diff --git a/cucul/canvas.c b/cucul/canvas.c
index 4b58cf9..483f69c 100644
--- a/cucul/canvas.c
+++ b/cucul/canvas.c
@@ -58,17 +58,18 @@
  *  \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)
+int cucul_putchar(cucul_canvas_t *cv, int x, int y, char ch)
 {
-    if(x < 0 || x >= (int)cv->width ||
-       y < 0 || y >= (int)cv->height)
-        return;
+    if(x < 0 || x >= (int)cv->width || y < 0 || y >= (int)cv->height)
+        return 0;
 
     if((unsigned char)ch < 0x20 || (unsigned char)ch > 0x7f)
         ch = 0x20;
 
     cv->chars[x + y * cv->width] = ch;
     cv->attr[x + y * cv->width] = (cv->bgcolor << 16) | cv->fgcolor;
+
+    return 0;
 }
 
 /** \brief Print a string.
@@ -86,20 +87,20 @@ void cucul_putchar(cucul_canvas_t *cv, int x, int y, char ch)
  *  \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)
+int cucul_putstr(cucul_canvas_t *cv, int x, int y, char const *s)
 {
     uint32_t *chars, *attr;
     unsigned int len;
 
     if(y < 0 || y >= (int)cv->height || x >= (int)cv->width)
-        return;
+        return 0;
 
     len = _cucul_strlen_utf8(s);
 
     if(x < 0)
     {
         if(len < (unsigned int)-x)
-            return;
+            return 0;
         len -= -x;
         s = _cucul_skip_utf8(s, -x);
         x = 0;
@@ -119,6 +120,8 @@ void cucul_putstr(cucul_canvas_t *cv, int x, int y, char const *s)
         s = _cucul_skip_utf8(s, 1);
         len--;
     }
+
+    return 0;
 }
 
 /** \brief Print a formated string.
@@ -138,14 +141,14 @@ void cucul_putstr(cucul_canvas_t *cv, int x, int y, char const *s)
  *  \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, ...)
+int cucul_printf(cucul_canvas_t *cv, int x, int y, char const *format, ...)
 {
     char tmp[BUFSIZ];
     char *buf = tmp;
     va_list args;
 
     if(y < 0 || y >= (int)cv->height || x >= (int)cv->width)
-        return;
+        return 0;
 
     if(cv->width - x + 1 > BUFSIZ)
         buf = malloc(cv->width - x + 1);
@@ -163,6 +166,8 @@ void cucul_printf(cucul_canvas_t *cv, int x, int y, char const *format, ...)
 
     if(buf != tmp)
         free(buf);
+
+    return 0;
 }
 
 /** \brief Clear the canvas.
@@ -174,7 +179,7 @@ void cucul_printf(cucul_canvas_t *cv, int x, int y, char const *format, ...)
  *  \param cv The canvas to clear.
  *  \return This function always returns 0.
  */
-void cucul_clear_canvas(cucul_canvas_t *cv)
+int cucul_clear_canvas(cucul_canvas_t *cv)
 {
     uint32_t color = (cv->bgcolor << 16) | cv->fgcolor;
     unsigned int n;
@@ -185,6 +190,8 @@ void cucul_clear_canvas(cucul_canvas_t *cv)
         cv->chars[n] = (uint32_t)' ';
         cv->attr[n] = color;
     }
+
+    return 0;
 }
 
 /** \brief Blit a canvas onto another one.
@@ -192,12 +199,16 @@ void cucul_clear_canvas(cucul_canvas_t *cv)
  *  This function blits a canvas onto another one at the given coordinates.
  *  An optional mask canvas can be used.
  *
+ *  If an error occurs, -1 is returned and \b errno is set accordingly:
+ *  - \c EINVAL A mask was specified but the mask size and source canvas
+ *    size do not match.
+ *
  *  \param dst The destination canvas.
  *  \param x X coordinate.
  *  \param y Y coordinate.
  *  \param src The source canvas.
  *  \param mask The mask canvas.
- *  \return 0 in case of success, -1 otherwise.
+ *  \return 0 in case of success, -1 if an error occurred.
  */
 int cucul_blit(cucul_canvas_t *dst, int x, int y,
                cucul_canvas_t const *src, cucul_canvas_t const *mask)
diff --git a/cucul/colour.c b/cucul/colour.c
index cbdf3b4..efb2d86 100644
--- a/cucul/colour.c
+++ b/cucul/colour.c
@@ -19,6 +19,10 @@
 #include "config.h"
 #include "common.h"
 
