This bug report was migrated from our old Bugzilla tracker.

These attachments are available in the static archive:

• Implements SDL_BLENDMODE_BLEND_DSTA on opengl, d3d, d3d11, and gles2 w/o shaders renderers. (SDL_BLENDMODE_BLEND_DSTA.patch, text/plain, 2014-06-19 20:24:02 +0000, 5789 bytes)
• screenshot (Screenshot from 2017-08-14 17-01-40.png, image/png, 2017-08-14 15:03:09 +0000, 62871 bytes)

Reported in version: 2.0.3
Reported for operating system, platform: Other, x86_64

Comments on the original bug report:

On 2014-06-19 20:24:02 +0000, Trygve Vea wrote:

Created attachment 1693
Implements SDL_BLENDMODE_BLEND_DSTA on opengl, d3d, d3d11, and gles2 w/o shaders renderers.

Hello,

I want to propose a new blend mode (SDL_BLENDMODE_BLEND_DSTA), which is
based on SDL_BLENDMODE_BLEND, but without modifying the destination alpha.

The use case for this is when I am rendering to a texture containing an
irregular shape - and do not want to modify the alpha channel of the
destination target.

I need something like this for a project I'm doing, but I would prefer to
not maintain my own patchset if I can avoid it.

I've attached a patch, which I've tested on Linux with the OpenGL renderer

• however, the patch does contain code that I THINK will work with d3d,
  d3d11, and gles2 without shaders as well - these are currently untested,
  but I left them in as the code looks pretty straight forward.

I looked briefly through SDLs website without finding any information of
how you deal with third party patches - but I would gladly make any
necessary modifications to help get this merged, if you would accept it.

Regards

Trygve Vea

On 2017-08-14 13:00:13 +0000, Sam Lantinga wrote:

This is implemented for accelerated renderers in this commit:
https://hg.libsdl.org/SDL/rev/180e8906dc3c

I think this is what you want:

    blendMode = SDL_ComposeCustomBlendMode(SDL_BLENDFACTOR_SRC_ALPHA,
                                           SDL_BLENDFACTOR_ONE_MINUS_SRC_ALPHA,
                                           SDL_BLENDOPERATION_ADD,
                                           SDL_BLENDFACTOR_ZERO,
                                           SDL_BLENDFACTOR_ONE,
                                           SDL_BLENDOPERATION_ADD);

On 2017-08-14 13:00:30 +0000, Sam Lantinga wrote:

Implemented!

On 2017-08-14 14:06:40 +0000, Sylvain wrote:

Just wondering: could this has introduced an issue within opengles2 renderer ?
I think I start to see pink colorkey with this commit. (and not when switching to opengles, or opengl).

On 2017-08-14 14:14:21 +0000, Sam Lantinga wrote:

It's possible, can you back out the commit and see if that fixes it?

On 2017-08-14 14:15:29 +0000, Sylvain wrote:

have tried yet, but this can be reproduced with

testspriteminimal.c

SDL_SetHint(SDL_HINT_RENDER_DRIVER, "opengles2");

On 2017-08-14 14:21:04 +0000, Sylvain wrote:

indeed,

hg update -r 42b62c737891 is ok

hg update -r 180e8906dc3c is bad : wrong display when using opengles2

On 2017-08-14 14:50:39 +0000, Sam Lantinga wrote:

Interesting, I'm not seeing that here. OpenGLES renderer is fine with testspriteminimal and testsprite2. Could it be a different screen format that's causing problems?

On 2017-08-14 15:02:45 +0000, Sylvain wrote:

This is not OpenGLES 1 (which is fine) but OpenGLES2 !
For testspritemininal, I dont see pink, but white background (instead of transparent).

see screenshot

On 2017-08-14 15:03:09 +0000, Sylvain wrote:

Created attachment 2852
screenshot

On 2017-08-14 15:30:33 +0000, Sylvain wrote:

I haved tested with opengles1 on deskop (it fallback to opengl). But I tested it on android.

so on desktop :

• opengl = ok
• opengles2 = fail

on android :

• opengles = ok
• opengles2 = fail

On 2017-08-14 15:30:57 +0000, Sylvain wrote:

oops:
I haved not tested with opengles1 on deskop (it fallback to opengl). But I tested it on android.

On 2017-08-14 16:21:06 +0000, Sylvain wrote:

I think the issue is in GLES2_SetupCopy()

it may be :

GLES2_SetBlendMode(data, texture->blendMode);

and not

GLES2_SetBlendMode(data, renderer->blendMode);

On 2017-08-14 16:50:08 +0000, Sylvain wrote:

And also some warning when compiling application:

include/SDL2/SDL_blendmode.h:68:46: warning: commas at the end of enumerator lists are a C++11 extension [-Wc++11-extensions]
SDL_BLENDOPERATION_MAXIMUM = 0x5, /< max(dst, src) : supported by D3D11 */
^~
include/SDL2/SDL_blendmode.h:86:46: warning: commas at the end of enumerator lists are a C++11 extension [-Wc++11-extensions]
SDL_BLENDFACTOR_ONE_MINUS_DST_ALPHA = 0xA, /< 1-dstA, 1-dstA, 1-dstA, 1-dstA */

On 2017-08-14 17:16:31 +0000, Sam Lantinga wrote:

Fixed, thanks!