fontselect: expose a fontprovider listing API

This allows client code to query libass for the font providers it was compiled
with. It can be useful for clients so that they can show selection interfaces
to their users.

4 files changed, 46 insertions, 0 deletions

diff --git a/libass/ass.h b/libass/ass.h
index a3feb0b..1fb2234 100644
--- a/libass/ass.h
+++ b/libass/ass.h
@@ -401,6 +401,14 @@ void ass_set_line_spacing(ASS_Renderer *priv, double line_spacing);
 void ass_set_line_position(ASS_Renderer *priv, double line_position);
 
 /**
+ * \brief Get the list of available font providers.
+ * \return list of available font providers (user owns the returned array)
+ */
+void ass_get_available_font_providers(ASS_Library *priv,
+                                      ASS_DefaultFontProvider **providers,
+                                      size_t *size);
+
+/**
  * \brief Set font lookup defaults.
  * \param default_font path to default font to use. Must be supplied if
  * fontconfig is disabled or unavailable.
diff --git a/libass/ass_fontselect.c b/libass/ass_fontselect.c
index dacff11..dc475b1 100644
--- a/libass/ass_fontselect.c
+++ b/libass/ass_fontselect.c
@@ -848,6 +848,21 @@ ass_fontselect_init(ASS_Library *library,
     return priv;
 }
 
+void ass_get_available_font_providers(ASS_Library *priv,
+                                      ASS_DefaultFontProvider **providers,
+                                      size_t *size)
+{
+    size_t offset = 2;
+    *size = offset;
+    for (int i = 0; font_constructors[i].constructor; i++)
+        (*size)++;
+    *providers = calloc(*size, sizeof(ASS_DefaultFontProvider));
+    (*providers)[0] = ASS_FONTPROVIDER_NONE;
+    (*providers)[1] = ASS_FONTPROVIDER_AUTODETECT;
+    for (int i = offset; i < *size; i++)
+        (*providers)[i] = font_constructors[i-offset].id;
+}
+
 /**
  * \brief Free font selector and release associated data
  * \param the font selector
diff --git a/libass/libass.sym b/libass/libass.sym
index aafb7a8..8a6826a 100644
--- a/libass/libass.sym
+++ b/libass/libass.sym
@@ -14,6 +14,7 @@ ass_set_aspect_ratio
 ass_set_font_scale
 ass_set_hinting
 ass_set_line_spacing
+ass_get_available_font_providers
 ass_set_fonts
 ass_render_frame
 ass_new_track
diff --git a/test/test.c b/test/test.c
index 8522840..33aa94c 100644
--- a/test/test.c
+++ b/test/test.c
@@ -166,6 +166,26 @@ static void blend(image_t * frame, ASS_Image *img)
     printf("%d images blended\n", cnt);
 }
 
+char *font_provider_labels[] = {
+    [ASS_FONTPROVIDER_NONE]       = "None",
+    [ASS_FONTPROVIDER_AUTODETECT] = "Autodetect",
+    [ASS_FONTPROVIDER_CORETEXT]   = "CoreText",
+    [ASS_FONTPROVIDER_FONTCONFIG] = "Fontconfig",
+};
+
+static void print_font_providers(ASS_Library *ass_library)
+{
+    ASS_DefaultFontProvider *providers;
+    size_t providers_size = 0;
+    ass_get_available_font_providers(ass_library, &providers, &providers_size);
+    printf("test.c: Available font providers (%zu): ", providers_size);
+    for (int i = 0; i < providers_size; i++) {
+        const char *separator = i > 0 ? ", ": "";
+        printf("%s'%s'", separator,  font_provider_labels[providers[i]]);
+    }
+    printf(".\n");
+}
+
 int main(int argc, char *argv[])
 {
     const int frame_w = 1280;
@@ -179,6 +199,8 @@ int main(int argc, char *argv[])
     char *subfile = argv[2];
     double tm = strtod(argv[3], 0);
 
+    print_font_providers(ass_library);
+
     init(frame_w, frame_h);
     ASS_Track *track = ass_read_file(ass_library, subfile, NULL);
     if (!track) {