[CoordinatedGraphics] Handle null native surface handle for surfacele…

…ss rendering

https://bugs.webkit.org/show_bug.cgi?id=226165

Patch by Zan Dobersek <zdobersek@igalia.com> on 2021-05-24
Reviewed by Philippe Normand.

During ThreadedCompositor initialization, a null native surface handle
would represent a surfaceless rendering target. Assuming corresponding
driver support for this behavior, the GL context creation would still
succeed and composition could be performed.

To support this behavior, the GL context is now spawned first, and if
successful, the scene is set as active. But in case of a null native
surface (i.e. surfaceless rendering), the painting has to be mirrored
by default because of the OpenGL coordinate system being the immediate
coordinate system inside which we end up working.

* Shared/CoordinatedGraphics/threadedcompositor/ThreadedCompositor.cpp:
(WebKit::m_displayRefreshMonitor):
(WebKit::ThreadedCompositor::createGLContext):

Canonical link: https://commits.webkit.org/238111@main
git-svn-id: https://svn.webkit.org/repository/webkit/trunk@277998 268f45cc-cd09-0410-ab3c-d52691b4dbfc

Source/WebKit/ChangeLog

@@ -1,3 +1,25 @@
+2021-05-24  Zan Dobersek  <zdobersek@igalia.com>
+
+        [CoordinatedGraphics] Handle null native surface handle for surfaceless rendering
+        https://bugs.webkit.org/show_bug.cgi?id=226165
+
+        Reviewed by Philippe Normand.
+
+        During ThreadedCompositor initialization, a null native surface handle
+        would represent a surfaceless rendering target. Assuming corresponding
+        driver support for this behavior, the GL context creation would still
+        succeed and composition could be performed.
+
+        To support this behavior, the GL context is now spawned first, and if
+        successful, the scene is set as active. But in case of a null native
+        surface (i.e. surfaceless rendering), the painting has to be mirrored
+        by default because of the OpenGL coordinate system being the immediate
+        coordinate system inside which we end up working.
+
+        * Shared/CoordinatedGraphics/threadedcompositor/ThreadedCompositor.cpp:
+        (WebKit::m_displayRefreshMonitor):
+        (WebKit::ThreadedCompositor::createGLContext):
+
 2021-05-24  Chris Dumez  <cdumez@apple.com>
 
         [GLIB] Stop using UncheckedLock in IconDatabase

Source/WebKit/Shared/CoordinatedGraphics/threadedcompositor/ThreadedCompositor.cpp

@@ -70,9 +70,12 @@ ThreadedCompositor::ThreadedCompositor(Client& client, ThreadedDisplayRefreshMon
         m_scene = adoptRef(new CoordinatedGraphicsScene(this));
         m_nativeSurfaceHandle = m_client.nativeSurfaceHandleForCompositing();
 
-        m_scene->setActive(!!m_nativeSurfaceHandle);
-        if (m_nativeSurfaceHandle)
-            createGLContext();
+        createGLContext();
+        if (m_context) {
+            if (!m_nativeSurfaceHandle)
+                m_paintFlags |= TextureMapper::PaintingMirrored;
+            m_scene->setActive(true);
+        }
     });
 }
 
@@ -84,8 +87,6 @@ void ThreadedCompositor::createGLContext()
 {
     ASSERT(!RunLoop::isMain());
 
-    ASSERT(m_nativeSurfaceHandle);
-
     // GLNativeWindowType depends on the EGL implementation: reinterpret_cast works
     // for pointers (only if they are 64-bit wide and not for other cases), and static_cast for
     // numeric types (and when needed they get extended to 64-bit) but not for pointers. Using