tor-browser

nsPlaceholderFrame.h (7161B)

---

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */

/*
* rendering object for the point that anchors out-of-flow rendering
* objects such as floats and absolutely positioned elements
*/

/*
* Destruction of a placeholder and its out-of-flow must observe the
* following constraints:
*
* - The mapping from the out-of-flow to the placeholder must be
*   removed from the frame manager before the placeholder is destroyed.
* - The mapping from the out-of-flow to the placeholder must be
*   removed from the frame manager before the out-of-flow is destroyed.
* - The placeholder must be removed from the frame tree, or have the
*   mapping from it to its out-of-flow cleared, before the out-of-flow
*   is destroyed (so that the placeholder will not point to a destroyed
*   frame while it's in the frame tree).
*
* Furthermore, some code assumes that placeholders point to something
* useful, so placeholders without an associated out-of-flow should not
* remain in the tree.
*
* The placeholder's Destroy() implementation handles the destruction of
* the placeholder and its out-of-flow. To avoid crashes, frame removal
* and destruction code that works with placeholders must not assume
* that the placeholder points to its out-of-flow.
*/

#ifndef nsPlaceholderFrame_h___
#define nsPlaceholderFrame_h___

#include "nsGkAtoms.h"
#include "nsIFrame.h"

namespace mozilla {
class PresShell;
}  // namespace mozilla

class nsPlaceholderFrame;
nsPlaceholderFrame* NS_NewPlaceholderFrame(mozilla::PresShell* aPresShell,
                                          mozilla::ComputedStyle* aStyle,
                                          nsFrameState aTypeBits);

#define PLACEHOLDER_TYPE_MASK                                                  \
 (PLACEHOLDER_FOR_FLOAT | PLACEHOLDER_FOR_ABSPOS | PLACEHOLDER_FOR_FIXEDPOS | \
  PLACEHOLDER_FOR_TOPLAYER)

/**
* Implementation of a frame that's used as a placeholder for a frame that
* has been moved out of the flow.
*/
class nsPlaceholderFrame final : public nsIFrame {
public:
 NS_DECL_FRAMEARENA_HELPERS(nsPlaceholderFrame)
#ifdef DEBUG
 NS_DECL_QUERYFRAME
#endif

 /**
  * Create a new placeholder frame.  aTypeBit must be one of the
  * PLACEHOLDER_FOR_* constants above.
  */
 friend nsPlaceholderFrame* NS_NewPlaceholderFrame(
     mozilla::PresShell* aPresShell, ComputedStyle* aStyle,
     nsFrameState aTypeBits);

 nsPlaceholderFrame(ComputedStyle* aStyle, nsPresContext* aPresContext,
                    nsFrameState aTypeBits)
     : nsIFrame(aStyle, aPresContext, kClassID), mOutOfFlowFrame(nullptr) {
   MOZ_ASSERT(
       aTypeBits == PLACEHOLDER_FOR_FLOAT ||
           aTypeBits == PLACEHOLDER_FOR_ABSPOS ||
           aTypeBits == PLACEHOLDER_FOR_FIXEDPOS ||
           aTypeBits == (PLACEHOLDER_FOR_TOPLAYER | PLACEHOLDER_FOR_ABSPOS) ||
           aTypeBits == (PLACEHOLDER_FOR_TOPLAYER | PLACEHOLDER_FOR_FIXEDPOS),
       "Unexpected type bit");
   AddStateBits(aTypeBits);
 }

 // Get/Set the associated out of flow frame
 nsIFrame* GetOutOfFlowFrame() const { return mOutOfFlowFrame; }
 void SetOutOfFlowFrame(nsIFrame* aFrame) {
   NS_ASSERTION(!aFrame || !aFrame->GetPrevContinuation(),
                "OOF must be first continuation");
   mOutOfFlowFrame = aFrame;
 }

 void AddInlineMinISize(const mozilla::IntrinsicSizeInput& aInput,
                        InlineMinISizeData* aData) override;
 void AddInlinePrefISize(const mozilla::IntrinsicSizeInput& aInput,
                         InlinePrefISizeData* aData) override;

 void Reflow(nsPresContext* aPresContext, ReflowOutput& aDesiredSize,
             const ReflowInput& aReflowInput,
             nsReflowStatus& aStatus) override;

 void Destroy(DestroyContext&) override;

