"uifont" option: tell us what we wanted & what we got

The requested font & actual font loaded will be echo'd to STDOUT
when specifying the `uifont` option.

This uses Pango library directly (I was unable to convice SDL2_Pango.h
to actually notice that pango.h was #include'd before it, and expose
its SDLPango_GetPangoFontDescription() function!).  This is okay,
since we want to also add a "--uifont list" option (or similar),
that will list all of the available fonts, if a user wishes to
query them.  (And similar code will be added to tuxpaint-config to make
the setting available as a pull-down, rather than (or as well as) a
freeform type-in field.)

src/fonts.c

@@ -19,7 +19,7 @@
   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
   (See COPYING.txt)
 
-  Last modified: April 30, 2023
+  Last modified: June 1, 2023
 */
 
 #include <stdio.h>
@@ -38,9 +38,9 @@
 #endif
 
 /*
-	The following section renames global variables defined in SDL_Pango.h to avoid errors during linking.
+	The following section renames global variables defined in SDL2_Pango.h to avoid errors during linking.
 	It is okay to rename these variables because they are constants.
-	SDL_Pang.h is included by fonts.h.  
+	SDL2_Pango.h is included by fonts.h.  
 */
 #define _MATRIX_WHITE_BACK _MATRIX_WHITE_BACK2
 #define MATRIX_WHITE_BACK MATRIX_WHITE_BACK2
@@ -119,12 +119,22 @@ static const char *problemFontExtensions[] = {
 SDL_Thread *font_thread;
 #endif
 
+#include "pango/pango.h"
+#include "pango/pangoft2.h"
+#if !defined(__PANGO_H__)
+#error "---------------------------------------------------"
+#error "If you installed pango from a package, be sure"
+#error "to get the development package, as well!"
+#error "(e.g., 'libpango1.0-dev.rpm')"
+#error "---------------------------------------------------"
+#endif
+
 #include "SDL2_Pango.h"
 #if !defined(SDL_PANGO_H)
 #error "---------------------------------------------------"
-#error "If you installed SDL_Pango from a package, be sure"
+#error "If you installed SDL2_Pango from a package, be sure"
 #error "to get the development package, as well!"
-#error "(e.g., 'libsdl-pango1-dev.rpm')"
+#error "(e.g., 'SDL2_Pango-2.1.5-dev.rpm')"
 #error "---------------------------------------------------"
 #endif
 
@@ -1668,3 +1678,80 @@ void sdl_color_to_pango_color(SDL_Color sdl_color, SDLPango_Matrix * pango_color
 
   memcpy(pango_color, pc, 16);
 }
+
+/**
+ * Given a font description, do the very bare minimum to
+ * have Pango library try to load it, then retrieve the description
+ * of the font that was _actually_ loaded.
+ * (e.g., "tuxpaint --uifont bookman" finds and uses "URW Bookman"
+ * on my system -bjk 2023.06.01)
+ */
+char * ask_pango_for_font(char * pangodesc)
+{
+    PangoFontMap * font_map;
+    PangoContext * context;
+    PangoFontDescription * font_desc;
+    PangoFont *font;
+    PangoFontDescription * pfd;
+    char * descr;
+
+    font_map = pango_ft2_font_map_new();
+    if (font_map == NULL)
+    {
+      fprintf(stderr, "pango_ft2_font_map_new() failed\n");
+      fflush(stderr);
+      return NULL;
+    }
+
+    context = pango_font_map_create_context(font_map);
+    if (context == NULL)
+    {
+      fprintf(stderr, "pango_font_map_create_context() failed\n");
+      fflush(stderr);
+      g_object_unref(font_map);
+      return NULL;
+    }
+
+    font_desc = pango_font_description_from_string(pangodesc);
+    if (font_desc == NULL)
+    {
+      fprintf(stderr, "pango_font_description_from_string() failed\n");
+      fflush(stderr);
+      g_object_unref(font_map);
+      g_object_unref(context);
+      return NULL;
+    }
+
+    font = pango_font_map_load_font(font_map, context, font_desc);
+    if (font == NULL)
+    {
+      fprintf(stderr, "pango_font_map_load_font() failed\n");
+      fflush(stderr);
+      g_object_unref(font_map);
+      g_object_unref(context);
+      pango_font_description_free(font_desc);
+      return NULL;
+    }
+
+    pfd = pango_font_describe(font);
+    if (pfd == NULL)
+    {
+      fprintf(stderr, "pango_font_describe() failed\n");
+      fflush(stderr);
+      g_object_unref(font_map);
+      g_object_unref(context);
+      pango_font_description_free(font_desc);
+      g_object_unref(font);
+      return NULL;
+    }
+
+    descr = strdup(pango_font_description_get_family(pfd));
+
+    g_object_unref(font_map);
+    g_object_unref(context);
+    pango_font_description_free(font_desc);
+    g_object_unref(font);
+    /* N.B. Not free'ing `pfd`: The data is owned by the instance */
+
+    return descr;
+}

src/fonts.h

@@ -19,7 +19,7 @@
   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
   (See COPYING.txt)
 
-  Last updated: May 29, 2023
+  Last updated: May 31, 2023
 */
 
 #ifndef FONTS_H
@@ -164,5 +164,6 @@ void sdl_color_to_pango_color(SDL_Color sdl_color, SDLPango_Matrix * pango_color
 
 int load_user_fonts(SDL_Surface * screen, SDL_Texture * texture,
                     SDL_Renderer * renderer, void *vp, const char *restrict const locale);
+char * ask_pango_for_font(char * pangodesc);
 
 #endif

src/tuxpaint.c

@@ -27879,15 +27879,28 @@ static void setup_config(char *argv[])
 
   if (tmpcfg.tp_ui_font)
   {
+    char * tmp_str;
+
     if (strcmp(tmpcfg.tp_ui_font, "default") == 0)
     {
-      printf/*DEBUG_PRINTF*/("UI font will be default: %s\n", PANGO_DEFAULT_FONT);
+      printf/*DEBUG_PRINTF*/("Requested default UI font, \"%s\"\n", PANGO_DEFAULT_FONT);
       tp_ui_font = strdup(PANGO_DEFAULT_FONT);
     }
     else
     {
       tp_ui_font = strdup(tmpcfg.tp_ui_font);
-      printf/*DEBUG_PRINTF*/("UI font will be: %s\n", tp_ui_font);
+      printf/*DEBUG_PRINTF*/("Requested UI font described by \"%s\"\n", tp_ui_font);
+    }
+
+    tmp_str = ask_pango_for_font(tp_ui_font);
+    if (tmp_str != NULL)
+    {
+      printf("Actual UI font will be \"%s\"\n", tmp_str);
+      free(tmp_str);
+    }
+    else
+    {
+      printf("Error asking pango for actual font!\n");
     }
   }
   else