2D Vector Graphics Engine
Global C API functions exported as
extern "C" (C API).
We do not document these functions as they are called from C++ wrappers, which are documented and should be used as a reference. The most important thing in using C API is to understand how lifetime of objects is managed.
Each type that requires initialization provides
Init, 'Destroy', and
Reset functions. Init/Destroy are called by C++ constructors and destructors on C++ side and must be used the same way by C users. Although these functions return
BLResult it's guaranteed the result is always
BL_SUCCESS - the return value is only provided for consistency and possible tail calling.
The following example should illustrate how
Some init functions may provide shortcuts for the most used scenarios that merge initialization and resource allocation into a single function:
It's worth knowing that default initialization in Blend2D costs nothing and no resources are allocated, thus initialization never fails and in theory default initialized objects don't have to be destroyed as they don't hold any data that would have to be deallocated (however never do that in practice).
There is a distinction between 'Destroy' and 'Reset' functionality. Destroy would destroy the object and put it into a non-reusable state. Thus if the object is used by accident it should crash on null-pointer access. In the contrary resetting the object with 'Reset' explicitly states that the instance will be reused so 'Reset' basically destroys the object and puts it into its default initialized state for further use. This means that it's not needed to explicitly call 'Destroy' on instance that was reset, and it also is not needed for a default constructed instance. However, we recommend to not count on this behavior and to always properly initialize and destroy Blend2D objects.
The following example should explain how init/reset can avoid destroy:
``` BLImageCore img;
// Now image is default constructed/initialized. if you did just this and // abandon it then no resources will be leaked as default construction is // not allocating any resources nor increasing any reference counters. blImageInit(&img);
// Now image will have to dynamically allocate some memory to store pixel // data. If this succeeds the image will have to be reset to destroy the // data it holds. BLResult result = blImageCreate(&img, 128, 128, BL_FORMAT_PRGB32);
// If function fails it should behave like it was never called, so
img // would still be default initialized in this case. this means that you // don't have to destroy it explicitly although the C++ API would do it in // BLImage destructor. if (result != BL_SUCCESS) return result;
// Resetting image would destroy its data and make it default constructed. blImageReset(&img);
// You can still use the image after it has been reset, however, since the // image is default initialized it's empty. printf("%p", img.impl);
// The instance is still valid, to make it invalid we can destroy it for good. blImageDestroy(&img);
// At the moment null will be printed, but that's implementation dependent // and such behavior can change at any time. printf("%p", img.impl); ```
C API users must call either generic functions with
Item suffix or correct specialized functions in case of typed arrays. For example if you create a
BLArray<uint32_t> in C then you can only modify it through functions that have either
Item suffix. Arrays of signed types are treated as arrays of unsigned types at API level as there is no difference between them from implementation perspective.
Filesystem API is provided by functions prefixed with
blFileSystem and wrapped by BLFileSystem namespace in C++ API.
Matrix functionality is provided by BLMatrix2D, C++ API adds methods to the struct when compiling in C++ mode.
Blend2D runtime functions are provided either as a C-API or wrapped by BLRuntime namespace in C++ API.