src/ports/SkFontHost_simple.cpp

/*
 * Copyright (C) 2011 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include "SkFontHost.h"
#include "SkDescriptor.h"
#include "SkMMapStream.h"
#include "SkPaint.h"
#include "SkString.h"
#include "SkStream.h"
#include "SkThread.h"
#include "SkTSearch.h"
#include <stdio.h>

#define FONT_CACHE_MEMORY_BUDGET    (768 * 1024)

#define SK_FONT_FILE_PREFIX          "/skimages/"

SkTypeface::Style find_name_and_style(SkStream* stream, SkString* name);

static void GetFullPathForSysFonts(SkString* full, const char name[]) {
    full->set(SK_FONT_FILE_PREFIX);
    full->append(name);
}

///////////////////////////////////////////////////////////////////////////////

struct FamilyRec;

/*  This guy holds a mapping of a name -> family, used for looking up fonts.
    Since it is stored in a stretchy array that doesn't preserve object
    semantics, we don't use constructor/destructors, but just have explicit
    helpers to manage our internal bookkeeping.
*/
struct NameFamilyPair {
    const char* fName;      // we own this
    FamilyRec*  fFamily;    // we don't own this, we just reference it
    
    void construct(const char name[], FamilyRec* family) {
        fName = strdup(name);
        fFamily = family;   // we don't own this, so just record the referene
    }

    void destruct() {
        free((char*)fName);
        // we don't own family, so just ignore our reference
    }
};

// we use atomic_inc to grow this for each typeface we create
static int32_t gUniqueFontID;

// this is the mutex that protects these globals
static SkMutex gFamilyMutex;
static FamilyRec* gFamilyHead;
static SkTDArray<NameFamilyPair> gNameList;

struct FamilyRec {
    FamilyRec*  fNext;
    SkTypeface* fFaces[4];
    
    FamilyRec()
    {
        fNext = gFamilyHead;
        memset(fFaces, 0, sizeof(fFaces));
        gFamilyHead = this;
    }
};

static SkTypeface* find_best_face(const FamilyRec* family,
                                  SkTypeface::Style style) {
    SkTypeface* const* faces = family->fFaces;

    if (faces[style] != NULL) { // exact match
        return faces[style];
    }
    // look for a matching bold
    style = (SkTypeface::Style)(style ^ SkTypeface::kItalic);
    if (faces[style] != NULL) {
        return faces[style];
    }
    // look for the plain
    if (faces[SkTypeface::kNormal] != NULL) {
        return faces[SkTypeface::kNormal];
    }
    // look for anything
    for (int i = 0; i < 4; i++) {
        if (faces[i] != NULL) {
            return faces[i];
        }
    }
    // should never get here, since the faces list should not be empty
    SkASSERT(!"faces list is empty");
    return NULL;
}

static FamilyRec* find_family(const SkTypeface* member) {
    FamilyRec* curr = gFamilyHead;
    while (curr != NULL) {
        for (int i = 0; i < 4; i++) {
            if (curr->fFaces[i] == member) {
                return curr;
            }
        }
        curr = curr->fNext;
    }
    return NULL;
}

/*  Returns the matching typeface, or NULL. If a typeface is found, its refcnt
    is not modified.
 */
static SkTypeface* find_from_uniqueID(uint32_t uniqueID) {
    FamilyRec* curr = gFamilyHead;
    while (curr != NULL) {
        for (int i = 0; i < 4; i++) {
            SkTypeface* face = curr->fFaces[i];
            if (face != NULL && face->uniqueID() == uniqueID) {
                return face;
            }
        }
        curr = curr->fNext;
    }
    return NULL;
}

/*  Remove reference to this face from its family. If the resulting family
    is empty (has no faces), return that family, otherwise return NULL
*/
static FamilyRec* remove_from_family(const SkTypeface* face) {
    FamilyRec* family = find_family(face);
    SkASSERT(family->fFaces[face->style()] == face);
    family->fFaces[face->style()] = NULL;
    
    for (int i = 0; i < 4; i++) {
        if (family->fFaces[i] != NULL) {    // family is non-empty
            return NULL;
        }
    }
    return family;  // return the empty family
}

