Merge lp:~kdub/mir/nested-buffer into lp:mir

[Kevin DuBois]

nested: add mgn::NestedBuffer in preparation for "nested-passthrough" (bypass for clients of nested server).

nested: add mgn::NestedBuffer in preparation for "nested-passthrough" (bypass for clients of nested server). Side-steps choosing mg::NativeBuffer for this type for now, until that situation is sorted out in the other line of work.

[Mir CI Bot (mir-ci-bot)]

FAILED: Continuous integration, rev:3623
https://mir-jenkins.ubuntu.com/job/mir-ci/1456/
Executed test runs:
    FAILURE: https://mir-jenkins.ubuntu.com/job/build-mir/1798/console
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-0-fetch/1852
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-1-sourcepkg/release=vivid+overlay/1843
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-1-sourcepkg/release=xenial+overlay/1843
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-1-sourcepkg/release=yakkety/1843
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=amd64,compiler=clang,platform=mesa,release=yakkety/1822
        deb: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=amd64,compiler=clang,platform=mesa,release=yakkety/1822/artifact/output/*zip*/output.zip
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=amd64,compiler=gcc,platform=mesa,release=xenial+overlay/1822
        deb: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=amd64,compiler=gcc,platform=mesa,release=xenial+overlay/1822/artifact/output/*zip*/output.zip
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=amd64,compiler=gcc,platform=mesa,release=yakkety/1822
        deb: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=amd64,compiler=gcc,platform=mesa,release=yakkety/1822/artifact/output/*zip*/output.zip
    FAILURE: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=cross-armhf,compiler=gcc,platform=android,release=vivid+overlay/1822/console
    FAILURE: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=i386,compiler=gcc,platform=android,release=vivid+overlay/1822/console
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=i386,compiler=gcc,platform=mesa,release=xenial+overlay/1822
        deb: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=i386,compiler=gcc,platform=mesa,release=xenial+overlay/1822/artifact/output/*zip*/output.zip

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review: Needs Fixing (continuous-integration)

[Mir CI Bot (mir-ci-bot)]

PASSED: Continuous integration, rev:3624
https://mir-jenkins.ubuntu.com/job/mir-ci/1458/
Executed test runs:
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-mir/1800
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-0-fetch/1854
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-1-sourcepkg/release=vivid+overlay/1845
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-1-sourcepkg/release=xenial+overlay/1845
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-1-sourcepkg/release=yakkety/1845
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=amd64,compiler=clang,platform=mesa,release=yakkety/1824
        deb: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=amd64,compiler=clang,platform=mesa,release=yakkety/1824/artifact/output/*zip*/output.zip
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=amd64,compiler=gcc,platform=mesa,release=xenial+overlay/1824
        deb: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=amd64,compiler=gcc,platform=mesa,release=xenial+overlay/1824/artifact/output/*zip*/output.zip
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=amd64,compiler=gcc,platform=mesa,release=yakkety/1824
        deb: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=amd64,compiler=gcc,platform=mesa,release=yakkety/1824/artifact/output/*zip*/output.zip
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=cross-armhf,compiler=gcc,platform=android,release=vivid+overlay/1824
        deb: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=cross-armhf,compiler=gcc,platform=android,release=vivid+overlay/1824/artifact/output/*zip*/output.zip
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=i386,compiler=gcc,platform=android,release=vivid+overlay/1824
        deb: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=i386,compiler=gcc,platform=android,release=vivid+overlay/1824/artifact/output/*zip*/output.zip
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=i386,compiler=gcc,platform=mesa,release=xenial+overlay/1824
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review: Approve (continuous-integration)

[Chris Halse Rogers (raof)]

So, this is going to segfault all over the place on mesa. get_graphics_region returns NULL for hardware buffers there, as they can't be mmapped.

It's *probably* fine to just unconditionally throw a logic_error from Buffer::read() and Buffer::write()? (Leading to the obvious question: why are those methods there? GBMBuffer unconditionally throws if either are called)

If we need stride elsewhere (for GL import?) we should indeed add that as an mir_buffer_get_stride() accessor.

review: Needs Fixing

[Kevin DuBois (kdub)]

I've thought that the read/write should be regrouped into a "NativeBufferBase" sort of thing (like we do for GL).

Would be easier to add a mir_buffer_get_stride() accessor, so will do that.

[Kevin DuBois (kdub)]

Actually, not sure that mir_buffer_get_stride() to the public api is useful to non-software users of the buffer. Seems like NativeBufferBase for sw is the way to go to resolve.

[Kevin DuBois (kdub)]

Decided to have mir_buffer_get_stride, and now use that instead of mapping the region and figuring out the stride from there.

[Mir CI Bot (mir-ci-bot)]

PASSED: Continuous integration, rev:3628
https://mir-jenkins.ubuntu.com/job/mir-ci/1483/
Executed test runs:
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-mir/1836
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-0-fetch/1890
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-1-sourcepkg/release=vivid+overlay/1881
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-1-sourcepkg/release=xenial+overlay/1881
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-1-sourcepkg/release=yakkety/1881
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=amd64,compiler=clang,platform=mesa,release=yakkety/1860
        deb: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=amd64,compiler=clang,platform=mesa,release=yakkety/1860/artifact/output/*zip*/output.zip
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=amd64,compiler=gcc,platform=mesa,release=xenial+overlay/1860
        deb: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=amd64,compiler=gcc,platform=mesa,release=xenial+overlay/1860/artifact/output/*zip*/output.zip
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=amd64,compiler=gcc,platform=mesa,release=yakkety/1860
        deb: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=amd64,compiler=gcc,platform=mesa,release=yakkety/1860/artifact/output/*zip*/output.zip
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=cross-armhf,compiler=gcc,platform=android,release=vivid+overlay/1860
        deb: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=cross-armhf,compiler=gcc,platform=android,release=vivid+overlay/1860/artifact/output/*zip*/output.zip
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=i386,compiler=gcc,platform=android,release=vivid+overlay/1860
        deb: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=i386,compiler=gcc,platform=android,release=vivid+overlay/1860/artifact/output/*zip*/output.zip
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=i386,compiler=gcc,platform=mesa,release=xenial+overlay/1860
        deb: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=i386,compiler=gcc,platform=mesa,release=xenial+overlay/1860/artifact/output/*zip*/output.zip

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review: Approve (continuous-integration)

[Chris Halse Rogers (raof)]

Needs fixing: Again, mgn::Buffer::write() and mgn::Buffer::read will segfault on Mesa.

