diff --git a/configure.ac b/configure.ac
index a87ccfd..547204d 100644
--- a/configure.ac
+++ b/configure.ac
@@ -65,7 +65,7 @@ dnl conditional builds
 AC_ARG_ENABLE(doc,
   [  --enable-doc            build documentation (needs doxygen and LaTeX)])
 
-AC_CHECK_HEADERS(stdio.h stdarg.h signal.h sys/ioctl.h sys/time.h inttypes.h endian.h unistd.h arpa/inet.h netinet/in.h winsock2.h)
+AC_CHECK_HEADERS(stdio.h stdarg.h signal.h sys/ioctl.h sys/time.h inttypes.h endian.h unistd.h arpa/inet.h netinet/in.h winsock2.h errno.h)
 AC_CHECK_FUNCS(signal ioctl vsnprintf getenv putenv strcasecmp htons)
 AC_CHECK_FUNCS(usleep gettimeofday)
 
diff --git a/cucul/box.c b/cucul/box.c
index c512385..03c3b0f 100644
--- a/cucul/box.c
+++ b/cucul/box.c
@@ -26,6 +26,8 @@
 #include "cucul_internals.h"
 
 /** \brief Draw a box on the canvas using the given character.
+ *
+ *  This function never fails.
  *
  *  \param cv The handle to the libcucul canvas.
  *  \param x1 X coordinate of the upper-left corner of the box.
@@ -33,27 +35,31 @@
  *  \param x2 X coordinate of the lower-right corner of the box.
  *  \param y2 Y coordinate of the lower-right corner of the box.
  *  \param str UTF-8 string containing the character to use to draw the box.
- *  \return void
+ *  \return This function always returns 0.
  */
-void cucul_draw_box(cucul_canvas_t *cv, int x1, int y1, int x2, int y2, 
-                    char const *str)
+int cucul_draw_box(cucul_canvas_t *cv, int x1, int y1, int x2, int y2, 
+                   char const *str)
 {
     cucul_draw_line(cv, x1, y1, x1, y2, str);
     cucul_draw_line(cv, x1, y2, x2, y2, str);
     cucul_draw_line(cv, x2, y2, x2, y1, str);
     cucul_draw_line(cv, x2, y1, x1, y1, str);
+
+    return 0;
 }
 
 /** \brief Draw a thin box on the canvas.
+ *
+ *  This function never fails.
  *
  *  \param cv The handle to the libcucul canvas.
  *  \param x1 X coordinate of the upper-left corner of the box.
  *  \param y1 Y coordinate of the upper-left corner of the box.
  *  \param x2 X coordinate of the lower-right corner of the box.
  *  \param y2 Y coordinate of the lower-right corner of the box.
- *  \return void
+ *  \return This function always returns 0.
  */
-void cucul_draw_thin_box(cucul_canvas_t *cv, int x1, int y1, int x2, int y2)
+int cucul_draw_thin_box(cucul_canvas_t *cv, int x1, int y1, int x2, int y2)
 {
     int x, y, xmax, ymax;
 
@@ -73,7 +79,7 @@ void cucul_draw_thin_box(cucul_canvas_t *cv, int x1, int y1, int x2, int y2)
     ymax = cv->height - 1;
 
     if(x2 < 0 || y2 < 0 || x1 > xmax || y1 > ymax)
-        return;
+        return 0;
 
     /* Draw edges */
     if(y1 >= 0)
@@ -104,9 +110,13 @@ void cucul_draw_thin_box(cucul_canvas_t *cv, int x1, int y1, int x2, int y2)
 
     if(x2 <= xmax && y2 <= ymax)
         _cucul_putchar32(cv, x2, y2, (uint32_t)'\'');
+
+    return 0;
 }
 
