Error handling

Error handling — Decoding cairo's status

Synopsis

enum                cairo_status_t;
const char *        cairo_status_to_string              (cairo_status_t status);
void                cairo_debug_reset_static_data       (void);

Description

Cairo uses a single status type to represent all kinds of errors. A status value of CAIRO_STATUS_SUCCESS represents no error and has an integer value of zero. All other status values represent an error.

Cairo's error handling is designed to be easy to use and safe. All major cairo objects retain an error status internally which can be queried anytime by the users using cairo*_status() calls. In the mean time, it is safe to call all cairo functions normally even if the underlying object is in an error status. This means that no error handling code is required before or after each individual cairo function call.

Details

enum cairo_status_t

typedef enum {
    CAIRO_STATUS_SUCCESS = 0,

    CAIRO_STATUS_NO_MEMORY,
    CAIRO_STATUS_INVALID_RESTORE,
    CAIRO_STATUS_INVALID_POP_GROUP,
    CAIRO_STATUS_NO_CURRENT_POINT,
    CAIRO_STATUS_INVALID_MATRIX,
    CAIRO_STATUS_INVALID_STATUS,
    CAIRO_STATUS_NULL_POINTER,
    CAIRO_STATUS_INVALID_STRING,
    CAIRO_STATUS_INVALID_PATH_DATA,
    CAIRO_STATUS_READ_ERROR,
    CAIRO_STATUS_WRITE_ERROR,
    CAIRO_STATUS_SURFACE_FINISHED,
    CAIRO_STATUS_SURFACE_TYPE_MISMATCH,
    CAIRO_STATUS_PATTERN_TYPE_MISMATCH,
    CAIRO_STATUS_INVALID_CONTENT,
    CAIRO_STATUS_INVALID_FORMAT,
    CAIRO_STATUS_INVALID_VISUAL,
    CAIRO_STATUS_FILE_NOT_FOUND,
    CAIRO_STATUS_INVALID_DASH,
    CAIRO_STATUS_INVALID_DSC_COMMENT,
    CAIRO_STATUS_INVALID_INDEX,
    CAIRO_STATUS_CLIP_NOT_REPRESENTABLE,
    CAIRO_STATUS_TEMP_FILE_ERROR,
    CAIRO_STATUS_INVALID_STRIDE,
    CAIRO_STATUS_FONT_TYPE_MISMATCH,
    CAIRO_STATUS_USER_FONT_IMMUTABLE,
    CAIRO_STATUS_USER_FONT_ERROR,
    CAIRO_STATUS_NEGATIVE_COUNT,
    CAIRO_STATUS_INVALID_CLUSTERS,
    CAIRO_STATUS_INVALID_SLANT,
    CAIRO_STATUS_INVALID_WEIGHT,
    CAIRO_STATUS_INVALID_SIZE,
    CAIRO_STATUS_USER_FONT_NOT_IMPLEMENTED,
    CAIRO_STATUS_DEVICE_TYPE_MISMATCH,
    CAIRO_STATUS_DEVICE_ERROR,
    CAIRO_STATUS_INVALID_MESH_CONSTRUCTION,
    CAIRO_STATUS_DEVICE_FINISHED,
    CAIRO_STATUS_JBIG2_GLOBAL_MISSING,

    CAIRO_STATUS_LAST_STATUS
} cairo_status_t;

cairo_status_t is used to indicate errors that can occur when using Cairo. In some cases it is returned directly by functions. but when using cairo_t, the last error, if any, is stored in the context and can be retrieved with cairo_status().

New entries may be added in future versions. Use cairo_status_to_string() to get a human-readable representation of an error message.

CAIRO_STATUS_SUCCESS

no error has occurred (Since 1.0)

CAIRO_STATUS_NO_MEMORY

out of memory (Since 1.0)

CAIRO_STATUS_INVALID_RESTORE

cairo_restore() called without matching cairo_save() (Since 1.0)

CAIRO_STATUS_INVALID_POP_GROUP

no saved group to pop, i.e. cairo_pop_group() without matching cairo_push_group() (Since 1.0)

CAIRO_STATUS_NO_CURRENT_POINT

no current point defined (Since 1.0)

CAIRO_STATUS_INVALID_MATRIX

invalid matrix (not invertible) (Since 1.0)

CAIRO_STATUS_INVALID_STATUS

invalid value for an input cairo_status_t (Since 1.0)

CAIRO_STATUS_NULL_POINTER

NULL pointer (Since 1.0)

CAIRO_STATUS_INVALID_STRING

input string not valid UTF-8 (Since 1.0)

CAIRO_STATUS_INVALID_PATH_DATA

input path data not valid (Since 1.0)

CAIRO_STATUS_READ_ERROR

error while reading from input stream (Since 1.0)

CAIRO_STATUS_WRITE_ERROR

error while writing to output stream (Since 1.0)

