tdf#127529 vertical text not drawn in slideshow canvas

because the canvas text drawing impl falls back to using an OutputDevice view
of the canvas to use the vcl text drawing apis to achieve vertical text

To get an OutputDevice view of the canvas there is a specific VirtualDevice
ctor available to create a VirtualDevice that, unlike the normal case, doesn't
have its own specific backing buffer, but instead draws to the underlying target
provided via the SystemGraphicsData arg

The svp/gtk impl missed that understanding and provided an ordinary
VirtualDevice with its own backing buffer, not a VirtualDevice that would draw
to the expected target surface of the canvas. So the vertical text was drawn to
a different surface than the intended one, and was just discarded.

The cairo use in the canvas long precedes the use of cairo in vcl itself.

Seeing as text is now rendered with cairo in all cases where the canvas uses
cairo its probably now pointless for canvas to have its own text rendering
path.

Change-Id: Ie3b0a43ca2b746cbfe25e2d0415315b3d5403cd2
Reviewed-on: https://gerrit.libreoffice.org/80162
Tested-by: Jenkins
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>

3 files changed, 30 insertions, 8 deletions

diff --git a/vcl/qt5/Qt5Instance.cxx b/vcl/qt5/Qt5Instance.cxx
index 64481b64108e..129eb8e5c221 100644
--- a/vcl/qt5/Qt5Instance.cxx
+++ b/vcl/qt5/Qt5Instance.cxx
@@ -288,16 +288,20 @@ void Qt5Instance::DestroyObject(SalObject* pObject)
     }
 }
 
-std::unique_ptr<SalVirtualDevice>
-Qt5Instance::CreateVirtualDevice(SalGraphics* pGraphics, long& nDX, long& nDY, DeviceFormat eFormat,
-                                 const SystemGraphicsData* /* pData */)
+std::unique_ptr<SalVirtualDevice> Qt5Instance::CreateVirtualDevice(SalGraphics* pGraphics,
+                                                                   long& nDX, long& nDY,
+                                                                   DeviceFormat eFormat,
+                                                                   const SystemGraphicsData* pGd)
 {
     if (m_bUseCairo)
     {
         SvpSalGraphics* pSvpSalGraphics = dynamic_cast<Qt5SvpGraphics*>(pGraphics);
         assert(pSvpSalGraphics);
+        // tdf#127529 see SvpSalInstance::CreateVirtualDevice for the rare case of a non-null pPreExistingTarget
+        cairo_surface_t* pPreExistingTarget
+            = pGd ? static_cast<cairo_surface_t*>(pGd->pSurface) : nullptr;
         std::unique_ptr<SalVirtualDevice> pVD(
-            new Qt5SvpVirtualDevice(eFormat, pSvpSalGraphics->getSurface()));
+            new Qt5SvpVirtualDevice(eFormat, pSvpSalGraphics->getSurface(), pPreExistingTarget));
         pVD->SetSize(nDX, nDY);
         return pVD;
     }
diff --git a/vcl/qt5/Qt5SvpSurface.cxx b/vcl/qt5/Qt5SvpSurface.cxx
index 3e300755a992..21e0ca03b5b2 100644
--- a/vcl/qt5/Qt5SvpSurface.cxx
+++ b/vcl/qt5/Qt5SvpSurface.cxx
@@ -19,6 +19,18 @@
 #include <vcl/window.hxx>
 #include <basegfx/vector/b2isize.hxx>
 
+namespace
+{
+Size get_surface_size(cairo_surface_t* surface)
+{
+    cairo_t* cr = cairo_create(surface);
+    double x1, x2, y1, y2;
+    cairo_clip_extents(cr, &x1, &y1, &x2, &y2);
+    cairo_destroy(cr);
+    return Size(x2 - x1, y2 - y1);
+}
+}
+
 namespace cairo
 {
 Qt5SvpSurface::Qt5SvpSurface(const CairoSurfaceSharedPtr& pSurface)
@@ -65,8 +77,13 @@ void Qt5SvpSurface::flush() const
 
 VclPtr<VirtualDevice> Qt5SvpSurface::createVirtualDevice() const
 {
-    //TODO allow creating a VirtualDevice to draw to the current surface
-    return VclPtrInstance<VirtualDevice>(DeviceFormat::DEFAULT);
+    SystemGraphicsData aSystemGraphicsData;
+
+    aSystemGraphicsData.nSize = sizeof(SystemGraphicsData);
+    aSystemGraphicsData.pSurface = m_pSurface.get();
+
+    return VclPtr<VirtualDevice>::Create(aSystemGraphicsData, get_surface_size(m_pSurface.get()),
+                                         DeviceFormat::DEFAULT);
 }
 
 } // namespace cairo
diff --git a/vcl/qt5/Qt5SvpVirtualDevice.hxx b/vcl/qt5/Qt5SvpVirtualDevice.hxx
index 75c446bafb33..0eb4ed26ed2f 100644
--- a/vcl/qt5/Qt5SvpVirtualDevice.hxx
+++ b/vcl/qt5/Qt5SvpVirtualDevice.hxx
@@ -25,8 +25,9 @@
 class VCL_DLLPUBLIC Qt5SvpVirtualDevice : public SvpSalVirtualDevice
 {
 public:
-    Qt5SvpVirtualDevice(DeviceFormat eFormat, cairo_surface_t* pRefSurface)
-        : SvpSalVirtualDevice(eFormat, pRefSurface)
+    Qt5SvpVirtualDevice(DeviceFormat eFormat, cairo_surface_t* pRefSurface,
+                        cairo_surface_t* pPreExistingTarget)
+        : SvpSalVirtualDevice(eFormat, pRefSurface, pPreExistingTarget)
     {
     }