The Tor Browser: layout/base/nsCSSRendering.h@b8a032363ba2 (annotated)

layout/base/nsCSSRendering.h@b8a032363ba2 (annotated)

layout/base/nsCSSRendering.h

Thu, 22 Jan 2015 13:21:57 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Thu, 22 Jan 2015 13:21:57 +0100
branch: TOR_BUG_9701
changeset 15: b8a032363ba2
permissions: -rw-r--r--

Incorporate requested changes from Mozilla in review:
https://bugzilla.mozilla.org/show_bug.cgi?id=1123480#c6

 /* -*- 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/. */
 /* utility functions for drawing borders and backgrounds */
 #ifndef nsCSSRendering_h___
 #define nsCSSRendering_h___
 #include "gfxBlur.h"
 #include "gfxContext.h"
 #include "nsLayoutUtils.h"
 #include "nsStyleStruct.h"
 #include "nsIFrame.h"
 class nsStyleContext;
 class nsPresContext;
 class nsRenderingContext;
 namespace mozilla {
 namespace layers {
 class ImageContainer;
 }
 // A CSSSizeOrRatio represents a (possibly partially specified) size for use
 // in computing image sizes. Either or both of the width and height might be
 // given. A ratio of width to height may also be given. If we at least two
 // of these then we can compute a concrete size, that is a width and height.
 struct CSSSizeOrRatio
 {
   CSSSizeOrRatio()
     : mRatio(0, 0)
     , mHasWidth(false)
     , mHasHeight(false) {}
   bool CanComputeConcreteSize() const
   {
     return mHasWidth + mHasHeight + HasRatio() >= 2;
   }
   bool IsConcrete() const { return mHasWidth && mHasHeight; }
   bool HasRatio() const { return mRatio.width > 0 && mRatio.height > 0; }
   bool IsEmpty() const
   {
     return (mHasWidth && mWidth <= 0) ||
            (mHasHeight && mHeight <= 0) ||
            mRatio.width <= 0 || mRatio.height <= 0;
   }
   // CanComputeConcreteSize must return true when ComputeConcreteSize is
   // called.
   nsSize ComputeConcreteSize() const;
   void SetWidth(nscoord aWidth)
   {
     mWidth = aWidth;
     mHasWidth = true;
     if (mHasHeight) {
       mRatio = nsSize(mWidth, mHeight);
     }
   }
   void SetHeight(nscoord aHeight)
   {
     mHeight = aHeight;
     mHasHeight = true;
     if (mHasWidth) {
       mRatio = nsSize(mWidth, mHeight);
     }
   }
   void SetSize(const nsSize& aSize)
   {
     mWidth = aSize.width;
     mHeight = aSize.height;
     mHasWidth = true;
     mHasHeight = true;
     mRatio = aSize;
   }
   void SetRatio(const nsSize& aRatio)
   {
     MOZ_ASSERT(!mHasWidth || !mHasHeight,
                "Probably shouldn't be setting a ratio if we have a concrete size");
     mRatio = aRatio;
   }
   nsSize mRatio;
   nscoord mWidth;
   nscoord mHeight;
   bool mHasWidth;
   bool mHasHeight;
 };
 }
 /**
  * This is a small wrapper class to encapsulate image drawing that can draw an
  * nsStyleImage image, which may internally be a real image, a sub image, or a
  * CSS gradient.
  *
  * @note Always call the member functions in the order of PrepareImage(),
  * SetSize(), and Draw*().
  */
 class nsImageRenderer {
 public:
   typedef mozilla::layers::LayerManager LayerManager;
   typedef mozilla::layers::ImageContainer ImageContainer;
   enum {
     FLAG_SYNC_DECODE_IMAGES = 0x01,
     FLAG_PAINTING_TO_WINDOW = 0x02
   };
   enum FitType
   {
     CONTAIN,
     COVER
   };
   nsImageRenderer(nsIFrame* aForFrame, const nsStyleImage* aImage, uint32_t aFlags);
   ~nsImageRenderer();
   /**
    * Populates member variables to get ready for rendering.
    * @return true iff the image is ready, and there is at least a pixel to
    * draw.
    */
   bool PrepareImage();
   /**
    * The three Compute*Size functions correspond to the sizing algorthms and
    * definitions from the CSS Image Values and Replaced Content spec. See
    * http://dev.w3.org/csswg/css-images-3/#sizing .
    */
   /**
    * Compute the intrinsic size of the image as defined in the CSS Image Values
    * spec. The intrinsic size is the unscaled size which the image would ideally
    * like to be in app units.