Needs info: Hm. Now that I think about it, what's your plan for providing native_buffer_base()? This isn't actually useful at all until we can provide that, and might significantly change the approach?

review: Needs Fixing

[Kevin DuBois (kdub)]

quick sketch:
native_buffer_base() needs to provide gl support so the nested server can use the buffers for GL composition. The different platforms have different EGLImage import methods, still working out how that will work.

native_buffer_handle() needs to provide a mg::NativeBuffer that gives mgn::DisplayBuffer access to the MirBuffer* so it can use MirPresentationChain to forward the MirBuffer* along without composition.

[Kevin DuBois (kdub)]

re segfault, seems the mesa platform would throw trying to make a ShmRegion, but that should also be caught and give a height of 0. So, it wouldn't segfault, but it should give some indication of error. Will correct.

[Kevin DuBois (kdub)]

Also, improved the native_buffer_base() so that it read/write are not member functions of mgn::Buffer, but of a member instance. Should be easy to expand with gl access this way.

[Mir CI Bot (mir-ci-bot)]

FAILED: Continuous integration, rev:3631
https://mir-jenkins.ubuntu.com/job/mir-ci/1497/
Executed test runs:
    FAILURE: https://mir-jenkins.ubuntu.com/job/build-mir/1860/console
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-0-fetch/1914
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-1-sourcepkg/release=vivid+overlay/1905
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-1-sourcepkg/release=xenial+overlay/1905
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-1-sourcepkg/release=yakkety/1905
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=amd64,compiler=clang,platform=mesa,release=yakkety/1884
        deb: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=amd64,compiler=clang,platform=mesa,release=yakkety/1884/artifact/output/*zip*/output.zip
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=amd64,compiler=gcc,platform=mesa,release=xenial+overlay/1884
        deb: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=amd64,compiler=gcc,platform=mesa,release=xenial+overlay/1884/artifact/output/*zip*/output.zip
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=amd64,compiler=gcc,platform=mesa,release=yakkety/1884
        deb: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=amd64,compiler=gcc,platform=mesa,release=yakkety/1884/artifact/output/*zip*/output.zip
    FAILURE: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=cross-armhf,compiler=gcc,platform=android,release=vivid+overlay/1884/console
        deb: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=cross-armhf,compiler=gcc,platform=android,release=vivid+overlay/1884/artifact/output/*zip*/output.zip
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=i386,compiler=gcc,platform=android,release=vivid+overlay/1884
        deb: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=i386,compiler=gcc,platform=android,release=vivid+overlay/1884/artifact/output/*zip*/output.zip
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=i386,compiler=gcc,platform=mesa,release=xenial+overlay/1884
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review: Needs Fixing (continuous-integration)

[Chris Halse Rogers (raof)]

Hm, now that I think of it, this approach in fundamentally unsuited to an EGLStream-based platform, where we can only provide a mg::Buffer abstraction at a performance cost.

To provide an mg::Buffer from a client we need to read out of the EGLStream with an gl_texture_consumer sink; to forward that on to the host server we'd need to blit it to the egl_surface_producer of a separate stream.

I'm not really sure where I'm going with this. Maybe that we shouldn't try to design for it until the necessary EGL extensions are implemented in a driver, presumably nvidia's?

[Kevin DuBois (kdub)]

> Hm, now that I think of it, this approach in fundamentally unsuited to an
> EGLStream-based platform, where we can only provide a mg::Buffer abstraction
> at a performance cost.

Sure, the eglstream platform needs to provide an abstraction for mc::BufferStream. The mesa and android platforms though need mgn::Buffers so that they can re-use the code in mc::Stream.

> To provide an mg::Buffer from a client we need to read out of the EGLStream
> with an gl_texture_consumer sink; to forward that on to the host server we'd
> need to blit it to the egl_surface_producer of a separate stream.
>
> I'm not really sure where I'm going with this. Maybe that we shouldn't try to
> design for it until the necessary EGL extensions are implemented in a driver,
> presumably nvidia's?

Right, I think that we have to carve out some holes in the platform to accommodate the eglstreams. Namely, we need the platform to provide a mc::BufferStream factory. I don't really expect eglstreams to use mgn::Buffer, because the primary thing it gets us is 'nested passthrough' for mesa+android, and eglstreams are designed around 'nested passthrough'

[Kevin DuBois (kdub)]

branch needs restacking, WIP

=== modified file 'include/platform/mir/graphics/buffer.h'
--- include/platform/mir/graphics/buffer.h	2016-08-16 19:34:28 +0000
+++ include/platform/mir/graphics/buffer.h	2016-08-23 11:55:27 +0000
@@ -49,7 +49,6 @@
     virtual std::shared_ptr<NativeBuffer> native_buffer_handle() const = 0;
     virtual BufferID id() const = 0;
     virtual geometry::Size size() const = 0;
-    virtual geometry::Stride stride() const = 0;
     virtual MirPixelFormat pixel_format() const = 0;
 
     virtual NativeBufferBase* native_buffer_base() = 0;

=== modified file 'include/renderers/sw/mir/renderer/sw/pixel_source.h'
--- include/renderers/sw/mir/renderer/sw/pixel_source.h	2016-08-16 19:34:28 +0000
+++ include/renderers/sw/mir/renderer/sw/pixel_source.h	2016-08-23 11:55:27 +0000
@@ -38,6 +38,7 @@
     virtual void write(unsigned char const* pixels, size_t size) = 0;
     //FIXME: correct read, it doesn't give size or format information about the pixels.
     virtual void read(std::function<void(unsigned char const*)> const& do_with_pixels) = 0;
+    virtual geometry::Stride stride() const = 0;
 
 protected:
     PixelSource() = default;

