mesa/swrast: handle sRGB FBOs correctly (v2)

From reading EXT_texture_sRGB and EXT_framebuffer_sRGB and interactions
with FBO I've found that swrast is converting the sRGB values to linear for
blending when an sRGB texture is bound as an FBO. According to the spec
and further explained in the framebuffer_sRGB spec this behaviour is not
required unless the GL_FRAMEBUFFER_SRGB is enabled and the Visual/config
exposes GL_FRAMEBUFFER_SRGB_CAPABLE_EXT.

This patch fixes swrast to use a separate Fetch call for FBOs bound to
SRGB and avoid the conversions.

v2: export _mesa_get_texture_dimensions as per Brian's comments.

Signed-off-by: Dave Airlie <airlied@redhat.com>

1 files changed, 24 insertions, 12 deletions

diff --git a/src/mesa/main/texrender.c b/src/mesa/main/texrender.c
index 8961b92648..e7cb18a87a 100644
--- a/src/mesa/main/texrender.c
+++ b/src/mesa/main/texrender.c
@@ -20,6 +20,7 @@ struct texture_renderbuffer
    struct gl_renderbuffer Base;   /**< Base class object */
    struct gl_texture_image *TexImage;
    StoreTexelFunc Store;
+   FetchTexelFuncF Fetchf;
    GLint Yoffset;                 /**< Layer for 1D array textures. */
    GLint Zoffset;                 /**< Layer for 2D array textures, or slice
 				   * for 3D textures
@@ -48,7 +49,7 @@ texture_get_row(struct gl_context *ctx, struct gl_renderbuffer *rb, GLuint count
       GLchan *rgbaOut = (GLchan *) values;
       for (i = 0; i < count; i++) {
          GLfloat rgba[4];
-         trb->TexImage->FetchTexelf(trb->TexImage, x + i, y, z, rgba);
+         trb->Fetchf(trb->TexImage, x + i, y, z, rgba);
          UNCLAMPED_FLOAT_TO_RGBA_CHAN(rgbaOut + 4 * i, rgba);
       }
    }
@@ -56,7 +57,7 @@ texture_get_row(struct gl_context *ctx, struct gl_renderbuffer *rb, GLuint count
       GLushort *zValues = (GLushort *) values;
       for (i = 0; i < count; i++) {
          GLfloat flt;
-         trb->TexImage->FetchTexelf(trb->TexImage, x + i, y, z, &flt);
+         trb->Fetchf(trb->TexImage, x + i, y, z, &flt);
          zValues[i] = (GLushort) (flt * 0xffff);
       }
    }
@@ -67,7 +68,7 @@ texture_get_row(struct gl_context *ctx, struct gl_renderbuffer *rb, GLuint count
       */
       for (i = 0; i < count; i++) {
          GLfloat flt;
-         trb->TexImage->FetchTexelf(trb->TexImage, x + i, y, z, &flt);
+         trb->Fetchf(trb->TexImage, x + i, y, z, &flt);
 #if 0
          /* this should work, but doesn't (overflow due to low precision) */
          zValues[i] = (GLuint) (flt * scale);
@@ -81,7 +82,7 @@ texture_get_row(struct gl_context *ctx, struct gl_renderbuffer *rb, GLuint count
       GLuint *zValues = (GLuint *) values;
       for (i = 0; i < count; i++) {
          GLfloat flt;
-         trb->TexImage->FetchTexelf(trb->TexImage, x + i, y, z, &flt);
+         trb->Fetchf(trb->TexImage, x + i, y, z, &flt);
          zValues[i] = ((GLuint) (flt * 0xffffff)) << 8;
       }
    }
@@ -89,7 +90,7 @@ texture_get_row(struct gl_context *ctx, struct gl_renderbuffer *rb, GLuint count
       GLuint *zValues = (GLuint *) values;
       for (i = 0; i < count; i++) {
          GLfloat flt;
-         trb->TexImage->FetchTexelf(trb->TexImage, x + i, y, z, &flt);
+         trb->Fetchf(trb->TexImage, x + i, y, z, &flt);
          zValues[i] = (GLuint) (flt * 0xffffff);
       }
    }
@@ -112,7 +113,7 @@ texture_get_values(struct gl_context *ctx, struct gl_renderbuffer *rb, GLuint co
       GLchan *rgbaOut = (GLchan *) values;
       for (i = 0; i < count; i++) {
          GLfloat rgba[4];
-         trb->TexImage->FetchTexelf(trb->TexImage, x[i], y[i] + trb->Yoffset,
+         trb->Fetchf(trb->TexImage, x[i], y[i] + trb->Yoffset,
 				    z, rgba);
          UNCLAMPED_FLOAT_TO_RGBA_CHAN(rgbaOut + 4 * i, rgba);
       }
@@ -121,7 +122,7 @@ texture_get_values(struct gl_context *ctx, struct gl_renderbuffer *rb, GLuint co
       GLushort *zValues = (GLushort *) values;
       for (i = 0; i < count; i++) {
          GLfloat flt;
-         trb->TexImage->FetchTexelf(trb->TexImage, x[i], y[i] + trb->Yoffset,
+         trb->Fetchf(trb->TexImage, x[i], y[i] + trb->Yoffset,
 				    z, &flt);
          zValues[i] = (GLushort) (flt * 0xffff);
       }
@@ -130,7 +131,7 @@ texture_get_values(struct gl_context *ctx, struct gl_renderbuffer *rb, GLuint co
       GLuint *zValues = (GLuint *) values;
       for (i = 0; i < count; i++) {
          GLfloat flt;
-         trb->TexImage->FetchTexelf(trb->TexImage, x[i], y[i] + trb->Yoffset,
+         trb->Fetchf(trb->TexImage, x[i], y[i] + trb->Yoffset,
 				    z, &flt);
 #if 0
          zValues[i] = (GLuint) (flt * 0xffffffff);
@@ -143,7 +144,7 @@ texture_get_values(struct gl_context *ctx, struct gl_renderbuffer *rb, GLuint co
       GLuint *zValues = (GLuint *) values;
       for (i = 0; i < count; i++) {
          GLfloat flt;
-         trb->TexImage->FetchTexelf(trb->TexImage, x[i], y[i] + trb->Yoffset,
+         trb->Fetchf(trb->TexImage, x[i], y[i] + trb->Yoffset,
 				    z, &flt);
          zValues[i] = ((GLuint) (flt * 0xffffff)) << 8;
       }
@@ -152,7 +153,7 @@ texture_get_values(struct gl_context *ctx, struct gl_renderbuffer *rb, GLuint co
       GLuint *zValues = (GLuint *) values;
       for (i = 0; i < count; i++) {
          GLfloat flt;
-         trb->TexImage->FetchTexelf(trb->TexImage, x[i], y[i] + trb->Yoffset,
+         trb->Fetchf(trb->TexImage, x[i], y[i] + trb->Yoffset,
 				    z, &flt);
          zValues[i] = (GLuint) (flt * 0xffffff);
       }
@@ -517,8 +518,6 @@ wrap_texture(struct gl_context *ctx, struct gl_renderbuffer_attachment *att)
    _mesa_reference_renderbuffer(&att->Renderbuffer, &(trb->Base));
 }
 