+#if defined(HAVE_ERRNO_H)
+#   include <errno.h>
+#endif
+
 #include "cucul.h"
 #include "cucul_internals.h"
 
@@ -37,17 +41,28 @@ static const uint16_t ansitab[16] =
  *  Color values are those defined in cucul.h, such as CUCUL_COLOR_RED
  *  or CUCUL_COLOR_TRANSPARENT.
  *
+ *  If an error occurs, -1 is returned and \b errno is set accordingly:
+ *  - \c EINVAL At least one of the colour values is invalid.
+ *
  *  \param cv A handle to the libcucul canvas.
  *  \param fg The requested foreground colour.
  *  \param bg The requested background colour.
+ *  \return 0 in case of success, -1 if an error occurred.
  */
-void cucul_set_color(cucul_canvas_t *cv, unsigned char fg, unsigned char bg)
+int cucul_set_color(cucul_canvas_t *cv, unsigned char fg, unsigned char bg)
 {
     if(fg > 0x20 || bg > 0x20)
-        return;
+    {
+#if defined(HAVE_ERRNO_H)
+        errno = EINVAL;
+#endif
+        return -1;
+    }
 
     cv->fgcolor = fg;
     cv->bgcolor = bg;
+
+    return 0;
 }
 
 /** \brief Set the default colour pair (truecolor version).
@@ -60,14 +75,23 @@ void cucul_set_color(cucul_canvas_t *cv, unsigned char fg, unsigned char bg)
  *  instance, 0xf088 is solid dark cyan (A=15 R=0 G=8 B=8), and 0x8fff is
  *  white with 50% alpha (A=8 R=15 G=15 B=15).
  *
+ *  If an error occurs, -1 is returned and \b errno is set accordingly:
+ *  - \c EINVAL At least one of the colour values is invalid.
+ *
  *  \param cv A handle to the libcucul canvas.
  *  \param fg The requested foreground colour.
  *  \param bg The requested background colour.
+ *  \return 0 in case of success, -1 if an error occurred.
  */
-void cucul_set_truecolor(cucul_canvas_t *cv, unsigned int fg, unsigned int bg)
+int cucul_set_truecolor(cucul_canvas_t *cv, unsigned int fg, unsigned int bg)
 {
     if(fg > 0xffff || bg > 0xffff)
-        return;
+    {
+#if defined(HAVE_ERRNO_H)
+        errno = EINVAL;
+#endif
+        return -1;
+    }
 
     if(fg < 0x100)
         fg += 0x100;
@@ -77,6 +101,8 @@ void cucul_set_truecolor(cucul_canvas_t *cv, unsigned int fg, unsigned int bg)
 
     cv->fgcolor = fg;
     cv->bgcolor = bg;
+
+    return 0;
 }
 
 /*
diff --git a/cucul/cucul.c b/cucul/cucul.c
index 9239fb8..732bdcd 100644
--- a/cucul/cucul.c
+++ b/cucul/cucul.c
@@ -23,6 +23,9 @@
 #   include <stdio.h>
 #   include <stdlib.h>
 #   include <string.h>
+#   if defined(HAVE_ERRNO_H)
+#       include <errno.h>
+#   endif
 #endif
 
 #include "cucul.h"
@@ -38,6 +41,9 @@
  *  If one of the desired canvas coordinates is zero, a default canvas size
  *  of 80x32 is used instead.
  *
+ *  If an error occurs, -1 is returned and \b errno is set accordingly:
+ *  - \c ENOMEM Not enough memory for the requested canvas size.
+ *
  *  \param width The desired canvas width
  *  \param height The desired canvas height
  *  \return A libcucul canvas handle upon success, NULL if an error occurred.
@@ -45,6 +51,10 @@
 cucul_canvas_t * cucul_create_canvas(unsigned int width, unsigned int height)
 {
     cucul_canvas_t *cv = malloc(sizeof(cucul_canvas_t));
+    int ret;
+
+    if(!cv)
+        goto nomem;
 
     cv->refcount = 0;
 
@@ -58,7 +68,18 @@ cucul_canvas_t * cucul_create_canvas(unsigned int width, unsigned int height)
     cv->frame = 0;
     cv->framecount = 1;
     cv->allchars = malloc(sizeof(uint32_t *));
+    if(!cv->allchars)
+    {
+        free(cv);
+        goto nomem;
+    }
     cv->allattr = malloc(sizeof(uint32_t *));
+    if(!cv->allattr)
+    {
+        free(cv->allchars);
+        free(cv);
+        goto nomem;
+    }
     cv->allchars[0] = NULL;
     cv->allattr[0] = NULL;
 