=== modified file 'src/platform/symbols.map'
--- src/platform/symbols.map	2016-08-17 11:55:42 +0000
+++ src/platform/symbols.map	2016-08-23 11:55:27 +0000
@@ -10,7 +10,6 @@
     mir::graphics::Buffer::native_buffer_handle*;
     mir::graphics::Buffer::pixel_format*;
     mir::graphics::Buffer::size*;
-    mir::graphics::Buffer::stride*;
     mir::graphics::Cursor::?Cursor*;
     mir::graphics::Cursor::Cursor*;
     mir::graphics::Cursor::hide*;

=== modified file 'src/platforms/android/server/ipc_operations.cpp'
--- src/platforms/android/server/ipc_operations.cpp	2016-05-03 06:55:25 +0000
+++ src/platforms/android/server/ipc_operations.cpp	2016-08-23 11:55:27 +0000
@@ -62,7 +62,9 @@
             msg.pack_data(buffer_handle->data[offset++]);
         }
 
-        msg.pack_stride(buffer.stride());
+        mir::geometry::Stride byte_stride{
+            native_buffer->anwb()->stride * MIR_BYTES_PER_PIXEL(buffer.pixel_format())};
+        msg.pack_stride(byte_stride);
         msg.pack_size(buffer.size());
     }
 }

=== modified file 'src/platforms/android/utils/test_android_hardware_sanity.cpp'
--- src/platforms/android/utils/test_android_hardware_sanity.cpp	2016-08-16 19:34:28 +0000
+++ src/platforms/android/utils/test_android_hardware_sanity.cpp	2016-08-23 11:55:27 +0000
@@ -136,10 +136,10 @@
     auto pixel_source = dynamic_cast<mrs::PixelSource*>(buffer->native_buffer_base());
     ASSERT_THAT(pixel_source, testing::Ne(nullptr));
 
-    pixel_source->read([&valid_content, &buffer](unsigned char const* data){
+    pixel_source->read([&](unsigned char const* data){
         MirGraphicsRegion region{
             buffer->size().width.as_int(), buffer->size().height.as_int(),
-            buffer->stride().as_int(), buffer->pixel_format(),
+            pixel_source->stride().as_int(), buffer->pixel_format(),
             reinterpret_cast<char*>(const_cast<unsigned char*>(data))};
         valid_content = draw_pattern.check(region);
     });
@@ -196,10 +196,10 @@
     auto valid_content = false;
     auto pixel_source = dynamic_cast<mrs::PixelSource*>(buffer->native_buffer_base());
     ASSERT_THAT(pixel_source, testing::Ne(nullptr));
-    pixel_source->read([&valid_content, &buffer](unsigned char const* data){
+    pixel_source->read([&](unsigned char const* data){
         MirGraphicsRegion region{
             buffer->size().width.as_int(), buffer->size().height.as_int(),
-            buffer->stride().as_int(), buffer->pixel_format(),
+            pixel_source->stride().as_int(), buffer->pixel_format(),
             reinterpret_cast<char*>(const_cast<unsigned char*>(data))};
         mt::DrawPatternSolid green_pattern(0xFF00FF00);
         valid_content = green_pattern.check(region);
@@ -310,7 +310,7 @@
     pixel_source->read([&](unsigned char const* data){
         MirGraphicsRegion region{
             buffer->size().width.as_int(), buffer->size().height.as_int(),
-            buffer->stride().as_int(), buffer->pixel_format(),
+            pixel_source->stride().as_int(), buffer->pixel_format(),
             reinterpret_cast<char*>(const_cast<unsigned char*>(data))};
         valid_content = green_pattern.check(region);
     });

=== modified file 'src/platforms/eglstream-kms/server/platform.cpp'
--- src/platforms/eglstream-kms/server/platform.cpp	2016-08-03 12:27:57 +0000
+++ src/platforms/eglstream-kms/server/platform.cpp	2016-08-23 11:55:27 +0000
@@ -130,7 +130,7 @@
                     packer.pack_fd(mir::Fd(IntOwnedFd{native_handle->fd[i]}));
                 }
 
-                packer.pack_stride(buffer.stride());
+                packer.pack_stride(mir::geometry::Stride{native_handle->stride});
                 packer.pack_flags(native_handle->flags);
                 packer.pack_size(buffer.size());
             }

=== modified file 'src/platforms/mesa/server/gbm_buffer.h'
--- src/platforms/mesa/server/gbm_buffer.h	2016-08-19 13:38:31 +0000
+++ src/platforms/mesa/server/gbm_buffer.h	2016-08-23 11:55:27 +0000
@@ -58,7 +58,7 @@
 
     virtual geometry::Size size() const override;
 
-    virtual geometry::Stride stride() const override;
+    virtual geometry::Stride stride() const;
 
     virtual MirPixelFormat pixel_format() const override;
 

=== modified file 'src/platforms/mesa/server/ipc_operations.cpp'
--- src/platforms/mesa/server/ipc_operations.cpp	2016-08-02 18:30:00 +0000
+++ src/platforms/mesa/server/ipc_operations.cpp	2016-08-23 11:55:27 +0000
@@ -84,7 +84,7 @@
             packer.pack_fd(mir::Fd(IntOwnedFd{native_handle->fd[i]}));
         }
 
-        packer.pack_stride(buffer.stride());
+        packer.pack_stride(mir::geometry::Stride{native_handle->stride});
         packer.pack_flags(native_handle->flags);
         packer.pack_size(buffer.size());
     }

=== modified file 'src/server/compositor/temporary_buffers.cpp'
--- src/server/compositor/temporary_buffers.cpp	2016-08-16 19:34:28 +0000
+++ src/server/compositor/temporary_buffers.cpp	2016-08-23 11:55:27 +0000
@@ -60,11 +60,6 @@
     return buffer->size();
 }
 
-geom::Stride mc::TemporaryBuffer::stride() const
-{
-    return buffer->stride();
-}
-
 MirPixelFormat mc::TemporaryBuffer::pixel_format() const
 {
     return buffer->pixel_format();

=== modified file 'src/server/compositor/temporary_buffers.h'
--- src/server/compositor/temporary_buffers.h	2016-08-16 19:34:28 +0000
+++ src/server/compositor/temporary_buffers.h	2016-08-23 11:55:27 +0000
@@ -36,7 +36,6 @@
 {
 public:
     geometry::Size size() const override;
-    geometry::Stride stride() const override;
     MirPixelFormat pixel_format() const override;
     mg::BufferID id() const override;
     std::shared_ptr<mg::NativeBuffer> native_buffer_handle() const override;

