meta: Add a meta implementation of GL_ARB_clear_texture

Adds an implementation of the ClearTexSubImage driver entry point that tries
to set up an FBO to render to the texture and then calls glClearBuffer with a
scissor to perform the actual clear. If an FBO can't be created for the
texture then it will fall back to using _mesa_store_ClearTexSubImage.

When used in combination with _mesa_store_ClearTexSubImage this should provide
an implementation that works for all DRI-based drivers. However as this has
only been tested with the i965 driver it is currently only enabled there.

v2: Only enable the extension for the i965 driver instead of all DRI drivers.
    Remove an unnecessary goto. Don't require GL_ARB_framebuffer_object. Add
    some more comments.

v3: Use glClearBuffer* to avoid having to modify glClearColor and friends.
    Handle sRGB textures. Explicitly disable dithering.

Reviewed-by: Topi Pohjolainen <topi.pohjolainen at intel.com>

4 files changed, 198 insertions, 0 deletions

diff --git a/src/mesa/drivers/common/driverfuncs.c b/src/mesa/drivers/common/driverfuncs.c
index 6ece5d80e1a..4f0f7a686ab 100644
--- a/src/mesa/drivers/common/driverfuncs.c
+++ b/src/mesa/drivers/common/driverfuncs.c
@@ -95,6 +95,7 @@ _mesa_init_driver_functions(struct dd_function_table *driver)
    driver->TexImage = _mesa_store_teximage;
    driver->TexSubImage = _mesa_store_texsubimage;
    driver->GetTexImage = _mesa_meta_GetTexImage;
+   driver->ClearTexSubImage = _mesa_meta_ClearTexSubImage;
    driver->CopyTexSubImage = _mesa_meta_CopyTexSubImage;
    driver->GenerateMipmap = _mesa_meta_GenerateMipmap;
    driver->TestProxyTexImage = _mesa_test_proxy_teximage;
diff --git a/src/mesa/drivers/common/meta.c b/src/mesa/drivers/common/meta.c
index 604bc218b72..b12898f265a 100644
--- a/src/mesa/drivers/common/meta.c
+++ b/src/mesa/drivers/common/meta.c
@@ -40,6 +40,7 @@
 #include "main/blit.h"
 #include "main/bufferobj.h"
 #include "main/buffers.h"
+#include "main/clear.h"
 #include "main/colortab.h"
 #include "main/condrender.h"
 #include "main/depth.h"
@@ -47,6 +48,7 @@
 #include "main/fbobject.h"
 #include "main/feedback.h"
 #include "main/formats.h"
+#include "main/format_unpack.h"
 #include "main/glformats.h"
 #include "main/image.h"
 #include "main/macros.h"
@@ -71,6 +73,7 @@
 #include "main/teximage.h"
 #include "main/texparam.h"
 #include "main/texstate.h"
+#include "main/texstore.h"
 #include "main/transformfeedback.h"
 #include "main/uniforms.h"
 #include "main/varray.h"
@@ -3347,3 +3350,189 @@ _mesa_meta_DrawTex(struct gl_context *ctx, GLfloat x, GLfloat y, GLfloat z,
 
