Linux: Load libfontconfig at runtime to allow the binaries to work for running kittens on servers without FontConfig

docs/changelog.rst

@@ -61,6 +61,9 @@ Detailed list of changes
 
 - Fix deleting images by row not calculating image bounds correctly (:iss:`5081`)
 
+- Linux: Load libfontconfig at runtime to allow the binaries to work for
+  running kittens on servers without FontConfig
+
 
 0.25.0 [2022-04-11]
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

kitty/fontconfig.c

@@ -10,6 +10,7 @@
 #include "lineops.h"
 #include "fonts.h"
 #include <fontconfig/fontconfig.h>
+#include <dlfcn.h>
 #include "emoji.h"
 #include "freetype_render_ui_text.h"
 #ifndef FC_COLOR
@@ -18,10 +19,111 @@
 
 
 static bool initialized = false;
+static void* libfontconfig_handle = NULL;
+
+#define FcInit dynamically_loaded_fc_symbol.Init
+#define FcFini dynamically_loaded_fc_symbol.Fini
+#define FcCharSetAddChar dynamically_loaded_fc_symbol.CharSetAddChar
+#define FcPatternDestroy dynamically_loaded_fc_symbol.PatternDestroy
+#define FcObjectSetDestroy dynamically_loaded_fc_symbol.ObjectSetDestroy
+#define FcPatternAddDouble dynamically_loaded_fc_symbol.PatternAddDouble
+#define FcPatternAddString dynamically_loaded_fc_symbol.PatternAddString
+#define FcFontMatch dynamically_loaded_fc_symbol.FontMatch
+#define FcCharSetCreate dynamically_loaded_fc_symbol.CharSetCreate
+#define FcPatternGetString dynamically_loaded_fc_symbol.PatternGetString
+#define FcFontSetDestroy dynamically_loaded_fc_symbol.FontSetDestroy
+#define FcPatternGetInteger dynamically_loaded_fc_symbol.PatternGetInteger
+#define FcPatternAddBool dynamically_loaded_fc_symbol.PatternAddBool
+#define FcFontList dynamically_loaded_fc_symbol.FontList
+#define FcObjectSetBuild dynamically_loaded_fc_symbol.ObjectSetBuild
+#define FcCharSetDestroy dynamically_loaded_fc_symbol.CharSetDestroy
+#define FcConfigSubstitute dynamically_loaded_fc_symbol.ConfigSubstitute
+#define FcDefaultSubstitute dynamically_loaded_fc_symbol.DefaultSubstitute
+#define FcPatternAddInteger dynamically_loaded_fc_symbol.PatternAddInteger
+#define FcPatternCreate dynamically_loaded_fc_symbol.PatternCreate
+#define FcPatternGetBool dynamically_loaded_fc_symbol.PatternGetBool
+#define FcPatternAddCharSet dynamically_loaded_fc_symbol.PatternAddCharSet
+
+static struct {
+    FcBool(*Init)(void);
+    void(*Fini)(void);
+    FcBool (*CharSetAddChar) (FcCharSet *fcs, FcChar32 ucs4);
+    void (*PatternDestroy) (FcPattern *p);
+    void (*ObjectSetDestroy) (FcObjectSet *os);
+    FcBool (*PatternAddDouble) (FcPattern *p, const char *object, double d);
+    FcBool (*PatternAddString) (FcPattern *p, const char *object, const FcChar8 *s);
+    FcPattern * (*FontMatch) (FcConfig	*config, FcPattern	*p, FcResult	*result);
+    FcCharSet* (*CharSetCreate) (void);
+    FcResult (*PatternGetString) (const FcPattern *p, const char *object, int n, FcChar8 ** s);
+    void (*FontSetDestroy) (FcFontSet *s);
+    FcResult (*PatternGetInteger) (const FcPattern *p, const char *object, int n, int *i);
+    FcBool (*PatternAddBool) (FcPattern *p, const char *object, FcBool b);
+    FcFontSet * (*FontList) (FcConfig	*config, FcPattern	*p, FcObjectSet *os);
+    FcObjectSet * (*ObjectSetBuild) (const char *first, ...);
+    void (*CharSetDestroy) (FcCharSet *fcs);
+    FcBool (*ConfigSubstitute) (FcConfig	*config, FcPattern	*p, FcMatchKind	kind);
+    void (*DefaultSubstitute) (FcPattern *pattern);
+    FcBool (*PatternAddInteger) (FcPattern *p, const char *object, int i);
+    FcPattern * (*PatternCreate) (void);
+    FcResult (*PatternGetBool) (const FcPattern *p, const char *object, int n, FcBool *b);
+    FcBool (*PatternAddCharSet) (FcPattern *p, const char *object, const FcCharSet *c);
+} dynamically_loaded_fc_symbol = {0};
+#define LOAD_FUNC(name) {\
+    *(void **) (&dynamically_loaded_fc_symbol.name) = dlsym(libfontconfig_handle, "Fc" #name); \
+    if (!dynamically_loaded_fc_symbol.name) { \
+        const char* error = dlerror(); \
+        fatal("Failed to load the function Fc" #name " with error: %s", error ? error : ""); \
+    } \
+}
+
+
+static void
+load_fontconfig_lib(void) {
+        const char* libnames[] = {
+#if defined(_KITTY_FONTCONFIG_LIBRARY)
+            _KITTY_FONTCONFIG_LIBRARY,
+#else
+            "libfontconfig.so",
+            // some installs are missing the .so symlink, so try the full name
+            "libfontconfig.so.1",
+#endif
+            NULL
+        };
+        for (int i = 0; libnames[i]; i++) {
+            libfontconfig_handle = dlopen(libnames[i], RTLD_LAZY);
+            if (libfontconfig_handle) break;
+        }
+        if (libfontconfig_handle == NULL) { fatal("Failed to find and load fontconfig"); }
+        dlerror();    /* Clear any existing error */
+        LOAD_FUNC(Init);
+        LOAD_FUNC(Fini);
+        LOAD_FUNC(CharSetAddChar);
+        LOAD_FUNC(PatternDestroy);
+        LOAD_FUNC(ObjectSetDestroy);
+        LOAD_FUNC(PatternAddDouble);
+        LOAD_FUNC(PatternAddString);
+        LOAD_FUNC(FontMatch);
+        LOAD_FUNC(CharSetCreate);
+        LOAD_FUNC(PatternGetString);
+        LOAD_FUNC(FontSetDestroy);
+        LOAD_FUNC(PatternGetInteger);
+        LOAD_FUNC(PatternAddBool);
+        LOAD_FUNC(FontList);
+        LOAD_FUNC(ObjectSetBuild);
+        LOAD_FUNC(CharSetDestroy);
+        LOAD_FUNC(ConfigSubstitute);
+        LOAD_FUNC(DefaultSubstitute);
+        LOAD_FUNC(PatternAddInteger);
+        LOAD_FUNC(PatternCreate);
+        LOAD_FUNC(PatternGetBool);
+        LOAD_FUNC(PatternAddCharSet);
+}
+#undef LOAD_FUNC
 