    */
   mozilla::CSSSizeOrRatio ComputeIntrinsicSize();
   /**
    * Compute the size of the rendered image using either the 'cover' or
    * 'contain' constraints (aFitType).
    * aIntrinsicRatio may be an invalid ratio, that is one or both of its
    * dimensions can be less than or equal to zero.
    */
   static nsSize ComputeConstrainedSize(const nsSize& aConstrainingSize,
                                        const nsSize& aIntrinsicRatio,
                                        FitType aFitType);
   /**
    * Compute the size of the rendered image (the concrete size) where no cover/
    * contain constraints are given. The 'default algorithm' from the CSS Image
    * Values spec.
    */
   static nsSize ComputeConcreteSize(const mozilla::CSSSizeOrRatio& aSpecifiedSize,
                                     const mozilla::CSSSizeOrRatio& aIntrinsicSize,
                                     const nsSize& aDefaultSize);
   /**
    * Set this image's preferred size. This will be its intrinsic size where
    * specified and the default size where it is not. Used as the unscaled size
    * when rendering the image.
    */
   void SetPreferredSize(const mozilla::CSSSizeOrRatio& aIntrinsicSize,
                         const nsSize& aDefaultSize);
   /**
    * Draws the image to the target rendering context.
    * aSrc is a rect on the source image which will be mapped to aDest.
    * @see nsLayoutUtils::DrawImage() for other parameters.
    */
   void Draw(nsPresContext*       aPresContext,
             nsRenderingContext&  aRenderingContext,
             const nsRect&        aDirtyRect,
             const nsRect&        aFill,
             const nsRect&        aDest,
             const mozilla::CSSIntRect& aSrc);
   /**
    * Draws the image to the target rendering context using background-specific
    * arguments.
    * @see nsLayoutUtils::DrawImage() for parameters.
    */
   void DrawBackground(nsPresContext*       aPresContext,
                       nsRenderingContext&  aRenderingContext,
                       const nsRect&        aDest,
                       const nsRect&        aFill,
                       const nsPoint&       aAnchor,
                       const nsRect&        aDirty);
   /**
    * Draw the image to a single component of a border-image style rendering.
    * aFill The destination rect to be drawn into
    * aSrc is the part of the image to be rendered into a tile (aUnitSize in
    * aFill), if aSrc and the dest tile are different sizes, the image will be
    * scaled to map aSrc onto the dest tile.
    * aHFill and aVFill are the repeat patterns for the component -
    * NS_STYLE_BORDER_IMAGE_REPEAT_*
    * aUnitSize The scaled size of a single source rect (in destination coords)
    * aIndex identifies the component: 0 1 2
    *                                  3 4 5
    *                                  6 7 8
    */
   void
   DrawBorderImageComponent(nsPresContext*       aPresContext,
                            nsRenderingContext&  aRenderingContext,
                            const nsRect&        aDirtyRect,
                            const nsRect&        aFill,
                            const mozilla::CSSIntRect& aSrc,
                            uint8_t              aHFill,
                            uint8_t              aVFill,
                            const nsSize&        aUnitSize,
                            uint8_t              aIndex);
   bool IsRasterImage();
   bool IsAnimatedImage();
   already_AddRefed<ImageContainer> GetContainer(LayerManager* aManager);
   bool IsReady() { return mIsReady; }
 private:
   /**
    * Helper method for creating a gfxDrawable from mPaintServerFrame or
    * mImageElementSurface.
    * Requires mType is eStyleImageType_Element.
    * Returns null if we cannot create the drawable.
    */
   already_AddRefed<gfxDrawable> DrawableForElement(const nsRect& aImageRect,
                                                    nsRenderingContext&  aRenderingContext);
   nsIFrame*                 mForFrame;
   const nsStyleImage*       mImage;
   nsStyleImageType          mType;
   nsCOMPtr<imgIContainer>   mImageContainer;
   nsRefPtr<nsStyleGradient> mGradientData;
   nsIFrame*                 mPaintServerFrame;
   nsLayoutUtils::SurfaceFromElementResult mImageElementSurface;
   bool                      mIsReady;
   nsSize                    mSize; // unscaled size of the image, in app units
   uint32_t                  mFlags;
 };
 /**
  * A struct representing all the information needed to paint a background
  * image to some target, taking into account all CSS background-* properties.
  * See PrepareBackgroundLayer.
