
  14 struct nsRect;
  15
  16 /**
  17  * Line iterator API.
  18  *
  19  * Lines are numbered from 0 to N, where 0 is the top line and N is
  20  * the bottom line.
  21  *
  22  * Obtain this interface from frames via nsIFrame::GetLineIterator.
  23  * When you are finished using the iterator, call DisposeLineIterator()
  24  * to destroy the iterator if appropriate.
  25  */
  26 class nsILineIterator {
  27  protected:
  28   ~nsILineIterator() {}
  29
  30  public:
  31   virtual void DisposeLineIterator() = 0;
  32
  33   /**
  34    * The number of lines in the block
  35    */
  36   virtual int32_t GetNumLines() = 0;
  37
  38   /**
  39    * The prevailing direction of lines.
  40    *
  41    * @return true if the CSS direction property for the block is
  42    *         "rtl", otherwise false
  43    *
  44    *XXX after bug 924851 change this to return a UBiDiDirection
  45    */
  46   virtual bool GetDirection() = 0;
  47
  48   // Return structural information about a line. aFirstFrameOnLine is
  49   // the first frame on the line and aNumFramesOnLine is the number of
  50   // frames that are on the line. If the line-number is invalid then
  51   // aFirstFrameOnLine will be nullptr and aNumFramesOnLine will be
  52   // zero.
  53   //
  54   // For valid line numbers, aLineBounds is set to the bounding box of
  55   // the line (which is based on the in-flow position of the frames on
  56   // the line; if a frame was moved because of relative positioning
  57   // then its coordinates may be outside the line bounds).
  58   NS_IMETHOD GetLine(int32_t aLineNumber, nsIFrame** aFirstFrameOnLine,
  59                      int32_t* aNumFramesOnLine, nsRect& aLineBounds) = 0;
  60
  61   /**
  62    * Given a frame that's a child of the block, find which line its on
  63    * and return that line index, as long as it's at least as big as
  64    * aStartLine.  Returns -1 if the frame cannot be found on lines
  65    * starting with aStartLine.
  66    */
  67   virtual int32_t FindLineContaining(nsIFrame* aFrame,
  68                                      int32_t aStartLine = 0) = 0;
  69
  70   // Given a line number and a coordinate, find the frame on the line
  71   // that is nearest to aPos along the inline axis. (The block-axis coord
  72   // of aPos is irrelevant.)
  73   // The aPosIsBeforeFirstFrame and aPosIsAfterLastFrame flags are updated
  74   // appropriately.
  75   NS_IMETHOD FindFrameAt(int32_t aLineNumber, nsPoint aPos,
  76                          nsIFrame** aFrameFound, bool* aPosIsBeforeFirstFrame,
  77                          bool* aPosIsAfterLastFrame) = 0;
  78
  79   // Give the line iterator implementor a chance todo something more complicated
  80   // than nsIFrame::GetNextSibling()
  81   NS_IMETHOD GetNextSiblingOnLine(nsIFrame*& aFrame, int32_t aLineNumber) = 0;
  82
  83   // Check whether visual and logical order of frames within a line are
  84   // identical.
  85   //  If not, return the first and last visual frames
  86   NS_IMETHOD CheckLineOrder(int32_t aLine, bool* aIsReordered,
  87                             nsIFrame** aFirstVisual,
  88                             nsIFrame** aLastVisual) = 0;
  89 };
  90
  91 class nsAutoLineIterator {
  92  public:
  93   nsAutoLineIterator() : mRawPtr(nullptr) {}
  94   MOZ_IMPLICIT nsAutoLineIterator(nsILineIterator* i) : mRawPtr(i) {}
  95
  96   ~nsAutoLineIterator() {
  97     if (mRawPtr) mRawPtr->DisposeLineIterator();
  98   }
  99
 100   operator nsILineIterator*() { return mRawPtr; }
 101   nsILineIterator* operator->() { return mRawPtr; }
 102
 103   nsILineIterator* operator=(nsILineIterator* i) {
 104     if (i == mRawPtr) return i;
 105
 106     if (mRawPtr) mRawPtr->DisposeLineIterator();
 107
 108     mRawPtr = i;
 109     return i;
 110   }
 111
 112  private:
 113   nsILineIterator* mRawPtr;
 114 };
 115
 116 #endif /* nsILineIterator_h___ */