@@ -66,17 +87,34 @@ cucul_canvas_t * cucul_create_canvas(unsigned int width, unsigned int height)
      * default X11 window. When a graphic driver attaches to us, it can set
      * a different size. */
     if(width && height)
-        _cucul_set_canvas_size(cv, width, height);
+        ret = _cucul_set_canvas_size(cv, width, height);
     else
-        _cucul_set_canvas_size(cv, 80, 32);
+        ret = _cucul_set_canvas_size(cv, 80, 32);
 
-    if(_cucul_init_dither())
+    if(ret < 0)
     {
+#if defined(HAVE_ERRNO_H)
+        int saved_errno = errno;
+#endif
+        free(cv->allattr);
+        free(cv->allchars);
         free(cv);
+#if defined(HAVE_ERRNO_H)
+        errno = saved_errno;
+#endif
         return NULL;
     }
 
+    /* FIXME: this shouldn't happen here */
+    _cucul_init_dither();
+
     return cv;
+
+nomem:
+#if defined(HAVE_ERRNO_H)
+    errno = ENOMEM;
+#endif
+    return NULL;
 }
 
 /** \brief Resize a canvas.
@@ -94,23 +132,36 @@ cucul_canvas_t * cucul_create_canvas(unsigned int width, unsigned int height)
  *  canvas resize through user interaction. See the caca_event() documentation
  *  for more about this.
  *
+ *  If an error occurs, -1 is returned and \b errno is set accordingly:
+ *  - \c EBUSY The canvas is in use by a display driver and cannot be resized.
+ *  - \c ENOMEM Not enough memory for the requested canvas size. If this
+ *    happens, the canvas handle becomes invalid and should not be used.
+ *
  *  \param cv A libcucul canvas
  *  \param width The desired canvas width
  *  \param height The desired canvas height
+ *  \return 0 in case of success, -1 if an error occurred.
  */
-void cucul_set_canvas_size(cucul_canvas_t *cv, unsigned int width,
-                                               unsigned int height)
+int cucul_set_canvas_size(cucul_canvas_t *cv, unsigned int width,
+                                              unsigned int height)
 {
     if(cv->refcount)
-        return;
+    {
+#if defined(HAVE_ERRNO_H)
+        errno = EBUSY;
+#endif
+        return -1;
+    }
 
-    _cucul_set_canvas_size(cv, width, height);
+    return _cucul_set_canvas_size(cv, width, height);
 }
 
 /** \brief Get the canvas width.
  *
  *  This function returns the current canvas width, in character cells.
  *
+ *  This function never fails.
+ *
  *  \param cv A libcucul canvas
  *  \return The canvas width.
  */
@@ -123,6 +174,8 @@ unsigned int cucul_get_canvas_width(cucul_canvas_t *cv)
  *
  *  This function returns the current canvas height, in character cells.
  *
+ *  This function never fails.
+ *
  *  \param cv A libcucul canvas
  *  \return The canvas height.
  */
@@ -136,8 +189,11 @@ unsigned int cucul_get_canvas_height(cucul_canvas_t *cv)
  *  This function translates a cucul_color enum into a human-readable
  *  description string of the associated colour.
  *
+ *  This function never fails.
+ *
  *  \param color The colour value.
- *  \return A static string containing the colour's name.
+ *  \return A static string containing the colour's name, or \c "unknown" if
+ *  the colour is unknown.
  */
 char const *cucul_get_color_name(unsigned int color)
 {
@@ -173,12 +229,25 @@ char const *cucul_get_color_name(unsigned int color)
  *  cucul_free_canvas() has been called, no other \e libcucul functions may be
  *  used unless a new call to cucul_create_canvas() is done.
  *
+ *  If an error occurs, -1 is returned and \b errno is set accordingly:
+ *  - \c EBUSY The canvas is in use by a display driver and cannot be freed.
+ *
  *  \param cv A libcucul canvas
+ *  \return 0 in case of success, -1 if an error occurred.
  */
-void cucul_free_canvas(cucul_canvas_t *cv)
+int cucul_free_canvas(cucul_canvas_t *cv)
 {
     unsigned int f;
 
