gallium: more elaborate tracking of front color buffer state

This fixes the case where the app calls SwapBuffers then calls glReadPixels
to read the front color buffer.  We now keep track of when the front buffer
is a _logically_ copy of the back buffer (after SwapBuffers) and read from
the back color buffer instead of the front.

diff --git a/src/mesa/state_tracker/st_atom_framebuffer.c b/src/mesa/state_tracker/st_atom_framebuffer.c
index 02573af8f0a7fff1ecbc1aa8ba05c23f3b549289..8a95096ec9af78ffbf0c52e9ef9b009038793732 100644 (file)
--- a/src/mesa/state_tracker/st_atom_framebuffer.c
+++ b/src/mesa/state_tracker/st_atom_framebuffer.c
@@ -81,6 +81,14 @@ update_framebuffer_state( struct st_context *st )
    }
 
    cso_set_framebuffer(st->cso_context, framebuffer);
+
+   if (fb->_ColorDrawBufferMask[0] & BUFFER_BIT_FRONT_LEFT) {
+      if (st->frontbuffer_status == FRONT_STATUS_COPY_OF_BACK) {
+         /* XXX copy back buf to front? */
+      }
+      /* we're assuming we'll really draw to the front buffer */
+      st->frontbuffer_status = FRONT_STATUS_DIRTY;
+   }
 }
 
 

diff --git a/src/mesa/state_tracker/st_cb_drawpixels.c b/src/mesa/state_tracker/st_cb_drawpixels.c
index b1affc4a91563b3dfdd85c48b4cc46f4835abf40..5f8c90cbba43f6b844267379de3ab696d7a16aaa 100644 (file)
--- a/src/mesa/state_tracker/st_cb_drawpixels.c
+++ b/src/mesa/state_tracker/st_cb_drawpixels.c
@@ -961,7 +961,7 @@ st_CopyPixels(GLcontext *ctx, GLint srcx, GLint srcy,
    }
 
    if (type == GL_COLOR) {
-      rbRead = st_renderbuffer(ctx->ReadBuffer->_ColorReadBuffer);
+      rbRead = st_get_color_read_renderbuffer(ctx);
       color = NULL;
       stfp = combined_drawpix_fragment_program(ctx);
       stvp = st_make_passthrough_vertex_shader(ctx->st, GL_FALSE);

diff --git a/src/mesa/state_tracker/st_cb_flush.c b/src/mesa/state_tracker/st_cb_flush.c
index 1bcd1b4cd98e7840e54cfa70135445e88eb74a96..1b3402cee245413d9b2e36a70adc664ccfed6c3b 100644 (file)
--- a/src/mesa/state_tracker/st_cb_flush.c
+++ b/src/mesa/state_tracker/st_cb_flush.c
@@ -44,30 +44,10 @@
 #include "pipe/p_winsys.h"
 
 
-static GLboolean
+static INLINE GLboolean
 is_front_buffer_dirty(struct st_context *st)
 {
-   GLframebuffer *fb = st->ctx->DrawBuffer;
-
-   if (!fb)
-      return GL_FALSE;
-
-   /* XXX: temporary hack.  This flag should only be set if we do any
-    * rendering to the front buffer.
-    *
-    * Further more, the scissor rectangle could be tracked to
-    * construct a dirty region of the front buffer, to avoid
-    * situations where it must be copied repeatedly.
-    *
-    * In the extreme case, some kind of timer could be set up to allow
-    * coalescing of multiple flushes to the frontbuffer, which can be
-    * quite a performance drain if there are a sufficient number of
-    * them.
-    */
-   st->flags.frontbuffer_dirty
-      = (fb->_ColorDrawBufferMask[0] & BUFFER_BIT_FRONT_LEFT);
-
-   return st->flags.frontbuffer_dirty;
+   return st->frontbuffer_status == FRONT_STATUS_DIRTY;
 }
 
 
@@ -86,7 +66,8 @@ display_front_buffer(struct st_context *st)
     */
    st->pipe->winsys->flush_frontbuffer( st->pipe->winsys, front_surf,
                                         st->pipe->priv );
-   st->flags.frontbuffer_dirty = 0;
+
+   st->frontbuffer_status = FRONT_STATUS_UNDEFINED;
 }
 
 

diff --git a/src/mesa/state_tracker/st_cb_readpixels.c b/src/mesa/state_tracker/st_cb_readpixels.c
index 2bcc8c99fb70105d8fa498a94cc42ecc0630aaaf..29a06ffaa90160cc838e680ffbe15a25ac0f3128 100644 (file)
--- a/src/mesa/state_tracker/st_cb_readpixels.c
+++ b/src/mesa/state_tracker/st_cb_readpixels.c
@@ -128,6 +128,34 @@ st_read_stencil_pixels(GLcontext *ctx, GLint x, GLint y,
 }
 