 /** \brief Fill a box on the canvas using the given character.
+ *
+ *  This function never fails.
  *
  *  \param cv The handle to the libcucul canvas.
  *  \param x1 X coordinate of the upper-left corner of the box.
@@ -114,10 +124,10 @@ void cucul_draw_thin_box(cucul_canvas_t *cv, int x1, int y1, int x2, int y2)
  *  \param x2 X coordinate of the lower-right corner of the box.
  *  \param y2 Y coordinate of the lower-right corner of the box.
  *  \param str UTF-8 string containing the character to fill the box with.
- *  \return void
+ *  \return This function always returns 0.
  */
-void cucul_fill_box(cucul_canvas_t *cv, int x1, int y1, int x2, int y2,
-                    char const *str)
+int cucul_fill_box(cucul_canvas_t *cv, int x1, int y1, int x2, int y2,
+                   char const *str)
 {
     int x, y, xmax, ymax;
     uint32_t ch;
@@ -138,7 +148,7 @@ void cucul_fill_box(cucul_canvas_t *cv, int x1, int y1, int x2, int y2,
     ymax = cv->height - 1;
 
     if(x2 < 0 || y2 < 0 || x1 > xmax || y1 > ymax)
-        return;
+        return 0;
 
     if(x1 < 0) x1 = 0;
     if(y1 < 0) y1 = 0;
@@ -150,5 +160,7 @@ void cucul_fill_box(cucul_canvas_t *cv, int x1, int y1, int x2, int y2,
     for(y = y1; y <= y2; y++)
         for(x = x1; x <= x2; x++)
             _cucul_putchar32(cv, x, y, ch);
+
+    return 0;
 }
 
diff --git a/cucul/buffer.c b/cucul/buffer.c
index 1b47140..a4e779c 100644
--- a/cucul/buffer.c
+++ b/cucul/buffer.c
@@ -32,6 +32,8 @@
  *  This function returns the length (in bytes) of the memory area stored
  *  in the given \e libcucul buffer.
  *
+ *  This function never fails.
+ *
  *  \param buf A \e libcucul buffer
  *  \return The buffer data length.
  */
@@ -45,6 +47,8 @@ unsigned long int cucul_get_buffer_size(cucul_buffer_t *buf)
  *  This function returns a pointer to the memory area stored in the given
  *  \e libcucul buffer.
  *
+ *  This function never fails.
+ *
  *  \param buf A \e libcucul buffer
  *  \return A pointer to the buffer memory area.
  */
@@ -58,11 +62,16 @@ void * cucul_get_buffer_data(cucul_buffer_t *buf)
  *  This function frees the structures associated with the given
  *  \e libcucul buffer.
  *
+ *  This function never fails.
+ *
  *  \param buf A \e libcucul buffer
+ *  \return This function always returns 0.
  */
-void cucul_free_buffer(cucul_buffer_t *buf)
+int cucul_free_buffer(cucul_buffer_t *buf)
 {
     free(buf->data);
     free(buf);
+
+    return 0;
 }
 
