LibGUI+WindowServer: Use anonymous files for window backing stores :^)

This patch replaces the use of shbufs for GUI::Window backing stores
with the new anonymous files mechanism.

Backing bitmaps are now built on memory allocated with anon_create().
They are passed across the IPC socket as IPC::File. This means that
WindowServer now pledges "recvfd" and graphical clients need to pledge
"sendfd" to work.

To support the cached bitmap swapping optimization on the WindowServer
side, each backing store is assigned an incrementing serial number on
the client side. (This allows us to re-use an already mapped file.)

1 files changed, 25 insertions, 7 deletions

diff --git a/Userland/Libraries/LibGUI/Window.cpp b/Userland/Libraries/LibGUI/Window.cpp
index 5fd2625dc4..e89bfffce6 100644
--- a/Userland/Libraries/LibGUI/Window.cpp
+++ b/Userland/Libraries/LibGUI/Window.cpp
@@ -39,6 +39,7 @@
 #include <LibGUI/Window.h>
 #include <LibGUI/WindowServerConnection.h>
 #include <LibGfx/Bitmap.h>
+#include <fcntl.h>
 #include <serenity.h>
 #include <stdio.h>
 #include <stdlib.h>
@@ -48,10 +49,13 @@
 
 namespace GUI {
 
+static i32 s_next_backing_store_serial;
+
 class WindowBackingStore {
 public:
     WindowBackingStore(NonnullRefPtr<Gfx::Bitmap> bitmap)
         : m_bitmap(bitmap)
+        , m_serial(++s_next_backing_store_serial)
     {
     }
 
@@ -60,8 +64,11 @@ public:
 
     Gfx::IntSize size() const { return m_bitmap->size(); }
 
+    i32 serial() const { return m_serial; }
+
 private:
     NonnullRefPtr<Gfx::Bitmap> m_bitmap;
+    const i32 m_serial;
 };
 
 static NeverDestroyed<HashTable<Window*>> all_windows;
@@ -351,7 +358,7 @@ void Window::handle_multi_paint_event(MultiPaintEvent& event)
         m_back_store = create_backing_store(event.window_size());
         ASSERT(m_back_store);
     } else if (m_double_buffering_enabled) {
-        bool still_has_pixels = m_back_store->bitmap().shared_buffer()->set_nonvolatile();
+        bool still_has_pixels = m_back_store->bitmap().set_nonvolatile();
         if (!still_has_pixels) {
             m_back_store = create_backing_store(event.window_size());
             ASSERT(m_back_store);
@@ -678,7 +685,7 @@ void Window::set_hovered_widget(Widget* widget)
 void Window::set_current_backing_store(WindowBackingStore& backing_store, bool flush_immediately)
 {
     auto& bitmap = backing_store.bitmap();
-    WindowServerConnection::the().send_sync<Messages::WindowServer::SetWindowBackingStore>(m_window_id, 32, bitmap.pitch(), bitmap.shbuf_id(), bitmap.has_alpha_channel(), bitmap.size(), flush_immediately);
+    WindowServerConnection::the().send_sync<Messages::WindowServer::SetWindowBackingStore>(m_window_id, 32, bitmap.pitch(), bitmap.anon_fd(), backing_store.serial(), bitmap.has_alpha_channel(), bitmap.size(), flush_immediately);
 }
 
 void Window::flip(const Vector<Gfx::IntRect, 32>& dirty_rects)
@@ -691,7 +698,7 @@ void Window::flip(const Vector<Gfx::IntRect, 32>& dirty_rects)
         m_back_store = create_backing_store(m_front_store->size());
         ASSERT(m_back_store);
         memcpy(m_back_store->bitmap().scanline(0), m_front_store->bitmap().scanline(0), m_front_store->bitmap().size_in_bytes());
-        m_back_store->bitmap().shared_buffer()->set_volatile();
+        m_back_store->bitmap().set_volatile();
         return;
     }
 
@@ -700,7 +707,7 @@ void Window::flip(const Vector<Gfx::IntRect, 32>& dirty_rects)
     for (auto& dirty_rect : dirty_rects)
         painter.blit(dirty_rect.location(), m_front_store->bitmap(), dirty_rect);
 
-    m_back_store->bitmap().shared_buffer()->set_volatile();
+    m_back_store->bitmap().set_volatile();
 }
 
 RefPtr<Gfx::Bitmap> Window::create_shared_bitmap(Gfx::BitmapFormat format, const Gfx::IntSize& size)
@@ -718,7 +725,18 @@ RefPtr<Gfx::Bitmap> Window::create_shared_bitmap(Gfx::BitmapFormat format, const
 OwnPtr<WindowBackingStore> Window::create_backing_store(const Gfx::IntSize& size)
 {
     auto format = m_has_alpha_channel ? Gfx::BitmapFormat::RGBA32 : Gfx::BitmapFormat::RGB32;
-    auto bitmap = create_shared_bitmap(format, size);
+
+    ASSERT(!size.is_empty());
+    size_t pitch = Gfx::Bitmap::minimum_pitch(size.width(), format);
+    size_t size_in_bytes = size.height() * pitch;
+
+    auto anon_fd = anon_create(round_up_to_power_of_two(size_in_bytes, PAGE_SIZE), O_CLOEXEC);
+    if (anon_fd < 0) {
+        perror("anon_create");
+        return {};
+    }
+
+    auto bitmap = Gfx::Bitmap::create_with_anon_fd(format, anon_fd, size, Gfx::Bitmap::ShouldCloseAnonymousFile::No);
     if (!bitmap)
         return {};
     return make<WindowBackingStore>(bitmap.release_nonnull());
@@ -870,9 +888,9 @@ void Window::notify_state_changed(Badge<WindowServerConnection>, bool minimized,
     if (!store)
         return;
     if (minimized || occluded) {
-        store->bitmap().shared_buffer()->set_volatile();
+        store->bitmap().set_volatile();
     } else {
-        if (!store->bitmap().shared_buffer()->set_nonvolatile()) {
+        if (!store->bitmap().set_nonvolatile()) {
             store = nullptr;
             update();
         }