cogl/texture: Add API to check whether _get_data() will work

Currently, GL_TEXTURE_EXTERNAL_OES textures doesn't support getting pixel data.
Make it possible for texture users to know this.

https://gitlab.gnome.org/GNOME/mutter/merge_requests/362

cogl/cogl/cogl-atlas-texture.c

@@ -1043,5 +1043,6 @@ cogl_atlas_texture_vtable =
     _cogl_atlas_texture_get_gl_format,
     _cogl_atlas_texture_get_type,
     NULL, /* is_foreign */
-    NULL /* set_auto_mipmap */
+    NULL, /* set_auto_mipmap */
+    NULL  /* is_get_data_supported */
   };

cogl/cogl/cogl-driver.h

@@ -210,6 +210,9 @@ struct _CoglDriverVtable
                            int rowstride,
                            uint8_t *data);
 
+  CoglBool
+  (* texture_2d_is_get_data_supported) (CoglTexture2D *tex_2d);
+
   /* Prepares for drawing by flushing the journal, framebuffer state,
    * pipeline state and attribute state.
    */

cogl/cogl/cogl-sub-texture.c

@@ -454,6 +454,14 @@ _cogl_sub_texture_get_type (CoglTexture *tex)
   return _cogl_texture_get_type (sub_tex->full_texture);
 }
 
+static CoglBool
+_cogl_sub_texture_is_get_data_supported (CoglTexture *tex)
+{
+  CoglSubTexture *sub_tex = COGL_SUB_TEXTURE (tex);
+
+  return cogl_texture_is_get_data_supported (sub_tex->full_texture);
+}
+
 static const CoglTextureVtable
 cogl_sub_texture_vtable =
   {
@@ -476,5 +484,6 @@ cogl_sub_texture_vtable =
     _cogl_sub_texture_get_gl_format,
     _cogl_sub_texture_get_type,
     NULL, /* is_foreign */
-    NULL /* set_auto_mipmap */
+    NULL, /* set_auto_mipmap */
+    _cogl_sub_texture_is_get_data_supported
   };

cogl/cogl/cogl-texture-2d-sliced.c

@@ -1542,5 +1542,6 @@ cogl_texture_2d_sliced_vtable =
     _cogl_texture_2d_sliced_get_gl_format,
     _cogl_texture_2d_sliced_get_type,
     _cogl_texture_2d_sliced_is_foreign,
-    NULL /* set_auto_mipmap */
+    NULL, /* set_auto_mipmap */
+    NULL  /* is_get_data_supported */
   };

cogl/cogl/cogl-texture-2d.c

@@ -94,6 +94,15 @@ _cogl_texture_2d_set_auto_mipmap (CoglTexture *tex,
   tex_2d->auto_mipmap = value;
 }
 
+static CoglBool
+_cogl_texture_2d_is_get_data_supported (CoglTexture *tex)
+{
+  CoglTexture2D *tex_2d = COGL_TEXTURE_2D (tex);
+  CoglContext *ctx = tex->context;
+
+  return ctx->driver_vtable->texture_2d_is_get_data_supported (tex_2d);
+}
+
 CoglTexture2D *
 _cogl_texture_2d_create_base (CoglContext *ctx,
                               int width,
@@ -693,5 +702,6 @@ cogl_texture_2d_vtable =
     _cogl_texture_2d_get_gl_format,
     _cogl_texture_2d_get_type,
     _cogl_texture_2d_is_foreign,
-    _cogl_texture_2d_set_auto_mipmap
+    _cogl_texture_2d_set_auto_mipmap,
+    _cogl_texture_2d_is_get_data_supported
   };

cogl/cogl/cogl-texture-3d.c

@@ -755,5 +755,6 @@ cogl_texture_3d_vtable =
     _cogl_texture_3d_get_gl_format,
     _cogl_texture_3d_get_type,
     NULL, /* is_foreign */
-    _cogl_texture_3d_set_auto_mipmap
+    _cogl_texture_3d_set_auto_mipmap,
+    NULL  /* is_get_data_supported */
   };

cogl/cogl/cogl-texture-private.h

@@ -149,6 +149,8 @@ struct _CoglTextureVtable
   /* Only needs to be implemented if is_primitive == TRUE */
   void (* set_auto_mipmap) (CoglTexture *texture,
                             CoglBool value);
+
+  CoglBool (* is_get_data_supported) (CoglTexture *texture);
 };
 