 
+/**
+ * Return renderbuffer to use for reading color pixels for glRead/CopyPixel
+ * commands.
+ * Special care is needed for the front buffer.
+ */
+struct st_renderbuffer *
+st_get_color_read_renderbuffer(GLcontext *ctx)
+{
+   struct gl_framebuffer *fb = ctx->ReadBuffer;
+   struct st_renderbuffer *strb =
+      st_renderbuffer(fb->_ColorReadBuffer);
+   struct st_renderbuffer *front = 
+      st_renderbuffer(fb->Attachment[BUFFER_FRONT_LEFT].Renderbuffer);
+
+   if (strb == front
+       && ctx->st->frontbuffer_status == FRONT_STATUS_COPY_OF_BACK) {
+      /* reading from front color buffer, which is a logical copy of the
+       * back color buffer.
+       */
+      struct st_renderbuffer *back = 
+         st_renderbuffer(fb->Attachment[BUFFER_BACK_LEFT].Renderbuffer);
+      strb = back;
+   }
+
+   return strb;
+}
+
+
 /**
  * Do glReadPixels by getting rows from the framebuffer surface with
  * get_tile().  Convert to requested format/type with Mesa image routines.
@@ -173,12 +201,13 @@ st_readpixels(GLcontext *ctx, GLint x, GLint y, GLsizei width, GLsizei height,
       strb = st_renderbuffer(ctx->ReadBuffer->_DepthBuffer);
    }
    else {
-      strb = st_renderbuffer(ctx->ReadBuffer->_ColorReadBuffer);
+      /* Read color buffer */
+      strb = st_get_color_read_renderbuffer(ctx);
    }
+
    if (!strb)
       return;
 
-
    if (format == GL_RGBA && type == GL_FLOAT) {
       /* write tile(row) directly into user's buffer */
       df = (GLfloat *) _mesa_image_address2d(&clippedPacking, dest, width,

diff --git a/src/mesa/state_tracker/st_cb_readpixels.h b/src/mesa/state_tracker/st_cb_readpixels.h
index 79acdad88e1ce5746ce28ce2c47cb4cf98b97719..9e151be51fb6857e963542e3c43f8550faf60051 100644 (file)
--- a/src/mesa/state_tracker/st_cb_readpixels.h
+++ b/src/mesa/state_tracker/st_cb_readpixels.h
@@ -29,6 +29,9 @@
 #ifndef ST_CB_READPIXELS_H
 #define ST_CB_READPIXELS_H
 
+extern struct st_renderbuffer *
+st_get_color_read_renderbuffer(GLcontext *ctx);
+
 extern void
 st_read_stencil_pixels(GLcontext *ctx, GLint x, GLint y,
                        GLsizei width, GLsizei height, GLenum type,

diff --git a/src/mesa/state_tracker/st_context.h b/src/mesa/state_tracker/st_context.h
index 212687cf4ab56f7825062049bcad1a11ca39f9f7..d89e54c43c14e599862be6f1270a64c980d827db 100644 (file)
--- a/src/mesa/state_tracker/st_context.h
+++ b/src/mesa/state_tracker/st_context.h
@@ -45,6 +45,11 @@ struct blit_state;
 struct bitmap_cache;
 
 
+#define FRONT_STATUS_UNDEFINED    0
+#define FRONT_STATUS_DIRTY        1
+#define FRONT_STATUS_COPY_OF_BACK 2
+
+
 #define ST_NEW_MESA                    0x1 /* Mesa state has changed */
 #define ST_NEW_FRAGMENT_PROGRAM        0x2
 #define ST_NEW_VERTEX_PROGRAM          0x4
@@ -104,9 +109,7 @@ struct st_context
       struct gl_fragment_program *fragment_program;
    } cb;
 
-   struct {
-      GLuint frontbuffer_dirty:1;
-   } flags;
+   GLuint frontbuffer_status;  /**< one of FRONT_STATUS_ */
 
    char vendor[100];
    char renderer[100];

diff --git a/src/mesa/state_tracker/st_framebuffer.c b/src/mesa/state_tracker/st_framebuffer.c
index ea09d9234cdf1a8b00b74484d85b0e424e8a51bb..47466c97d81ce4a3e0ffa345cc6f5efcb23fec3b 100644 (file)
--- a/src/mesa/state_tracker/st_framebuffer.c
+++ b/src/mesa/state_tracker/st_framebuffer.c
@@ -188,6 +188,7 @@ st_notify_swapbuffers(struct st_framebuffer *stfb)
       st_flush( ctx->st, 
                PIPE_FLUSH_RENDER_CACHE | PIPE_FLUSH_SWAPBUFFERS,
                 NULL );
+      ctx->st->frontbuffer_status = FRONT_STATUS_COPY_OF_BACK;
    }
 }