[vlc-devel] [PATCH] opengl: insert shader headers at compile time

[Romain Vimont]

On Thu, Jun 18, 2020 at 10:23:21AM +0200, Alexandre Janniaux wrote:
> Hi,
> 
> It doesn't feel like a good idea, and goes against Haasn
> patches a few week ago.

I think this change is independant of his patches.

(We already discussed about this for commit
2fdbd23f2806cdad15ca03e0b83de46e543f6b6c.)

> Are there reasons to do so?

Currently, the renderer initializes two fields (glsl_version and
glsl_precision_header) from constants, and inject their value into the
shader code (via asprintf).

Using these struct fields is useless: it's simpler to just put the
constants in the string.

Btw, the sub_renderer already does that. This change had also been
independently proposed by Marvin:
https://mailman.videolan.org/pipermail/vlc-devel/2020-March/132784.html

> 
> Regards,
> --
> Alexandre Janniaux
> Videolabs
> 
> On Wed, Jun 17, 2020 at 09:33:11PM +0200, Romain Vimont wrote:
> > The version and precision header strings are different for OpenGL and
> > OpenGL ES.
> >
> > Insert them directly into the shader string literal, instead of
> > initializing renderer fields and inserting them at runtime.
> > ---
> >  modules/video_output/opengl/renderer.c | 31 ++++++++++++++------------
> >  modules/video_output/opengl/renderer.h |  6 -----
> >  2 files changed, 17 insertions(+), 20 deletions(-)
> >
> > diff --git a/modules/video_output/opengl/renderer.c b/modules/video_output/opengl/renderer.c
> > index 335ca27e4841..6f7d42ee7ab9 100644
> > --- a/modules/video_output/opengl/renderer.c
> > +++ b/modules/video_output/opengl/renderer.c
> > @@ -169,12 +169,23 @@ InitStereoMatrix(GLfloat matrix_out[static 3*3],
> >  #undef ROW
> >  }
> >
> > +/* https://en.wikipedia.org/wiki/OpenGL_Shading_Language#Versions */
> > +#ifdef USE_OPENGL_ES2
> > +# define SHADER_VERSION "#version 100\n"
> > +  /* In OpenGL ES, the fragment language has no default precision qualifier for
> > +   * floating point types. */
> > +# define FRAGMENT_SHADER_PRECISION "precision highp float;\n"
> > +#else
> > +# define SHADER_VERSION "#version 120\n"
> > +# define FRAGMENT_SHADER_PRECISION
> > +#endif
> > +
> >  static char *
> >  BuildVertexShader(const struct vlc_gl_renderer *renderer)
> >  {
> >      /* Basic vertex shader */
> >      static const char *template =
> > -        "#version %u\n"
> > +        SHADER_VERSION
> >          "attribute vec2 PicCoordsIn;\n"
> >          "varying vec2 PicCoords;\n"
> >          "attribute vec3 VertexPosition;\n"
> > @@ -188,8 +199,8 @@ BuildVertexShader(const struct vlc_gl_renderer *renderer)
> >          "               * vec4(VertexPosition, 1.0);\n"
> >          "}";
> >
> > -    char *code;
> > -    if (asprintf(&code, template, renderer->glsl_version) < 0)
> > +    char *code = strdup(template);
> > +    if (!code)
> >          return NULL;
> >
> >      if (renderer->dump_shaders)
> > @@ -204,9 +215,9 @@ BuildFragmentShader(struct vlc_gl_renderer *renderer)
> >      struct vlc_gl_sampler *sampler = renderer->sampler;
> >
> >      static const char *template =
> > -        "#version %u\n"
> > +        SHADER_VERSION
> >          "%s" /* extensions */
> > -        "%s" /* precision header */
> > +        FRAGMENT_SHADER_PRECISION
> >          "%s" /* vlc_texture definition */
> >          "varying vec2 PicCoords;\n"
> >          "void main() {\n"
> > @@ -217,8 +228,7 @@ BuildFragmentShader(struct vlc_gl_renderer *renderer)
> >                             ? sampler->shader.extensions : "";
> >
> >      char *code;
> > -    int ret = asprintf(&code, template, renderer->glsl_version, extensions,
> > -                       renderer->glsl_precision_header, sampler->shader.body);
> > +    int ret = asprintf(&code, template, extensions, sampler->shader.body);
> >      if (ret < 0)
> >          return NULL;
> >
> > @@ -328,13 +338,6 @@ vlc_gl_renderer_New(vlc_gl_t *gl, const struct vlc_gl_api *api,
> >      renderer->api = api;
> >      renderer->vt = vt;
> >      renderer->dump_shaders = var_InheritInteger(gl, "verbose") >= 4;
> > -#if defined(USE_OPENGL_ES2)
> > -    renderer->glsl_version = 100;
> > -    renderer->glsl_precision_header = "precision highp float;\n";
> > -#else
> > -    renderer->glsl_version = 120;
> > -    renderer->glsl_precision_header = "";
> > -#endif
> >
> >      int ret = opengl_link_program(renderer);
> >      if (ret != VLC_SUCCESS)
> > diff --git a/modules/video_output/opengl/renderer.h b/modules/video_output/opengl/renderer.h
> > index 6f4029504fb2..7130cfb26263 100644
> > --- a/modules/video_output/opengl/renderer.h
> > +++ b/modules/video_output/opengl/renderer.h
> > @@ -50,12 +50,6 @@ struct vlc_gl_renderer
> >      /* True to dump shaders */
> >      bool dump_shaders;
> >
> > -    /* GLSL version, set by the caller. 100 for GLSL ES, 120 for desktop GLSL */
> > -    unsigned glsl_version;
> > -    /* Precision header, set by the caller. In OpenGLES, the fragment language
> > -     * has no default precision qualifier for floating point types. */
> > -    const char *glsl_precision_header;
> > -
> >      GLuint program_id;
> >
> >      struct {
> > --
> > 2.27.0
> >
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