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 * for the specific language governing rights and limitations under the
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 * The Original Code is mozilla.org code.
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 * The Initial Developer of the Original Code is
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 *
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/* loading of CSS style sheets using the network APIs */

#ifndef nsICSSLoader_h___
#define nsICSSLoader_h___

#include "nsISupports.h"
#include "nsSubstring.h"
#include "nsCompatibility.h"

class nsIAtom;
class nsIURI;
class nsICSSParser;
class nsICSSStyleSheet;
class nsPresContext;
class nsIContent;
class nsIDocument;
class nsIUnicharInputStream;
class nsICSSLoaderObserver;
class nsMediaList;
class nsICSSImportRule;
class nsIPrincipal;

// IID for the nsICSSLoader interface
// 33c469dd-af03-4098-9984-b13cee34d86a
#define NS_ICSS_LOADER_IID     \
{ 0x33c469dd, 0xaf03, 0x4098, \
 { 0x99, 0x84, 0xb1, 0x3c, 0xee, 0x34, 0xd8, 0x6a } }

typedef void (*nsCSSLoaderCallbackFunc)(nsICSSStyleSheet* aSheet, void *aData, PRBool aDidNotify);

class nsICSSLoader : public nsISupports {
public:
  NS_DECLARE_STATIC_IID_ACCESSOR(NS_ICSS_LOADER_IID)

  NS_IMETHOD Init(nsIDocument* aDocument) = 0;
  NS_IMETHOD DropDocumentReference(void) = 0; // notification that doc is going away

  NS_IMETHOD SetCompatibilityMode(nsCompatibility aCompatMode) = 0;
  NS_IMETHOD SetPreferredSheet(const nsAString& aTitle) = 0;
  NS_IMETHOD GetPreferredSheet(nsAString& aTitle) = 0;

  // Get/Recycle a CSS parser for general use
  NS_IMETHOD GetParserFor(nsICSSStyleSheet* aSheet,
                          nsICSSParser** aParser) = 0;
  NS_IMETHOD RecycleParser(nsICSSParser* aParser) = 0;

  // XXXbz sort out what the deal is with events!  When should they fire?
  
  /**
   * Load an inline style sheet.  If a successful result is returned and
   * *aCompleted is false, then aObserver is guaranteed to be notified
   * asynchronously once the sheet is marked complete.  If an error is
   * returned, or if *aCompleted is true, aObserver will not be notified.  In
   * addition to parsing the sheet, this method will insert it into the
   * stylesheet list of this CSSLoader's document.
   *
   * @param aElement the element linking to the stylesheet.  This must not be
   *                 null and must implement nsIStyleSheetLinkingElement.
   * @param aStream the character stream that holds the stylesheet data.
   * @param aLineNumber the line number at which the stylesheet data started.
   * @param aTitle the title of the sheet.
   * @param aMedia the media string for the sheet.
   * @param aObserver the observer to notify when the load completes.
   *        May be null.
   * @param [out] aCompleted whether parsing of the sheet completed.
   * @param [out] aIsAlternate whether the stylesheet ended up being an
   *        alternate sheet.
   */
  NS_IMETHOD LoadInlineStyle(nsIContent* aElement,
                             nsIUnicharInputStream* aStream, 
                             PRUint32 aLineNumber,
                             const nsSubstring& aTitle,
                             const nsSubstring& aMedia,
                             nsICSSLoaderObserver* aObserver,
                             PRBool* aCompleted,
                             PRBool* aIsAlternate) = 0;

