Mesa (master): i965: fix polygon stipple when rendering to FBO

[Robert Ellison]

Module: Mesa
Branch: master
Commit: 29309b45b011b4c44721b8f7346272fb22a4d4c2
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=29309b45b011b4c44721b8f7346272fb22a4d4c2

Author: Robert Ellison <papillo at vmware.com>
Date:   Thu Mar 12 11:46:31 2009 -0600

i965: fix polygon stipple when rendering to FBO

The polygon stipple pattern, like the viewport and the
polygon face orientation, must be inverted on the i965
when rendering to a FBO (which itself has an inverted pixel
coordinate system compared to raw Mesa).

In addition, the polygon stipple offset, which orients
the stipple to the window system, disappears when rendering
to an FBO (because the window system offset doesn't apply,
and there's no associated FBO offset).

With these fixes, the conform triangle and polygon stipple
tests pass when rendering to texture.

---

 src/mesa/drivers/dri/i965/brw_misc_state.c |   35 ++++++++++++++++++++++++---
 src/mesa/main/mtypes.h                     |    6 ++--
 2 files changed, 34 insertions(+), 7 deletions(-)

diff --git a/src/mesa/drivers/dri/i965/brw_misc_state.c b/src/mesa/drivers/dri/i965/brw_misc_state.c
index 40cb7a3..5c94a49 100644
--- a/src/mesa/drivers/dri/i965/brw_misc_state.c
+++ b/src/mesa/drivers/dri/i965/brw_misc_state.c
@@ -290,8 +290,21 @@ static void upload_polygon_stipple(struct brw_context *brw)
    bps.header.opcode = CMD_POLY_STIPPLE_PATTERN;
    bps.header.length = sizeof(bps)/4-2;
 
-   for (i = 0; i < 32; i++)
-      bps.stipple[i] = ctx->PolygonStipple[31 - i]; /* invert */
+   /* Polygon stipple is provided in OpenGL order, i.e. bottom
+    * row first.  If we're rendering to a window (i.e. the
+    * default frame buffer object, 0), then we need to invert
+    * it to match our pixel layout.  But if we're rendering
+    * to a FBO (i.e. any named frame buffer object), we *don't*
+    * need to invert - we already match the layout.
+    */
+   if (ctx->DrawBuffer->Name == 0) {
+      for (i = 0; i < 32; i++)
+         bps.stipple[i] = ctx->PolygonStipple[31 - i]; /* invert */
+   }
+   else {
+      for (i = 0; i < 32; i++)
+         bps.stipple[i] = ctx->PolygonStipple[i]; /* don't invert */
+   }
 
    BRW_CACHED_BATCH_STRUCT(brw, &bps);
 }
@@ -319,8 +332,22 @@ static void upload_polygon_stipple_offset(struct brw_context *brw)
    bpso.header.opcode = CMD_POLY_STIPPLE_OFFSET;
    bpso.header.length = sizeof(bpso)/4-2;
 
-   bpso.bits0.x_offset = (32 - (dPriv->x & 31)) & 31;
-   bpso.bits0.y_offset = (32 - ((dPriv->y + dPriv->h) & 31)) & 31;
+   /* If we're drawing to a system window (ctx->DrawBuffer->Name == 0),
+    * we have to invert the Y axis in order to match the OpenGL
+    * pixel coordinate system, and our offset must be matched
+    * to the window position.  If we're drawing to a FBO
+    * (ctx->DrawBuffer->Name != 0), then our native pixel coordinate
+    * system works just fine, and there's no window system to
+    * worry about.
+    */
+   if (brw->intel.ctx.DrawBuffer->Name == 0) {
+      bpso.bits0.x_offset = (32 - (dPriv->x & 31)) & 31;
+      bpso.bits0.y_offset = (32 - ((dPriv->y + dPriv->h) & 31)) & 31;
+   }
+   else {
+      bpso.bits0.y_offset = 0;
+      bpso.bits0.x_offset = 0;
+   }
 
    BRW_CACHED_BATCH_STRUCT(brw, &bpso);
 }
diff --git a/src/mesa/main/mtypes.h b/src/mesa/main/mtypes.h
index 169f1af..3913828 100644
--- a/src/mesa/main/mtypes.h
+++ b/src/mesa/main/mtypes.h
@@ -2241,9 +2241,9 @@ struct gl_framebuffer
    /**
     * If zero, this is a window system framebuffer.  If non-zero, this
     * is a FBO framebuffer; note that for some devices (i.e. those with
-    * a natural pixel coordinate system for FBOs that differs from the 
-    * OpenGL/Mesa coordinate system), this means that both the viewport
-    * and polygon face orientation will have to be inverted.
+    * a natural pixel coordinate system for FBOs that differs from the
+    * OpenGL/Mesa coordinate system), this means that the viewport,
+    * polygon face orientation, and polygon stipple will have to be inverted.
     */
    GLuint Name;