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SDL.SDLRender

SDLRender contains functions for 2D accelerated rendering.

This API supports the following features:

  • single pixel points
  • single pixel lines
  • filled rectangles
  • texture images All of these may be drawn in opaque, blended, or additive modes.

The texture images can have an additional color tint or alpha modulation applied to them, and may also be stretched with linear interpolation, rotated or flipped/mirrored.

For advanced functionality like particle effects or actual 3D you should use SDL's OpenGL/Direct3D support or one of the many available 3D engines.

This API is not designed to be used from multiple threads.

Types

TypeDescription
TSDLRendererA 2D rendering context.
TSDLTextureAn efficient driver-specific representation of pixel data.

Structs

StructDescription
SDLRendererInfoA structure that contains information on the capabilities of a render driver or the current render context.

Functions

Function SDLGetNumRenderDrivers:Int()

Gets the number of 2D rendering drivers available for the current display.


Function SDLGetRenderDriverInfo:Int(index:Int, info:SDLRendererInfo Var)

Gets info about a specific 2D rendering driver for the current display.

Returns

0 on success or a negative error code on failure; call SDLGetError for more information.


Function SDLComposeCustomBlendMode:Int(srcColorFactor:ESDLBlendFactor, dstColorFactor:ESDLBlendFactor, colorOperation:ESDLBlendOperation, srcAlphaFactor:ESDLBlendFactor, dstAlphaFactor:ESDLBlendFactor, alphaOperation:ESDLBlendOperation)

Composes a custom blend mode for renderers.

The methods SetDrawBlendMode and texture SetBlendMode 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:

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 ESDLBlendFactor, respectively. The fourth component is not used.

The alpha component is always multiplied with the fourth component of the ESDLBlendFactor. 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 render SetDrawBlendMode or texture SetBlendMode. 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.

Returns

An SDL_BlendMode that represents the chosen factors and operations.


Consts

Const SDL_TEXTUREACCESS_STATIC:UInt = 0

Changes rarely, not lockable


Const SDL_TEXTUREACCESS_STREAMING:UInt = 1

Changes frequently, lockable


Const SDL_TEXTUREACCESS_TARGET:UInt = 2

Can be used as a render target


Const SDL_FLIP_NONE:Int = 0

Do not flip


Const SDL_FLIP_HORIZONTAL:Int = 1

Flip horizontally


Const SDL_FLIP_VERTICAL:Int = 2

Flip vertically


Const SDL_RENDERER_SOFTWARE:Int = $01

The renderer is a software fallback


Const SDL_RENDERER_ACCELERATED:Int = $02

The renderer uses hardware acceleration


Const SDL_RENDERER_PRESENTVSYNC:Int = $04

Present is synchronized with the refresh rate


Const SDL_RENDERER_TARGETTEXTURE:Int = $08

The renderer supports rendering to texture


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