  */
 struct nsBackgroundLayerState {
   /**
    * @param aFlags some combination of nsCSSRendering::PAINTBG_* flags
    */
   nsBackgroundLayerState(nsIFrame* aForFrame, const nsStyleImage* aImage, uint32_t aFlags)
     : mImageRenderer(aForFrame, aImage, aFlags), mCompositingOp(gfxContext::OPERATOR_OVER) {}
   /**
    * The nsImageRenderer that will be used to draw the background.
    */
   nsImageRenderer mImageRenderer;
   /**
    * A rectangle that one copy of the image tile is mapped onto. Same
    * coordinate system as aBorderArea/aBGClipRect passed into
    * PrepareBackgroundLayer.
    */
   nsRect mDestArea;
   /**
    * The actual rectangle that should be filled with (complete or partial)
    * image tiles. Same coordinate system as aBorderArea/aBGClipRect passed into
    * PrepareBackgroundLayer.
    */
   nsRect mFillArea;
   /**
    * The anchor point that should be snapped to a pixel corner. Same
    * coordinate system as aBorderArea/aBGClipRect passed into
    * PrepareBackgroundLayer.
    */
   nsPoint mAnchor;
   /**
    * The compositing operation that the image should use
    */
   gfxContext::GraphicsOperator mCompositingOp;
 };
 struct nsCSSRendering {
   /**
    * Initialize any static variables used by nsCSSRendering.
    */
   static void Init();
   /**
    * Clean up any static variables used by nsCSSRendering.
    */
   static void Shutdown();
   static void PaintBoxShadowInner(nsPresContext* aPresContext,
                                   nsRenderingContext& aRenderingContext,
                                   nsIFrame* aForFrame,
                                   const nsRect& aFrameArea,
                                   const nsRect& aDirtyRect);
   static void PaintBoxShadowOuter(nsPresContext* aPresContext,
                                   nsRenderingContext& aRenderingContext,
                                   nsIFrame* aForFrame,
                                   const nsRect& aFrameArea,
                                   const nsRect& aDirtyRect,
                                   float aOpacity = 1.0);
   static void ComputePixelRadii(const nscoord *aAppUnitsRadii,
                                 nscoord aAppUnitsPerPixel,
                                 gfxCornerSizes *oBorderRadii);
   /**
    * Render the border for an element using css rendering rules
    * for borders. aSkipSides is a bitmask of the sides to skip
    * when rendering. If 0 then no sides are skipped.
    */
   static void PaintBorder(nsPresContext* aPresContext,
                           nsRenderingContext& aRenderingContext,
                           nsIFrame* aForFrame,
                           const nsRect& aDirtyRect,
                           const nsRect& aBorderArea,
                           nsStyleContext* aStyleContext,
                           int aSkipSides = 0);
   /**
    * Like PaintBorder, but taking an nsStyleBorder argument instead of
    * getting it from aStyleContext.
    */
   static void PaintBorderWithStyleBorder(nsPresContext* aPresContext,
                                          nsRenderingContext& aRenderingContext,
                                          nsIFrame* aForFrame,
                                          const nsRect& aDirtyRect,
                                          const nsRect& aBorderArea,
                                          const nsStyleBorder& aBorderStyle,
                                          nsStyleContext* aStyleContext,
                                          int aSkipSides = 0);
   /**
    * Render the outline for an element using css rendering rules
    * for borders. aSkipSides is a bitmask of the sides to skip
    * when rendering. If 0 then no sides are skipped.
    */
   static void PaintOutline(nsPresContext* aPresContext,
                           nsRenderingContext& aRenderingContext,
                           nsIFrame* aForFrame,
                           const nsRect& aDirtyRect,
                           const nsRect& aBorderArea,
                           nsStyleContext* aStyleContext);
   /**
    * Render keyboard focus on an element.
    * |aFocusRect| is the outer rectangle of the focused element.
    * Uses a fixed style equivalent to "1px dotted |aColor|".
    * Not used for controls, because the native theme may differ.
    */
   static void PaintFocus(nsPresContext* aPresContext,
                          nsRenderingContext& aRenderingContext,
                          const nsRect& aFocusRect,
                          nscolor aColor);
   /**
    * Render a gradient for an element.
    * aDest is the rect for a single tile of the gradient on the destination.
    * aFill is the rect on the destination to be covered by repeated tiling of
    * the gradient.
    * aSrc is the part of the gradient to be rendered into a tile (aDest), if
    * aSrc and aDest are different sizes, the image will be scaled to map aSrc
    * onto aDest.
    * aIntrinsicSize is the size of the source gradient.