#if defined(DEBUG) || (defined(MOZ_REFLOW_PERF_DSP) && defined(MOZ_REFLOW_PERF))
 void BuildDisplayList(nsDisplayListBuilder* aBuilder,
                       const nsDisplayListSet& aLists) override;
#endif  // DEBUG || (MOZ_REFLOW_PERF_DSP && MOZ_REFLOW_PERF)

#ifdef DEBUG_FRAME_DUMP
 void List(FILE* out = stderr, const char* aPrefix = "",
           ListFlags aFlags = ListFlags()) const override;
 nsresult GetFrameName(nsAString& aResult) const override;
#endif  // DEBUG

 bool IsEmpty() override { return true; }
 bool IsSelfEmpty() override { return true; }

 bool CanContinueTextRun() const override;

 void SetLineIsEmptySoFar(bool aValue) {
   AddOrRemoveStateBits(PLACEHOLDER_LINE_IS_EMPTY_SO_FAR, aValue);
   AddStateBits(PLACEHOLDER_HAVE_LINE_IS_EMPTY_SO_FAR);
 }
 bool GetLineIsEmptySoFar(bool* aResult) const {
   bool haveValue = HasAnyStateBits(PLACEHOLDER_HAVE_LINE_IS_EMPTY_SO_FAR);
   if (haveValue) {
     *aResult = HasAnyStateBits(PLACEHOLDER_LINE_IS_EMPTY_SO_FAR);
   }
   return haveValue;
 }
 void ForgetLineIsEmptySoFar() {
   RemoveStateBits(PLACEHOLDER_HAVE_LINE_IS_EMPTY_SO_FAR);
 }

#ifdef ACCESSIBILITY
 mozilla::a11y::AccType AccessibleType() override {
   nsIFrame* realFrame = GetRealFrameForPlaceholder(this);
   return realFrame ? realFrame->AccessibleType() : nsIFrame::AccessibleType();
 }
#endif

 ComputedStyle* GetParentComputedStyleForOutOfFlow(
     nsIFrame** aProviderFrame) const;

 // Like GetParentComputedStyleForOutOfFlow, but ignores display:contents bits.
 ComputedStyle* GetLayoutParentStyleForOutOfFlow(
     nsIFrame** aProviderFrame) const;

 bool RenumberFrameAndDescendants(int32_t* aOrdinal, int32_t aDepth,
                                  int32_t aIncrement,
                                  bool aForCounting) override {
   return mOutOfFlowFrame->RenumberFrameAndDescendants(
       aOrdinal, aDepth, aIncrement, aForCounting);
 }

 /**
  * @return the out-of-flow for aFrame if aFrame is a placeholder; otherwise
  * aFrame
  */
 static nsIFrame* GetRealFrameFor(nsIFrame* aFrame) {
   MOZ_ASSERT(aFrame, "Must have a frame to work with");
   if (aFrame->IsPlaceholderFrame()) {
     return GetRealFrameForPlaceholder(aFrame);
   }
   return aFrame;
 }

 /**
  * @return the out-of-flow for aFrame, which is known to be a placeholder
  */
 static nsIFrame* GetRealFrameForPlaceholder(const nsIFrame* aFrame) {
   MOZ_ASSERT(aFrame->IsPlaceholderFrame(),
              "Must have placeholder frame as input");
   nsIFrame* outOfFlow =
       static_cast<const nsPlaceholderFrame*>(aFrame)->GetOutOfFlowFrame();
   NS_ASSERTION(outOfFlow, "Null out-of-flow for placeholder?");
   return outOfFlow;
 }

protected:
 // A helper to implement AddInlineMinISize() and AddInlinePrefISize().
 void AddFloatToIntrinsicISizeData(const mozilla::IntrinsicSizeInput& aInput,
                                   mozilla::IntrinsicISizeType aType,
                                   InlineIntrinsicISizeData* aData) const;

 nsIFrame* mOutOfFlowFrame;
};

#endif /* nsPlaceholderFrame_h___ */