avoid Xlib cairo surfaces for small virtual devices (bsc#1183308)

The (private :( ) document contains a large number of small shapes
for which VclProcessor2D::RenderTransparencePrimitive2D() gets
called, which results in GetBitmapEx() on the VirtualDevice.
And Cairo normally needs to do a roundtrip to the XServer to fetch
the content, which makes the rendering pretty slow. Forcing
image-based surface for small sizes of VirtualDevice actually has
better performance for the document, and the lack of possible
HW acceleration generally shouldn't matter for a surface this small.

Additionally drawinglayer's VirtualDevice reusing tries to reuse
even a large one when a small one is needed, so a hack is needed
to avoid that in this case, I couldn't find a better way.

Change-Id: I0f58659ab88165a6bd915f100fc3b1d4802a0fa9
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/128309
Tested-by: Jenkins
Reviewed-by: Luboš Luňák <l.lunak@collabora.com>

1 files changed, 27 insertions, 7 deletions

diff --git a/drawinglayer/source/processor2d/vclhelperbufferdevice.cxx b/drawinglayer/source/processor2d/vclhelperbufferdevice.cxx
index 9129271bcb6b..7f20d094b446 100644
--- a/drawinglayer/source/processor2d/vclhelperbufferdevice.cxx
+++ b/drawinglayer/source/processor2d/vclhelperbufferdevice.cxx
@@ -63,6 +63,8 @@ private:
     // virtualdevice because that isn't safe to do at least for Gtk2
     std::map<VclPtr<VirtualDevice>, VclPtr<OutputDevice>> maDeviceTemplates;
 
+    static bool isSizeSuitable(const VclPtr<VirtualDevice>& device, const Size& size);
+
 public:
     VDevBuffer();
     virtual ~VDevBuffer() override;
@@ -98,6 +100,28 @@ VDevBuffer::~VDevBuffer()
     }
 }
 
+bool VDevBuffer::isSizeSuitable(const VclPtr<VirtualDevice>& device, const Size& rSizePixel)
+{
+    if (device->GetOutputWidthPixel() >= rSizePixel.getWidth()
+        && device->GetOutputHeightPixel() >= rSizePixel.getHeight())
+    {
+#if defined(UNX)
+        // HACK: See the small size handling in SvpSalVirtualDevice::CreateSurface().
+        // Make sure to not reuse a larger device when a small one should be preferred.
+        if (device->GetRenderBackendName() == "svp")
+        {
+            if (rSizePixel.getWidth() <= 32 && rSizePixel.getHeight() <= 32
+                && (device->GetOutputWidthPixel() > 32 || device->GetOutputHeightPixel() > 32))
+            {
+                return false;
+            }
+        }
+#endif
+        return true;
+    }
+    return false;
+}
+
 VclPtr<VirtualDevice> VDevBuffer::alloc(OutputDevice& rOutDev, const Size& rSizePixel,
                                         bool bTransparent)
 {
@@ -124,9 +148,7 @@ VclPtr<VirtualDevice> VDevBuffer::alloc(OutputDevice& rOutDev, const Size& rSize
                     if (bOkay)
                     {
                         // found is valid
-                        const bool bCandidateOkay(
-                            a->buf->GetOutputWidthPixel() >= rSizePixel.getWidth()
-                            && a->buf->GetOutputHeightPixel() >= rSizePixel.getHeight());
+                        const bool bCandidateOkay = isSizeSuitable(a->buf, rSizePixel);
 
                         if (bCandidateOkay)
                         {
@@ -151,16 +173,14 @@ VclPtr<VirtualDevice> VDevBuffer::alloc(OutputDevice& rOutDev, const Size& rSize
                     {
                         // found is invalid, use candidate
                         aFound = a;
-                        bOkay = aFound->buf->GetOutputWidthPixel() >= rSizePixel.getWidth()
-                                && aFound->buf->GetOutputHeightPixel() >= rSizePixel.getHeight();
+                        bOkay = isSizeSuitable(aFound->buf, rSizePixel);
                     }
                 }
                 else
                 {
                     // none yet, use candidate
                     aFound = a;
-                    bOkay = aFound->buf->GetOutputWidthPixel() >= rSizePixel.getWidth()
-                            && aFound->buf->GetOutputHeightPixel() >= rSizePixel.getHeight();
+                    bOkay = isSizeSuitable(aFound->buf, rSizePixel);
                 }
             }
         }