    */
   static void PaintGradient(nsPresContext* aPresContext,
                             nsRenderingContext& aRenderingContext,
                             nsStyleGradient* aGradient,
                             const nsRect& aDirtyRect,
                             const nsRect& aDest,
                             const nsRect& aFill,
                             const mozilla::CSSIntRect& aSrc,
                             const nsSize& aIntrinsiceSize);
   /**
    * Find the frame whose background style should be used to draw the
    * canvas background. aForFrame must be the frame for the root element
    * whose background style should be used. This function will return
    * aForFrame unless the <body> background should be propagated, in
    * which case we return the frame associated with the <body>'s background.
    */
   static nsIFrame* FindBackgroundStyleFrame(nsIFrame* aForFrame);
   /**
    * @return true if |aFrame| is a canvas frame, in the CSS sense.
    */
   static bool IsCanvasFrame(nsIFrame* aFrame);
   /**
    * Fill in an aBackgroundSC to be used to paint the background
    * for an element.  This applies the rules for propagating
    * backgrounds between BODY, the root element, and the canvas.
    * @return true if there is some meaningful background.
    */
   static bool FindBackground(nsIFrame* aForFrame,
                              nsStyleContext** aBackgroundSC);
   /**
    * As FindBackground, but the passed-in frame is known to be a root frame
    * (returned from nsCSSFrameConstructor::GetRootElementStyleFrame())
    * and there is always some meaningful background returned.
    */
   static nsStyleContext* FindRootFrameBackground(nsIFrame* aForFrame);
   /**
    * Returns background style information for the canvas.
    *
    * @param aForFrame
    *   the frame used to represent the canvas, in the CSS sense (i.e.
    *   nsCSSRendering::IsCanvasFrame(aForFrame) must be true)
    * @param aRootElementFrame
    *   the frame representing the root element of the document
    * @param aBackground
    *   contains background style information for the canvas on return
    */
   static nsStyleContext*
   FindCanvasBackground(nsIFrame* aForFrame, nsIFrame* aRootElementFrame)
   {
     NS_ABORT_IF_FALSE(IsCanvasFrame(aForFrame), "not a canvas frame");
     if (aRootElementFrame)
       return FindRootFrameBackground(aRootElementFrame);
     // This should always give transparent, so we'll fill it in with the
     // default color if needed.  This seems to happen a bit while a page is
     // being loaded.
     return aForFrame->StyleContext();
   }
   /**
    * Find a frame which draws a non-transparent background,
    * for various table-related and HR-related backwards-compatibility hacks.
    * This function will also stop if it finds themed frame which might draw
    * background.
    *
    * Be very hesitant if you're considering calling this function -- it's
    * usually not what you want.
    */
   static nsIFrame*
   FindNonTransparentBackgroundFrame(nsIFrame* aFrame,
                                     bool aStartAtParent = false);
   /**
    * Determine the background color to draw taking into account print settings.
    */
   static nscolor
   DetermineBackgroundColor(nsPresContext* aPresContext,
                            nsStyleContext* aStyleContext,
                            nsIFrame* aFrame,
                            bool& aDrawBackgroundImage,
                            bool& aDrawBackgroundColor);
   static nsRect
   ComputeBackgroundPositioningArea(nsPresContext* aPresContext,
                                    nsIFrame* aForFrame,
                                    const nsRect& aBorderArea,
                                    const nsStyleBackground& aBackground,
                                    const nsStyleBackground::Layer& aLayer,
                                    nsIFrame** aAttachedToFrame);
   static nsBackgroundLayerState
   PrepareBackgroundLayer(nsPresContext* aPresContext,
                          nsIFrame* aForFrame,
                          uint32_t aFlags,
                          const nsRect& aBorderArea,
                          const nsRect& aBGClipRect,
                          const nsStyleBackground& aBackground,
                          const nsStyleBackground::Layer& aLayer);
   /**
    * Render the background for an element using css rendering rules
    * for backgrounds.
    */
   enum {
     /**
      * When this flag is passed, the element's nsDisplayBorder will be
      * painted immediately on top of this background.
      */
     PAINTBG_WILL_PAINT_BORDER = 0x01,
     /**
      * When this flag is passed, images are synchronously decoded.
      */
     PAINTBG_SYNC_DECODE_IMAGES = 0x02,
     /**
      * When this flag is passed, painting will go to the screen so we can
      * take advantage of the fact that it will be clipped to the viewport.
