[Mesa-dev] [PATCH] meta: Always do GenerateMipmaps in linear colorspace.

[Kenneth Graunke]

When generating mipmaps for sRGB textures, force both decode and encode,
so the filtering is done in linear colorspace, regardless of settings.

Fixes a WebGL conformance test in Chrome:
https://www.khronos.org/registry/webgl/sdk/tests/conformance2/textures/misc/tex-srgb-mipmap.html?webglVersion=2

Signed-off-by: Kenneth Graunke <kenneth at whitecape.org>
---
 src/mesa/drivers/common/meta_generate_mipmap.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/src/mesa/drivers/common/meta_generate_mipmap.c b/src/mesa/drivers/common/meta_generate_mipmap.c
index 9cebbf7..bbe9d6d 100644
--- a/src/mesa/drivers/common/meta_generate_mipmap.c
+++ b/src/mesa/drivers/common/meta_generate_mipmap.c
@@ -221,9 +221,17 @@ _mesa_meta_GenerateMipmap(struct gl_context *ctx, GLenum target,
                                 GL_LINEAR);
       _mesa_set_sampler_wrap(ctx, mipmap->samp_obj, GL_CLAMP_TO_EDGE,
                              GL_CLAMP_TO_EDGE, GL_CLAMP_TO_EDGE);
+   }
+
+   if (ctx->Extensions.EXT_texture_sRGB_decode) {
+      const struct gl_texture_image *baseImage =
+         _mesa_select_tex_image(texObj, target, texObj->BaseLevel);
+      const bool srgb =
+         _mesa_get_format_color_encoding(baseImage->TexFormat) == GL_SRGB;
 
-      /* We don't want to encode or decode sRGB values; treat them as linear. */
-      _mesa_set_sampler_srgb_decode(ctx, mipmap->samp_obj, GL_SKIP_DECODE_EXT);
+      _mesa_set_sampler_srgb_decode(ctx, mipmap->samp_obj,
+                                    srgb ? GL_DECODE_EXT : GL_SKIP_DECODE_EXT);
+      _mesa_set_framebuffer_srgb(ctx, srgb);
    }
 
    _mesa_bind_sampler(ctx, ctx->Texture.CurrentUnit, mipmap->samp_obj);
-- 
2.9.2