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>
(cherry picked from commit cf9be3417bc2be5f772c03180b7cbd248b82cad5)
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/128815
Reviewed-by: Caolán McNamara <caolanm@redhat.com>

1 files changed, 26 insertions, 13 deletions

diff --git a/vcl/headless/svpvd.cxx b/vcl/headless/svpvd.cxx
index f8e9cb5e6874..21d231b229e9 100644
--- a/vcl/headless/svpvd.cxx
+++ b/vcl/headless/svpvd.cxx
@@ -76,29 +76,42 @@ void SvpSalVirtualDevice::CreateSurface(tools::Long nNewDX, tools::Long nNewDY,
         cairo_surface_destroy(m_pSurface);
     }
 
+    double fXScale, fYScale;
+    if (comphelper::LibreOfficeKit::isActive())
+    {
+        // Force scaling of the painting
+        fXScale = fYScale = comphelper::LibreOfficeKit::getDPIScale();
+    }
+    else
+    {
+        dl_cairo_surface_get_device_scale(m_pRefSurface, &fXScale, &fYScale);
+    }
+
     if (pBuffer)
     {
-        double fXScale, fYScale;
-        if (comphelper::LibreOfficeKit::isActive())
-        {
-            // Force scaling of the painting
-            fXScale = fYScale = comphelper::LibreOfficeKit::getDPIScale();
-        }
-        else
-        {
-            dl_cairo_surface_get_device_scale(m_pRefSurface, &fXScale, &fYScale);
-            nNewDX *= fXScale;
-            nNewDY *= fYScale;
-        }
+        nNewDX *= fXScale;
+        nNewDY *= fYScale;
 
         m_pSurface = cairo_image_surface_create_for_data(pBuffer, CAIRO_FORMAT_ARGB32,
                             nNewDX, nNewDY, cairo_format_stride_for_width(CAIRO_FORMAT_ARGB32, nNewDX));
-
+        dl_cairo_surface_set_device_scale(m_pSurface, fXScale, fYScale);
+    }
+    else if(nNewDX <= 32 && nNewDY <= 32)
+    {
+        nNewDX *= fXScale;
+        nNewDY *= fYScale;
+
+        // Force image-based surface if small. Small VirtualDevice instances are often used for small
+        // temporary bitmaps that will eventually have GetBitmap() called on them, which would cause
+        // X Server roundtrip with Xlib-based surface, which may be way more costly than doing the drawing
+        // in software (which should be fairly cheap for small surfaces anyway).
+        m_pSurface = cairo_surface_create_similar_image(m_pRefSurface, CAIRO_FORMAT_ARGB32, nNewDX, nNewDY);
         dl_cairo_surface_set_device_scale(m_pSurface, fXScale, fYScale);
     }
     else
     {
         m_pSurface = cairo_surface_create_similar(m_pRefSurface, CAIRO_CONTENT_COLOR_ALPHA, nNewDX, nNewDY);
+        // Device scale is inherited in this case.
     }
 }