      */
     PAINTBG_TO_WINDOW = 0x04
   };
   static void PaintBackground(nsPresContext* aPresContext,
                               nsRenderingContext& aRenderingContext,
                               nsIFrame* aForFrame,
                               const nsRect& aDirtyRect,
                               const nsRect& aBorderArea,
                               uint32_t aFlags,
                               nsRect* aBGClipRect = nullptr,
                               int32_t aLayer = -1);
   static void PaintBackgroundColor(nsPresContext* aPresContext,
                                    nsRenderingContext& aRenderingContext,
                                    nsIFrame* aForFrame,
                                    const nsRect& aDirtyRect,
                                    const nsRect& aBorderArea,
                                    uint32_t aFlags);
   /**
    * Same as |PaintBackground|, except using the provided style structs.
    * This short-circuits the code that ensures that the root element's
    * background is drawn on the canvas.
    * The aLayer parameter allows you to paint a single layer of the background.
    * The default value for aLayer, -1, means that all layers will be painted.
    * The background color will only be painted if the back-most layer is also
    * being painted.
    */
   static void PaintBackgroundWithSC(nsPresContext* aPresContext,
                                     nsRenderingContext& aRenderingContext,
                                     nsIFrame* aForFrame,
                                     const nsRect& aDirtyRect,
                                     const nsRect& aBorderArea,
                                     nsStyleContext *aStyleContext,
                                     const nsStyleBorder& aBorder,
                                     uint32_t aFlags,
                                     nsRect* aBGClipRect = nullptr,
                                     int32_t aLayer = -1);
   static void PaintBackgroundColorWithSC(nsPresContext* aPresContext,
                                          nsRenderingContext& aRenderingContext,
                                          nsIFrame* aForFrame,
                                          const nsRect& aDirtyRect,
                                          const nsRect& aBorderArea,
                                          nsStyleContext *aStyleContext,
                                          const nsStyleBorder& aBorder,
                                          uint32_t aFlags);
   /**
    * Returns the rectangle covered by the given background layer image, taking
    * into account background positioning, sizing, and repetition, but not
    * clipping.
    */
   static nsRect GetBackgroundLayerRect(nsPresContext* aPresContext,
                                        nsIFrame* aForFrame,
                                        const nsRect& aBorderArea,
                                        const nsRect& aClipRect,
                                        const nsStyleBackground& aBackground,
                                        const nsStyleBackground::Layer& aLayer,
                                        uint32_t aFlags);
   /**
    * Checks if image in layer aLayer of aBackground is currently decoded.
    */
   static bool IsBackgroundImageDecodedForStyleContextAndLayer(
     const nsStyleBackground *aBackground, uint32_t aLayer);
   /**
    * Checks if all images that are part of the background for aFrame are
    * currently decoded.
    */
   static bool AreAllBackgroundImagesDecodedForFrame(nsIFrame* aFrame);
   /**
    * Called when we start creating a display list. The frame tree will not
    * change until a matching EndFrameTreeLocked is called.
    */
   static void BeginFrameTreesLocked();
   /**
    * Called when we've finished using a display list. When all
    * BeginFrameTreeLocked calls have been balanced by an EndFrameTreeLocked,
    * the frame tree may start changing again.
    */
   static void EndFrameTreesLocked();
   // Draw a border segment in the table collapsing border model without
   // beveling corners
   static void DrawTableBorderSegment(nsRenderingContext& aContext,
                                      uint8_t              aBorderStyle,
                                      nscolor              aBorderColor,
                                      const nsStyleBackground* aBGColor,
                                      const nsRect&        aBorderRect,
                                      int32_t              aAppUnitsPerCSSPixel,
                                      uint8_t              aStartBevelSide = 0,
                                      nscoord              aStartBevelOffset = 0,
                                      uint8_t              aEndBevelSide = 0,
                                      nscoord              aEndBevelOffset = 0);
   /**
    * Function for painting the decoration lines for the text.
    * NOTE: aPt, aLineSize, aAscent and aOffset are non-rounded device pixels,
    *       not app units.
    *   input:
    *     @param aFrame            the frame which needs the decoration line
    *     @param aGfxContext
    *     @param aDirtyRect        no need to paint outside this rect
    *     @param aColor            the color of the decoration line
    *     @param aPt               the top/left edge of the text
    *     @param aXInFrame         the distance between aPt.x and left edge of
    *                              aFrame.  If the decoration line is for shadow,
    *                              set the distance between the left edge of
    *                              the aFrame and the position of the text as
    *                              positioned without offset of the shadow.