diff --git a/cucul/canvas.c b/cucul/canvas.c
index 0fb9759..4b58cf9 100644
--- a/cucul/canvas.c
+++ b/cucul/canvas.c
@@ -24,6 +24,9 @@
 #   include <string.h>
 #   include <stdlib.h>
 #   include <stdarg.h>
+#   if defined(HAVE_ERRNO_H)
+#       include <errno.h>
+#   endif
 #   if defined(HAVE_UNISTD_H)
 #       include <unistd.h>
 #   endif
@@ -47,10 +50,13 @@
  *  replaced with a space. To print a sequence of bytes forming an UTF-8
  *  character, use cucul_putstr() instead.
  *
+ *  This function never fails.
+ *
  *  \param cv A handle to the libcucul canvas.
  *  \param x X coordinate.
  *  \param y Y coordinate.
  *  \param ch The character to print.
+ *  \return This function always returns 0.
  */
 void cucul_putchar(cucul_canvas_t *cv, int x, int y, char ch)
 {
@@ -72,10 +78,13 @@ void cucul_putchar(cucul_canvas_t *cv, int x, int y, char ch)
  *  the canvas boundaries (eg. a negative Y coordinate) and the string will
  *  be cropped accordingly if it is too long.
  *
+ *  This function never fails.
+ *
  *  \param cv A handle to the libcucul canvas.
  *  \param x X coordinate.
  *  \param y Y coordinate.
  *  \param s The string to print.
+ *  \return This function always returns 0.
  */
 void cucul_putstr(cucul_canvas_t *cv, int x, int y, char const *s)
 {
@@ -120,11 +129,14 @@ void cucul_putstr(cucul_canvas_t *cv, int x, int y, char const *s)
  *  be cropped accordingly if it is too long. The syntax of the format
  *  string is the same as for the C printf() function.
  *
+ *  This function never fails.
+ *
  *  \param cv A handle to the libcucul canvas.
  *  \param x X coordinate.
  *  \param y Y coordinate.
  *  \param format The format string to print.
  *  \param ... Arguments to the format string.
+ *  \return This function always returns 0.
  */
 void cucul_printf(cucul_canvas_t *cv, int x, int y, char const *format, ...)
 {
@@ -157,7 +169,10 @@ void cucul_printf(cucul_canvas_t *cv, int x, int y, char const *format, ...)
  *
  *  This function clears the canvas using the current background colour.
  *
+ *  This function never fails.
+ *
  *  \param cv The canvas to clear.
+ *  \return This function always returns 0.
  */
 void cucul_clear_canvas(cucul_canvas_t *cv)
 {
@@ -182,14 +197,20 @@ void cucul_clear_canvas(cucul_canvas_t *cv)
  *  \param y Y coordinate.
  *  \param src The source canvas.
  *  \param mask The mask canvas.
+ *  \return 0 in case of success, -1 otherwise.
  */
-void cucul_blit(cucul_canvas_t *dst, int x, int y,
-                cucul_canvas_t const *src, cucul_canvas_t const *mask)
+int cucul_blit(cucul_canvas_t *dst, int x, int y,
+               cucul_canvas_t const *src, cucul_canvas_t const *mask)
 {
     int i, j, starti, startj, endi, endj;
 
     if(mask && (src->width != mask->width || src->height != mask->height))
-        return;
+    {
+#if defined(HAVE_ERRNO_H)
+        errno = EINVAL;
+#endif
+        return -1;
+    }
 
     starti = x < 0 ? -x : 0;
     startj = y < 0 ? -y : 0;
@@ -197,7 +218,7 @@ void cucul_blit(cucul_canvas_t *dst, int x, int y,
     endj = (y + src->height >= dst->height) ? dst->height - y : src->height;
 
     if(starti >= endi || startj >= endj)
-        return;
+        return 0;
 
     for(j = startj; j < endj; j++)
     {
@@ -224,6 +245,8 @@ void cucul_blit(cucul_canvas_t *dst, int x, int y,
                    (endi - starti) * 4);
         }
     }
+
+    return 0;
 }
 
 /*
diff --git a/cucul/conic.c b/cucul/conic.c
index 13e39ec..2380829 100644
--- a/cucul/conic.c
+++ b/cucul/conic.c
@@ -29,6 +29,8 @@
 static void ellipsepoints(cucul_canvas_t *, int, int, int, int, uint32_t);
 
 /** \brief Draw a circle on the canvas using the given character.
+ *
+ *  This function never fails.
  *
  *  \param cv The handle to the libcucul canvas.
  *  \param x Center X coordinate.
@@ -36,9 +38,9 @@ static void ellipsepoints(cucul_canvas_t *, int, int, int, int, uint32_t);
  *  \param r Circle radius.
  *  \param str UTF-8 string representing the character that should be used
  *         to draw the circle outline.
- *  \return void
+ *  \return This function always returns 0.
  */
-void cucul_draw_circle(cucul_canvas_t *cv, int x, int y, int r, char const *str)
+int cucul_draw_circle(cucul_canvas_t *cv, int x, int y, int r, char const *str)
 {
     int test, dx, dy;
     uint32_t ch = _cucul_utf8_to_utf32(str);
@@ -51,9 +53,13 @@ void cucul_draw_circle(cucul_canvas_t *cv, int x, int y, int r, char const *str)
 