// maybe we should make FamilyRec be doubly-linked
static void detach_and_delete_family(FamilyRec* family) {
    FamilyRec* curr = gFamilyHead;
    FamilyRec* prev = NULL;

    while (curr != NULL) {
        FamilyRec* next = curr->fNext;
        if (curr == family) {
            if (prev == NULL) {
                gFamilyHead = next;
            } else {
                prev->fNext = next;
            }
            SkDELETE(family);
            return;
        }
        prev = curr;
        curr = next;
    }
    SkASSERT(!"Yikes, couldn't find family in our list to remove/delete");
}

static SkTypeface* find_typeface(const char name[], SkTypeface::Style style) {
    NameFamilyPair* list = gNameList.begin();
    int             count = gNameList.count();
    
    int index = SkStrLCSearch(&list[0].fName, count, name, sizeof(list[0]));

    if (index >= 0) {
        return find_best_face(list[index].fFamily, style);
    }
    return NULL;
}

static SkTypeface* find_typeface(const SkTypeface* familyMember,
                                 SkTypeface::Style style) {
    const FamilyRec* family = find_family(familyMember);
    return family ? find_best_face(family, style) : NULL;
}

static void add_name(const char name[], FamilyRec* family) {
    SkAutoAsciiToLC tolc(name);
    name = tolc.lc();

    NameFamilyPair* list = gNameList.begin();
    int             count = gNameList.count();
    
    int index = SkStrLCSearch(&list[0].fName, count, name, sizeof(list[0]));

    if (index < 0) {
        list = gNameList.insert(~index);
        list->construct(name, family);
    }
}

static void remove_from_names(FamilyRec* emptyFamily)
{
#ifdef SK_DEBUG
    for (int i = 0; i < 4; i++) {
        SkASSERT(emptyFamily->fFaces[i] == NULL);
    }
#endif

    SkTDArray<NameFamilyPair>& list = gNameList;
    
    // must go backwards when removing
    for (int i = list.count() - 1; i >= 0; --i) {
        NameFamilyPair* pair = &list[i];
        if (pair->fFamily == emptyFamily) {
            pair->destruct();
            list.remove(i);
        }
    }
}

///////////////////////////////////////////////////////////////////////////////

class FamilyTypeface : public SkTypeface {
public:
    FamilyTypeface(Style style, bool sysFont, SkTypeface* familyMember)
    : SkTypeface(style, sk_atomic_inc(&gUniqueFontID) + 1) {
        fIsSysFont = sysFont;
        
        SkAutoMutexAcquire  ac(gFamilyMutex);
        
        FamilyRec* rec = NULL;
        if (familyMember) {
            rec = find_family(familyMember);
            SkASSERT(rec);
        } else {
            rec = SkNEW(FamilyRec);
        }
        rec->fFaces[style] = this;
    }
    
    virtual ~FamilyTypeface() {
        SkAutoMutexAcquire  ac(gFamilyMutex);
        
        // remove us from our family. If the family is now empty, we return
        // that and then remove that family from the name list
        FamilyRec* family = remove_from_family(this);
        if (NULL != family) {
            remove_from_names(family);
            detach_and_delete_family(family);
        }
    }
    
    bool isSysFont() const { return fIsSysFont; }
    
    virtual SkStream* openStream() = 0;
    virtual const char* getUniqueString() const = 0;
    virtual const char* getFilePath() const = 0;
    
private:
    bool    fIsSysFont;
    
    typedef SkTypeface INHERITED;
};

///////////////////////////////////////////////////////////////////////////////

class StreamTypeface : public FamilyTypeface {
public:
    StreamTypeface(Style style, bool sysFont, SkTypeface* familyMember,
                   SkStream* stream)
    : INHERITED(style, sysFont, familyMember) {
        SkASSERT(stream);
        stream->ref();
        fStream = stream;
    }
    virtual ~StreamTypeface() {
        fStream->unref();
    }
    
