st/mesa: change viewport Z scale/bias for glBitmap/glDrawPixels

This fixes incorrect Z position of glBitmap, glDraw/CopyPixels for the
svga driver.  Now we use 0.5, 0.5 as is typical for ordinary 3D rendering.

(cherry picked from commit bcd561c66777e58dbb29a573c4d2279772bac6c5)

1 files changed, 5 insertions, 2 deletions

diff --git a/src/mesa/state_tracker/st_cb_bitmap.c b/src/mesa/state_tracker/st_cb_bitmap.c
index 5968426a1d..0332d4dbdf 100644
--- a/src/mesa/state_tracker/st_cb_bitmap.c
+++ b/src/mesa/state_tracker/st_cb_bitmap.c
@@ -481,15 +481,18 @@ draw_bitmap_quad(GLcontext *ctx, GLint x, GLint y, GLfloat z,
       struct pipe_viewport_state vp;
       vp.scale[0] =  0.5f * width;
       vp.scale[1] = height * (invert ? -0.5f : 0.5f);
-      vp.scale[2] = 1.0f;
+      vp.scale[2] = 0.5f;
       vp.scale[3] = 1.0f;
       vp.translate[0] = 0.5f * width;
       vp.translate[1] = 0.5f * height;
-      vp.translate[2] = 0.0f;
+      vp.translate[2] = 0.5f;
       vp.translate[3] = 0.0f;
       cso_set_viewport(cso, &vp);
    }
 
+   /* convert Z from [0,1] to [-1,-1] to match viewport Z scale/bias */
+   z = z * 2.0 - 1.0;
+
    /* draw textured quad */
    offset = setup_bitmap_vertex_data(st, x, y, width, height, z, color);