On Wed, Apr 29, 2015 at 12:44 PM, Jose Fonseca <jfons...@vmware.com> wrote:
> I think there are two different things here: one is the driver internally
> fakes BGRX with BGRA, and obviously it's the pipe driver that needs to fix
> up alpha channel blending to simulate it's one.
>
> The other is the state tracker is faking BGRX with BGRA, and in that case,
> it's the state tracker that needs to do the fix up (as the pipe has no way
> to know if that's intentional or not).
That's a fair point. On the other hand, I don't see why drivers can't
support BGRX even if they can force A=1 for texturing only.
>
> Or are you saying that state trackers should never attempt to fulfill BGRX
> formats with BGRA, and that every driver needs to workaround this
> internally?
Not necessarily.
>
> I don't fill too strongly about this, but it wouldn't sound consistent.
> Nowadays have a pipe cap for every single little thing out there. I don't
> see a reason to treat render target formats differently. Otherwise something
> that can be easily done once in the state tracker now needs to be replicated
> in every driver.
>
>
> But you have a point about _NEW_BUFFERS. It could be avoided. We could
> introduce a new flag _NEW_BUFFERS_EMULATED, set when fbo's with emulated
> formats (e.g., backing BGRX with BGRA), so that drivers that support (or
> workaround) these things internally don't . On the other hand, _NEW_BUFFERS
> probably doesn't change that frequently, blend state probably changes much
> more often.
A new CAP would work. There is an easier way to do it though, see the
attached patch (assuming blend_force_dst_alpha_to_one is set
correctly).
Marek
diff --git a/src/mesa/state_tracker/st_atom_blend.c
b/src/mesa/state_tracker/st_atom_blend.c
index 6bb4077..0d1542f 100644
--- a/src/mesa/state_tracker/st_atom_blend.c
+++ b/src/mesa/state_tracker/st_atom_blend.c
@@ -286,7 +286,7 @@ const struct st_tracked_state st_update_blend = {
"st_update_blend", /* name */
{ /* dirty */
(_NEW_COLOR | _NEW_MULTISAMPLE), /* XXX _NEW_BLEND someday? */ /* mesa
*/
- 0, /* st */
+ ST_NEW_BLEND, /* st */
},
update_blend, /* update */
};
diff --git a/src/mesa/state_tracker/st_context.c
b/src/mesa/state_tracker/st_context.c
index 5fe132a..d7ebe22 100644
--- a/src/mesa/state_tracker/st_context.c
+++ b/src/mesa/state_tracker/st_context.c
@@ -95,6 +95,10 @@ void st_invalidate_state(struct gl_context * ctx, GLuint
new_state)
st->dirty.st |= ST_NEW_VERTEX_PROGRAM;
}
+ if (st->blend_force_dst_alpha_to_one && (new_state & _NEW_BUFFERS)) {
+ st->dirty.st |= ST_NEW_BLEND;
+ }
+
st->dirty.mesa |= new_state;
st->dirty.st |= ST_NEW_MESA;
diff --git a/src/mesa/state_tracker/st_context.h
b/src/mesa/state_tracker/st_context.h
index 8a9504b..a9c861d 100644
--- a/src/mesa/state_tracker/st_context.h
+++ b/src/mesa/state_tracker/st_context.h
@@ -53,7 +53,7 @@ struct u_upload_mgr;
#define ST_NEW_FRAGMENT_PROGRAM (1 << 1)
#define ST_NEW_VERTEX_PROGRAM (1 << 2)
#define ST_NEW_FRAMEBUFFER (1 << 3)
-/* gap, re-use it */
+#define ST_NEW_BLEND (1 << 4)
#define ST_NEW_GEOMETRY_PROGRAM (1 << 5)
#define ST_NEW_VERTEX_ARRAYS (1 << 6)
#define ST_NEW_RASTERIZER (1 << 7)
@@ -89,6 +89,7 @@ struct st_context
struct draw_stage *rastpos_stage; /**< For glRasterPos */
GLboolean clamp_frag_color_in_shader;
GLboolean clamp_vert_color_in_shader;
+ GLboolean blend_force_dst_alpha_to_one;
boolean has_stencil_export; /**< can do shader stencil export? */
boolean has_time_elapsed;
boolean has_shader_model3;
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