summaryrefslogtreecommitdiffstats
path: root/layout/generic/nsPlaceholderFrame.h
blob: 0c23a4f75c6ab6997a1b18f6a275a0f95141ea65 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* 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 "mozilla/Attributes.h"
#include "nsFrame.h"
#include "nsGkAtoms.h"

nsIFrame* NS_NewPlaceholderFrame(nsIPresShell* aPresShell,
                                 nsStyleContext* aContext,
                                 nsFrameState aTypeBit);

#define PLACEHOLDER_TYPE_MASK    (PLACEHOLDER_FOR_FLOAT | \
                                  PLACEHOLDER_FOR_ABSPOS | \
                                  PLACEHOLDER_FOR_FIXEDPOS | \
                                  PLACEHOLDER_FOR_POPUP | \
                                  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 nsFrame {
public:
  NS_DECL_FRAMEARENA_HELPERS
#ifdef DEBUG
  NS_DECL_QUERYFRAME_TARGET(nsPlaceholderFrame)
  NS_DECL_QUERYFRAME
#endif

  /**
   * Create a new placeholder frame.  aTypeBit must be one of the
   * PLACEHOLDER_FOR_* constants above.
   */
  friend nsIFrame* NS_NewPlaceholderFrame(nsIPresShell* aPresShell,
                                          nsStyleContext* aContext,
                                          nsFrameState aTypeBit);
  nsPlaceholderFrame(nsStyleContext* aContext, nsFrameState aTypeBit)
    : nsFrame(aContext)
  {
    NS_PRECONDITION(aTypeBit == PLACEHOLDER_FOR_FLOAT ||
                    aTypeBit == PLACEHOLDER_FOR_ABSPOS ||
                    aTypeBit == PLACEHOLDER_FOR_FIXEDPOS ||
                    aTypeBit == PLACEHOLDER_FOR_POPUP ||
                    aTypeBit == PLACEHOLDER_FOR_TOPLAYER,
                    "Unexpected type bit");
    AddStateBits(aTypeBit);
  }

  // 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;
             }

  // nsIFrame overrides
  // We need to override GetXULMinSize and GetXULPrefSize because XUL uses
  // placeholders not within lines.
  virtual void AddInlineMinISize(nsRenderingContext* aRenderingContext,
                                 InlineMinISizeData* aData) override;
  virtual void AddInlinePrefISize(nsRenderingContext* aRenderingContext,
                                  InlinePrefISizeData* aData) override;
  virtual nsSize GetXULMinSize(nsBoxLayoutState& aBoxLayoutState) override;
  virtual nsSize GetXULPrefSize(nsBoxLayoutState& aBoxLayoutState) override;
  virtual nsSize GetXULMaxSize(nsBoxLayoutState& aBoxLayoutState) override;

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

  virtual void DestroyFrom(nsIFrame* aDestructRoot) override;

#if defined(DEBUG) || (defined(MOZ_REFLOW_PERF_DSP) && defined(MOZ_REFLOW_PERF))
  virtual void BuildDisplayList(nsDisplayListBuilder*   aBuilder,
                                const nsRect&           aDirtyRect,
                                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 = "", uint32_t aFlags = 0) const override;
  virtual nsresult GetFrameName(nsAString& aResult) const override;
#endif // DEBUG

  /**
   * Get the "type" of the frame
   *
   * @see nsGkAtoms::placeholderFrame
   */
  virtual nsIAtom* GetType() const override;

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

  virtual bool CanContinueTextRun() const override;

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

  virtual nsStyleContext* GetParentStyleContext(nsIFrame** aProviderFrame) const override;

  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) {
    NS_PRECONDITION(aFrame, "Must have a frame to work with");
    if (aFrame->GetType() == nsGkAtoms::placeholderFrame) {
      return GetRealFrameForPlaceholder(aFrame);
    }
    return aFrame;
  }

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

protected:
  nsIFrame* mOutOfFlowFrame;
};

#endif /* nsPlaceholderFrame_h___ */