src/ports/FontHostConfiguration_android.cpp

/* libs/graphics/ports/FontHostConfiguration_android.cpp
**
** Copyright 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 "FontHostConfiguration_android.h"
#include <expat.h>
#include "SkTDArray.h"

#define SYSTEM_FONTS_FILE "/system/etc/system_fonts.xml"
#define FALLBACK_FONTS_FILE "/system/etc/fallback_fonts.xml"
#define VENDOR_FONTS_FILE "/vendor/etc/fallback_fonts.xml"


// These defines are used to determine the kind of tag that we're currently populating with data.
// We only care about the sibling tags nameset and fileset for now.
#define NO_TAG 0
#define NAMESET_TAG 1
#define FILESET_TAG 2

/**
 * The FamilyData structure is passed around by the parser so that each handler can read these
 * variables that are relevant to the current parsing.
 */
struct FamilyData {
    FamilyData(XML_Parser *parserRef, SkTDArray<FontFamily*> &familiesRef) :
            parser(parserRef), families(familiesRef), currentTag(NO_TAG) {};

    XML_Parser *parser;                // The expat parser doing the work
    SkTDArray<FontFamily*> &families;  // The array that each family is put into as it is parsed
    FontFamily *currentFamily;         // The current family being created
    int currentTag;                    // A flag to indicate whether we're in nameset/fileset tags
};

/**
 * Handler for arbitrary text. This is used to parse the text inside each name or file tag. The
 * resulting strings are put into the fNames or fFileNames arrays.
 */
void textHandler(void *data, const char *s, int len) {
    FamilyData *familyData = (FamilyData*) data;
    // Make sure we're in the right state to store this name information
    if (familyData->currentFamily &&
            (familyData->currentTag == NAMESET_TAG || familyData->currentTag == FILESET_TAG)) {
        // Malloc new buffer to store the string
        char *buff;
        buff = (char*) malloc((len + 1) * sizeof(char));
        strncpy(buff, s, len);
        buff[len] = '\0';
        switch (familyData->currentTag) {
        case NAMESET_TAG:
            *(familyData->currentFamily->fNames.append()) = buff;
            break;
        case FILESET_TAG:
            *(familyData->currentFamily->fFileNames.append()) = buff;
            break;
        default:
            // Noop - don't care about any text that's not in the Fonts or Names list
            break;
        }
    }
}

/**
 * Handler for the start of a tag. The only tags we expect are family, nameset, fileset, name,
 * and file.
 */
void startElementHandler(void *data, const char *tag, const char **atts) {
    FamilyData *familyData = (FamilyData*) data;
    int len = strlen(tag);
    if (strncmp(tag, "family", len)== 0) {
        familyData->currentFamily = new FontFamily();
        familyData->currentFamily->order = -1;
        // The Family tag has an optional "order" attribute with an integer value >= 0
        // If this attribute does not exist, the default value is -1
        for (int i = 0; atts[i] != NULL; i += 2) {
            const char* attribute = atts[i];
            const char* valueString = atts[i+1];
            int value;
            int len = sscanf(valueString, "%d", &value);
            if (len > 0) {
                familyData->currentFamily->order = value;
            }
        }
    } else if (len == 7 && strncmp(tag, "nameset", len)== 0) {
        familyData->currentTag = NAMESET_TAG;
    } else if (len == 7 && strncmp(tag, "fileset", len) == 0) {
        familyData->currentTag = FILESET_TAG;
    } else if ((strncmp(tag, "name", len) == 0 && familyData->currentTag == NAMESET_TAG) ||
            (strncmp(tag, "file", len) == 0 && familyData->currentTag == FILESET_TAG)) {
        // If it's a Name, parse the text inside
        XML_SetCharacterDataHandler(*familyData->parser, textHandler);
    }
}

/**
 * Handler for the end of tags. We only care about family, nameset, fileset, name, and file.
 */
void endElementHandler(void *data, const char *tag) {
    FamilyData *familyData = (FamilyData*) data;
    int len = strlen(tag);
    if (strncmp(tag, "family", len)== 0) {
        // Done parsing a Family - store the created currentFamily in the families array
        *familyData->families.append() = familyData->currentFamily;
        familyData->currentFamily = NULL;
    } else if (len == 7 && strncmp(tag, "nameset", len)== 0) {
        familyData->currentTag = NO_TAG;
    } else if (len == 7 && strncmp(tag, "fileset", len)== 0) {
        familyData->currentTag = NO_TAG;
    } else if ((strncmp(tag, "name", len) == 0 && familyData->currentTag == NAMESET_TAG) ||
            (strncmp(tag, "file", len) == 0 && familyData->currentTag == FILESET_TAG)) {
        // Disable the arbitrary text handler installed to load Name data
        XML_SetCharacterDataHandler(*familyData->parser, NULL);
    }
}

/**
 * This function parses the given filename and stores the results in the given families array.
 */
void parseConfigFile(const char *filename, SkTDArray<FontFamily*> &families) {
    XML_Parser parser = XML_ParserCreate(NULL);
    FamilyData *familyData = new FamilyData(&parser, families);
    XML_SetUserData(parser, familyData);
    XML_SetElementHandler(parser, startElementHandler, endElementHandler);
    FILE *file = fopen(filename, "r");
    if (file == NULL) {
        // Some of the files we attempt to parse (in particular, /vendor/etc/fallback_fonts.xml)
        // are optional - failure here is okay because one of these optional files may not exist.
        return;
    }
    char buffer[512];
    bool done = false;
    while (!done) {
        fgets(buffer, sizeof(buffer), file);
        int len = strlen(buffer);
        if (feof(file) != 0) {
            done = true;
        }
        XML_Parse(parser, buffer, len, done);
    }
}

/**
 * Loads data on font families from various expected configuration files. The resulting data
 * is returned in the given fontFamilies array.
 */
void getFontFamilies(SkTDArray<FontFamily*> &fontFamilies) {

    SkTDArray<FontFamily*> fallbackFonts;
    SkTDArray<FontFamily*> vendorFonts;
    parseConfigFile(SYSTEM_FONTS_FILE, fontFamilies);
    parseConfigFile(FALLBACK_FONTS_FILE, fallbackFonts);
    parseConfigFile(VENDOR_FONTS_FILE, vendorFonts);

    // This loop inserts the vendor fallback fonts in the correct order in the overall
    // fallbacks list.
    int currentOrder = -1;
    for (int i = 0; i < vendorFonts.count(); ++i) {
        FontFamily* family = vendorFonts[i];
        int order = family->order;
        if (order < 0) {
            if (currentOrder < 0) {
                // Default case - just add it to the end of the fallback list
                *fallbackFonts.append() = family;
            } else {
                // no order specified on this font, but we're incrementing the order
                // based on an earlier order insertion request
                *fallbackFonts.insert(currentOrder++) = family;
            }
        } else {
            // Add the font into the fallback list in the specified order. Set currentOrder
            // for correct placement of other fonts in the vendor list.
            *fallbackFonts.insert(order) = family;
            currentOrder = order + 1;
        }
    }
    // Append all fallback fonts to system fonts
    for (int i = 0; i < fallbackFonts.count(); ++i) {
        *fontFamilies.append() = fallbackFonts[i];
    }
}