    // overrides
    virtual SkStream* openStream() {
        // we just ref our existing stream, since the caller will call unref()
        // when they are through
        fStream->ref();
        return fStream;
    }
    virtual const char* getUniqueString() const { return NULL; }
    virtual const char* getFilePath() const { return NULL; }

private:
    SkStream* fStream;
    
    typedef FamilyTypeface INHERITED;
};

class FileTypeface : public FamilyTypeface {
public:
    FileTypeface(Style style, bool sysFont, SkTypeface* familyMember,
                 const char path[])
    : INHERITED(style, sysFont, familyMember) {
        SkString fullpath;
        
        if (sysFont) {
            GetFullPathForSysFonts(&fullpath, path);
            path = fullpath.c_str();
        }
        fPath.set(path);
    }
    
    // overrides
    virtual SkStream* openStream() {
        SkStream* stream = SkNEW_ARGS(SkMMAPStream, (fPath.c_str()));

        // check for failure
        if (stream->getLength() <= 0) {
            SkDELETE(stream);
            // maybe MMAP isn't supported. try FILE
            stream = SkNEW_ARGS(SkFILEStream, (fPath.c_str()));
            if (stream->getLength() <= 0) {
                SkDELETE(stream);
                stream = NULL;
            }
        }
        return stream;
    }
    virtual const char* getUniqueString() const {
        const char* str = strrchr(fPath.c_str(), '/');
        if (str) {
            str += 1;   // skip the '/'
        }
        return str;
    }
    virtual const char* getFilePath() const {
        return fPath.c_str();
    }

private:
    SkString fPath;
    
    typedef FamilyTypeface INHERITED;
};

///////////////////////////////////////////////////////////////////////////////
///////////////////////////////////////////////////////////////////////////////

static bool get_name_and_style(const char path[], SkString* name,
                               SkTypeface::Style* style, bool isExpected) {
    SkString        fullpath;
    GetFullPathForSysFonts(&fullpath, path);

    SkMMAPStream stream(fullpath.c_str());
    if (stream.getLength() > 0) {
        *style = find_name_and_style(&stream, name);
        return true;
    }
    else {
        SkFILEStream stream(fullpath.c_str());
        if (stream.getLength() > 0) {
            *style = find_name_and_style(&stream, name);
            return true;
        }
    }

    if (isExpected) {
        SkDebugf("---- failed to open <%s> as a font\n", fullpath.c_str());
    }
    return false;
}

// used to record our notion of the pre-existing fonts
struct FontInitRec {
    const char*         fFileName;
    const char* const*  fNames;     // null-terminated list
};

static const char* gSansNames[] = {
    "sans-serif", "arial", "helvetica", "tahoma", "verdana", NULL
};

static const char* gSerifNames[] = {
    "serif", "times", "times new roman", "palatino", "georgia", "baskerville",
    "goudy", "fantasy", "cursive", "ITC Stone Serif", NULL
};

static const char* gMonoNames[] = {
    "monospace", "courier", "courier new", "monaco", NULL
};

// deliberately empty, but we use the address to identify fallback fonts
static const char* gFBNames[] = { NULL };

/*  Fonts must be grouped by family, with the first font in a family having the
    list of names (even if that list is empty), and the following members having
    null for the list. The names list must be NULL-terminated
*/
static const FontInitRec gSystemFonts[] = {
    { "samplefont.ttf",              gSansNames  },
};

#define DEFAULT_NAMES   gSansNames

// these globals are assigned (once) by load_system_fonts()
static FamilyRec* gDefaultFamily;
static SkTypeface* gDefaultNormal;

/*  This is sized conservatively, assuming that it will never be a size issue.
    It will be initialized in load_system_fonts(), and will be filled with the
    fontIDs that can be used for fallback consideration, in sorted order (sorted
    meaning element[0] should be used first, then element[1], etc. When we hit
    a fontID==0 in the array, the list is done, hence our allocation size is
    +1 the total number of possible system fonts. Also see NextLogicalFont().
 */
static uint32_t gFallbackFonts[SK_ARRAY_COUNT(gSystemFonts)+1];

