layout/generic/nsSplittableFrame.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 /*
   8  * base class for rendering objects that can be split across lines,
   9  * columns, or pages
  10  */
  11
  12 #ifndef nsSplittableFrame_h___
  13 #define nsSplittableFrame_h___
  14
  15 #include "mozilla/Attributes.h"
  16 #include "nsIFrame.h"
  17
  18 // Derived class that allows splitting
  19 class nsSplittableFrame : public nsIFrame {
  20  public:
  21   NS_DECL_ABSTRACT_FRAME(nsSplittableFrame)
  22   NS_DECL_QUERYFRAME_TARGET(nsSplittableFrame)
  23   NS_DECL_QUERYFRAME
  24
  25   void Init(nsIContent* aContent, nsContainerFrame* aParent,
  26             nsIFrame* aPrevInFlow) override;
  27
  28   void Destroy(DestroyContext&) override;
  29
  30   /*
  31    * Frame continuations can be either fluid or non-fluid.
  32    *
  33    * Fluid continuations ("in-flows") are the result of line breaking,
  34    * column breaking, or page breaking.
  35    *
  36    * Non-fluid continuations can be the result of BiDi frame splitting,
  37    * column-span splitting, or <col span="N"> where N > 1.
  38    *
  39    * A "flow" is a chain of fluid continuations.
  40    *
  41    * For more information, see https://wiki.mozilla.org/Gecko:Continuation_Model
  42    */
  43
  44   // Get the previous/next continuation, regardless of its type (fluid or
  45   // non-fluid).
  46   nsIFrame* GetPrevContinuation() const final;
  47   nsIFrame* GetNextContinuation() const final;
  48
  49   // Set a previous/next non-fluid continuation.
  50   void SetPrevContinuation(nsIFrame*) final;
  51   void SetNextContinuation(nsIFrame*) final;
  52
  53   // Get the first/last continuation for this frame.
  54   nsIFrame* FirstContinuation() const override;
  55   nsIFrame* LastContinuation() const final;
  56
  57 #ifdef DEBUG
  58   // Can aFrame2 be reached from aFrame1 by following prev/next continuations?
  59   static bool IsInPrevContinuationChain(nsIFrame* aFrame1, nsIFrame* aFrame2);
  60   static bool IsInNextContinuationChain(nsIFrame* aFrame1, nsIFrame* aFrame2);
  61 #endif
  62
  63   // Get the previous/next continuation, only if it is fluid (an "in-flow").
  64   nsIFrame* GetPrevInFlow() const final;
  65   nsIFrame* GetNextInFlow() const final;
  66
  67   // Set a previous/next fluid continuation.
  68   void SetPrevInFlow(nsIFrame*) final;
  69   void SetNextInFlow(nsIFrame*) final;
  70
  71   // Get the first/last frame in the current flow.
  72   nsIFrame* FirstInFlow() const final;
  73   nsIFrame* LastInFlow() const final;
  74
  75   // Remove the frame from the flow. Connects the frame's prev-in-flow
  76   // and its next-in-flow. This should only be called in frame Destroy()
  77   // methods.
  78   static void RemoveFromFlow(nsIFrame* aFrame);
  79
  80  protected:
  81   nsSplittableFrame(ComputedStyle* aStyle, nsPresContext* aPresContext,
  82                     ClassID aID)
  83       : nsIFrame(aStyle, aPresContext, aID) {}
  84
  85   /**
  86    * Return the sum of the block-axis content size of our previous
  87    * continuations.
  88    *
  89    * Classes that call this are _required_ to call this at least once for each
  90    * reflow (unless you're the first continuation, in which case you can skip
  91    * it, because as an optimization we don't cache it there).
  92    *
  93    * This guarantees that the internal cache works, by refreshing it. Calling it
  94    * multiple times in the same reflow is wasteful, but not an error.
  95    */
  96   nscoord CalcAndCacheConsumedBSize();
  97
  98   /**
  99    * This static wrapper over CalcAndCacheConsumedBSize() is intended for a
 100    * specific scenario where an nsSplittableFrame's subclass needs to access
 101    * another subclass' consumed block-size. For ordinary use cases,
 102    * CalcAndCacheConsumedBSize() should be called.
 103    *
 104    * This has the same requirements as CalcAndCacheConsumedBSize(). In
 105    * particular, classes that call this are _required_ to call this at least
 106    * once for each reflow.
 107    */
 108   static nscoord ConsumedBSize(nsSplittableFrame* aFrame) {
 109     return aFrame->CalcAndCacheConsumedBSize();
 110   }
 111
 112   /**
 113    * Retrieve the effective computed block size of this frame, which is the
 114    * computed block size, minus the block size consumed by any previous
 115    * continuations.
 116    */
 117   nscoord GetEffectiveComputedBSize(const ReflowInput& aReflowInput,
 118                                     nscoord aConsumed) const;
 119
 120   /**
 121    * @see nsIFrame::GetLogicalSkipSides()
 122    */
 123   LogicalSides GetLogicalSkipSides() const override {
 124     return GetBlockLevelLogicalSkipSides(true);
 125   }
 126
 127   LogicalSides GetBlockLevelLogicalSkipSides(bool aAfterReflow) const;
 128
 129   /**
 130    * A version of GetLogicalSkipSides() that is intended to be used inside
 131    * Reflow before it's known if |this| frame will be COMPLETE or not.
 132    * It returns a result that assumes this fragment is the last and thus
 133    * should apply the block-end border/padding etc (except for "true" overflow
 134    * containers which always skip block sides).  You're then expected to
 135    * recalculate the block-end side (as needed) when you know |this| frame's
 136    * reflow status is INCOMPLETE.
 137    * This method is intended for frames that break in the block axis.
 138    */
 139   LogicalSides PreReflowBlockLevelLogicalSkipSides() const {
 140     return GetBlockLevelLogicalSkipSides(false);
 141   };
 142
 143   nsIFrame* mPrevContinuation = nullptr;
 144   nsIFrame* mNextContinuation = nullptr;
 145 };
 146
 147 #endif /* nsSplittableFrame_h___ */