-
-
 /**
  * Update the renderbuffer wrapper for rendering to a texture.
  * For example, update the width, height of the RB based on the texture size,
@@ -542,6 +541,8 @@ update_wrapper(struct gl_context *ctx, const struct gl_renderbuffer_attachment *
       trb->Store = store_nop;
    }
 
+   trb->Fetchf = trb->TexImage->FetchTexelf;
+
    if (att->Texture->Target == GL_TEXTURE_1D_ARRAY_EXT) {
       trb->Yoffset = att->Zoffset;
       trb->Zoffset = 0;
@@ -582,6 +583,17 @@ update_wrapper(struct gl_context *ctx, const struct gl_renderbuffer_attachment *
       trb->Base.DataType = GL_UNSIGNED_INT;
       trb->Base._BaseFormat = GL_DEPTH_COMPONENT;
       break;
+   /* SRGB formats pre EXT_framebuffer_sRGB don't do sRGB translations on FBO readback */
+   case MESA_FORMAT_SRGB8:
+      trb->Fetchf = _mesa_get_texel_fetch_func(MESA_FORMAT_RGB888, _mesa_get_texture_dimensions(att->Texture->Target));
+      trb->Base.DataType = CHAN_TYPE;
+      trb->Base._BaseFormat = GL_RGBA;
+      break;
+   case MESA_FORMAT_SRGBA8:
+      trb->Fetchf = _mesa_get_texel_fetch_func(MESA_FORMAT_RGBA8888, _mesa_get_texture_dimensions(att->Texture->Target));
+      trb->Base.DataType = CHAN_TYPE;
+      trb->Base._BaseFormat = GL_RGBA;
+      break;
    default:
       trb->Base.DataType = CHAN_TYPE;
       trb->Base._BaseFormat = GL_RGBA;