GL paint-flushing guard re-work.

Unfortunately, since we can have 2x SalGraphics' on a OutputDevice,
and one of these can be a printer - things got very confused around
which context to glFlush. This de-tangles the various reference-counts.

Change-Id: I1062be0b02a91fc9009deaa3ec29c5dbb227df20
Reviewed-on: https://gerrit.libreoffice.org/18604
Reviewed-by: Michael Meeks <michael.meeks@collabora.com>
Tested-by: Michael Meeks <michael.meeks@collabora.com>

1 files changed, 15 insertions, 3 deletions

diff --git a/include/vcl/outdev.hxx b/include/vcl/outdev.hxx
index c8ba06a112fe..20bd81ae197f 100644
--- a/include/vcl/outdev.hxx
+++ b/include/vcl/outdev.hxx
@@ -606,9 +606,21 @@ public:
                                     const Point& rSrcPt,  const Size& rSrcSize,
                                     bool bWindowInvalidate = false );
 
-    // Call before and after a paint operation to reduce flushing
-    void                        BeginPaint();
-    void                        EndPaint();
+    /**
+     * Instantiate across a paint operation to defer flushing
+     * to the end.
+     *
+     * NB. holding a handle avoids problems with
+     * the underlying SalGraphics and it's implementation
+     * changing.
+     */
+    class PaintScope {
+        void *pHandle;
+    public:
+        PaintScope(OutputDevice *);
+        ~PaintScope();
+        void flush();
+    };
 
 protected: