lok: sc: make hi-dpi/zoom compatible with retrieving cell cursor

A bit different approach than trying to handle different zoom levels
at the samet time: instead, always handle the spreadsheet at 100%, but
use cairo to scale to the actual zoom level.

Change-Id: I318aec8fa4baaab2ee1f271223b2e10e26d41fcf
Reviewed-on: https://gerrit.libreoffice.org/63040
Tested-by: Jenkins
Reviewed-by: Jan Holesovsky <kendy@collabora.com>

desktop/qa/desktop_lib/test_desktop_lib.cxx

@@ -784,7 +784,7 @@ void DesktopLOKTest::testCellCursor()
 
     OString aRectangle(aTree.get<std::string>("commandValues").c_str());
     // cell cursor geometry + col + row
-    CPPUNIT_ASSERT_EQUAL(OString("0, 0, 1279, 255, 0, 0"), aRectangle);
+    CPPUNIT_ASSERT_EQUAL(OString("0, 0, 1274, 254, 0, 0"), aRectangle);
 
     comphelper::LibreOfficeKit::setActive(false);
 }

sc/source/ui/view/gridwin.cxx

@@ -5658,7 +5658,7 @@ OString ScGridWindow::getCellCursor( int nOutputWidth, int nOutputHeight,
     return getCellCursor(zoomX, zoomY);
 }
 
-OString ScGridWindow::getCellCursor(const Fraction& rZoomX, const Fraction& rZoomY) const
+OString ScGridWindow::getCellCursor(const Fraction& /*rZoomX*/, const Fraction& /*rZoomY*/) const
 {
     // GridWindow stores a shown cell cursor in mpOOCursors, hence
     // we can use that to determine whether we would want to be showing
@@ -5674,7 +5674,10 @@ OString ScGridWindow::getCellCursor(const Fraction& rZoomX, const Fraction& rZoo
     Fraction defaultZoomX = pViewData->GetZoomX();
     Fraction defaultZoomY = pViewData->GetZoomY();
 
-    pViewData->SetZoom(rZoomX, rZoomY, true);
+    // hardcode to what we mean as 100% (256px tiles meaning 3840 twips)
+    Fraction aFracX(long(256 * TWIPS_PER_PIXEL), 3840);
+    Fraction aFracY(long(256 * TWIPS_PER_PIXEL), 3840);
+    pViewData->SetZoom(aFracX, aFracY, true);
 
     Point aScrPos = pViewData->GetScrPos( nX, nY, eWhich, true );
     long nSizeXPix;