зеркало из https://github.com/mozilla/gecko-dev.git
Bug 299239 - BiDi: Caret is stuck when reaching a single LTR character in RTL text. patch from Eyal Rozenberg <eyalroz@technion.ac.il>. r+sr=roc
This commit is contained in:
mozilla.mano%sent.com
Родитель
d56d8d8b5b
Коммит
53cbfe48e6
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@ -4312,15 +4312,81 @@ NS_IMETHODIMP
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nsTextFrame::PeekOffset(nsPresContext* aPresContext, nsPeekOffsetStruct *aPos)
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{
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#ifdef IBMBIDI
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// XXX TODO: - this explanation may not be accurate
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// - need to better explain what aPos->mPreferLeft means
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// for two frames on the same line
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// - need to better explain for what happens when you move
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// from the end of a line to the beginning of the next
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// despite not making a move logically within the text.
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// - need to explain why XORing with the embedding level
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// achieves the desired effect
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//
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// When you move your caret by in some visual direction, and you find the
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// new position is at the edge of a line (beginning or end), you want to
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// stay on the current line rather than move to the next or the previous
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// one.
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//
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// When your frames are ordered the same way logically as they are
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// visually (e.g. when they're frames of LTR text displayed in
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// left-then-down order), this translates to terms of 'prefer left' or
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// 'prefer right', i.e. if you move to the left and hit the beginning of
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// the line you have to choose between the frame "on the left" - the last
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// frame on the previous line - rather than the frame "on the right" - the
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// first frame of the text line. So you could say that you always prefer
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// the frame closer to where you are now, i.e. the frame opposite to the
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// movement.
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// (see nsSelection::MoveCaret() for an example in code)
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//
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// When the frames are displayed in right-then-down order (i.e. frames
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// within an RTL line), the last sentence remains correct, but now
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// the directions are reversed - if you're moving left, the frame
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// closer to you is the one "on the right" - the last frame on the current
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// line - rather than the one "on the left" - the first frame on the next
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// line. Now, although this implementation of this method (i.e.
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// for nsTextFrame) has no use itself for aPos->mPreferLeft, we may
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// be delegating the PeekOffset to another frame, and nsFrame's
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// implementation does use aPos->mPreferLeft, so we have to set it
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// here (why?), and we have to maintain consistency along calls
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// to PeekOffset of nsTextFrames on the same line.
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//
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// Note:
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// eDirPrevious actually means 'in the visual left-then-down direction'
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// eDirNext actually means 'in the visual right-then-down direction'
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// (this is again due to the LTRish bias of the nomenclature)
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PRBool isOddLevel = NS_GET_EMBEDDING_LEVEL(this) & 1;
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if ((eSelectCharacter == aPos->mAmount)
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|| (eSelectWord == aPos->mAmount))
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aPos->mPreferLeft ^= isOddLevel;
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aPos->mPreferLeft = (eDirPrevious == aPos->mDirection) ^ isOddLevel;
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#endif
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if (!aPos || !mContent)
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return NS_ERROR_NULL_POINTER;
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// XXX TODO: explain this policy; why the assymetry between
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// too high and too low start offsets?
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//
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// There are 4 possible ranges from aPos->mStartOffset:
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//
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// 0 mContentLength mContentLength+mContentLength
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// | | |
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// range #1 | range #2 | range #3 | range #4
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// ***************
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// our frame's part
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// of the content
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//
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// Range Policy
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// ------------------------------------------------------------------------
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// #1 Assume the start position is at the end of the content of 'this'
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// #2 Round up the position to the beginning of our frame
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// #3 No change necessary
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// #4 Delegate the PeekOffset() to the next frame (according
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// to the direction, either to our left or our right)
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//
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// Note: the diagram above is drawn left-to-right, but advancing
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// in the content may sometimes mean going right-to-left
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if (aPos->mStartOffset < 0 )
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aPos->mStartOffset = mContentLength + mContentOffset;
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if (aPos->mStartOffset < mContentOffset){
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@ -4344,6 +4410,13 @@ nsTextFrame::PeekOffset(nsPresContext* aPresContext, nsPeekOffsetStruct *aPos)
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return nextInFlow->PeekOffset(aPresContext, aPos);
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}
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// XXX TODO: explain the following:
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// - if this frame is the first of the last in the line according
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// to the content indices, why not handle the cases of
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// eSelectBeginLine/eSelectEndLine
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// - why can't we make the hand-off to the parent class' method
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// before the of aPos->mStartOffset and aPos->mPreferLeft?
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if (aPos->mAmount == eSelectLine || aPos->mAmount == eSelectBeginLine
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|| aPos->mAmount == eSelectEndLine || aPos->mAmount == eSelectParagraph)
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{
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@ -4531,6 +4604,10 @@ nsTextFrame::PeekOffset(nsPresContext* aPresContext, nsPeekOffsetStruct *aPos)
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*/
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if (i > mContentLength){
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found = PR_FALSE;
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// XXX TODO: explain why in this case GetNextInFlow() is good enough,
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// but in the case of
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// aPos->mStartOffset > (mContentOffset + mContentLength)
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// above, we use the presentation context and get the 'nextBidi'
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frameUsed = GetNextInFlow();
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start = mContentOffset + mContentLength;
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aPos->mContentOffset = start;//in case next call fails we stop at this offset
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@ -4686,12 +4763,18 @@ nsTextFrame::PeekOffset(nsPresContext* aPresContext, nsPeekOffsetStruct *aPos)
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}
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}
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TryNextFrame:
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TryNextFrame:
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// XXX TODO: explain why in this case GetNextInFlow() is good enough,
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// but in the case of
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// aPos->mStartOffset > (mContentOffset + mContentLength)
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// above, we use the presentation context and get the 'nextBidi'
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frameUsed = GetNextInFlow();
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start = 0;
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}
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}
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if (!found || (aPos->mContentOffset > (mContentOffset + mContentLength)) || (aPos->mContentOffset < mContentOffset))
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if (!found ||
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(aPos->mContentOffset > (mContentOffset + mContentLength)) ||
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(aPos->mContentOffset < mContentOffset))
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{
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aPos->mContentOffset = PR_MIN(aPos->mContentOffset, mContentOffset + mContentLength);
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aPos->mContentOffset = PR_MAX(aPos->mContentOffset, mContentOffset);
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