Mesa (master): i965: Fix gl_FragCoord inversion when drawing to an FBO.

[Eric Anholt]

Module: Mesa
Branch: master
Commit: 3b337f5cd94384d2d5918fb630aa8089e49b1d8d
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=3b337f5cd94384d2d5918fb630aa8089e49b1d8d

Author: Eric Anholt <eric at anholt.net>
Date:   Sat Nov 13 14:00:58 2010 -0800

i965: Fix gl_FragCoord inversion when drawing to an FBO.

This showed up as cairo-gl gradients being inverted on everyone but
Intel, where I'd apparently tweaked the transformation to work around
the bug.  Fixes piglit fbo-fragcoord.

---

 src/mesa/drivers/dri/i965/brw_fs.cpp |    5 +++--
 src/mesa/drivers/dri/i965/brw_wm.c   |    1 +
 src/mesa/drivers/dri/i965/brw_wm.h   |    3 ++-
 3 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/src/mesa/drivers/dri/i965/brw_fs.cpp b/src/mesa/drivers/dri/i965/brw_fs.cpp
index b24655b..4648298 100644
--- a/src/mesa/drivers/dri/i965/brw_fs.cpp
+++ b/src/mesa/drivers/dri/i965/brw_fs.cpp
@@ -400,6 +400,7 @@ fs_visitor::emit_fragcoord_interpolation(ir_variable *ir)
    fs_reg wpos = *reg;
    fs_reg neg_y = this->pixel_y;
    neg_y.negate = true;
+   bool flip = !ir->origin_upper_left ^ c->key.render_to_fbo;
 
    /* gl_FragCoord.x */
    if (ir->pixel_center_integer) {
@@ -410,13 +411,13 @@ fs_visitor::emit_fragcoord_interpolation(ir_variable *ir)
    wpos.reg_offset++;
 
    /* gl_FragCoord.y */
-   if (ir->origin_upper_left && ir->pixel_center_integer) {
+   if (!flip && ir->pixel_center_integer) {
       emit(fs_inst(BRW_OPCODE_MOV, wpos, this->pixel_y));
    } else {
       fs_reg pixel_y = this->pixel_y;
       float offset = (ir->pixel_center_integer ? 0.0 : 0.5);
 
-      if (!ir->origin_upper_left) {
+      if (flip) {
 	 pixel_y.negate = true;
 	 offset += c->key.drawable_height - 1.0;
       }
diff --git a/src/mesa/drivers/dri/i965/brw_wm.c b/src/mesa/drivers/dri/i965/brw_wm.c
index a6d2a23..ccdc18e 100644
--- a/src/mesa/drivers/dri/i965/brw_wm.c
+++ b/src/mesa/drivers/dri/i965/brw_wm.c
@@ -423,6 +423,7 @@ static void brw_wm_populate_key( struct brw_context *brw,
     */
    if (fp->program.Base.InputsRead & FRAG_BIT_WPOS) {
       key->drawable_height = ctx->DrawBuffer->Height;
+      key->render_to_fbo = ctx->DrawBuffer->Name != 0;
    }
 
    key->nr_color_regions = brw->state.nr_color_regions;
diff --git a/src/mesa/drivers/dri/i965/brw_wm.h b/src/mesa/drivers/dri/i965/brw_wm.h
index 99bd15c..2ca6857 100644
--- a/src/mesa/drivers/dri/i965/brw_wm.h
+++ b/src/mesa/drivers/dri/i965/brw_wm.h
@@ -70,7 +70,8 @@ struct brw_wm_prog_key {
    GLuint linear_color:1;  /**< linear interpolation vs perspective interp */
    GLuint runtime_check_aads_emit:1;
    GLuint nr_color_regions:5;
-   
+   GLuint render_to_fbo:1;
+
    GLbitfield proj_attrib_mask; /**< one bit per fragment program attribute */
    GLuint shadowtex_mask:16;
    GLuint yuvtex_mask:16;