    _mesa_meta_end(ctx);
 }
+
+static bool
+cleartexsubimage_color(struct gl_context *ctx,
+                       struct gl_texture_image *texImage,
+                       const GLvoid *clearValue,
+                       GLint zoffset)
+{
+   mesa_format format;
+   union gl_color_union colorValue;
+   GLenum datatype;
+   GLenum status;
+
+   _mesa_meta_bind_fbo_image(GL_COLOR_ATTACHMENT0, texImage, zoffset);
+
+   status = _mesa_CheckFramebufferStatus(GL_DRAW_FRAMEBUFFER);
+   if (status != GL_FRAMEBUFFER_COMPLETE)
+      return false;
+
+   /* We don't want to apply an sRGB conversion so override the format */
+   format = _mesa_get_srgb_format_linear(texImage->TexFormat);
+   datatype = _mesa_get_format_datatype(format);
+
+   switch (datatype) {
+   case GL_UNSIGNED_INT:
+   case GL_INT:
+      if (clearValue)
+         _mesa_unpack_uint_rgba_row(format, 1, clearValue,
+                                    (GLuint (*)[4]) colorValue.ui);
+      else
+         memset(&colorValue, 0, sizeof colorValue);
+      if (datatype == GL_INT)
+         _mesa_ClearBufferiv(GL_COLOR, 0, colorValue.i);
+      else
+         _mesa_ClearBufferuiv(GL_COLOR, 0, colorValue.ui);
+      break;
+   default:
+      if (clearValue)
+         _mesa_unpack_rgba_row(format, 1, clearValue,
+                               (GLfloat (*)[4]) colorValue.f);
+      else
+         memset(&colorValue, 0, sizeof colorValue);
+      _mesa_ClearBufferfv(GL_COLOR, 0, colorValue.f);
+      break;
+   }
+
+   return true;
+}
+
+static bool
+cleartexsubimage_depth_stencil(struct gl_context *ctx,
+                               struct gl_texture_image *texImage,
+                               const GLvoid *clearValue,
+                               GLint zoffset)
+{
+   GLint stencilValue;
+   GLfloat depthValue;
+   GLenum status;
+
+   _mesa_meta_bind_fbo_image(GL_DEPTH_ATTACHMENT, texImage, zoffset);
+
+   if (texImage->_BaseFormat == GL_DEPTH_STENCIL)
+      _mesa_meta_bind_fbo_image(GL_STENCIL_ATTACHMENT, texImage, zoffset);
+
+   status = _mesa_CheckFramebufferStatus(GL_DRAW_FRAMEBUFFER);
+   if (status != GL_FRAMEBUFFER_COMPLETE)
+      return false;
+
+   if (clearValue) {
+      GLuint depthStencilValue[2];
+
+      /* Convert the clearValue from whatever format it's in to a floating
+       * point value for the depth and an integer value for the stencil index
+       */
+      _mesa_unpack_float_32_uint_24_8_depth_stencil_row(texImage->TexFormat,
+                                                        1, /* n */
+                                                        clearValue,
+                                                        depthStencilValue);
+      /* We need a memcpy here instead of a cast because we need to
+       * reinterpret the bytes as a float rather than converting it
+       */
+      memcpy(&depthValue, depthStencilValue, sizeof depthValue);
+      stencilValue = depthStencilValue[1] & 0xff;
+   } else {
+      depthValue = 0.0f;
+      stencilValue = 0;
+   }
+
+   if (texImage->_BaseFormat == GL_DEPTH_STENCIL)
+      _mesa_ClearBufferfi(GL_DEPTH_STENCIL, 0, depthValue, stencilValue);
+   else
+      _mesa_ClearBufferfv(GL_DEPTH, 0, &depthValue);
+
+   return true;
+}
+
+static bool
+cleartexsubimage_for_zoffset(struct gl_context *ctx,
+                             struct gl_texture_image *texImage,
+                             GLint zoffset,
+                             const GLvoid *clearValue)
+{
+   GLuint fbo;
+   bool success;
+
+   _mesa_GenFramebuffers(1, &fbo);
+   _mesa_BindFramebuffer(GL_DRAW_FRAMEBUFFER, fbo);
+
+   switch(texImage->_BaseFormat) {
+   case GL_DEPTH_STENCIL:
+   case GL_DEPTH_COMPONENT:
+      success = cleartexsubimage_depth_stencil(ctx, texImage,
+                                               clearValue, zoffset);
+      break;
+   default:
+      success = cleartexsubimage_color(ctx, texImage, clearValue, zoffset);
+      break;
+   }
+
+   _mesa_DeleteFramebuffers(1, &fbo);
+
+   return success;
+}
+
+static bool
+cleartexsubimage_using_fbo(struct gl_context *ctx,
+                           struct gl_texture_image *texImage,
+                           GLint xoffset, GLint yoffset, GLint zoffset,
+                           GLsizei width, GLsizei height, GLsizei depth,
+                           const GLvoid *clearValue)
+{
+   bool success = true;
+   GLint z;
+
+   _mesa_meta_begin(ctx,
+                    MESA_META_SCISSOR |
+                    MESA_META_COLOR_MASK |
+                    MESA_META_DITHER |
+                    MESA_META_FRAMEBUFFER_SRGB);
+
+   _mesa_set_enable(ctx, GL_DITHER, GL_FALSE);
+
+   _mesa_set_enable(ctx, GL_SCISSOR_TEST, GL_TRUE);
+   _mesa_Scissor(xoffset, yoffset, width, height);
+
+   for (z = zoffset; z < zoffset + depth; z++) {
+      if (!cleartexsubimage_for_zoffset(ctx, texImage, z, clearValue)) {
+         success = false;
+         break;
+      }
+   }
+
+   _mesa_meta_end(ctx);
+
+   return success;
+}
+
+extern void
+_mesa_meta_ClearTexSubImage(struct gl_context *ctx,
+                            struct gl_texture_image *texImage,
+                            GLint xoffset, GLint yoffset, GLint zoffset,
+                            GLsizei width, GLsizei height, GLsizei depth,
+                            const GLvoid *clearValue)
+{
+   bool res;
+
+   _mesa_unlock_texture(ctx, texImage->TexObject);
+
+   res = cleartexsubimage_using_fbo(ctx, texImage,
+                                    xoffset, yoffset, zoffset,
+                                    width, height, depth,
+                                    clearValue);
+
+   _mesa_lock_texture(ctx, texImage->TexObject);
+
+   if (res)
+      return;
+
+   _mesa_warning(ctx,
+                 "Falling back to mapping the texture in "
+                 "glClearTexSubImage\n");
+
+   _mesa_store_cleartexsubimage(ctx, texImage,
+                                xoffset, yoffset, zoffset,
+                                width, height, depth,
+                                clearValue);
+}
diff --git a/src/mesa/drivers/common/meta.h b/src/mesa/drivers/common/meta.h
index b8d992ce96f..b269dceedde 100644
--- a/src/mesa/drivers/common/meta.h
+++ b/src/mesa/drivers/common/meta.h
@@ -477,6 +477,13 @@ _mesa_meta_CopyTexSubImage(struct gl_context *ctx, GLuint dims,
                            GLsizei width, GLsizei height);
 