=== modified file 'src/server/graphics/nested/CMakeLists.txt'
--- src/server/graphics/nested/CMakeLists.txt	2016-07-26 03:56:14 +0000
+++ src/server/graphics/nested/CMakeLists.txt	2016-08-23 11:55:27 +0000
@@ -12,4 +12,5 @@
   mir_client_host_connection.cpp
   cursor.cpp
   platform.cpp
+  buffer.cpp
 )

=== added file 'src/server/graphics/nested/buffer.cpp'
--- src/server/graphics/nested/buffer.cpp	1970-01-01 00:00:00 +0000
+++ src/server/graphics/nested/buffer.cpp	2016-08-23 11:55:27 +0000
@@ -0,0 +1,122 @@
+/*
+ * Copyright © 2016 Canonical Ltd.
+ *
+ * This program is free software: you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 3,
+ * as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * Authored by: Kevin DuBois <[e-mail]>
+ */
+
+#include "host_connection.h"
+#include "mir_toolkit/mir_buffer.h"
+#include "mir/renderer/sw/pixel_source.h"
+#include "buffer.h"
+#include <string.h>
+#include <boost/throw_exception.hpp>
+#include <stdexcept>
+
+namespace mg = mir::graphics;
+namespace mgn = mir::graphics::nested;
+namespace mrs = mir::renderer::software;
+namespace geom = mir::geometry;
+
+namespace
+{
+class PixelAccess : public mg::NativeBufferBase,
+                    public mrs::PixelSource
+{
+public:
+    PixelAccess(
+        mgn::Buffer& buffer,
+        std::shared_ptr<MirBuffer> const& native_buffer,
+        std::shared_ptr<mgn::HostConnection> const& connection) :
+        buffer(buffer),
+        native_buffer(native_buffer),
+        connection(connection),
+        stride_(geom::Stride{connection->get_graphics_region(native_buffer.get()).stride})
+    {
+    }
+
+    void write(unsigned char const* pixels, size_t pixel_size) override
+    {
+        auto bpp = MIR_BYTES_PER_PIXEL(buffer.pixel_format());
+        size_t buffer_size_bytes = buffer.size().height.as_int() * buffer.size().width.as_int() * bpp;
+        if (buffer_size_bytes != pixel_size)
+            BOOST_THROW_EXCEPTION(std::logic_error("Size of pixels is not equal to size of buffer"));
+
+        auto region = connection->get_graphics_region(native_buffer.get());
+        if (!region.vaddr)
+            BOOST_THROW_EXCEPTION(std::logic_error("could not map buffer"));
+
+        for (int i = 0; i < region.height; i++)
+        {
+            int line_offset_in_buffer = stride().as_uint32_t() * i;
+            int line_offset_in_source = bpp * region.width * i;
+            memcpy(region.vaddr + line_offset_in_buffer, pixels + line_offset_in_source, region.width * bpp);
+        }
+    }
+
+    void read(std::function<void(unsigned char const*)> const& do_with_pixels) override
+    {
+        auto region = connection->get_graphics_region(native_buffer.get());
+        do_with_pixels(reinterpret_cast<unsigned char*>(region.vaddr));
+    }
+
+    geom::Stride stride() const override
+    {
+        return stride_;
+    }
+
+private:
+    mgn::Buffer& buffer;
+    std::shared_ptr<MirBuffer> const native_buffer;
+    std::shared_ptr<mgn::HostConnection> const connection;
+    geom::Stride const stride_;
+};
+}
+
+std::shared_ptr<mg::NativeBufferBase> mgn::Buffer::create_native_base(mg::BufferUsage const usage)
+{
+    if (usage == mg::BufferUsage::software)
+        return std::make_shared<PixelAccess>(*this, buffer, connection);
+    else
+        return nullptr;
+}
+
+mgn::Buffer::Buffer(
+    std::shared_ptr<HostConnection> const& connection,
+    mg::BufferProperties const& properties) :
+    connection(connection),
+    buffer(connection->create_buffer(properties)),
+    native_base(create_native_base(properties.usage))
+{
+}
+
+std::shared_ptr<mg::NativeBuffer> mgn::Buffer::native_buffer_handle() const
+{
+    return nullptr;
+}
+
+geom::Size mgn::Buffer::size() const
+{
+    return geom::Size{ mir_buffer_get_width(buffer.get()), mir_buffer_get_height(buffer.get()) };
+}
+
+MirPixelFormat mgn::Buffer::pixel_format() const
+{
+    return mir_buffer_get_pixel_format(buffer.get());
+}
+
+mg::NativeBufferBase* mgn::Buffer::native_buffer_base()
+{
+    return native_base.get();
+}

=== added file 'src/server/graphics/nested/buffer.h'
--- src/server/graphics/nested/buffer.h	1970-01-01 00:00:00 +0000
+++ src/server/graphics/nested/buffer.h	2016-08-23 11:55:27 +0000
@@ -0,0 +1,57 @@
+/*
+ * Copyright © 2016 Canonical Ltd.
+ *
+ * This program is free software: you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 3,
+ * as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * Authored by: Kevin DuBois <[e-mail]>
+ */
+
+#ifndef MIR_GRAPHICS_NESTED_BUFFER_H_
+#define MIR_GRAPHICS_NESTED_BUFFER_H_
+
+#include "mir_toolkit/client_types_nbs.h"
+#include "mir/graphics/buffer_basic.h"
+#include "mir/graphics/buffer_properties.h"
+#include "mir/renderer/sw/pixel_source.h"
+#include <memory>
+
+namespace mir
+{
+namespace graphics
+{
+class BufferProperties;
+namespace nested
+{
+class HostConnection;
+class Buffer : public BufferBasic
+{
+public:
+    Buffer(std::shared_ptr<HostConnection> const& connection, BufferProperties const& properties);
+
+    std::shared_ptr<NativeBuffer> native_buffer_handle() const override;
+    geometry::Size size() const override;
+    MirPixelFormat pixel_format() const override;
+    NativeBufferBase* native_buffer_base() override;
+
+private:
+    std::shared_ptr<NativeBufferBase> create_native_base(BufferUsage const usage);
+
+    std::shared_ptr<HostConnection> const connection;
+    std::shared_ptr<MirBuffer> buffer;
+    geometry::Stride const stride_;
+    std::shared_ptr<NativeBufferBase> const native_base;
+};
+}
+}
+}
+#endif /* MIR_GRAPHICS_NESTED_BUFFERH_H_ */