    *     @param aLineSize         the width and the height of the decoration
    *                              line
    *     @param aAscent           the ascent of the text
    *     @param aOffset           the offset of the decoration line from
    *                              the baseline of the text (if the value is
    *                              positive, the line is lifted up)
    *     @param aDecoration       which line will be painted. The value can be
    *                              NS_STYLE_TEXT_DECORATION_LINE_UNDERLINE or
    *                              NS_STYLE_TEXT_DECORATION_LINE_OVERLINE or
    *                              NS_STYLE_TEXT_DECORATION_LINE_LINE_THROUGH.
    *     @param aStyle            the style of the decoration line such as
    *                              NS_STYLE_TEXT_DECORATION_STYLE_*.
    *     @param aDescentLimit     If aDescentLimit is zero or larger and the
    *                              underline overflows from the descent space,
    *                              the underline should be lifted up as far as
    *                              possible.  Note that this does not mean the
    *                              underline never overflows from this
    *                              limitation.  Because if the underline is
    *                              positioned to the baseline or upper, it causes
    *                              unreadability.  Note that if this is zero
    *                              or larger, the underline rect may be shrunken
    *                              if it's possible.  Therefore, this value is
    *                              used for strikeout line and overline too.
    */
   static void PaintDecorationLine(nsIFrame* aFrame,
                                   gfxContext* aGfxContext,
                                   const gfxRect& aDirtyRect,
                                   const nscolor aColor,
                                   const gfxPoint& aPt,
                                   const gfxFloat aXInFrame,
                                   const gfxSize& aLineSize,
                                   const gfxFloat aAscent,
                                   const gfxFloat aOffset,
                                   const uint8_t aDecoration,
                                   const uint8_t aStyle,
                                   const gfxFloat aDescentLimit = -1.0);
   /**
    * Adds a path corresponding to the outline of the decoration line to
    * the specified context.  Arguments have the same meaning as for
    * PaintDecorationLine.  Currently this only works for solid
    * decorations; for other decoration styles, an empty path is added
    * to the context.
    */
   static void DecorationLineToPath(nsIFrame* aFrame,
                                    gfxContext* aGfxContext,
                                    const gfxRect& aDirtyRect,
                                    const nscolor aColor,
                                    const gfxPoint& aPt,
                                    const gfxFloat aXInFrame,
                                    const gfxSize& aLineSize,
                                    const gfxFloat aAscent,
                                    const gfxFloat aOffset,
                                    const uint8_t aDecoration,
                                    const uint8_t aStyle,
                                    const gfxFloat aDescentLimit = -1.0);
   /**
    * Function for getting the decoration line rect for the text.
    * NOTE: aLineSize, aAscent and aOffset are non-rounded device pixels,
    *       not app units.
    *   input:
    *     @param aPresContext
    *     @param aLineSize         the width and the height of the decoration
    *                              line
    *     @param aAscent           the ascent of the text
    *     @param aOffset           the offset of the decoration line from
    *                              the baseline of the text (if the value is
    *                              positive, the line is lifted up)
    *     @param aDecoration       which line will be painted. The value can be
    *                              NS_STYLE_TEXT_DECORATION_LINE_UNDERLINE or
    *                              NS_STYLE_TEXT_DECORATION_LINE_OVERLINE or
    *                              NS_STYLE_TEXT_DECORATION_LINE_LINE_THROUGH.
    *     @param aStyle            the style of the decoration line such as
    *                              NS_STYLE_TEXT_DECORATION_STYLE_*.
    *     @param aDescentLimit     If aDescentLimit is zero or larger and the
    *                              underline overflows from the descent space,
    *                              the underline should be lifted up as far as
    *                              possible.  Note that this does not mean the
    *                              underline never overflows from this
    *                              limitation.  Because if the underline is
    *                              positioned to the baseline or upper, it causes
    *                              unreadability.  Note that if this is zero
    *                              or larger, the underline rect may be shrunken
    *                              if it's possible.  Therefore, this value is
    *                              used for strikeout line and overline too.
    *   output:
    *     @return                  the decoration line rect for the input,
    *                              the each values are app units.
