/* -*- 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 css3 multi-column layout */ #include "mozilla/Attributes.h" #include "nsContainerFrame.h" class nsColumnSetFrame : public nsContainerFrame { public: NS_DECL_FRAMEARENA_HELPERS nsColumnSetFrame(nsStyleContext* aContext); NS_IMETHOD SetInitialChildList(ChildListID aListID, nsFrameList& aChildList) MOZ_OVERRIDE; NS_IMETHOD Reflow(nsPresContext* aPresContext, nsHTMLReflowMetrics& aDesiredSize, const nsHTMLReflowState& aReflowState, nsReflowStatus& aStatus) MOZ_OVERRIDE; NS_IMETHOD AppendFrames(ChildListID aListID, nsFrameList& aFrameList) MOZ_OVERRIDE; NS_IMETHOD InsertFrames(ChildListID aListID, nsIFrame* aPrevFrame, nsFrameList& aFrameList) MOZ_OVERRIDE; NS_IMETHOD RemoveFrame(ChildListID aListID, nsIFrame* aOldFrame) MOZ_OVERRIDE; virtual nscoord GetMinWidth(nsRenderingContext *aRenderingContext) MOZ_OVERRIDE; virtual nscoord GetPrefWidth(nsRenderingContext *aRenderingContext) MOZ_OVERRIDE; /** * Retrieve the available height for content of this frame. The available content * height is the available height for the frame, minus borders and padding. */ virtual nscoord GetAvailableContentHeight(const nsHTMLReflowState& aReflowState); virtual nsIFrame* GetContentInsertionFrame() MOZ_OVERRIDE { nsIFrame* frame = GetFirstPrincipalChild(); // if no children return nullptr if (!frame) return nullptr; return frame->GetContentInsertionFrame(); } virtual nsresult StealFrame(nsIFrame* aChild, bool aForceNormal) MOZ_OVERRIDE { // nsColumnSetFrame keeps overflow containers in main child list return nsContainerFrame::StealFrame(aChild, true); } virtual bool IsFrameOfType(uint32_t aFlags) const MOZ_OVERRIDE { return nsContainerFrame::IsFrameOfType(aFlags & ~(nsIFrame::eCanContainOverflowContainers)); } virtual void BuildDisplayList(nsDisplayListBuilder* aBuilder, const nsRect& aDirtyRect, const nsDisplayListSet& aLists) MOZ_OVERRIDE; virtual nsIAtom* GetType() const MOZ_OVERRIDE; virtual void PaintColumnRule(nsRenderingContext* aCtx, const nsRect& aDirtyRect, const nsPoint& aPt); #ifdef DEBUG_FRAME_DUMP NS_IMETHOD GetFrameName(nsAString& aResult) const MOZ_OVERRIDE { return MakeFrameName(NS_LITERAL_STRING("ColumnSet"), aResult); } #endif protected: nscoord mLastBalanceHeight; nsReflowStatus mLastFrameStatus; /** * These are the parameters that control the layout of columns. */ struct ReflowConfig { // The number of columns that we want to balance across. If we're not // balancing, this will be set to INT32_MAX. int32_t mBalanceColCount; // The width of each individual column. nscoord mColWidth; // The amount of width that is expected to be left over after all the // columns and column gaps are laid out. nscoord mExpectedWidthLeftOver; // The width of each column gap. nscoord mColGap; // The maximum height of any individual column during a reflow iteration. // This parameter is set during each iteration of the binary search for // the best column height. nscoord mColMaxHeight; // A boolean controlling whether or not we are balancing. This should be // equivalent to mBalanceColCount == INT32_MAX. bool mIsBalancing; // The last known column height that was 'feasible'. A column height is // feasible if all child content fits within the specified height. nscoord mKnownFeasibleHeight; // The last known height that was 'infeasible'. A column height is // infeasible if not all child content fits within the specified height. nscoord mKnownInfeasibleHeight; // Height of the column set frame nscoord mComputedHeight; // The height "consumed" by previous-in-flows. // The computed height should be equal to the height of the element (i.e. // the computed height itself) plus the consumed height. nscoord mConsumedHeight; }; /** * Some data that is better calculated during reflow */ struct ColumnBalanceData { // The maximum "content height" of any column nscoord mMaxHeight; // The sum of the "content heights" for all columns nscoord mSumHeight; // The "content height" of the last column nscoord mLastHeight; // The maximum "content height" of all columns that overflowed // their available height nscoord mMaxOverflowingHeight; // This flag determines whether the last reflow of children exceeded the // computed height of the column set frame. If so, we set the height to // this maximum allowable height, and continue reflow without balancing. bool mHasExcessHeight; void Reset() { mMaxHeight = mSumHeight = mLastHeight = mMaxOverflowingHeight = 0; mHasExcessHeight = false; } }; /** * Similar to nsBlockFrame::DrainOverflowLines. Locate any columns not * handled by our prev-in-flow, and any columns sitting on our own * overflow list, and put them in our primary child list for reflowing. */ void DrainOverflowColumns(); bool ReflowColumns(nsHTMLReflowMetrics& aDesiredSize, const nsHTMLReflowState& aReflowState, nsReflowStatus& aReflowStatus, ReflowConfig& aConfig, bool aLastColumnUnbounded, nsCollapsingMargin* aCarriedOutBottomMargin, ColumnBalanceData& aColData); /** * The basic reflow strategy is to call this function repeatedly to * obtain specific parameters that determine the layout of the * columns. This function will compute those parameters from the CSS * style. This function will also be responsible for implementing * the state machine that controls column balancing. */ ReflowConfig ChooseColumnStrategy(const nsHTMLReflowState& aReflowState, bool aForceAuto, nscoord aFeasibleHeight, nscoord aInfeasibleHeight); /** * Perform the binary search for the best balance height for this column set. * * @param aReflowState The input parameters for the current reflow iteration. * @param aPresContext The presentation context in which the current reflow * iteration is occurring. * @param aConfig The ReflowConfig object associated with this column set * frame, generated by ChooseColumnStrategy(). * @param aColData A data structure used to keep track of data needed between * successive iterations of the balancing process. * @param aDesiredSize The final output size of the column set frame (output * of reflow procedure). * @param aOutMargin The bottom margin of the column set frame that may be * carried out from reflow (and thus collapsed). * @param aUnboundedLastColumn A boolean value indicating that the last column * can be of any height. Used during the first iteration of the * balancing procedure to measure the height of all content in * descendant frames of the column set. * @param aRunWasFeasible An input/output parameter indicating whether or not * the last iteration of the balancing loop was a feasible height to * fit all content from descendant frames. * @param aStatus A final reflow status of the column set frame, passed in as * an output parameter. */ void FindBestBalanceHeight(const nsHTMLReflowState& aReflowState, nsPresContext* aPresContext, ReflowConfig& aConfig, ColumnBalanceData& aColData, nsHTMLReflowMetrics& aDesiredSize, nsCollapsingMargin& aOutMargin, bool& aUnboundedLastColumn, bool& aRunWasFeasible, nsReflowStatus& aStatus); /** * Reflow column children. Returns true iff the content that was reflowed * fit into the mColMaxHeight. */ bool ReflowChildren(nsHTMLReflowMetrics& aDesiredSize, const nsHTMLReflowState& aReflowState, nsReflowStatus& aStatus, const ReflowConfig& aConfig, bool aLastColumnUnbounded, nsCollapsingMargin* aCarriedOutBottomMargin, ColumnBalanceData& aColData); };