CAIRO_STATUS_SURFACE_FINISHED

target surface has been finished (Since 1.0)

CAIRO_STATUS_SURFACE_TYPE_MISMATCH

the surface type is not appropriate for the operation (Since 1.0)

CAIRO_STATUS_PATTERN_TYPE_MISMATCH

the pattern type is not appropriate for the operation (Since 1.0)

CAIRO_STATUS_INVALID_CONTENT

invalid value for an input cairo_content_t (Since 1.0)

CAIRO_STATUS_INVALID_FORMAT

invalid value for an input cairo_format_t (Since 1.0)

CAIRO_STATUS_INVALID_VISUAL

invalid value for an input Visual* (Since 1.0)

CAIRO_STATUS_FILE_NOT_FOUND

file not found (Since 1.0)

CAIRO_STATUS_INVALID_DASH

invalid value for a dash setting (Since 1.0)

CAIRO_STATUS_INVALID_DSC_COMMENT

invalid value for a DSC comment (Since 1.2)

CAIRO_STATUS_INVALID_INDEX

invalid index passed to getter (Since 1.4)

CAIRO_STATUS_CLIP_NOT_REPRESENTABLE

clip region not representable in desired format (Since 1.4)

CAIRO_STATUS_TEMP_FILE_ERROR

error creating or writing to a temporary file (Since 1.6)

CAIRO_STATUS_INVALID_STRIDE

invalid value for stride (Since 1.6)

CAIRO_STATUS_FONT_TYPE_MISMATCH

the font type is not appropriate for the operation (Since 1.8)

CAIRO_STATUS_USER_FONT_IMMUTABLE

the user-font is immutable (Since 1.8)

CAIRO_STATUS_USER_FONT_ERROR

error occurred in a user-font callback function (Since 1.8)

CAIRO_STATUS_NEGATIVE_COUNT

negative number used where it is not allowed (Since 1.8)

CAIRO_STATUS_INVALID_CLUSTERS

input clusters do not represent the accompanying text and glyph array (Since 1.8)

CAIRO_STATUS_INVALID_SLANT

invalid value for an input cairo_font_slant_t (Since 1.8)

CAIRO_STATUS_INVALID_WEIGHT

invalid value for an input cairo_font_weight_t (Since 1.8)

CAIRO_STATUS_INVALID_SIZE

invalid value (typically too big) for the size of the input (surface, pattern, etc.) (Since 1.10)

CAIRO_STATUS_USER_FONT_NOT_IMPLEMENTED

user-font method not implemented (Since 1.10)

CAIRO_STATUS_DEVICE_TYPE_MISMATCH

the device type is not appropriate for the operation (Since 1.10)

CAIRO_STATUS_DEVICE_ERROR

an operation to the device caused an unspecified error (Since 1.10)

CAIRO_STATUS_INVALID_MESH_CONSTRUCTION

a mesh pattern construction operation was used outside of a cairo_mesh_pattern_begin_patch()/cairo_mesh_pattern_end_patch() pair (Since 1.12)

CAIRO_STATUS_DEVICE_FINISHED

target device has been finished (Since 1.12)

CAIRO_STATUS_JBIG2_GLOBAL_MISSING

CAIRO_MIME_TYPE_JBIG2_GLOBAL_ID has been used on at least one image but no image provided CAIRO_MIME_TYPE_JBIG2_GLOBAL (Since 1.14)

CAIRO_STATUS_LAST_STATUS

this is a special value indicating the number of status values defined in this enumeration. When using this value, note that the version of cairo at run-time may have additional status values defined than the value of this symbol at compile-time. (Since 1.10)

Since 1.0


cairo_status_to_string ()

const char *        cairo_status_to_string              (cairo_status_t status);

Provides a human-readable description of a cairo_status_t.

status :

a cairo status

Returns :

a string representation of the status

Since 1.0


cairo_debug_reset_static_data ()

void                cairo_debug_reset_static_data       (void);

Resets all static data within cairo to its original state, (ie. identical to the state at the time of program invocation). For example, all caches within cairo will be flushed empty.

This function is intended to be useful when using memory-checking tools such as valgrind. When valgrind's memcheck analyzes a cairo-using program without a call to cairo_debug_reset_static_data(), it will report all data reachable via cairo's static objects as "still reachable". Calling cairo_debug_reset_static_data() just prior to program termination will make it easier to get squeaky clean reports from valgrind.

WARNING: It is only safe to call this function when there are no active cairo objects remaining, (ie. the appropriate destroy functions have been called as necessary). If there are active cairo objects, this call is likely to cause a crash, (eg. an assertion failure due to a hash table being destroyed when non-empty).

Since 1.0

See Also

cairo_status(), cairo_surface_status(), cairo_pattern_status(), cairo_font_face_status(), cairo_scaled_font_status(), cairo_region_status()