    */
   static nsRect GetTextDecorationRect(nsPresContext* aPresContext,
                                       const gfxSize& aLineSize,
                                       const gfxFloat aAscent,
                                       const gfxFloat aOffset,
                                       const uint8_t aDecoration,
                                       const uint8_t aStyle,
                                       const gfxFloat aDescentLimit = -1.0);
   static gfxContext::GraphicsOperator GetGFXBlendMode(uint8_t mBlendMode) {
     switch (mBlendMode) {
       case NS_STYLE_BLEND_NORMAL:      return gfxContext::OPERATOR_OVER;
       case NS_STYLE_BLEND_MULTIPLY:    return gfxContext::OPERATOR_MULTIPLY;
       case NS_STYLE_BLEND_SCREEN:      return gfxContext::OPERATOR_SCREEN;
       case NS_STYLE_BLEND_OVERLAY:     return gfxContext::OPERATOR_OVERLAY;
       case NS_STYLE_BLEND_DARKEN:      return gfxContext::OPERATOR_DARKEN;
       case NS_STYLE_BLEND_LIGHTEN:     return gfxContext::OPERATOR_LIGHTEN;
       case NS_STYLE_BLEND_COLOR_DODGE: return gfxContext::OPERATOR_COLOR_DODGE;
       case NS_STYLE_BLEND_COLOR_BURN:  return gfxContext::OPERATOR_COLOR_BURN;
       case NS_STYLE_BLEND_HARD_LIGHT:  return gfxContext::OPERATOR_HARD_LIGHT;
       case NS_STYLE_BLEND_SOFT_LIGHT:  return gfxContext::OPERATOR_SOFT_LIGHT;
       case NS_STYLE_BLEND_DIFFERENCE:  return gfxContext::OPERATOR_DIFFERENCE;
       case NS_STYLE_BLEND_EXCLUSION:   return gfxContext::OPERATOR_EXCLUSION;
       case NS_STYLE_BLEND_HUE:         return gfxContext::OPERATOR_HUE;
       case NS_STYLE_BLEND_SATURATION:  return gfxContext::OPERATOR_SATURATION;
       case NS_STYLE_BLEND_COLOR:       return gfxContext::OPERATOR_COLOR;
       case NS_STYLE_BLEND_LUMINOSITY:  return gfxContext::OPERATOR_LUMINOSITY;
       default:                         MOZ_ASSERT(false); return gfxContext::OPERATOR_OVER;
     }
     return gfxContext::OPERATOR_OVER;
   }
 protected:
   static gfxRect GetTextDecorationRectInternal(const gfxPoint& aPt,
                                                const gfxSize& aLineSize,
                                                const gfxFloat aAscent,
                                                const gfxFloat aOffset,
                                                const uint8_t aDecoration,
                                                const uint8_t aStyle,
                                                const gfxFloat aDscentLimit);
   /**
    * Returns inflated rect for painting a decoration line.
    * Complex style decoration lines should be painted from leftmost of nearest
    * ancestor block box because that makes better look of connection of lines
    * for different nodes.  ExpandPaintingRectForDecorationLine() returns
    * a rect for actual painting rect for the clipped rect.
    *
    * input:
    *     @param aFrame            the frame which needs the decoration line.
    *     @param aStyle            the style of the complex decoration line
    *                              NS_STYLE_TEXT_DECORATION_STYLE_DOTTED or
    *                              NS_STYLE_TEXT_DECORATION_STYLE_DASHED or
    *                              NS_STYLE_TEXT_DECORATION_STYLE_WAVY.
    *     @param aClippedRect      the clipped rect for the decoration line.
    *                              in other words, visible area of the line.
    *     @param aXInFrame         the distance between left edge of aFrame and
    *                              aClippedRect.pos.x.
    *     @param aCycleLength      the width of one cycle of the line style.
    */
   static gfxRect ExpandPaintingRectForDecorationLine(
                    nsIFrame* aFrame,
                    const uint8_t aStyle,
                    const gfxRect &aClippedRect,
                    const gfxFloat aXInFrame,
                    const gfxFloat aCycleLength);
 };
 /*
  * nsContextBoxBlur
  * Creates an 8-bit alpha channel context for callers to draw in, blurs the
  * contents of that context and applies it as a 1-color mask on a
  * different existing context. Uses gfxAlphaBoxBlur as its back end.
  *
  * You must call Init() first to create a suitable temporary surface to draw
  * on.  You must then draw any desired content onto the given context, then
  * call DoPaint() to apply the blurred content as a single-color mask. You
  * can only call Init() once, so objects cannot be reused.
  *
  * This is very useful for creating drop shadows or silhouettes.
  */
 class nsContextBoxBlur {
 public:
   enum {
     FORCE_MASK = 0x01
   };
   /**
    * Prepares a gfxContext to draw on. Do not call this twice; if you want
    * to get the gfxContext again use GetContext().
    *
    * @param aRect                The coordinates of the surface to create.
    *                             All coordinates must be in app units.
    *                             This must not include the blur radius, pass
    *                             it as the second parameter and everything
    *                             is taken care of.