         test += test > 0 ? dx - dy-- : dx;
     }
+
+    return 0;
 }
 
 /** \brief Fill an ellipse on the canvas using the given character.
+ *
+ *  This function never fails.
  *
  *  \param cv The handle to the libcucul canvas.
  *  \param xo Center X coordinate.
@@ -62,10 +68,10 @@ void cucul_draw_circle(cucul_canvas_t *cv, int x, int y, int r, char const *str)
  *  \param b Ellipse Y radius.
  *  \param str UTF-8 string representing the character that should be used
  *         to fill the ellipse.
- *  \return void
+ *  \return This function always returns 0.
  */
-void cucul_fill_ellipse(cucul_canvas_t *cv, int xo, int yo, int a, int b,
-                        char const *str)
+int cucul_fill_ellipse(cucul_canvas_t *cv, int xo, int yo, int a, int b,
+                       char const *str)
 {
     int d2;
     int x = 0;
@@ -108,9 +114,13 @@ void cucul_fill_ellipse(cucul_canvas_t *cv, int xo, int yo, int a, int b,
         cucul_draw_line(cv, xo - x, yo - y, xo + x, yo - y, str);
         cucul_draw_line(cv, xo - x, yo + y, xo + x, yo + y, str);
     }
+
+    return 0;
 }
 
 /** \brief Draw an ellipse on the canvas using the given character.
+ *
+ *  This function never fails.
  *
  *  \param cv The handle to the libcucul canvas.
  *  \param xo Center X coordinate.
@@ -119,10 +129,10 @@ void cucul_fill_ellipse(cucul_canvas_t *cv, int xo, int yo, int a, int b,
  *  \param b Ellipse Y radius.
  *  \param str UTF-8 string representing the character that should be used
  *         to draw the ellipse outline.
- *  \return void
+ *  \return This function always returns 0.
  */
-void cucul_draw_ellipse(cucul_canvas_t *cv, int xo, int yo, int a, int b,
-                        char const *str)
+int cucul_draw_ellipse(cucul_canvas_t *cv, int xo, int yo, int a, int b,
+                       char const *str)
 {
     int d2;
     int x = 0;
@@ -163,18 +173,22 @@ void cucul_draw_ellipse(cucul_canvas_t *cv, int xo, int yo, int a, int b,
         y--;
         ellipsepoints(cv, xo, yo, x, y, ch);
     }
+
+    return 0;
 }
 
 /** \brief Draw a thin ellipse on the canvas.
+ *
+ *  This function never fails.
  *
  *  \param cv The handle to the libcucul canvas.
  *  \param xo Center X coordinate.
  *  \param yo Center Y coordinate.
  *  \param a Ellipse X radius.
  *  \param b Ellipse Y radius.
- *  \return void
+ *  \return This function always returns 0.
  */
-void cucul_draw_thin_ellipse(cucul_canvas_t *cv, int xo, int yo, int a, int b)
+int cucul_draw_thin_ellipse(cucul_canvas_t *cv, int xo, int yo, int a, int b)
 {
     /* FIXME: this is not correct */
     int d2;
@@ -215,6 +229,8 @@ void cucul_draw_thin_ellipse(cucul_canvas_t *cv, int xo, int yo, int a, int b)
         y--;
         ellipsepoints(cv, xo, yo, x, y, '|');
     }
+
+    return 0;
 }
 
 static void ellipsepoints(cucul_canvas_t *cv, int xo, int yo, int x, int y,
diff --git a/cucul/cucul.h b/cucul/cucul.h
index cf335b1..9426be6 100644
--- a/cucul/cucul.h
+++ b/cucul/cucul.h
@@ -86,7 +86,7 @@ int cucul_rand(int, int);
  *  @{ */
 unsigned long int cucul_get_buffer_size(cucul_buffer_t *);
 void * cucul_get_buffer_data(cucul_buffer_t *);
-void cucul_free_buffer(cucul_buffer_t *);
+int cucul_free_buffer(cucul_buffer_t *);
 /*  @} */
 
 /** \defgroup canvas libcucul canvas drawing
@@ -102,7 +102,7 @@ void cucul_putchar(cucul_canvas_t *, int, int, char);
 void cucul_putstr(cucul_canvas_t *, int, int, char const *);
 void cucul_printf(cucul_canvas_t *, int, int, char const *, ...);
 void cucul_clear_canvas(cucul_canvas_t *);
-void cucul_blit(cucul_canvas_t *, int, int, cucul_canvas_t const *, cucul_canvas_t const *);
+int cucul_blit(cucul_canvas_t *, int, int, cucul_canvas_t const *, cucul_canvas_t const *);
 /*  @} */
 
