IMPLEMENTATION MODULE GtkUtils ;

(*
   Implementation notes
   --------------------
   CStrToM2 uses libc strncpy(): when the source is shorter than the
   buffer strncpy() pads with NUL, and we force the last byte to NUL so
   the result is always terminated.  This avoids pointer walking (gm2
   has no pointer arithmetic) and any CAST between integer sizes.

   IntToStr works on a LONGINT so that the magnitude of MIN(INTEGER)
   is representable, then reverses the digits into the caller buffer.
*)

FROM SYSTEM IMPORT ADDRESS, ADR;
FROM libc IMPORT strncpy;
FROM GObject IMPORT g_signal_connect_data, GConnectDefault, g_object_unref;
FROM GLib IMPORT g_free;
FROM GError IMPORT GError, g_error_free;
FROM GtkApplication IMPORT gtk_application_set_accels_for_action;

PROCEDURE CStrToM2 (src: ADDRESS; VAR dst: ARRAY OF CHAR);
BEGIN
   IF src = NIL THEN
      dst[0] := 0C;
      RETURN
   END;
   strncpy(ADR(dst), src, HIGH(dst) + 1);
   dst[HIGH(dst)] := 0C
END CStrToM2;

PROCEDURE StrAppend (VAR dst: ARRAY OF CHAR; src: ARRAY OF CHAR);
VAR
   i, j: CARDINAL;
BEGIN
   (* locate the current end of dst *)
   i := 0;
   WHILE (i <= HIGH(dst)) AND (dst[i] # 0C) DO
      INC(i)
   END;

   (* append src, leaving room for the terminator *)
   j := 0;
   WHILE (i < HIGH(dst)) AND (j <= HIGH(src)) AND (src[j] # 0C) DO
      dst[i] := src[j];
      INC(i);
      INC(j)
   END;
   IF i <= HIGH(dst) THEN dst[i] := 0C ELSE dst[HIGH(dst)] := 0C END
END StrAppend;

PROCEDURE IntToStr (n: INTEGER; VAR dst: ARRAY OF CHAR);
VAR
   digits: ARRAY [0..31] OF CHAR;
   v: INTEGER;
   i, j: CARDINAL;
   negative: BOOLEAN;
BEGIN
   v := n;
   negative := v < 0;
   IF negative THEN v := -v END;

   (* collect digits least-significant first *)
   i := 0;
   REPEAT
      digits[i] := CHR(ORD('0') + CARDINAL(v MOD 10));
      v := v DIV 10;
      INC(i)
   UNTIL v = 0;
   IF negative THEN
      digits[i] := '-';
      INC(i)
   END;

   (* reverse into dst *)
   j := 0;
   WHILE (i > 0) AND (j <= HIGH(dst)) DO
      DEC(i);
      dst[j] := digits[i];
      INC(j)
   END;
   IF j <= HIGH(dst) THEN dst[j] := 0C ELSE dst[HIGH(dst)] := 0C END
END IntToStr;

PROCEDURE Connect (instance: ADDRESS; signal: ARRAY OF CHAR;
                   handler: ADDRESS; data: ADDRESS) : [ LONGCARD ];
BEGIN
   RETURN g_signal_connect_data(instance, signal, handler, data, NIL,
                                GConnectDefault)
END Connect;

PROCEDURE SetAccel (application: ADDRESS; action: ARRAY OF CHAR;
                    accel: ARRAY OF CHAR);
VAR
   accels: ARRAY [0..1] OF ADDRESS;
BEGIN
   accels[0] := ADR(accel);
   accels[1] := NIL;
   gtk_application_set_accels_for_action(application, action, ADR(accels))
END SetAccel;

PROCEDURE Unref (obj: ADDRESS);
BEGIN
   IF obj # NIL THEN g_object_unref(obj) END
END Unref;

PROCEDURE Free (ptr: ADDRESS);
BEGIN
   IF ptr # NIL THEN g_free(ptr) END
END Free;

PROCEDURE ErrorMessage (err: GError; VAR dst: ARRAY OF CHAR);
BEGIN
   IF err = NIL THEN
      dst[0] := 0C
   ELSE
      CStrToM2(err^.message, dst)
   END
END ErrorMessage;

PROCEDURE ClearError (VAR err: GError);
BEGIN
   IF err # NIL THEN
      g_error_free(err);
      err := NIL
   END
END ClearError;

END GtkUtils.