/*  Called once (ensured by the sentinel check at the beginning of our body).
    Initializes all the globals, and register the system fonts.
 */
static void load_system_fonts() {
    // check if we've already be called
    if (NULL != gDefaultNormal) {
        return;
    }
    
    const FontInitRec* rec = gSystemFonts;
    SkTypeface* firstInFamily = NULL;
    int fallbackCount = 0;

    for (size_t i = 0; i < SK_ARRAY_COUNT(gSystemFonts); i++) {
        // if we're the first in a new family, clear firstInFamily
        if (rec[i].fNames != NULL) {
            firstInFamily = NULL;
        }
        
        SkString name;
        SkTypeface::Style style;

        // we expect all the fonts, except the "fallback" fonts
        bool isExpected = (rec[i].fNames != gFBNames);
        if (!get_name_and_style(rec[i].fFileName, &name, &style, isExpected)) {
            continue;
        }

        SkTypeface* tf = SkNEW_ARGS(FileTypeface,
                                    (style,
                                     true,  // system-font (cannot delete)
                                     firstInFamily, // what family to join
                                     rec[i].fFileName) // filename
                                    );

        if (rec[i].fNames != NULL) {
            // see if this is one of our fallback fonts
            if (rec[i].fNames == gFBNames) {
            //    SkDebugf("---- adding %s as fallback[%d] fontID %d\n",
            //             rec[i].fFileName, fallbackCount, tf->uniqueID());
                gFallbackFonts[fallbackCount++] = tf->uniqueID();
            }

            firstInFamily = tf;
            FamilyRec* family = find_family(tf);
            const char* const* names = rec[i].fNames;

            // record the default family if this is it
            if (names == DEFAULT_NAMES) {
                gDefaultFamily = family;
            }
            // add the names to map to this family
            while (*names) {
                add_name(*names, family);
                names += 1;
            }
        }
    }

    // do this after all fonts are loaded. This is our default font, and it
    // acts as a sentinel so we only execute load_system_fonts() once
    gDefaultNormal = find_best_face(gDefaultFamily, SkTypeface::kNormal);
    // now terminate our fallback list with the sentinel value
    gFallbackFonts[fallbackCount] = 0;
}

///////////////////////////////////////////////////////////////////////////////

void SkFontHost::Serialize(const SkTypeface* face, SkWStream* stream) {
    const char* name = ((FamilyTypeface*)face)->getUniqueString();

    stream->write8((uint8_t)face->style());

    if (NULL == name || 0 == *name) {
        stream->writePackedUInt(0);
//        SkDebugf("--- fonthost serialize null\n");
    } else {
        uint32_t len = strlen(name);
        stream->writePackedUInt(len);
        stream->write(name, len);
//      SkDebugf("--- fonthost serialize <%s> %d\n", name, face->style());
    }
}

SkTypeface* SkFontHost::Deserialize(SkStream* stream) {
    load_system_fonts();

    int style = stream->readU8();

    int len = stream->readPackedUInt();
    if (len > 0) {
        SkString str;
        str.resize(len);
        stream->read(str.writable_str(), len);
        
        const FontInitRec* rec = gSystemFonts;
        for (size_t i = 0; i < SK_ARRAY_COUNT(gSystemFonts); i++) {
            if (strcmp(rec[i].fFileName, str.c_str()) == 0) {
                // backup until we hit the fNames
                for (int j = i; j >= 0; --j) {
                    if (rec[j].fNames != NULL) {
                        return SkFontHost::CreateTypeface(NULL,
                                    rec[j].fNames[0], NULL, 0, (SkTypeface::Style)style);
                    }
                }
            }
        }
    }
    return NULL;
}

///////////////////////////////////////////////////////////////////////////////

SkTypeface* SkFontHost::CreateTypeface(const SkTypeface* familyFace,
                                       const char familyName[],
                                       const void* data, size_t bytelength,
                                       SkTypeface::Style style) {
    load_system_fonts();