=== modified file 'src/server/graphics/nested/host_connection.h'
--- src/server/graphics/nested/host_connection.h	2016-06-07 16:20:53 +0000
+++ src/server/graphics/nested/host_connection.h	2016-08-23 11:55:27 +0000
@@ -20,8 +20,11 @@
 #define MIR_GRAPHICS_NESTED_HOST_CONNECTION_H_
 
 #include "mir_toolkit/client_types.h"
+#include "mir_toolkit/client_types_nbs.h"
+#include "mir_toolkit/mir_native_buffer.h"
 #include "mir/graphics/nested_context.h"
 #include "mir/geometry/rectangle.h"
+#include "mir/graphics/buffer_properties.h"
 
 #include <memory>
 #include <vector>
@@ -61,6 +64,9 @@
     virtual void set_input_device_change_callback(std::function<void(UniqueInputConfig)> const& cb) = 0;
     virtual void set_input_event_callback(std::function<void(MirEvent const&, mir::geometry::Rectangle const&)> const& cb) = 0;
     virtual void emit_input_event(MirEvent const& event, mir::geometry::Rectangle const& source_frame) = 0;
+    virtual std::shared_ptr<MirBuffer> create_buffer(graphics::BufferProperties const&) = 0;
+    virtual MirNativeBuffer* get_native_handle(MirBuffer*) = 0;
+    virtual MirGraphicsRegion get_graphics_region(MirBuffer*) = 0;
 
 protected:
     HostConnection() = default;

=== modified file 'src/server/graphics/nested/mir_client_host_connection.cpp'
--- src/server/graphics/nested/mir_client_host_connection.cpp	2016-07-07 09:54:02 +0000
+++ src/server/graphics/nested/mir_client_host_connection.cpp	2016-08-23 11:55:27 +0000
@@ -19,6 +19,7 @@
 #include "mir_client_host_connection.h"
 #include "host_surface.h"
 #include "mir_toolkit/mir_client_library.h"
+#include "mir_toolkit/mir_buffer.h"
 #include "mir/raii.h"
 #include "mir/graphics/platform_operation_message.h"
 #include "mir/graphics/cursor_image.h"
@@ -418,3 +419,19 @@
 {
     event_callback(event, source_frame);
 }
+
+std::shared_ptr<MirBuffer> mgn::MirClientHostConnection::create_buffer(
+    mg::BufferProperties const&)
+{
+    BOOST_THROW_EXCEPTION(std::runtime_error("not implemented yet"));
+}
+
+MirNativeBuffer* mgn::MirClientHostConnection::get_native_handle(MirBuffer*)
+{
+    BOOST_THROW_EXCEPTION(std::runtime_error("not implemented yet"));
+}
+
+MirGraphicsRegion mgn::MirClientHostConnection::get_graphics_region(MirBuffer*)
+{
+    BOOST_THROW_EXCEPTION(std::runtime_error("not implemented yet"));
+}

=== modified file 'src/server/graphics/nested/mir_client_host_connection.h'
--- src/server/graphics/nested/mir_client_host_connection.h	2016-06-07 20:53:08 +0000
+++ src/server/graphics/nested/mir_client_host_connection.h	2016-08-23 11:55:27 +0000
@@ -29,6 +29,7 @@
 #include <string>
 #include <vector>
 #include <mutex>
+#include <condition_variable>
 
 struct MirConnection;
 
@@ -79,6 +80,9 @@
     void set_input_device_change_callback(std::function<void(UniqueInputConfig)> const& cb) override;
     void set_input_event_callback(std::function<void(MirEvent const&, mir::geometry::Rectangle const&)> const& cb) override;
     void emit_input_event(MirEvent const& cb, mir::geometry::Rectangle const& source_frame) override;
+    std::shared_ptr<MirBuffer> create_buffer(graphics::BufferProperties const&) override;
+    MirNativeBuffer* get_native_handle(MirBuffer*) override;
+    MirGraphicsRegion get_graphics_region(MirBuffer*) override;
 
 private:
     void update_input_config(UniqueInputConfig input_config);

=== modified file 'tests/include/mir/test/doubles/mock_buffer.h'
--- tests/include/mir/test/doubles/mock_buffer.h	2016-05-03 06:55:25 +0000
+++ tests/include/mir/test/doubles/mock_buffer.h	2016-08-23 11:55:27 +0000
@@ -22,6 +22,7 @@
 #include "mir/graphics/buffer_basic.h"
 #include "mir/geometry/size.h"
 #include "mir/graphics/buffer_id.h"
+#include "mir/renderer/sw/pixel_source.h"
 
 #include <gmock/gmock.h>
 #include <gtest/gtest.h>
@@ -33,7 +34,8 @@
 namespace doubles
 {
 
-struct MockBuffer : public graphics::Buffer, public graphics::NativeBufferBase
+struct MockBuffer : public graphics::Buffer, public graphics::NativeBufferBase,
+    public renderer::software::PixelSource
 {
  public:
     MockBuffer()

=== modified file 'tests/include/mir/test/doubles/stub_host_connection.h'
--- tests/include/mir/test/doubles/stub_host_connection.h	2016-08-10 10:43:39 +0000
+++ tests/include/mir/test/doubles/stub_host_connection.h	2016-08-23 11:55:27 +0000
@@ -97,6 +97,21 @@
     void emit_input_event(MirEvent const&, mir::geometry::Rectangle const&) override
     {
     }
+    
+    std::shared_ptr<MirBuffer> create_buffer(graphics::BufferProperties const&)
+    {
+        return nullptr;
+    }
+
+    MirNativeBuffer* get_native_handle(MirBuffer*)
+    {
+        return nullptr;
+    }
+
+    MirGraphicsRegion get_graphics_region(MirBuffer*)
+    {
+        return MirGraphicsRegion{ 0, 0, 0, mir_pixel_format_invalid, nullptr } ;
+    }
 };
 