 static void
 ensure_initialized(void) {
     if (!initialized) {
+        load_fontconfig_lib();
         if (!FcInit()) fatal("Failed to initialize fontconfig library");
         initialized = true;
     }
@@ -31,6 +133,8 @@ static void
 finalize(void) {
     if (initialized) {
         FcFini();
+        dlclose(libfontconfig_handle);
+        libfontconfig_handle = NULL;
         initialized = false;
     }
 }

setup.py

@@ -77,6 +77,7 @@ class Options(argparse.Namespace):
     egl_library: Optional[str] = os.getenv('KITTY_EGL_LIBRARY')
     startup_notification_library: Optional[str] = os.getenv('KITTY_STARTUP_NOTIFICATION_LIBRARY')
     canberra_library: Optional[str] = os.getenv('KITTY_CANBERRA_LIBRARY')
+    fontconfig_library: Optional[str] = os.getenv('KITTY_FONTCONFIG_LIBRARY')
 
 
 def emphasis(text: str) -> str:
@@ -296,6 +297,7 @@ def init_env(
     egl_library: Optional[str] = None,
     startup_notification_library: Optional[str] = None,
     canberra_library: Optional[str] = None,
+    fontconfig_library: Optional[str] = None,
     extra_logging: Iterable[str] = (),
     extra_include_dirs: Iterable[str] = (),
     ignore_compiler_warnings: bool = False,
@@ -381,6 +383,10 @@ def init_env(
         assert('"' not in canberra_library)
         desktop_libs += [f'_KITTY_CANBERRA_LIBRARY="{canberra_library}"']
 
+    if fontconfig_library is not None:
+        assert('"' not in fontconfig_library)
+        desktop_libs += [f'_KITTY_FONTCONFIG_LIBRARY="{fontconfig_library}"']
+
     if desktop_libs != []:
         library_paths['kitty/desktop.c'] = desktop_libs
 
@@ -432,7 +438,7 @@ def kitty_env() -> Env:
         cppflags.append('-DGL_SILENCE_DEPRECATION')
     else:
         cflags.extend(pkg_config('fontconfig', '--cflags-only-I'))
-        platform_libs = pkg_config('fontconfig', '--libs')
+        platform_libs = []
     cflags.extend(pkg_config('harfbuzz', '--cflags-only-I'))
     platform_libs.extend(pkg_config('harfbuzz', '--libs'))
     pylib = get_python_flags(cflags)
@@ -810,7 +816,7 @@ def init_env_from_args(args: Options, native_optimizations: bool = False) -> Non
     global env
     env = init_env(
         args.debug, args.sanitize, native_optimizations, args.link_time_optimization, args.profile,
-        args.egl_library, args.startup_notification_library, args.canberra_library,
+        args.egl_library, args.startup_notification_library, args.canberra_library, args.fontconfig_library,
         args.extra_logging, args.extra_include_dirs, args.ignore_compiler_warnings,
         args.build_universal_binary, args.extra_library_dirs
     )
@@ -1470,6 +1476,13 @@ def option_parser() -> argparse.ArgumentParser:  # {{{
         help='The filename argument passed to dlopen for libcanberra.'
         ' This can be used to change the name of the loaded library or specify an absolute path.'
     )
+    p.add_argument(
+        '--fontconfig-library',
+        type=str,
+        default=Options.fontconfig_library,
+        help='The filename argument passed to dlopen for libfontconfig.'
+        ' This can be used to change the name of the loaded library or specify an absolute path.'
+    )
     p.add_argument(
         '--disable-link-time-optimization',
         dest='link_time_optimization',