    SkAutoMutexAcquire  ac(gFamilyMutex);
    
    // clip to legal style bits
    style = (SkTypeface::Style)(style & SkTypeface::kBoldItalic);
    
    SkTypeface* tf = NULL;

    if (NULL != familyFace) {
        tf = find_typeface(familyFace, style);
    } else if (NULL != familyName) {
//        SkDebugf("======= familyName <%s>\n", familyName);
        tf = find_typeface(familyName, style);
    }

    if (NULL == tf) {
        tf = find_best_face(gDefaultFamily, style);
    }

    // we ref(), since the symantic is to return a new instance
    tf->ref();
    return tf;
}

bool SkFontHost::ValidFontID(uint32_t fontID) {
    SkAutoMutexAcquire  ac(gFamilyMutex);
    
    return find_from_uniqueID(fontID) != NULL;
}

SkStream* SkFontHost::OpenStream(uint32_t fontID) {
    SkAutoMutexAcquire  ac(gFamilyMutex);
    
    FamilyTypeface* tf = (FamilyTypeface*)find_from_uniqueID(fontID);
    SkStream* stream = tf ? tf->openStream() : NULL;

    if (stream && stream->getLength() == 0) {
        stream->unref();
        stream = NULL;
    }
    return stream;
}

// static
SkAdvancedTypefaceMetrics* SkFontHost::GetAdvancedTypefaceMetrics(
        uint32_t fontID, bool perGlyphInfo) {
    SkASSERT(!"SkFontHost::GetAdvancedTypefaceMetrics unimplemented");
    return NULL;
}

size_t SkFontHost::GetFileName(SkFontID fontID, char path[], size_t length,
                               int32_t* index) {
    SkAutoMutexAcquire  ac(gFamilyMutex);

    FamilyTypeface* tf = (FamilyTypeface*)find_from_uniqueID(fontID);
    const char* src = tf ? tf->getFilePath() : NULL;

    if (src) {
        size_t size = strlen(src);
        if (path) {
            memcpy(path, src, SkMin32(size, length));
        }
        if (index) {
            *index = 0; // we don't have collections (yet)
        }
        return size;
    } else {
        return 0;
    }
}

uint32_t SkFontHost::NextLogicalFont(uint32_t fontID) {
    load_system_fonts();

    /*  First see if fontID is already one of our fallbacks. If so, return
        its successor. If fontID is not in our list, then return the first one
        in our list. Note: list is zero-terminated, and returning zero means
        we have no more fonts to use for fallbacks.
     */
    const uint32_t* list = gFallbackFonts;
    for (int i = 0; list[i] != 0; i++) {
        if (list[i] == fontID) {
            return list[i+1];
        }
    }
    return list[0];
}

///////////////////////////////////////////////////////////////////////////////

SkTypeface* SkFontHost::CreateTypefaceFromStream(SkStream* stream) {
    if (NULL == stream || stream->getLength() <= 0) {
        return NULL;
    }
    
    SkString name;
    SkTypeface::Style style = find_name_and_style(stream, &name);

    return SkNEW_ARGS(StreamTypeface, (style, false, NULL, stream));
}

SkTypeface* SkFontHost::CreateTypefaceFromFile(const char path[]) {
    SkStream* stream = SkNEW_ARGS(SkMMAPStream, (path));
    SkTypeface* face = SkFontHost::CreateTypefaceFromStream(stream);
    // since we created the stream, we let go of our ref() here
    stream->unref();
    return face;
}

///////////////////////////////////////////////////////////////////////////////

size_t SkFontHost::ShouldPurgeFontCache(size_t sizeAllocatedSoFar) {
    if (sizeAllocatedSoFar > FONT_CACHE_MEMORY_BUDGET)
        return sizeAllocatedSoFar - FONT_CACHE_MEMORY_BUDGET;
    else
        return 0;   // nothing to do
}