gallium: clear interface changes

clears were a bit limited in gallium:
- no scissoring (OGL only) nor explicit rectangle list (d3d9)
- no color/stencil masks (OGL only)
- no separate depth/stencil clears (d3d9/d3d10/OGL)
- cannot really clear single color buffer (only with resource_fill_region)

Additionally, d3d can clear surfaces not currently bound to the framebuffer.

It is, however, not easy to find some common ground what a clear should be able
to do, due to both API requirements and also hw differences (a case which might
be able to use a special clear path on one hw might need a "normal" quad render
on another).

Hence several clear methods are provided, and a driver should implement all of
them.
- clear: slightly modified to also be able to clear only depth or stencil in a
  combined depth/stencil surface. This is however optional based on driver
  capability though ideally it wouldn't be optional. AFAIK this is in fact
  something used by applications quite a bit.
  Otherwise, for now still doesn't allow clearing with scissors/mask (or single
  color buffers)
- clearRT: clears a single (potentially unbound) color surface. This was formerly
  roughly known as resource_fill_region. mesa st will not currently use this,
  though potentially would be useful for GL ClearBuffer.
- clearDS: similar to above except for depth stencil surfaces.

Note that clearDS/clearRT currently handle can handle partial clear. This might
change however.

src/gallium/docs/d3d11ddi.txt

@@ -79,7 +79,7 @@ set_clip_state
 set_polygon_stipple
 	+ Gallium supports polygon stipple
 
-resource_fill_region
+clearRT/clearDS
 	+ Gallium supports subrectangle fills of surfaces, D3D10 only supports full clears of views
 
 * DirectX 10/11 DDI functions and Gallium equivalents

src/gallium/docs/source/context.rst

@@ -102,14 +102,29 @@ the LOD range the texture is going to be constrained to.
 Clearing
 ^^^^^^^^
 
+Clear is one of the most difficult concepts to nail down to a single
+interface (due to both different requirements from APIs and also driver/hw
+specific differences).
+
 ``clear`` initializes some or all of the surfaces currently bound to
 the framebuffer to particular RGBA, depth, or stencil values.
+Currently, this does not take into account color or stencil write masks (as
+used by GL), and always clears the whole surfaces (no scissoring as used by
+GL clear or explicit rectangles like d3d9 uses). It can, however, also clear
+only depth or stencil in a combined depth/stencil surface, if the driver
+supports PIPE_CAP_DEPTHSTENCIL_CLEAR_SEPARATE.
+If a surface includes several layers/slices (XXX: not yet...) then all layers
+will be cleared.
 
-Clear is one of the most difficult concepts to nail down to a single
-interface and it seems likely that we will want to add additional
-clear paths, for instance clearing surfaces not bound to the
-framebuffer, or read-modify-write clears such as depth-only or
-stencil-only clears of packed depth-stencil buffers.  
+``clearRT`` clears a single color rendertarget with the specified color
+value. While it is only possible to clear one surface at a time (which can
+include several layers), this surface need not be bound to the framebuffer.
+
+``clearDS``clears a single depth, stencil or depth/stencil surface with
+the specified depth and stencil values (for combined depth/stencil buffers,
+is is also possible to only clear one or the other part). While it is only
+possible to clear one surface at a time (which can include several layers),
+this surface need not be bound to the framebuffer.
 
 
 Drawing
@@ -266,8 +281,6 @@ These methods operate directly on ``pipe_resource`` objects, and stand
 apart from any 3D state in the context.  Blitting functionality may be
 moved to a separate abstraction at some point in the future.
 
-``resource_fill_region`` performs a fill operation on a section of a resource.
-
 ``resource_copy_region`` blits a region of a subresource of a resource to a
 region of another subresource of a resource, provided that both resources have the
 same format. The source and destination may be the same resource, but overlapping

src/gallium/include/pipe/p_context.h

@@ -256,17 +256,6 @@ struct pipe_context {
                                 unsigned srcx, unsigned srcy, unsigned srcz,
                                 unsigned width, unsigned height);
 
-   /**
-    * Fill a region of a resource with a constant value.
-    * Resources with nr_samples > 1 are not allowed.
-    */
-   void (*resource_fill_region)(struct pipe_context *pipe,
-                                struct pipe_resource *dst,
-                                struct pipe_subresource subdst,
-                                unsigned dstx, unsigned dsty, unsigned dstz,
-                                unsigned width, unsigned height,
-                                unsigned value);
-
    /**
     * Resolve a multisampled resource into a non-multisampled one.
     * Source and destination must have the same size and same format.
@@ -290,9 +279,33 @@ struct pipe_context {
     */
    void (*clear)(struct pipe_context *pipe,
                  unsigned buffers,
-		 const float *rgba,
+                 const float *rgba,
                  double depth,
-		 unsigned stencil);
+                 unsigned stencil);
+
+   /**
+    * Clear a color rendertarget surface.
+    * \param rgba  pointer to an array of one float for each of r, g, b, a.
+    */
+   void (*clearRT)(struct pipe_context *pipe,
+                   struct pipe_surface *dst,
+                   const float *rgba,
+                   unsigned dstx, unsigned dsty,
+                   unsigned width, unsigned height);
+
+   /**
+    * Clear a depth-stencil surface.
+    * \param clear_flags  bitfield of PIPE_CLEAR_DEPTH/STENCIL values.
+    * \param depth  depth clear value in [0,1].
+    * \param stencil  stencil clear value
+    */
+   void (*clearDS)(struct pipe_context *pipe,
+                   struct pipe_surface *dst,
+                   unsigned clear_flags,
+                   double depth,
+                   unsigned stencil,
+                   unsigned dstx, unsigned dsty,
+                   unsigned width, unsigned height);
 
    /** Flush rendering
     * \param flags  bitmask of PIPE_FLUSH_x tokens)

src/gallium/include/pipe/p_defines.h

@@ -189,9 +189,10 @@ enum pipe_texture_target {
  */
 /** All color buffers currently bound */
 #define PIPE_CLEAR_COLOR        (1 << 0)
+#define PIPE_CLEAR_DEPTH        (1 << 1)
+#define PIPE_CLEAR_STENCIL      (1 << 2)
 /** Depth/stencil combined */
-#define PIPE_CLEAR_DEPTHSTENCIL (1 << 1)
-
+#define PIPE_CLEAR_DEPTHSTENCIL (PIPE_CLEAR_DEPTH | PIPE_CLEAR_STENCIL)
 
 /**
  * Transfer object usage flags
@@ -453,6 +454,7 @@ enum pipe_cap {
    PIPE_CAP_INDEP_BLEND_ENABLE,
    /** different blend funcs per rendertarget */
    PIPE_CAP_INDEP_BLEND_FUNC,
+   PIPE_CAP_DEPTHSTENCIL_CLEAR_SEPARATE,
    PIPE_CAP_TGSI_FS_COORD_ORIGIN_UPPER_LEFT,
    PIPE_CAP_TGSI_FS_COORD_ORIGIN_LOWER_LEFT,
    PIPE_CAP_TGSI_FS_COORD_PIXEL_CENTER_HALF_INTEGER,