 

=== modified file 'tests/mir_test_framework/stubbed_graphics_platform.cpp'
--- tests/mir_test_framework/stubbed_graphics_platform.cpp	2016-08-12 18:41:07 +0000
+++ tests/mir_test_framework/stubbed_graphics_platform.cpp	2016-08-23 11:55:27 +0000
@@ -24,6 +24,7 @@
 #include "mir_test_framework/stub_platform_helpers.h"
 #include "mir_test_framework/stub_platform_native_buffer.h"
 
+#include "mir_toolkit/common.h"
 #include "mir/test/doubles/stub_buffer_allocator.h"
 #include "mir/test/doubles/stub_display.h"
 #include "mir/fd.h"
@@ -136,7 +137,8 @@
             message.pack_data(static_cast<int>(native_handle->properties.usage));
             message.pack_data(native_handle->data);
             message.pack_fd(native_handle->fd);
-            message.pack_stride(buffer.stride());
+            message.pack_stride(
+                geom::Stride{buffer.size().width.as_int() * MIR_BYTES_PER_PIXEL(buffer.pixel_format())});
             message.pack_size(buffer.size());
         }
     }

=== modified file 'tests/unit-tests/compositor/test_temporary_buffers.cpp'
--- tests/unit-tests/compositor/test_temporary_buffers.cpp	2016-05-03 06:55:25 +0000
+++ tests/unit-tests/compositor/test_temporary_buffers.cpp	2016-08-23 11:55:27 +0000
@@ -105,17 +105,6 @@
     EXPECT_EQ(buffer_size, size);
 }
 
-TEST_F(TemporaryBuffersTest, base_test_stride)
-{
-    TemporaryTestBuffer proxy_buffer(mock_buffer);
-    EXPECT_CALL(*mock_buffer, stride())
-        .Times(1);
-
-    geom::Stride stride;
-    stride = proxy_buffer.stride();
-    EXPECT_EQ(buffer_stride, stride);
-}
-
 TEST_F(TemporaryBuffersTest, base_test_pixel_format)
 {
     TemporaryTestBuffer proxy_buffer(mock_buffer);

=== modified file 'tests/unit-tests/platforms/android/server/test_platform.cpp'
--- tests/unit-tests/platforms/android/server/test_platform.cpp	2016-08-23 08:09:17 +0000
+++ tests/unit-tests/platforms/android/server/test_platform.cpp	2016-08-23 11:55:27 +0000
@@ -57,7 +57,6 @@
 
         stub_display_builder = std::make_shared<mtd::StubDisplayBuilder>();
         stub_display_report = mr::null_display_report();
-        stride = geom::Stride(300*4);
 
         num_ints = 43;
         num_fds = 55;
@@ -72,19 +71,25 @@
             native_buffer_handle->data[i] = i;
         }
 
-        native_buffer = std::make_shared<mtd::MockAndroidNativeBuffer>();
+        native_buffer = std::make_shared<NiceMock<mtd::MockAndroidNativeBuffer>>();
         mock_buffer = std::make_shared<NiceMock<mtd::MockBuffer>>();
 
+        anwb.stride = pixel_stride.as_int();
         ON_CALL(*native_buffer, handle())
             .WillByDefault(Return(native_buffer_handle.get()));
+        ON_CALL(*native_buffer, anwb())
+            .WillByDefault(Return(&anwb));
         ON_CALL(*mock_buffer, native_buffer_handle())
             .WillByDefault(Return(native_buffer));
         ON_CALL(*mock_buffer, stride())
-            .WillByDefault(Return(stride));
+            .WillByDefault(Return(byte_stride));
+        ON_CALL(*mock_buffer, pixel_format())
+            .WillByDefault(Return(format));
 
         quirks = std::make_shared<mga::DeviceQuirks>(mga::PropertiesOps{}, context);
     }
 
+    ANativeWindowBuffer anwb;
     std::shared_ptr<mtd::MockAndroidNativeBuffer> native_buffer;
     std::shared_ptr<mtd::StubBufferAllocator> stub_buffer_allocator;
     std::shared_ptr<mtd::StubDisplayBuilder> stub_display_builder;
@@ -95,7 +100,9 @@
     testing::NiceMock<mtd::MockEGL> mock_egl;
     mtd::NullGLContext context;
     std::shared_ptr<mga::DeviceQuirks> quirks;
-    geom::Stride stride;
+    MirPixelFormat const format = mir_pixel_format_abgr_8888; 
+    geom::Stride const pixel_stride { 300 };
+    geom::Stride const byte_stride { 300 * MIR_BYTES_PER_PIXEL(format) };
     unsigned int num_ints, num_fds;
 };
 
@@ -120,12 +127,10 @@
     for (auto i = 0u; i < num_ints; i++)
         EXPECT_CALL(mock_ipc_msg, pack_data(native_buffer_handle->data[offset++]));
 
-    EXPECT_CALL(*mock_buffer, stride())
-        .WillOnce(Return(stride));
 #ifndef __clang__
     // FIXME: Why can't clang compile this on yakkety (with the
     //        gcc6 headers)? (LP: #1609612)
-    EXPECT_CALL(mock_ipc_msg, pack_stride(stride))
+    EXPECT_CALL(mock_ipc_msg, pack_stride(byte_stride))
         .Times(1);
 #endif
 
@@ -165,12 +170,10 @@
             .Times(1);
     }
 
-    EXPECT_CALL(*mock_buffer, stride())
-        .WillOnce(Return(stride));
 #ifndef __clang__
     // FIXME: Why can't clang compile this on yakkety (with the
     //        gcc6 headers)? (LP: #1609612)
-    EXPECT_CALL(mock_ipc_msg, pack_stride(stride))
+    EXPECT_CALL(mock_ipc_msg, pack_stride(byte_stride))
         .Times(1);
 #endif
 