 /** \defgroup transform libcucul canvas transformation
@@ -122,23 +122,23 @@ void cucul_rotate(cucul_canvas_t *);
  *  boxes, triangles and ellipses.
  *
  *  @{ */
-void cucul_draw_line(cucul_canvas_t *, int, int, int, int, char const *);
-void cucul_draw_polyline(cucul_canvas_t *, int const x[], int const y[], int, char const *);
-void cucul_draw_thin_line(cucul_canvas_t *, int, int, int, int);
-void cucul_draw_thin_polyline(cucul_canvas_t *, int const x[], int const y[], int);
-
-void cucul_draw_circle(cucul_canvas_t *, int, int, int, char const *);
-void cucul_draw_ellipse(cucul_canvas_t *, int, int, int, int, char const *);
-void cucul_draw_thin_ellipse(cucul_canvas_t *, int, int, int, int);
-void cucul_fill_ellipse(cucul_canvas_t *, int, int, int, int, char const *);
-
-void cucul_draw_box(cucul_canvas_t *, int, int, int, int, char const *);
-void cucul_draw_thin_box(cucul_canvas_t *, int, int, int, int);
-void cucul_fill_box(cucul_canvas_t *, int, int, int, int, char const *);
-
-void cucul_draw_triangle(cucul_canvas_t *, int, int, int, int, int, int, char const *);
-void cucul_draw_thin_triangle(cucul_canvas_t *, int, int, int, int, int, int);
-void cucul_fill_triangle(cucul_canvas_t *, int, int, int, int, int, int, char const *);
+int cucul_draw_line(cucul_canvas_t *, int, int, int, int, char const *);
+int cucul_draw_polyline(cucul_canvas_t *, int const x[], int const y[], int, char const *);
+int cucul_draw_thin_line(cucul_canvas_t *, int, int, int, int);
+int cucul_draw_thin_polyline(cucul_canvas_t *, int const x[], int const y[], int);
+
+int cucul_draw_circle(cucul_canvas_t *, int, int, int, char const *);
+int cucul_draw_ellipse(cucul_canvas_t *, int, int, int, int, char const *);
+int cucul_draw_thin_ellipse(cucul_canvas_t *, int, int, int, int);
+int cucul_fill_ellipse(cucul_canvas_t *, int, int, int, int, char const *);
+
+int cucul_draw_box(cucul_canvas_t *, int, int, int, int, char const *);
+int cucul_draw_thin_box(cucul_canvas_t *, int, int, int, int);
+int cucul_fill_box(cucul_canvas_t *, int, int, int, int, char const *);
+
+int cucul_draw_triangle(cucul_canvas_t *, int, int, int, int, int, int, char const *);
+int cucul_draw_thin_triangle(cucul_canvas_t *, int, int, int, int, int, int);
+int cucul_fill_triangle(cucul_canvas_t *, int, int, int, int, int, int, char const *);
 /*  @} */
 
 /** \defgroup frame libcucul canvas frame handling
diff --git a/cucul/line.c b/cucul/line.c
index 9d46188..151de5e 100644
--- a/cucul/line.c
+++ b/cucul/line.c
@@ -42,6 +42,8 @@ static void draw_solid_line(cucul_canvas_t*, struct line*);
 static void draw_thin_line(cucul_canvas_t*, struct line*);
 
 /** \brief Draw a line on the canvas using the given character.
+ *
+ *  This function never fails.
  *
  *  \param cv The handle to the libcucul canvas.
  *  \param x1 X coordinate of the first point.
@@ -49,10 +51,10 @@ static void draw_thin_line(cucul_canvas_t*, struct line*);
  *  \param x2 X coordinate of the second point.
  *  \param y2 Y coordinate of the second point.
  *  \param str UTF-8 string containing the character to use to draw the line.
- *  \return void
+ *  \return This function always returns 0.
  */
-void cucul_draw_line(cucul_canvas_t *cv, int x1, int y1, int x2, int y2,
-                     char const *str)
+int cucul_draw_line(cucul_canvas_t *cv, int x1, int y1, int x2, int y2,
+                    char const *str)
 {
     struct line s;
     s.x1 = x1;
@@ -62,6 +64,8 @@ void cucul_draw_line(cucul_canvas_t *cv, int x1, int y1, int x2, int y2,
     s.ch = _cucul_utf8_to_utf32(str);
     s.draw = draw_solid_line;
     clip_line(cv, &s);
+
+    return 0;
 }
 
 /** \brief Draw a polyline.
@@ -71,15 +75,17 @@ void cucul_draw_line(cucul_canvas_t *cv, int x1, int y1, int x2, int y2,
  *  draw a polygon you need to specify the starting point at the end of the
  *  list as well.
  *
+ *  This function never fails.
+ *
  *  \param cv The handle to the libcucul canvas.
  *  \param x Array of X coordinates. Must have \p n + 1 elements.
  *  \param y Array of Y coordinates. Must have \p n + 1 elements.
  *  \param n Number of lines to draw.
  *  \param str UTF-8 string containing the character to use to draw the lines.
- *  \return void
+ *  \return This function always returns 0.
  */
-void cucul_draw_polyline(cucul_canvas_t *cv, int const x[], int const y[],
-                         int n, char const *str)
+int cucul_draw_polyline(cucul_canvas_t *cv, int const x[], int const y[],
+                        int n, char const *str)
 {
     int i;
     struct line s;
@@ -94,18 +100,22 @@ void cucul_draw_polyline(cucul_canvas_t *cv, int const x[], int const y[],
         s.y2 = y[i+1];
         clip_line(cv, &s);
     }
+
+    return 0;
 }
 
 /** \brief Draw a thin line on the canvas, using ASCII art.
+ *
+ *  This function never fails.
  *
  *  \param cv The handle to the libcucul canvas.
  *  \param x1 X coordinate of the first point.
  *  \param y1 Y coordinate of the first point.
  *  \param x2 X coordinate of the second point.
  *  \param y2 Y coordinate of the second point.
- *  \return void
+ *  \return This function always returns 0.
  */
-void cucul_draw_thin_line(cucul_canvas_t *cv, int x1, int y1, int x2, int y2)
+int cucul_draw_thin_line(cucul_canvas_t *cv, int x1, int y1, int x2, int y2)
 {
     struct line s;
     s.x1 = x1;
@@ -114,6 +124,8 @@ void cucul_draw_thin_line(cucul_canvas_t *cv, int x1, int y1, int x2, int y2)
     s.y2 = y2;
     s.draw = draw_thin_line;
     clip_line(cv, &s);
+
+    return 0;
 }
 
 /** \brief Draw an ASCII art thin polyline.
@@ -123,14 +135,16 @@ void cucul_draw_thin_line(cucul_canvas_t *cv, int x1, int y1, int x2, int y2)
  *  to draw a polygon you need to specify the starting point at the end of
  *  the list as well.
  *
+ *  This function never fails.
+ *
  *  \param cv The handle to the libcucul canvas.
  *  \param x Array of X coordinates. Must have \p n + 1 elements.
  *  \param y Array of Y coordinates. Must have \p n + 1 elements.
  *  \param n Number of lines to draw.
- *  \return void
+ *  \return This function always returns 0.
  */
-void cucul_draw_thin_polyline(cucul_canvas_t *cv, int const x[], int const y[],
-                              int n)
+int cucul_draw_thin_polyline(cucul_canvas_t *cv, int const x[], int const y[],
+                             int n)
 {
     int i;
     struct line s;
@@ -144,6 +158,8 @@ void cucul_draw_thin_polyline(cucul_canvas_t *cv, int const x[], int const y[],
         s.y2 = y[i+1];
         clip_line(cv, &s);
     }
+
+    return 0;
 }
 
