Add infrastructure for partial layouts

Source/core/rendering/PartialLayoutState.h

Index: Source/core/rendering/PartialLayoutState.h
diff --git a/Source/modules/webmidi/MIDIConnectionEvent.h b/Source/core/rendering/PartialLayoutState.h
similarity index 51%
copy from Source/modules/webmidi/MIDIConnectionEvent.h
copy to Source/core/rendering/PartialLayoutState.h
index 4b193ee5df10f863f164b2eabb3a0a41185af54a..f2fcfa29196dbc93de0bfbe8485ff780595ae89f 100644
--- a/Source/modules/webmidi/MIDIConnectionEvent.h
+++ b/Source/core/rendering/PartialLayoutState.h
@@ -28,67 +28,73 @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
-#ifndef MIDIConnectionEvent_h
-#define MIDIConnectionEvent_h
+#ifndef PartialLayoutState_h
+#define PartialLayoutState_h
 
-#include "core/dom/Event.h"
-#include "modules/webmidi/MIDIPort.h"
+#include "core/rendering/RenderObject.h"
 
 namespace WebCore {
 
-struct MIDIConnectionEventInit : public EventInit {
-    MIDIConnectionEventInit()
-        : port(0)
-    {
-    };
-
-    RefPtr<MIDIPort> port;
-};
-
-class MIDIConnectionEvent : public Event {
+class PartialLayoutState {
+    friend class PartialLayoutDisabler;
 public:
-    static PassRefPtr<MIDIConnectionEvent> create()
+    PartialLayoutState()
+        : m_shouldStop(false)
+        , m_stopAtRenderer(0)
+        , m_disableCount(0)
     {
-        return adoptRef(new MIDIConnectionEvent());
     }
 
-    static PassRefPtr<MIDIConnectionEvent> create(const AtomicString& type, PassRefPtr<MIDIPort> port)
-    {
-        return adoptRef(new MIDIConnectionEvent(type, port));
-    }
+    bool shouldStop() const { return m_shouldStop; }

[eseidel, 2013/09/03 19:14:27]

I might have called this isStopping()?

[pdr., 2013/09/03 21:37:35]

Done.

+    bool checkPartialLayoutComplete(RenderObject*);

[eseidel, 2013/09/03 19:14:27]

const?

[pdr., 2013/09/03 21:37:35]

Done.

+    void setStopAtRenderer(RenderObject* renderer) { m_stopAtRenderer = renderer; }

[eseidel, 2013/09/03 19:14:27]

const?

[pdr., 2013/09/03 21:37:35]

Done.

+    RenderObject* stopAtRenderer() { return m_disableCount > 0 ? 0 : m_stopAtRenderer; }

[esprehn, 2013/09/03 18:15:36]

Is there a reason stopAtRenderer() needs to be public? I fear future
use-after-frees.

[eseidel, 2013/09/03 19:14:27]

const?

[pdr., 2013/09/03 21:37:35]

Done.

+    void reset() { m_shouldStop = false; m_stopAtRenderer = 0; }

[eseidel, 2013/09/03 19:14:27]

Yeah, I would probably have added assignment instead of bothered with a reset()
method, that way you can depend on the constructor to init everything for you.

[pdr., 2013/09/03 21:37:35]

Mind if we save this for a followup?

This may turn into a state pop in a followup patch.

 
-    static PassRefPtr<MIDIConnectionEvent> create(const AtomicString& type, const MIDIConnectionEventInit& initializer)
-    {
-        return adoptRef(new MIDIConnectionEvent(type, initializer));
-    }
+private:
+    void disable() { m_disableCount++; }

[eseidel, 2013/09/03 19:14:27]

ASSERT(!m_shouldStop);?

[pdr., 2013/09/03 21:37:35]

Done.

+    void enable() { ASSERT(m_disableCount > 0); m_disableCount--; }
 
-    RefPtr<MIDIPort> port() { return m_port; }
+    bool m_shouldStop;

[eseidel, 2013/09/03 19:14:27]

This tracks "did we reach the stopping renderer yet", correct?

[pdr., 2013/09/03 21:37:35]

EOn 2013/09/03 19:14:27, eseidel wrote:
Exactly

+    RenderObject* m_stopAtRenderer;
+    int m_disableCount;
+};
 
-    virtual const AtomicString& interfaceName() const OVERRIDE { return eventNames().interfaceForMIDIConnectionEvent; }
+inline bool PartialLayoutState::checkPartialLayoutComplete(RenderObject* renderer)
+{
+    if (m_shouldStop)

[eseidel, 2013/09/03 19:14:27]

Is it OK for this method to be called after shouldStop is set?  Once we enter
the "stopping" phase, it should be an error for any layout to continue, no?

[pdr., 2013/09/03 21:37:35]

This is a good question.

This function is combining two operations, since you always do them both:
1) checking if layout should stop
2) checking if this is the layout that should stop

Otherwise, all the callers would need to do:
if (partialLayout()->isStopping())
    return;
if (checkPartialLayoutComplete(...))
    return

+        return true;
 
-private:
-    MIDIConnectionEvent()
-    {
-        ScriptWrappable::init(this);
+    if (renderer == stopAtRenderer()) {
+        m_shouldStop = true;
+        m_stopAtRenderer = 0;

[eseidel, 2013/09/03 19:14:27]

You might add a note as to why you clear the m_stopAtRenderer member here.

+        return true;
     }
 
-    MIDIConnectionEvent(const AtomicString& type, PassRefPtr<MIDIPort> port)
-        : Event(type, false, false)
-        , m_port(port)
+    return false;
+}
+
+class PartialLayoutDisabler {
+    WTF_MAKE_NONCOPYABLE(PartialLayoutDisabler);
+public:
+    PartialLayoutDisabler(PartialLayoutState& partialLayout, bool disable)

[eseidel, 2013/09/03 19:14:27]

should disable default to true?

[pdr., 2013/09/03 21:37:35]

Done.

+        : m_partialLayout(partialLayout)
+        , m_disable(disable)
     {
-        ScriptWrappable::init(this);
+        if (m_disable)
+            m_partialLayout.disable();
     }
 
-    MIDIConnectionEvent(const AtomicString& type, const MIDIConnectionEventInit& initializer)
-        : Event(type, initializer)
-        , m_port(initializer.port)
+    ~PartialLayoutDisabler()
     {
-        ScriptWrappable::init(this);
+        if (m_disable)
+            m_partialLayout.enable();
     }
-
-    RefPtr<MIDIPort> m_port;
+private:
+    PartialLayoutState& m_partialLayout;
+    bool m_disable;
 };
 
 } // namespace WebCore
 
-#endif // MIDIConnectionEvent_h
+#endif // PartialLayoutState_h