[Mesa-dev] [PATCH] mesa/blit: only error when the stencil and depth bits do not match (v3)

[Max Qian]

This fixes some situations where glBlitFrameBuffer would error in Mesa,
but wouldn't error in other drivers (e.g Nvidia)

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=97921
v2 : fix unintentional line removal
v3 : author correction, add commit message, and change the error message
---
 src/mesa/main/blit.c | 84 +++++++++++++++++++++-------------------------------
 1 file changed, 34 insertions(+), 50 deletions(-)

diff --git a/src/mesa/main/blit.c b/src/mesa/main/blit.c
index e739130f98..62cc8c2360 100644
--- a/src/mesa/main/blit.c
+++ b/src/mesa/main/blit.c
@@ -334,41 +334,13 @@ _mesa_blit_framebuffer(struct gl_context *ctx,
          mask &= ~GL_STENCIL_BUFFER_BIT;
       }
       else {
-         int read_z_bits, draw_z_bits;
-
          if (_mesa_is_gles3(ctx) && (drawRb == readRb)) {
             _mesa_error(ctx, GL_INVALID_OPERATION,
                         "%s(source and destination stencil "
                         "buffer cannot be the same)", func);
             return;
          }
-
-         if (_mesa_get_format_bits(readRb->Format, GL_STENCIL_BITS) !=
-             _mesa_get_format_bits(drawRb->Format, GL_STENCIL_BITS)) {
-            /* There is no need to check the stencil datatype here, because
-             * there is only one: GL_UNSIGNED_INT.
-             */
-            _mesa_error(ctx, GL_INVALID_OPERATION,
-                        "%s(stencil attachment format mismatch)", func);
-            return;
-         }
-
-         read_z_bits = _mesa_get_format_bits(readRb->Format, GL_DEPTH_BITS);
-         draw_z_bits = _mesa_get_format_bits(drawRb->Format, GL_DEPTH_BITS);
-
-         /* If both buffers also have depth data, the depth formats must match
-          * as well.  If one doesn't have depth, it's not blitted, so we should
-          * ignore the depth format check.
-          */
-         if (read_z_bits > 0 && draw_z_bits > 0 &&
-             (read_z_bits != draw_z_bits ||
-              _mesa_get_format_datatype(readRb->Format) !=
-              _mesa_get_format_datatype(drawRb->Format))) {
-
-            _mesa_error(ctx, GL_INVALID_OPERATION,
-                        "%s(stencil attachment depth format mismatch)", func);
-            return;
-         }
+         // check formats later
       }
    }
 
@@ -388,36 +360,48 @@ _mesa_blit_framebuffer(struct gl_context *ctx,
          mask &= ~GL_DEPTH_BUFFER_BIT;
       }
       else {
-         int read_s_bit, draw_s_bit;
-
          if (_mesa_is_gles3(ctx) && (drawRb == readRb)) {
             _mesa_error(ctx, GL_INVALID_OPERATION,
                         "%s(source and destination depth "
                         "buffer cannot be the same)", func);
             return;
          }
+         // check formats later
+      }
+   }
 
-         if ((_mesa_get_format_bits(readRb->Format, GL_DEPTH_BITS) !=
-              _mesa_get_format_bits(drawRb->Format, GL_DEPTH_BITS)) ||
-             (_mesa_get_format_datatype(readRb->Format) !=
-              _mesa_get_format_datatype(drawRb->Format))) {
-            _mesa_error(ctx, GL_INVALID_OPERATION,
-                        "%s(depth attachment format mismatch)", func);
-            return;
-         }
+   /* From the glBlitFramebuffer Spec :
+    *
+    * "GL_INVALID_OPERATION is generated if mask contains
+    *  GL_DEPTH_BUFFER_BIT or GL_STENCIL_BUFFER_BIT and the source and
+    *  destination depth and stencil formats do not match."
+    */
+   if (mask & GL_STENCIL_BUFFER_BIT || mask & GL_DEPTH_BUFFER_BIT) {
+      struct gl_renderbuffer *readStencilRb =
+         readFb->Attachment[BUFFER_STENCIL].Renderbuffer;
+      struct gl_renderbuffer *drawStencilRb =
+         drawFb->Attachment[BUFFER_STENCIL].Renderbuffer;
+      struct gl_renderbuffer *readDepthRb =
+         readFb->Attachment[BUFFER_DEPTH].Renderbuffer;
+      struct gl_renderbuffer *drawDepthRb =
+         drawFb->Attachment[BUFFER_DEPTH].Renderbuffer;
 
-         read_s_bit = _mesa_get_format_bits(readRb->Format, GL_STENCIL_BITS);
-         draw_s_bit = _mesa_get_format_bits(drawRb->Format, GL_STENCIL_BITS);
+      int read_z_bits, draw_z_bits, read_s_bit, draw_s_bit;
+      read_z_bits = _mesa_get_format_bits(readDepthRb->Format, GL_DEPTH_BITS);
+      draw_z_bits = _mesa_get_format_bits(drawDepthRb->Format, GL_DEPTH_BITS);
+      boolean depth = read_z_bits > 0 && draw_z_bits > 0 &&
+          (read_z_bits != draw_z_bits ||
+           _mesa_get_format_datatype(readDepthRb->Format) !=
+           _mesa_get_format_datatype(drawDepthRb->Format));
 
-         /* If both buffers also have stencil data, the stencil formats must
-          * match as well.  If one doesn't have stencil, it's not blitted, so
-          * we should ignore the stencil format check.
-          */
-         if (read_s_bit > 0 && draw_s_bit > 0 && read_s_bit != draw_s_bit) {
-            _mesa_error(ctx, GL_INVALID_OPERATION,
-                        "%s(depth attachment stencil bits mismatch)", func);
-            return;
-         }
+      read_s_bit = _mesa_get_format_bits(readStencilRb->Format, GL_STENCIL_BITS);
+      draw_s_bit = _mesa_get_format_bits(drawStencilRb->Format, GL_STENCIL_BITS);
+      boolean stencil = read_s_bit > 0 && draw_s_bit > 0 && read_s_bit != draw_s_bit;
+
+      if (stencil && depth) {
+         _mesa_error(ctx, GL_INVALID_OPERATION,
+                     "%s(depth and stencil attachment bits and format mismatch)", func);
+         return;
       }
    }
 
-- 
2.11.1