Mesa (master): svga: fix FBO / viewport bugs

[Brian Paul]

Module: Mesa
Branch: master
Commit: 1459c18f45f5bd2a2d99145247093f1b540478ad
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=1459c18f45f5bd2a2d99145247093f1b540478ad

Author: Brian Paul <brianp at vmware.com>
Date:   Mon May 14 16:33:58 2012 -0600

svga: fix FBO / viewport bugs

When drawing to a FBO, the viewport wasn't always set correctly.  It
was fine in the usual case of the viewport dims matching the surface
dims but broken otherwise.  In particular, this was happening because
the viewport scale is negative for FBO rendering.

The piglit fbo-viewport test exercises this.

Reviewed-by: José Fonseca <jfonseca at vmware.com>

---

 src/gallium/drivers/svga/svga_state_framebuffer.c |   31 ++++++++++++++++-----
 1 files changed, 24 insertions(+), 7 deletions(-)

diff --git a/src/gallium/drivers/svga/svga_state_framebuffer.c b/src/gallium/drivers/svga/svga_state_framebuffer.c
index 3244023..402d5fe 100644
--- a/src/gallium/drivers/svga/svga_state_framebuffer.c
+++ b/src/gallium/drivers/svga/svga_state_framebuffer.c
@@ -175,6 +175,7 @@ emit_viewport( struct svga_context *svga,
    float range_max = 1.0;
    float flip = -1.0;
    boolean degenerate = FALSE;
+   boolean invertY = FALSE;
    enum pipe_error ret;
 
    float fb_width = svga->curr.framebuffer.width;
@@ -218,11 +219,12 @@ emit_viewport( struct svga_context *svga,
       fx =        viewport->scale[0] * 1.0 + viewport->translate[0];
    }
 
-   if (fh < 0) {
-      prescale.scale[1] *= -1.0;
-      prescale.translate[1] += -fh;
+   if (fh < 0.0) {
+      prescale.translate[1] = fh - 1 + fy * 2;
       fh = -fh;
-      fy = flip * viewport->scale[1] * 1.0 + viewport->translate[1];
+      fy -= fh;
+      prescale.scale[1] = -1.0;
+      invertY = TRUE;
    }
 
    if (fx < 0) {
@@ -233,7 +235,12 @@ emit_viewport( struct svga_context *svga,
    }
 
    if (fy < 0) {
-      prescale.translate[1] += fy;
+      if (invertY) {
+         prescale.translate[1] -= fy;
+      }
+      else {
+         prescale.translate[1] += fy;
+      }
       prescale.scale[1] *= fh / (fh + fy); 
       fh += fy;
       fy = 0;
@@ -249,8 +256,15 @@ emit_viewport( struct svga_context *svga,
 
    if (fy + fh > fb_height) {
       prescale.scale[1] *= fh / (fb_height - fy);
-      prescale.translate[1] -= fy * (fh / (fb_height - fy));
-      prescale.translate[1] += fy;
+      if (invertY) {
+         float in = fb_height - fy;       /* number of vp pixels inside view */
+         float out = fy + fh - fb_height; /* number of vp pixels out of view */
+         prescale.translate[1] += fy * out / in;
+      }
+      else {
+         prescale.translate[1] -= fy * (fh / (fb_height - fy));
+         prescale.translate[1] += fy;
+      }
       fh = fb_height - fy;
    }
 
@@ -307,6 +321,9 @@ emit_viewport( struct svga_context *svga,
          break;
       }
 
+      if (invertY)
+         adjust_y = -adjust_y;
+
       prescale.translate[0] += adjust_x;
       prescale.translate[1] += adjust_y;
       prescale.translate[2] = 0.5; /* D3D clip space */