@@ -207,12 +210,10 @@
             .Times(1);
     }
 
-    EXPECT_CALL(*mock_buffer, stride())
-        .WillOnce(Return(stride));
 #ifndef __clang__
     // FIXME: Why can't clang compile this on yakkety (with the
     //        gcc6 headers)? (LP: #1609612)
-    EXPECT_CALL(mock_ipc_msg, pack_stride(stride))
+    EXPECT_CALL(mock_ipc_msg, pack_stride(byte_stride))
         .Times(1);
 #endif
 

=== modified file 'tests/unit-tests/platforms/mesa/kms/test_gbm_buffer.cpp'
--- tests/unit-tests/platforms/mesa/kms/test_gbm_buffer.cpp	2016-08-03 13:09:13 +0000
+++ tests/unit-tests/platforms/mesa/kms/test_gbm_buffer.cpp	2016-08-23 11:55:27 +0000
@@ -139,7 +139,7 @@
 
     auto buffer(allocator->alloc_buffer(buffer_properties));
 
-    ASSERT_LE(minimum, buffer->stride());
+    ASSERT_LE(minimum, geom::Stride{buffer->native_buffer_handle()->stride});
 }
 
 TEST_F(GBMBufferTest, buffer_native_handle_has_correct_size)

=== modified file 'tests/unit-tests/platforms/mesa/kms/test_ipc_operations.cpp'
--- tests/unit-tests/platforms/mesa/kms/test_ipc_operations.cpp	2016-08-23 08:09:17 +0000
+++ tests/unit-tests/platforms/mesa/kms/test_ipc_operations.cpp	2016-08-23 11:55:27 +0000
@@ -55,13 +55,12 @@
         using namespace testing;
         ON_CALL(mock_buffer, native_buffer_handle())
             .WillByDefault(Return(mt::fake_shared(native_handle)));
-        ON_CALL(mock_buffer, stride())
-            .WillByDefault(Return(dummy_stride));
         ON_CALL(mock_buffer, size())
             .WillByDefault(Return(dummy_size));
 
         native_handle.data_items = 4;
         native_handle.fd_items = 2;
+        native_handle.stride = dummy_stride.as_int();
         for(auto i=0; i < mir_buffer_package_max; i++)
         {
             native_handle.fd[i] = i;

=== modified file 'tests/unit-tests/platforms/nested/CMakeLists.txt'
--- tests/unit-tests/platforms/nested/CMakeLists.txt	2016-08-23 08:09:17 +0000
+++ tests/unit-tests/platforms/nested/CMakeLists.txt	2016-08-23 11:55:27 +0000
@@ -3,6 +3,7 @@
   ${CMAKE_CURRENT_SOURCE_DIR}/test_nested_display.cpp
   ${CMAKE_CURRENT_SOURCE_DIR}/mir_display_configuration_builder.cpp
   ${CMAKE_CURRENT_SOURCE_DIR}/test_nested_cursor.cpp
+  ${CMAKE_CURRENT_SOURCE_DIR}/test_buffer.cpp
   ${CMAKE_CURRENT_SOURCE_DIR}/test_nested_display_buffer.cpp
   $<TARGET_OBJECTS:mir-test-doubles-udev>
   ${MIR_PLATFORM_OBJECTS}
@@ -18,6 +19,8 @@
 
   client_platform_common
   server_platform_common
+  mirclient-static
+  mirclientlttng-static
 )
 
 if (MIR_RUN_UNIT_TESTS)