  /**
   * Load a linked (document) stylesheet.  If a successful result is returned,
   * aObserver is guaranteed to be notified asynchronously once the sheet is
   * loaded and marked complete.  If an error is returned, aObserver will not
   * be notified.  In addition to loading the sheet, this method will insert it
   * into the stylesheet list of this CSSLoader's document.
   *
   * @param aElement the element linking to the the stylesheet.  May be null.
   * @param aURL the URL of the sheet.
   * @param aTitle the title of the sheet.
   * @param aMedia the media string for the sheet.
   * @param aHasAlternateRel whether the rel for this link included
   *        "alternate".
   * @param aObserver the observer to notify when the load completes.
   *                  May be null.
   * @param [out] aIsAlternate whether the stylesheet actually ended up beinga
   *        an alternate sheet.  Note that this need not match
   *        aHasAlternateRel.
   */
  NS_IMETHOD LoadStyleLink(nsIContent* aElement,
                           nsIURI* aURL, 
                           const nsSubstring& aTitle,
                           const nsSubstring& aMedia,
                           PRBool aHasAlternateRel,
                           nsICSSLoaderObserver* aObserver,
                           PRBool* aIsAlternate) = 0;

  /**
   * Load a child (@import-ed) style sheet.  In addition to loading the sheet,
   * this method will insert it into the child sheet list of aParentSheet.  If
   * there is no sheet currently being parsed and the child sheet is not
   * complete when this method returns, then when the child sheet becomes
   * complete aParentSheet will be QIed to nsICSSLoaderObserver and
   * asynchronously notified, just like for LoadStyleLink.  Note that if the
   * child sheet is already complete when this method returns, no
   * nsICSSLoaderObserver notification will be sent.
   *
   * @param aParentSheet the parent of this child sheet
   * @param aURL the URL of the child sheet
   * @param aMedia the already-parsed media list for the child sheet
   * @param aRule the @import rule importing this child.  This is used to
   *              properly order the child sheet list of aParentSheet.
   */
  NS_IMETHOD LoadChildSheet(nsICSSStyleSheet* aParentSheet,
                            nsIURI* aURL, 
                            nsMediaList* aMedia,
                            nsICSSImportRule* aRule) = 0;

  /**
   * Synchronously load and return the stylesheet at aURL.  Any child sheets
   * will also be loaded synchronously.  Note that synchronous loads over some
   * protocols may involve spinning up a new event loop, so use of this method
   * does NOT guarantee not receiving any events before the sheet loads.  This
   * method can be used to load sheets not associated with a document.
   *
   * @param aURL the URL of the sheet to load
   * @param aEnableUnsafeRules whether unsafe rules are enabled for this
   * sheet load
   * Unsafe rules are rules that can violate key Gecko invariants if misused.
   * In particular, most anonymous box pseudoelements must be very carefully
   * styled or we will have severe problems. Therefore unsafe rules should
   * never be enabled for stylesheets controlled by untrusted sites; preferably
   * unsafe rules should only be enabled for agent sheets.
   * @param aUseSystemPrincipal if true, give the resulting sheet the system
   * principal no matter where it's being loaded from.
   * @param [out] aSheet the loaded, complete sheet.
   *
   * NOTE: At the moment, this method assumes the sheet will be UTF-8, but
   * ideally it would allow arbitrary encodings.  Callers should NOT depend on
   * non-UTF8 sheets being treated as UTF-8 by this method.
   *
   * NOTE: A successful return from this method doesn't indicate anything about
   * whether the data could be parsed as CSS and doesn't indicate anything
   * about the status of child sheets of the returned sheet.
   */
  NS_IMETHOD LoadSheetSync(nsIURI* aURL, PRBool aEnableUnsafeRules,
                           PRBool aUseSystemPrincipal,
                           nsICSSStyleSheet** aSheet) = 0;

  /**
   * As above, but aUseSystemPrincipal and aEnableUnsafeRules are assumed false.
   */
  nsresult LoadSheetSync(nsIURI* aURL, nsICSSStyleSheet** aSheet) {
    return LoadSheetSync(aURL, PR_FALSE, PR_FALSE, aSheet);
  }

