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| Background - Keyman Core API |
Namespace
All calls, types and enums are prefixed with the namespace identifier km_core_
API idioms
Error Handling
Error handling and success failure notification are communicated through a
general mechanism similar to COM’s HRESULT scheme (unlike COM, any non-zero
value is an error). Any functions that can fail will always return a status
value and all results are returned via outparams passed to the function.
Passing variable length data out
Almost all calls marshalling variable length aggregate data in or out of an API object take the form:
km_core_status fn_name(object_ref, buffer_ptr, size_ptr)
where the buffer_ptr is nullable and all other arguments are required (will
result in an KM_CORE_STATUS_INVALID_ARGUMENT
status being returned if nulled). When buffer_ptr is nullptr or 0 the
function will place the size of the required buffer in the variable pointed to
by size_ptr.
Resource management
Calls which result in the allocation of resources, regardless of resulting ownership, are of the form:
km_core_status fn_name(object_ref, handle_out_ptr)
where handle_out_ptr is a valid pointer to a caller allocated variable to hold
the resulting resource handle. This is often a reference to a created object.
Unless stated all arguments are required (will result in an
KM_CORE_STATUS_INVALID_ARGUMENT status being
returned if nulled).
All dispose calls are designed to accept nullptr or 0 as a valid value and
will do nothing in that event.
Fixed size attribute access
For accessors to fixed size attributes of an object these will take the form:
attr_value fn_name(object_ref)
object_ref is required to be valid and will result in a nonsense value being returned if nullptr or 0.
Versioning scheme
This follows the libtool interface versioning scheme of current.age.revision:
current
The most recent interface number that the engine implements.
age
How many interface numbers back from current the library implements. E.g. 5.2.0 would mean the library provides interface versions 3-5 and 5.0.0 would mean just interface version 5 and nothing older.
revision
The implementation version of the current interface. This represents improvements to the code that don't change the intended behaviour of the interface such as bug fixes and optimisations.
For Linux and other OS which support this scheme the dynamic linker will automatically choose the most updated version if more than one implementation is available. For Windows or dynamic loaded shared objects on Linux you can use the km_core_get_engine_attrs call and Library version macros to check the loaded DLL supplies the correct interface.
km_core_cu type
Represents a UTF16 codepoint, most strings are passed as UTF16.
typedef uint16_t/char16_t km_core_cu;
km_core_usv type
An integral type capable of holding a single Unicode Scalar Value, a decoded UTF codepoint.
typedef uint32_t/char32_t km_core_usv;
km_core_virtual_key type
An integral type capable of holding a platform specific virtual key code.
typedef uint16_t km_core_virtual_key;
km_core_status type
An integral 32 bit wide type capable of holding any valid status code as
defined by the enum km_core_status_codes.
typedef uint32_t km_core_status;
km_core_keyboard struct
Represents a keyboard loaded from disk, that can be executed by the keyboard processor to consume events, update state associated with an insertion point and produce action items. A keyboard object may be referenced by any number of state objects but must be disposed of after all state objects referencing it have first been disposed of.
typedef struct km_core_keyboard km_core_keyboard;
km_core_state struct
Represents all state associated with an insertion point using a keyboard. This tracks context, and current action items resulting from a processed keyboard event. There can be many state objects using the same keyboard. A state object may not live longer than the keyboard it manages state for.
typedef struct km_core_state km_core_state;
km_core_options struct
Represents a set of option items for environmental state and keyboard state.
typedef struct km_core_options km_core_options;
typedef struct km_core_option_item km_core_option_item;
km_core_keyboard_imx_platform callback function
Callback function used to to access Input Method eXtension library functions from Keyman Core
typedef uint8_t (*km_core_keyboard_imx_platform)(km_core_state*, uint32_t, void*);
km_core_status_codes enum
An error code mechanism similar to COM's HRESULT scheme (unlike COM, any
non-zero value is an error).
enum km_core_status_codes {
/** Success code. Call completed as documented. */
KM_CORE_STATUS_OK = 0,
/** The call failed to allocate memory during its execution, causing it to fail. */
KM_CORE_STATUS_NO_MEM = 1,
/** The call performed an I/O operation which failed, causing it to fail. */
KM_CORE_STATUS_IO_ERROR = 2,
/** The call detected one of its parameters was invalid or unsafe. */
KM_CORE_STATUS_INVALID_ARGUMENT = 3,
/** The provided key or index into a collection object was not present. */
KM_CORE_STATUS_KEY_ERROR = 4,
/** The provided buffer did not contain enough space to fully encode or copy
* the result of this call. */
KM_CORE_STATUS_INSUFFICENT_BUFFER = 5,
/** A malformed or partial UTF sequence prevented complete decoding of a
* unicode string. */
KM_CORE_STATUS_INVALID_UTF = 6,
/** An attempt to decode a keyboard file failed. */
KM_CORE_STATUS_INVALID_KEYBOARD = 7,
KM_CORE_STATUS_NOT_IMPLEMENTED = 8,
/** This allows encapsulating a platform error code: the remaining 31 low bits
* are the error code returned by the OS for cases where the failure mode is
* platform specific. For HRESULT codes this only permits failure codes to be
* passed and not success codes. */
KM_CORE_STATUS_OS_ERROR = 0x80000000
};
km_core_attr struct
A structure describing information about Keyman Core implementing this API.
typedef struct {
/** Maximum context size supported by processor in code points. */
size_t max_context;
/** Current API number supported. */
uint16_t current;
/** Implementation number of current API. */
uint16_t revision;
/** current - age == Oldest API number supported. */
uint16_t age;
/** A bit field of [km_core_tech_value] values, specifiying which Keyboard
* technologies the engine supports. */
uint16_t technology;
/** A UTF-8 encoded string identifying the implementer of the processor. */
char const *vendor;
} km_core_attr;
km_core_tech_value enum
Values for a bit field indicating which keyboarding technologies a keyboard processor supports.
enum km_core_tech_value {
/** The keyboard processor implementation does not disclose which technologies
* it implements. */
KM_CORE_TECH_UNSPECIFIED = 0,
/** The keyboard processor implements a simple en-US keyboard for the purposes
* of testing the API. */
KM_CORE_TECH_MOCK = 1 << 0,
/** The keyboard processor implements a Keyman KMX compatible engine. */
KM_CORE_TECH_KMX = 1 << 1,
/** The keyboard processor implements a LDML capable processing engine. */
KM_CORE_TECH_LDML = 1 << 2
};
km_core_get_engine_attrs function
Get access processors attributes describing version and technology implemented.
Parameters
state
An opaque pointer to a km_core_state.
Returns
A pointer to a km_core_attr structure. Do not modify the contents of this structure.
KMN_API
km_core_attr const *
km_core_get_engine_attrs(
km_core_state const *state
);
km_core_bool enum
Defines a boolean state.
typedef enum { KM_CORE_FALSE = 0, KM_CORE_TRUE = 1 } km_core_bool;