+    if(cv->refcount)
+    {
+#if defined(HAVE_ERRNO_H)
+        errno = EBUSY;
+#endif
+        return -1;
+    }
+
+    /* FIXME: this shouldn't be here either (see above) */
     _cucul_end_dither();
 
     for(f = 0; f < cv->framecount; f++)
@@ -188,9 +257,13 @@ void cucul_free_canvas(cucul_canvas_t *cv)
     }
 
     free(cv);
+
+    return 0;
 }
 
 /** \brief Generate a random integer within a range.
+ *
+ *  This function never fails.
  *
  *  \param min The lower bound of the integer range.
  *  \param max The upper bound of the integer range.
@@ -206,8 +279,8 @@ int cucul_rand(int min, int max)
  * XXX: The following functions are local.
  */
 
-void _cucul_set_canvas_size(cucul_canvas_t *cv, unsigned int width,
-                                                unsigned int height)
+int _cucul_set_canvas_size(cucul_canvas_t *cv, unsigned int width,
+                                               unsigned int height)
 {
     unsigned int x, y, f, old_width, old_height, new_size, old_size;
 
@@ -228,6 +301,13 @@ void _cucul_set_canvas_size(cucul_canvas_t *cv, unsigned int width,
                                       new_size * sizeof(uint32_t));
             cv->allattr[f] = realloc(cv->allattr[f],
                                      new_size * sizeof(uint32_t));
+            if(!cv->allchars[f] || !cv->allattr[f])
+            {
+#if defined(HAVE_ERRNO_H)
+                errno = ENOMEM;
+#endif
+                return -1;
+            }
         }
     }
 
@@ -310,11 +390,20 @@ void _cucul_set_canvas_size(cucul_canvas_t *cv, unsigned int width,
                                       new_size * sizeof(uint32_t));
             cv->allattr[f] = realloc(cv->allattr[f],
                                      new_size * sizeof(uint32_t));
+            if(!cv->allchars[f] || !cv->allattr[f])
+            {
+#if defined(HAVE_ERRNO_H)
+                errno = ENOMEM;
+#endif
+                return -1;
+            }
         }
     }
 
     /* Reset the current frame shortcut */
     cv->chars = cv->allchars[cv->frame];
     cv->attr = cv->allattr[cv->frame];
+
+    return 0;
 }
 
diff --git a/cucul/cucul.h b/cucul/cucul.h
index 9426be6..eb73504 100644
--- a/cucul/cucul.h
+++ b/cucul/cucul.h
@@ -72,10 +72,10 @@ typedef struct cucul_font cucul_font_t;
  *
  *  @{ */
 cucul_canvas_t * cucul_create_canvas(unsigned int, unsigned int);
-void cucul_set_canvas_size(cucul_canvas_t *, unsigned int, unsigned int);
+int cucul_set_canvas_size(cucul_canvas_t *, unsigned int, unsigned int);
 unsigned int cucul_get_canvas_width(cucul_canvas_t *);
 unsigned int cucul_get_canvas_height(cucul_canvas_t *);
-void cucul_free_canvas(cucul_canvas_t *);
+int cucul_free_canvas(cucul_canvas_t *);
 int cucul_rand(int, int);
 /*  @} */
 
@@ -95,13 +95,13 @@ int cucul_free_buffer(cucul_buffer_t *);
  *  higher level graphics functions.
  *
  *  @{ */
-void cucul_set_color(cucul_canvas_t *, unsigned char, unsigned char);
-void cucul_set_truecolor(cucul_canvas_t *, unsigned int, unsigned int);
+int cucul_set_color(cucul_canvas_t *, unsigned char, unsigned char);
+int cucul_set_truecolor(cucul_canvas_t *, unsigned int, unsigned int);
 char const *cucul_get_color_name(unsigned int);
-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 *);
+int cucul_putchar(cucul_canvas_t *, int, int, char);
+int cucul_putstr(cucul_canvas_t *, int, int, char const *);
+int cucul_printf(cucul_canvas_t *, int, int, char const *, ...);
+int cucul_clear_canvas(cucul_canvas_t *);
 int cucul_blit(cucul_canvas_t *, int, int, cucul_canvas_t const *, cucul_canvas_t const *);
 /*  @} */
 
diff --git a/cucul/cucul_internals.h b/cucul/cucul_internals.h
index 341c8f6..dd3381a 100644
--- a/cucul/cucul_internals.h
+++ b/cucul/cucul_internals.h
@@ -50,7 +50,7 @@ extern int _cucul_init_dither(void);
 extern int _cucul_end_dither(void);
 
 /* Canvas functions */
-extern void _cucul_set_canvas_size(cucul_canvas_t *, unsigned int, unsigned int);
+extern int _cucul_set_canvas_size(cucul_canvas_t *, unsigned int, unsigned int);
 extern void _cucul_putchar32(cucul_canvas_t *, int, int, uint32_t);
 
 /* Charset functions */