Add support for the Fontconfig-based Skia font manager (#8977)

Author: jason-simmons

DEPS

@@ -121,7 +121,7 @@ allowed_hosts = [
 ]
 
 deps = {
-  'src': 'https://github.com/flutter/buildroot.git' + '@' + 'c5afcce6d7972b20eded5b090b489b76622e8ff3',
+  'src': 'https://github.com/flutter/buildroot.git' + '@' + 'bc8826aab0fc4f7e17b21f64dec4c8a28ea42e3e',
 
    # Fuchsia compatibility
    #
@@ -364,7 +364,7 @@ deps = {
    Var('chromium_git') + '/external/colorama.git' + '@' + '799604a1041e9b3bc5d2789ecbd7e8db2e18e6b8',
 
   'src/third_party/freetype2':
-   Var('fuchsia_git') + '/third_party/freetype2' + '@' + 'a10b062df0c8958d69377aa04ea6554a9961a111',
+   Var('fuchsia_git') + '/third_party/freetype2' + '@' + 'edab12c07ac05d1185616688f338b1ad15936796',
 
   'src/third_party/root_certificates':
    Var('dart_git') + '/root_certificates.git' + '@' + Var('dart_root_certificates_rev'),
@@ -381,6 +381,9 @@ deps = {
   'src/third_party/wuffs':
    Var('fuchsia_git') + '/third_party/wuffs' + '@' + 'a71538baa8f1f4053176c0d9f31bc12fd4e8e71b',
 
+  'src/third_party/fontconfig/src':
+   Var('chromium_git') + '/external/fontconfig.git' + '@' + 'c336b8471877371f0190ba06f7547c54e2b890ba',
+
   'src/third_party/gyp':
    Var('chromium_git') + '/external/gyp.git' + '@' + '4801a5331ae62da9769a327f11c4213d32fb0dad',
 

ci/licenses_golden/tool_signature

@@ -1,2 +1,2 @@
-Signature: 6d315fb6c8e9e949011f57c32b16cb48
+Signature: ab4f82ed4f38f0d3821073855c220992
 

third_party/txt/BUILD.gn

@@ -12,6 +12,14 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+declare_args() {
+  flutter_use_fontconfig = false
+}
+
+if (flutter_use_fontconfig) {
+  assert(is_linux)
+}
+
 config("txt_config") {
   visibility = [ ":*" ]
   include_dirs = [ "src" ]
@@ -24,6 +32,9 @@ source_set("txt") {
   if (is_android) {
     defines = [ "ANDROID_FONT_MANAGER_AVAILABLE" ]
   }
+  if (flutter_use_fontconfig) {
+    defines = [ "FONTCONFIG_FONT_MANAGER_AVAILABLE" ]
+  }
 
   sources = [
     "src/log/log.cc",
@@ -116,6 +127,10 @@ source_set("txt") {
     "//third_party/skia",
   ]
 
+  if (flutter_use_fontconfig) {
+    deps += [ "//third_party/fontconfig" ]
+  }
+
   if (is_mac || is_ios) {
     sources += [ "src/txt/platform_mac.mm" ]
     deps += [ "$flutter_root/fml" ]

third_party/txt/src/txt/platform_linux.cc

@@ -4,7 +4,11 @@
 
 #include "txt/platform.h"
 
+#ifdef FONTCONFIG_FONT_MANAGER_AVAILABLE
+#include "third_party/skia/include/ports/SkFontMgr_fontconfig.h"
+#else
 #include "third_party/skia/include/ports/SkFontMgr_directory.h"
+#endif
 
 namespace txt {
 
@@ -13,7 +17,11 @@ std::string GetDefaultFontFamily() {
 }
 
 sk_sp<SkFontMgr> GetDefaultFontManager() {
+#ifdef FONTCONFIG_FONT_MANAGER_AVAILABLE
+  return SkFontMgr_New_FontConfig(nullptr);
+#else
   return SkFontMgr_New_Custom_Directory("/usr/share/fonts/");
+#endif
 }
 
 }  // namespace txt

tools/gn

@@ -90,7 +90,8 @@ def to_gn_args(args):
     gn_args['skia_enable_pdf'] = False     # PDF handling.
     gn_args['skia_use_x11'] = False        # Never add the X11 dependency (only takes effect on Linux).
     gn_args['skia_use_expat'] = args.target_os == 'android'
-    gn_args['skia_use_fontconfig'] = False # Use the custom font manager instead.
+    gn_args['skia_use_fontconfig'] = args.enable_fontconfig
+    gn_args['flutter_use_fontconfig'] = args.enable_fontconfig
     gn_args['is_official_build'] = True    # Disable Skia test utilities.
     gn_args['dart_component_kind'] = 'static_library' # Always link Dart in statically.
     gn_args['is_debug'] = args.unoptimized
@@ -298,6 +299,8 @@ def parse_args(args):
   parser.add_argument('--enable-vulkan', action='store_true', default=False)
   parser.add_argument('--enable-metal', action='store_true', default=False)
 
+  parser.add_argument('--enable-fontconfig', action='store_true', default=False)
+
   parser.add_argument('--embedder-for-target', dest='embedder_for_target', action='store_true', default=False)
 
   parser.add_argument('--coverage', default=False, action='store_true')

tools/licenses/lib/main.dart

@@ -1752,6 +1752,7 @@ class _RepositoryRootThirdPartyDirectory extends _RepositoryGenericThirdPartyDir
         && entry.name != 'android_support' // build-time only
         && entry.name != 'googletest' // only used by tests
         && entry.name != 'skia' // treated as a separate component
+        && entry.name != 'fontconfig' // not used in standard configurations
         && super.shouldRecurse(entry);
   }