NAME¶

SDL_ComposeCustomBlendMode - Compose a custom blend mode for renderers.

SYNOPSIS¶

#include "SDL3/SDL.h"

SDL_BlendMode SDL_ComposeCustomBlendMode(SDL_BlendFactor srcColorFactor,
                                         SDL_BlendFactor dstColorFactor,
                                         SDL_BlendOperation colorOperation,
                                         SDL_BlendFactor srcAlphaFactor,
                                         SDL_BlendFactor dstAlphaFactor,
                                         SDL_BlendOperation alphaOperation);

DESCRIPTION¶

The functions SDL_SetRenderDrawBlendMode
and

SDL_SetTextureBlendMode
accept the

SDL_BlendMode
returned by this function if the renderer supports it.

A blend mode controls how the pixels from a drawing operation (source) get combined with the pixels from the render target (destination). First, the components of the source and destination pixels get multiplied with their blend factors. Then, the blend operation takes the two products and calculates the result that will get stored in the render target.

Expressed in pseudocode, it would look like this:

c dstRGB = colorOperation(srcRGB srcColorFactor, dstRGB dstColorFactor); dstA = alphaOperation(srcA srcAlphaFactor, dstA dstAlphaFactor);

Where the functions colorOperation(src,dst) and alphaOperation(src, dst) can return one of the following:

- src+dst - src-dst - dst-src - min(src,dst) - max(src,dst) The red, green, and blue components are always multiplied with the first, second, and third components of the SDL_BlendFactor , respectively. The fourth component is not used.

The alpha component is always multiplied with the fourth component of the

SDL_BlendFactor . The other components are not used in the alpha calculation.

Support for these blend modes varies for each renderer. To check if a specific SDL_BlendMode
is supported, create a renderer and pass it to either SDL_SetRenderDrawBlendMode

or SDL_SetTextureBlendMode . They will return with an error if the blend mode is not supported.

This list describes the support of custom blend modes for each renderer in SDL 2.0.6. All renderers support the four blend modes listed in the

SDL_BlendMode
enumeration.

- direct3d : Supports all operations with all factors. However, some
factors produce unexpected results with

SDL_BLENDOPERATION_MINIMUM and

SDL_BLENDOPERATION_MAXIMUM . - direct3d11 : Same as Direct3D 9. - opengl : Supports the

SDL_BLENDOPERATION_ADD operation with all
factors. OpenGL versions 1.1, 1.2, and 1.3 do not work correctly with SDL
2.0.6. - opengles : Supports the

SDL_BLENDOPERATION_ADD operation with all
factors. Color and alpha factors need to be the same. OpenGL ES 1
implementation specific: May also support

SDL_BLENDOPERATION_SUBTRACT and

SDL_BLENDOPERATION_REV_SUBTRACT . May
support color and alpha operations being different from each other. May
support color and alpha factors being different from each other. - opengles2 : Supports the

SDL_BLENDOPERATION_ADD ,

SDL_BLENDOPERATION_SUBTRACT ,

SDL_BLENDOPERATION_REV_SUBTRACT operations with all factors. - psp : No custom blend mode support. - software : No custom blend mode support.

Some renderers do not provide an alpha component for the default render target. The SDL_BLENDFACTOR_DST_ALPHA and

SDL_BLENDFACTOR_ONE_MINUS_DST_ALPHA factors do not have an effect in this case.

FUNCTION PARAMETERS¶

srcColorFactor

the SDL_BlendFactor
applied to the red, green, and blue components of the source pixels

dstColorFactor

the SDL_BlendFactor
applied to the red, green, and blue components of the destination pixels

colorOperation

the SDL_BlendOperation
used to combine the red, green, and blue components of the source and destination pixels

srcAlphaFactor

the SDL_BlendFactor
applied to the alpha component of the source pixels

dstAlphaFactor

the SDL_BlendFactor
applied to the alpha component of the destination pixels

alphaOperation

the SDL_BlendOperation
used to combine the alpha component of the source and destination pixels

RETURN VALUE¶

Returns an SDL_BlendMode
that represents the chosen factors and operations.

AVAILABILITY¶

This function is available since SDL 3.0.0.

SEE ALSO¶

SDL_SetRenderDrawBlendMode(3), SDL_GetRenderDrawBlendMode(3), SDL_SetTextureBlendMode(3), SDL_GetTextureBlendMode(3)