 extern void
+_mesa_meta_ClearTexSubImage(struct gl_context *ctx,
+                            struct gl_texture_image *texImage,
+                            GLint xoffset, GLint yoffset, GLint zoffset,
+                            GLsizei width, GLsizei height, GLsizei depth,
+                            const GLvoid *clearValue);
+
+extern void
 _mesa_meta_GetTexImage(struct gl_context *ctx,
                        GLenum format, GLenum type, GLvoid *pixels,
                        struct gl_texture_image *texImage);
diff --git a/src/mesa/drivers/dri/i965/intel_extensions.c b/src/mesa/drivers/dri/i965/intel_extensions.c
index fe4006882d2..4ee8636fb6b 100644
--- a/src/mesa/drivers/dri/i965/intel_extensions.c
+++ b/src/mesa/drivers/dri/i965/intel_extensions.c
@@ -163,6 +163,7 @@ intelInitExtensions(struct gl_context *ctx)
    assert(brw->gen >= 4);
 
    ctx->Extensions.ARB_buffer_storage = true;
+   ctx->Extensions.ARB_clear_texture = true;
    ctx->Extensions.ARB_depth_buffer_float = true;
    ctx->Extensions.ARB_depth_clamp = true;
    ctx->Extensions.ARB_depth_texture = true;