  /**
   * Asynchronously load the stylesheet at aURL.  If a successful result is
   * returned, aObserver is guaranteed to be notified asynchronously once the
   * sheet is loaded and marked complete.  This method can be used to load
   * sheets not associated with a document.
   *
   * @param aURL the URL of the sheet to load
   * @param aOriginPrincipal the principal to use for security checks.  This
   *                         can be null to indicate that these checks should
   *                         be skipped.
   * @param aCharset the encoding to use for converting the sheet data
   *        from bytes to Unicode.  May be empty to indicate that the
   *        charset of the CSSLoader's document should be used.  This
   *        is only used if neither the network transport nor the
   *        sheet itself indicate an encoding.
   * @param aObserver the observer to notify when the load completes.
   *                  Must not be null.
   * @param [out] aSheet the sheet to load. Note that the sheet may well
   *              not be loaded by the time this method returns.
   */
  NS_IMETHOD LoadSheet(nsIURI* aURL,
                       nsIPrincipal* aOriginPrincipal,
                       const nsCString& aCharset,
                       nsICSSLoaderObserver* aObserver,
                       nsICSSStyleSheet** aSheet) = 0;

  /**
   * Same as above, to be used when the caller doesn't care about the
   * not-yet-loaded sheet.
   */
  NS_IMETHOD LoadSheet(nsIURI* aURL,
                       nsIPrincipal* aOriginPrincipal,
                       const nsCString& aCharset,
                       nsICSSLoaderObserver* aObserver) = 0;

  /**
   * Stop loading all sheets.  All nsICSSLoaderObservers involved will be
   * notified with NS_BINDING_ABORTED as the status, possibly synchronously.
   */
  NS_IMETHOD Stop(void) = 0;

  /**
   * Stop loading one sheet.  The nsICSSLoaderObserver involved will be
   * notified with NS_BINDING_ABORTED as the status, possibly synchronously.
   */
  NS_IMETHOD StopLoadingSheet(nsIURI* aURL) = 0;

  /**
   * Whether the loader is enabled or not.
   * When disabled, processing of new styles is disabled and an attempt
   * to do so will fail with a return code of
   * NS_ERROR_NOT_AVAILABLE. Note that this DOES NOT disable
   * currently loading styles or already processed styles.
   */
  NS_IMETHOD GetEnabled(PRBool *aEnabled) = 0;
  NS_IMETHOD SetEnabled(PRBool aEnabled) = 0;

  /**
   * Return true if this nsICSSLoader has pending loads (ones that would send
   * notifications to an nsICSSLoaderObserver attached to this nsICSSLoader).
   * If called from inside nsICSSLoaderObserver::StyleSheetLoaded, this will
   * return PR_FALSE if and only if that is the last StyleSheetLoaded
   * notification the CSSLoader knows it's going to send.  In other words, if
   * two sheets load at once (via load coalescing, e.g.), HasPendingLoads()
   * will return PR_TRUE during notification for the first one, and PR_FALSE
   * during notification for the second one.
   */
  NS_IMETHOD_(PRBool) HasPendingLoads() = 0;

  /**
   * Add an observer to this nsICSSLoader.  The observer will be notified for
   * all loads that would have notified their own observers (even if those
   * loads don't have observers attached to them).  Load-specific observers
   * will be notified before generic observers.  The CSSLoader holds a
   * reference to the observer.
   *
   * aObserver must not be null.
   */
  NS_IMETHOD AddObserver(nsICSSLoaderObserver* aObserver) = 0;

  /**
   * Remove an observer added via AddObserver.
   */
  NS_IMETHOD_(void) RemoveObserver(nsICSSLoaderObserver* aObserver) = 0;
};

NS_DEFINE_STATIC_IID_ACCESSOR(nsICSSLoader, NS_ICSS_LOADER_IID)

nsresult 
NS_NewCSSLoader(nsIDocument* aDocument, nsICSSLoader** aLoader);

nsresult 
NS_NewCSSLoader(nsICSSLoader** aLoader);

#endif /* nsICSSLoader_h___ */