 /*
diff --git a/cucul/triangle.c b/cucul/triangle.c
index c7d098e..9c1aeff 100644
--- a/cucul/triangle.c
+++ b/cucul/triangle.c
@@ -26,6 +26,8 @@
 #include "cucul_internals.h"
 
 /** \brief Draw a triangle on the canvas using the given character.
+ *
+ *  This function never fails.
  *
  *  \param cv The handle to the libcucul canvas.
  *  \param x1 X coordinate of the first point.
@@ -36,17 +38,21 @@
  *  \param y3 Y coordinate of the third point.
  *  \param str UTF-8 string representing the character that should be used
  *         to draw the triangle outline.
- *  \return void
+ *  \return This function always returns 0.
  */
-void cucul_draw_triangle(cucul_canvas_t *cv, int x1, int y1, int x2, int y2,
-                         int x3, int y3, char const *str)
+int cucul_draw_triangle(cucul_canvas_t *cv, int x1, int y1, int x2, int y2,
+                        int x3, int y3, char const *str)
 {
     cucul_draw_line(cv, x1, y1, x2, y2, str);
     cucul_draw_line(cv, x2, y2, x3, y3, str);
     cucul_draw_line(cv, x3, y3, x1, y1, str);
+
+    return 0;
 }
 
 /** \brief Draw a thin triangle on the canvas.
+ *
+ *  This function never fails.
  *
  *  \param cv The handle to the libcucul canvas.
  *  \param x1 X coordinate of the first point.
@@ -55,17 +61,21 @@ void cucul_draw_triangle(cucul_canvas_t *cv, int x1, int y1, int x2, int y2,
  *  \param y2 Y coordinate of the second point.
  *  \param x3 X coordinate of the third point.
  *  \param y3 Y coordinate of the third point.
- *  \return void
+ *  \return This function always returns 0.
  */
-void cucul_draw_thin_triangle(cucul_canvas_t *cv, int x1, int y1,
-                              int x2, int y2, int x3, int y3)
+int cucul_draw_thin_triangle(cucul_canvas_t *cv, int x1, int y1,
+                             int x2, int y2, int x3, int y3)
 {
     cucul_draw_thin_line(cv, x1, y1, x2, y2);
     cucul_draw_thin_line(cv, x2, y2, x3, y3);
     cucul_draw_thin_line(cv, x3, y3, x1, y1);
+
+    return 0;
 }
 
 /** \brief Fill a triangle on the canvas using the given character.
+ *
+ *  This function never fails.
  *
  *  \param cv The handle to the libcucul canvas.
  *  \param x1 X coordinate of the first point.
@@ -76,26 +86,20 @@ void cucul_draw_thin_triangle(cucul_canvas_t *cv, int x1, int y1,
  *  \param y3 Y coordinate of the third point.
  *  \param str UTF-8 string representing the character that should be used
  *         to fill the triangle.
- *  \return void
+ *  \return This function always returns 0.
  */
-void cucul_fill_triangle(cucul_canvas_t *cv, int x1, int y1, int x2, int y2,
-                         int x3, int y3, char const *str)
+int cucul_fill_triangle(cucul_canvas_t *cv, int x1, int y1, int x2, int y2,
+                        int x3, int y3, char const *str)
 {
     int x, y, xa, xb, xmax, ymax;
     uint32_t ch;
 
     /* Bubble-sort y1 <= y2 <= y3 */
     if(y1 > y2)
-    {
-        cucul_fill_triangle(cv, x2, y2, x1, y1, x3, y3, str);
-        return;
-    }
+        return cucul_fill_triangle(cv, x2, y2, x1, y1, x3, y3, str);
 
     if(y2 > y3)
-    {
-        cucul_fill_triangle(cv, x1, y1, x3, y3, x2, y2, str);
-        return;
-    }
+        return cucul_fill_triangle(cv, x1, y1, x3, y3, x2, y2, str);
 
     /* Promote precision */
     x1 *= 4;
@@ -139,5 +143,7 @@ void cucul_fill_triangle(cucul_canvas_t *cv, int x1, int y1, int x2, int y2,
         for(x = xa; x <= xb; x++)
             _cucul_putchar32(cv, x, y, ch);
     }
+
+    return 0;
 }