=== added file 'tests/unit-tests/platforms/nested/test_buffer.cpp'
--- tests/unit-tests/platforms/nested/test_buffer.cpp	1970-01-01 00:00:00 +0000
+++ tests/unit-tests/platforms/nested/test_buffer.cpp	2016-08-23 11:55:27 +0000
@@ -0,0 +1,192 @@
+/*
+ * Copyright © 2016 Canonical Ltd.
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 3 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * Authored by: Kevin DuBois <[e-mail]>
+ */
+
+#include "src/server/graphics/nested/buffer.h"
+#include "src/client/buffer.h"
+#include "mir/graphics/buffer_properties.h"
+#include "mir/test/doubles/stub_host_connection.h"
+#include "mir/test/doubles/mock_client_buffer.h"
+#include "mir/test/fake_shared.h"
+#include "mir/renderer/gl/texture_source.h"
+#include "mir_toolkit/client_types_nbs.h"
+
+#include <gtest/gtest.h>
+#include <gmock/gmock.h>
+
+namespace mt = mir::test;
+namespace mtd = mir::test::doubles;
+namespace mg = mir::graphics;
+namespace mgn = mir::graphics::nested;
+namespace geom = mir::geometry;
+namespace mrs = mir::renderer::software;
+
+using namespace testing;
+namespace
+{
+struct MockHostConnection : mtd::StubHostConnection
+{
+    MOCK_METHOD1(create_buffer, std::shared_ptr<MirBuffer>(mg::BufferProperties const&));
+    MOCK_METHOD1(get_native_handle, MirNativeBuffer*(MirBuffer*));
+    MOCK_METHOD1(get_graphics_region, MirGraphicsRegion(MirBuffer*));
+};
+
+struct NestedBuffer : Test
+{
+    NestedBuffer()
+    {
+        ON_CALL(mock_connection, create_buffer(_))
+            .WillByDefault(Return(mirbuffer));
+        ON_CALL(*client_buffer, stride())
+            .WillByDefault(Return(geom::Stride{stride_with_padding}));
+        ON_CALL(*client_buffer, size())
+            .WillByDefault(Return(properties.size));
+        ON_CALL(*client_buffer, pixel_format())
+            .WillByDefault(Return(properties.format));
+        ON_CALL(mock_connection, get_graphics_region(_))
+            .WillByDefault(Return(region));
+    }
+    NiceMock<MockHostConnection> mock_connection;
+    mg::BufferProperties properties{{1, 1}, mir_pixel_format_abgr_8888, mg::BufferUsage::software};
+
+    std::shared_ptr<mtd::MockClientBuffer> client_buffer = std::make_shared<NiceMock<mtd::MockClientBuffer>>();
+    std::shared_ptr<mir::client::MirBuffer> buffer = std::make_shared<mir::client::Buffer>(
+        nullptr, nullptr, 0, client_buffer, nullptr, mir_buffer_usage_software);
+    std::shared_ptr<MirBuffer> mirbuffer { reinterpret_cast<MirBuffer*>(buffer.get()), [](auto){}};
+
+    unsigned int data = 0x11111111;
+    int stride_with_padding = properties.size.width.as_int() * MIR_BYTES_PER_PIXEL(properties.format) + 4;
+    MirGraphicsRegion region {
+        properties.size.width.as_int(), properties.size.height.as_int(),
+        stride_with_padding, properties.format, reinterpret_cast<char*>(&data)
+    };
+};
+}
+
+TEST_F(NestedBuffer, creates_buffer_when_constructed)
+{
+    EXPECT_CALL(mock_connection, create_buffer(properties))
+        .WillOnce(Return(mirbuffer));
+    mgn::Buffer buffer(mt::fake_shared(mock_connection), properties);
+}
+
+TEST_F(NestedBuffer, generates_valid_id)
+{
+    mgn::Buffer buffer(mt::fake_shared(mock_connection), properties);
+    EXPECT_THAT(buffer.id().as_value(), Gt(0));
+}
+
+TEST_F(NestedBuffer, has_correct_properties)
+{
+    mgn::Buffer buffer(mt::fake_shared(mock_connection), properties);
+    EXPECT_THAT(buffer.size(), Eq(properties.size));
+    EXPECT_THAT(buffer.pixel_format(), Eq(properties.format));
+}
+
+TEST_F(NestedBuffer, no_gl_support_for_now)
+{
+    mgn::Buffer buffer(mt::fake_shared(mock_connection), properties);
+    auto native_base = buffer.native_buffer_base();
+    EXPECT_THAT(dynamic_cast<mir::renderer::gl::TextureSource*>(native_base), Eq(nullptr));
+}
+
+TEST_F(NestedBuffer, sw_support_if_requested)
+{
+    mg::BufferProperties sw_properties{{1, 1}, mir_pixel_format_abgr_8888, mg::BufferUsage::software};
+    mg::BufferProperties hw_properties{{1, 1}, mir_pixel_format_abgr_8888, mg::BufferUsage::hardware};
+
+    {
+        mgn::Buffer buffer(mt::fake_shared(mock_connection), sw_properties);
+        EXPECT_THAT(dynamic_cast<mrs::PixelSource*>(buffer.native_buffer_base()), Ne(nullptr));
+    }
+
+    {
+        mgn::Buffer buffer(mt::fake_shared(mock_connection), hw_properties);
+        EXPECT_THAT(dynamic_cast<mrs::PixelSource*>(buffer.native_buffer_base()), Eq(nullptr));
+    }
+}
+
+TEST_F(NestedBuffer, writes_to_region)
+{
+    unsigned int data = 0x11223344;
+    MirGraphicsRegion region {
+        properties.size.width.as_int(), properties.size.height.as_int(),
+        properties.size.width.as_int() * MIR_BYTES_PER_PIXEL(properties.format),
+        properties.format, reinterpret_cast<char*>(&data)
+    };
+
+    unsigned int new_data = 0x11111111;
+    mgn::Buffer buffer(mt::fake_shared(mock_connection), properties);
+
+    EXPECT_CALL(mock_connection, get_graphics_region(_))
+        .WillOnce(Return(region));
+    auto pixel_source = dynamic_cast<mir::renderer::software::PixelSource*>(buffer.native_buffer_base());
+    ASSERT_THAT(pixel_source, Ne(nullptr));
+    pixel_source->write(reinterpret_cast<unsigned char*>(&new_data), sizeof(new_data));
+    EXPECT_THAT(data, Eq(new_data));
+}
+
+TEST_F(NestedBuffer, checks_for_null_vaddr)
+{
+    mgn::Buffer buffer(mt::fake_shared(mock_connection), properties);
+
+    MirGraphicsRegion region { 1, 1, 1, properties.format, nullptr };
+    EXPECT_CALL(mock_connection, get_graphics_region(_))
+        .WillOnce(Return(region));
+    auto pixel_source = dynamic_cast<mir::renderer::software::PixelSource*>(buffer.native_buffer_base());
+    ASSERT_THAT(pixel_source, Ne(nullptr));
+
+    unsigned int new_data = 0x11111111;
+    EXPECT_THROW({
+        pixel_source->write(reinterpret_cast<unsigned char*>(&new_data), sizeof(new_data));
+    }, std::logic_error);
+}
+
+//mg::Buffer::write could be improved so that the user doesn't have to generate potentially large buffers.
+TEST_F(NestedBuffer, throws_if_incorrect_sizing)
+{
+    auto too_large_size = 4 * sizeof(data);
+    mgn::Buffer buffer(mt::fake_shared(mock_connection), properties);
+    auto pixel_source = dynamic_cast<mir::renderer::software::PixelSource*>(buffer.native_buffer_base());
+    ASSERT_THAT(pixel_source, Ne(nullptr));
+    EXPECT_THROW({
+        pixel_source->write(reinterpret_cast<unsigned char*>(&data), too_large_size);
+    }, std::logic_error);
+}
+
+TEST_F(NestedBuffer, reads_from_region)
+{
+    unsigned int read_data = 0x11111111;
+    mgn::Buffer buffer(mt::fake_shared(mock_connection), properties);
+
+    EXPECT_CALL(mock_connection, get_graphics_region(_))
+        .WillOnce(Return(region));
+    auto pixel_source = dynamic_cast<mir::renderer::software::PixelSource*>(buffer.native_buffer_base());
+    ASSERT_THAT(pixel_source, Ne(nullptr));
+    pixel_source->read([&] (auto pix) {
+        read_data = *reinterpret_cast<decltype(data) const*>(pix);
+    } );
+    EXPECT_THAT(read_data, Eq(data));
+}
+
+TEST_F(NestedBuffer, has_correct_stride)
+{
+    mgn::Buffer buffer(mt::fake_shared(mock_connection), properties);
+    auto pixel_source = dynamic_cast<mir::renderer::software::PixelSource*>(buffer.native_buffer_base());
+    ASSERT_THAT(pixel_source, Ne(nullptr));
+    EXPECT_THAT(pixel_source->stride().as_int(), Eq(stride_with_padding));
+}