[Mesa-dev] [PATCH 2/3] i915: Blit RGBX<->RGBA drawpixels

[Chris Wilson]

The blitter already has code to accommodate filling in the alpha channel
for BGRX destination formats, so expand this to also allow filling the
alpha channgel in RGBX formats.

More importantly for the next patch is moving the test into its own
function for the purpose of exporting the check to the callers.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Jason Ekstrand <jason at jlekstrand.net>
Cc: Alexander Monakov <amonakov at gmail.com>
Cc: Kristian Høgsberg <krh at bitplanet.net>
Cc: Kenneth Graunke <kenneth at whitecape.org>
---
 src/mesa/drivers/dri/i965/intel_blit.c | 38 +++++++++++++++++++++++++++-------
 1 file changed, 30 insertions(+), 8 deletions(-)

diff --git a/src/mesa/drivers/dri/i965/intel_blit.c b/src/mesa/drivers/dri/i965/intel_blit.c
index 360bfe8..02666dc 100644
--- a/src/mesa/drivers/dri/i965/intel_blit.c
+++ b/src/mesa/drivers/dri/i965/intel_blit.c
@@ -138,6 +138,31 @@ static int blt_pitch(struct intel_mipmap_tree *mt)
    return pitch;
 }
 
+static bool blt_compatible_formats(mesa_format src, mesa_format dst)
+{
+   /* The BLT doesn't handle sRGB conversion */
+   assert(src == _mesa_get_srgb_format_linear(src));
+   assert(dst == _mesa_get_srgb_format_linear(dst));
+
+   /* No swizzle or format conversions possible, except... */
+   if (src == dst)
+      return true;
+
+   /*
+    * ... we can either discard the alpha channel when going from A->X,
+    * or we can fill the alpha channel with 0xff when going from X->A
+    */
+   if (src == MESA_FORMAT_B8G8R8A8_UNORM || src == MESA_FORMAT_B8G8R8X8_UNORM)
+      return (dst == MESA_FORMAT_B8G8R8A8_UNORM ||
+              dst == MESA_FORMAT_B8G8R8X8_UNORM);
+
+   if (src == MESA_FORMAT_R8G8B8A8_UNORM || src == MESA_FORMAT_R8G8B8X8_UNORM)
+      return (dst == MESA_FORMAT_R8G8B8A8_UNORM ||
+              dst == MESA_FORMAT_R8G8B8X8_UNORM);
+
+   return false;
+}
+
 /**
  * Implements a rectangular block transfer (blit) of pixels between two
  * miptrees.
@@ -180,11 +205,7 @@ intel_miptree_blit(struct brw_context *brw,
     * the X channel don't matter), and XRGB8888 to ARGB8888 by setting the A
     * channel to 1.0 at the end.
     */
-   if (src_format != dst_format &&
-      ((src_format != MESA_FORMAT_B8G8R8A8_UNORM &&
-        src_format != MESA_FORMAT_B8G8R8X8_UNORM) ||
-       (dst_format != MESA_FORMAT_B8G8R8A8_UNORM &&
-        dst_format != MESA_FORMAT_B8G8R8X8_UNORM))) {
+   if (!blt_compatible_formats(src_format, dst_format)) {
       perf_debug("%s: Can't use hardware blitter from %s to %s, "
                  "falling back.\n", __func__,
                  _mesa_get_format_name(src_format),
@@ -269,12 +290,13 @@ intel_miptree_blit(struct brw_context *brw,
       return false;
    }
 
-   if (src_mt->format == MESA_FORMAT_B8G8R8X8_UNORM &&
-       dst_mt->format == MESA_FORMAT_B8G8R8A8_UNORM) {
+   /* XXX This could be done in a single pass using XY_FULL_MONO_PATTERN_BLT */
+   if (src_format != dst_format &&
+       (dst_format == MESA_FORMAT_B8G8R8X8_UNORM ||
+        dst_format == MESA_FORMAT_R8G8B8X8_UNORM))
       intel_miptree_set_alpha_to_one(brw, dst_mt,
                                      dst_x, dst_y,
                                      width, height);
-   }
 
    return true;
 }
-- 
2.1.4