st/nine: Add D3DFMT_DF16 support

This depth buffer format, like D3DFMT_INTZ, can be used to read
the depth buffer values when bound to a shader.

Some apps may use this format to get better performance when
they don't need the precision of INTZ (24 bits for depth, 8 for
stencil, whereas DF16 is just 16 bits for depth)

We don't add support for DF24 yet, because it implies support
for FETCH4, which we don't support for now.

Reviewed-by: Tiziano Bacocco <[email protected]>
Signed-off-by: Axel Davy <[email protected]>

1 files changed, 10 insertions, 2 deletions

diff --git a/src/gallium/state_trackers/nine/basetexture9.c b/src/gallium/state_trackers/nine/basetexture9.c
index 8d183e65d46..f2ca35b0205 100644
--- a/src/gallium/state_trackers/nine/basetexture9.c
+++ b/src/gallium/state_trackers/nine/basetexture9.c
@@ -69,8 +69,16 @@ NineBaseTexture9_ctor( struct NineBaseTexture9 *This,
         D3DTEXF_LINEAR : D3DTEXF_NONE;
     This->lod = 0;
     This->lod_resident = -1;
-    This->shadow = This->format != D3DFMT_INTZ && util_format_has_depth(
-        util_format_description(This->base.info.format));
+    /* When a depth buffer is sampled, it is for shadow mapping, except for
+     * D3DFMT_INTZ, D3DFMT_DF16 and D3DFMT_DF24.
+     * In addition D3DFMT_INTZ can be used for both texturing and depth buffering
+     * if z write is disabled. This particular feature may not work for us in
+     * practice because OGL doesn't have that. However apparently it is known
+     * some cards have performance issues with this feature, so real apps
+     * shouldn't use it. */
+    This->shadow = (This->format != D3DFMT_INTZ && This->format != D3DFMT_DF16 &&
+                    This->format != D3DFMT_DF24) &&
+                   util_format_has_depth(util_format_description(This->base.info.format));
 
     list_inithead(&This->list);