    *
    * @param aBlurRadius          The blur radius in app units.
    *
    * @param aAppUnitsPerDevPixel The number of app units in a device pixel,
    *                             for conversion.  Most of the time you'll
    *                             pass this from the current PresContext if
    *                             available.
    *
    * @param aDestinationCtx      The graphics context to apply the blurred
    *                             mask to when you call DoPaint(). Make sure
    *                             it is not destroyed before you call
    *                             DoPaint(). To set the color of the
    *                             resulting blurred graphic mask, you must
    *                             set the color on this context before
    *                             calling Init().
    *
    * @param aDirtyRect           The absolute dirty rect in app units. Used to
    *                             optimize the temporary surface size and speed up blur.
    *
    * @param aSkipRect            An area in device pixels (NOT app units!) to avoid
    *                             blurring over, to prevent unnecessary work.
    *
    * @param aFlags               FORCE_MASK to ensure that the content drawn to the
    *                             returned gfxContext is used as a mask, and not
    *                             drawn directly to aDestinationCtx.
    *
    * @return            A blank 8-bit alpha-channel-only graphics context to
    *                    draw on, or null on error. Must not be freed. The
    *                    context has a device offset applied to it given by
    *                    aRect. This means you can use coordinates as if it
    *                    were at the desired position at aRect and you don't
    *                    need to worry about translating any coordinates to
    *                    draw on this temporary surface.
    *
    * If aBlurRadius is 0, the returned context is aDestinationCtx and
    * DoPaint() does nothing, because no blurring is required. Therefore, you
    * should prepare the destination context as if you were going to draw
    * directly on it instead of any temporary surface created in this class.
    */
   gfxContext* Init(const nsRect& aRect, nscoord aSpreadRadius,
                    nscoord aBlurRadius,
                    int32_t aAppUnitsPerDevPixel, gfxContext* aDestinationCtx,
                    const nsRect& aDirtyRect, const gfxRect* aSkipRect,
                    uint32_t aFlags = 0);
   /**
    * Does the actual blurring and mask applying. Users of this object *must*
    * have called Init() first, then have drawn whatever they want to be
    * blurred onto the internal gfxContext before calling this.
    */
   void DoPaint();
   /**
    * Gets the internal gfxContext at any time. Must not be freed. Avoid
    * calling this before calling Init() since the context would not be
    * constructed at that point.
    */
   gfxContext* GetContext();
   /**
    * Get the margin associated with the given blur radius, i.e., the
    * additional area that might be painted as a result of it.  (The
    * margin for a spread radius is itself, on all sides.)
    */
   static nsMargin GetBlurRadiusMargin(nscoord aBlurRadius,
                                       int32_t aAppUnitsPerDevPixel);
   /**
    * Blurs a coloured rectangle onto aDestinationCtx. This is equivalent
    * to calling Init(), drawing a rectangle onto the returned surface
    * and then calling DoPaint, but may let us optimize better in the
    * backend.
    *
    * @param aDestinationCtx      The destination to blur to.
    * @param aRect                The rectangle to blur in app units.
    * @param aAppUnitsPerDevPixel The number of app units in a device pixel,
    *                             for conversion.  Most of the time you'll
    *                             pass this from the current PresContext if
    *                             available.
    * @param aCornerRadii         Corner radii for aRect, if it is a rounded
    *                             rectangle.
    * @param aBlurRadius          The blur radius in app units.
    * @param aShadowColor         The color to draw the blurred shadow.
    * @param aDirtyRect           The absolute dirty rect in app units. Used to
    *                             optimize the temporary surface size and speed up blur.
    * @param aSkipRect            An area in device pixels (NOT app units!) to avoid
    *                             blurring over, to prevent unnecessary work.
    */
   static void BlurRectangle(gfxContext* aDestinationCtx,
                             const nsRect& aRect,
                             int32_t aAppUnitsPerDevPixel,
                             gfxCornerSizes* aCornerRadii,
                             nscoord aBlurRadius,
                             const gfxRGBA& aShadowColor,
                             const nsRect& aDirtyRect,
                             const gfxRect& aSkipRect);
 protected:
   gfxAlphaBoxBlur blur;
   nsRefPtr<gfxContext> mContext;
   gfxContext* mDestinationCtx;
   /* This is true if the blur already has it's content transformed
    * by mDestinationCtx's transform */
   bool mPreTransformed;
 };
 #endif /* nsCSSRendering_h___ */

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layout/base/nsCSSRendering.h