mesa/main: account for RTT samples when updating framebuffer

For EXT_multisampled_render_to_texture, we store the number of samples
in Attachment->NumSamples instead of Renderbuffer->NumSamples. This
meant that the previous code ignored that the framebuffer was
multisampled. Because of this, pipe_rasterizer_state::multisample is set
incorrectly, leading to visual artifacts on drivers that support MS-RTT
extension, such as panfrost.

Signed-off-by: Italo Nicola <italonicola@collabora.com>
Reviewed-by: Rob Clark <robclark@freedesktop.org>
Reviewed-by: Emma Anholt <emma@anholt.net>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/10747>

diff --git a/src/mesa/main/framebuffer.c b/src/mesa/main/framebuffer.c
index f2d4a60..5d2c004 100644 (file)
--- a/src/mesa/main/framebuffer.c
+++ b/src/mesa/main/framebuffer.c
@@ -423,15 +423,36 @@ _mesa_update_framebuffer_visual(struct gl_context *ctx,
    /* find first RGB renderbuffer */
    for (unsigned i = 0; i < BUFFER_COUNT; i++) {
       if (fb->Attachment[i].Renderbuffer) {
-         const struct gl_renderbuffer *rb = fb->Attachment[i].Renderbuffer;
+         const struct gl_renderbuffer_attachment *att = &fb->Attachment[i];
+         const struct gl_renderbuffer *rb = att->Renderbuffer;
          const GLenum baseFormat = _mesa_get_format_base_format(rb->Format);
          const mesa_format fmt = rb->Format;
 
          /* Grab samples and sampleBuffers from any attachment point (assuming
           * the framebuffer is complete, we'll get the same answer from all
-          * attachments).
+          * attachments). If using EXT_multisampled_render_to_texture, the
+          * number of samples will be on fb->Attachment[i].NumSamples instead
+          * of the usual rb->NumSamples, but it's still guarantted to be the
+          * same for every attachment.
+          *
+          * From EXT_multisampled_render_to_texture:
+          *
+          *    Also, FBOs cannot combine attachments that have associated
+          *    multisample data specified by the mechanisms described in this
+          *    extension with attachments allocated using the core OpenGL ES
+          *    3.1 mechanisms, such as TexStorage2DMultisample. Add to section
+          *    9.4.2 "Whole Framebuffer Completeness":
+          *
+          *    "* If the value of RENDERBUFFER_SAMPLES is non-zero, all or
+          *       none of the attached renderbuffers have been allocated
+          *       using RenderbufferStorage- MultisampleEXT; if the value of
+          *       TEXTURES_SAMPLES is non-zero, all or none of the attached
+          *       textures have been attached using Framebuffer-
+          *       Texture2DMultisampleEXT.
+          *       { GL_FRAMEBUFFER_INCOMPLETE_MULTISAMPLE_EXT }"
           */
-         fb->Visual.samples = rb->NumSamples;
+         fb->Visual.samples =
+            att->NumSamples ? att->NumSamples : rb->NumSamples;
 
          if (_mesa_is_legal_color_format(ctx, baseFormat)) {
             fb->Visual.redBits = _mesa_get_format_bits(fmt, GL_RED_BITS);