 typedef enum _CoglTextureSoureType {

cogl/cogl/cogl-texture-rectangle.c

@@ -773,5 +773,6 @@ cogl_texture_rectangle_vtable =
     _cogl_texture_rectangle_get_gl_format,
     _cogl_texture_rectangle_get_type,
     _cogl_texture_rectangle_is_foreign,
-    _cogl_texture_rectangle_set_auto_mipmap
+    _cogl_texture_rectangle_set_auto_mipmap,
+    NULL  /* is_get_data_supported */
   };

cogl/cogl/cogl-texture.c

@@ -205,6 +205,15 @@ _cogl_texture_is_foreign (CoglTexture *texture)
     return FALSE;
 }
 
+CoglBool
+cogl_texture_is_get_data_supported (CoglTexture *texture)
+{
+  if (texture->vtable->is_get_data_supported)
+    return texture->vtable->is_get_data_supported (texture);
+  else
+    return TRUE;
+}
+
 unsigned int
 cogl_texture_get_width (CoglTexture *texture)
 {

cogl/cogl/cogl-texture.h

@@ -511,6 +511,12 @@ CoglBool
 cogl_texture_allocate (CoglTexture *texture,
                        CoglError **error);
 
+/**
+ * cogl_texture_is_get_data_supported: (skip)
+ */
+CoglBool
+cogl_texture_is_get_data_supported (CoglTexture *texture);
+
 COGL_END_DECLS
 
 #endif /* __COGL_TEXTURE_H__ */

cogl/cogl/driver/gl/cogl-texture-2d-gl-private.h

@@ -116,4 +116,7 @@ _cogl_texture_2d_gl_get_data (CoglTexture2D *tex_2d,
                               int rowstride,
                               uint8_t *data);
 
+CoglBool
+_cogl_texture_2d_gl_is_get_data_supported (CoglTexture2D *tex_2d);
+
 #endif /* _COGL_TEXTURE_2D_GL_PRIVATE_H_ */

cogl/cogl/driver/gl/cogl-texture-2d-gl.c

@@ -869,3 +869,12 @@ _cogl_texture_2d_gl_get_data (CoglTexture2D *tex_2d,
                                          gl_type,
                                          data);
 }
+
+CoglBool
+_cogl_texture_2d_gl_is_get_data_supported (CoglTexture2D *tex_2d)
+{
+  if (tex_2d->gl_target == GL_TEXTURE_EXTERNAL_OES)
+    return FALSE;
+  else
+    return TRUE;
+}

cogl/cogl/driver/gl/gl/cogl-driver-gl.c

@@ -714,6 +714,7 @@ _cogl_driver_gl =
     _cogl_texture_2d_gl_generate_mipmap,
     _cogl_texture_2d_gl_copy_from_bitmap,
     _cogl_texture_2d_gl_get_data,
+    _cogl_texture_2d_gl_is_get_data_supported,
     _cogl_gl_flush_attributes_state,
     _cogl_clip_stack_gl_flush,
     _cogl_buffer_gl_create,

cogl/cogl/driver/gl/gles/cogl-driver-gles.c

@@ -493,6 +493,7 @@ _cogl_driver_gles =
     _cogl_texture_2d_gl_generate_mipmap,
     _cogl_texture_2d_gl_copy_from_bitmap,
     NULL, /* texture_2d_get_data */
+    NULL, /* texture_2d_is_get_data_supported */
     _cogl_gl_flush_attributes_state,
     _cogl_clip_stack_gl_flush,
     _cogl_buffer_gl_create,

cogl/cogl/driver/nop/cogl-driver-nop.c

@@ -82,6 +82,7 @@ _cogl_driver_nop =
     _cogl_texture_2d_nop_generate_mipmap,
     _cogl_texture_2d_nop_copy_from_bitmap,
     NULL, /* texture_2d_get_data */
+    NULL, /* texture_2d_is_get_data_supported */
     _cogl_nop_flush_attributes_state,
     _cogl_clip_stack_nop_flush,
   };

cogl/cogl/winsys/cogl-texture-pixmap-x11.c

@@ -1180,5 +1180,6 @@ cogl_texture_pixmap_x11_vtable =
     _cogl_texture_pixmap_x11_get_gl_format,
     _cogl_texture_pixmap_x11_get_type,
     NULL, /* is_foreign */
-    NULL /* set_auto_mipmap */
+    NULL, /* set_auto_mipmap */
+    NULL  /* is_get_data_supported */
   };