sc lok: Implement hi-dpi and zoom for spreadsheets.

A bit different approach than trying to paint different zoom levels at
the samet time, because it is terribly hard to achieve with Calc -
things misalign, because Calc tries to fit the lines into the pixels
etc.

Instead, always paint the spreadsheet at 100%, but use cairo to scale the
actual painting.

Change-Id: I228a9dd41bf29862bdd188825d12e61e1c86cccc
Reviewed-on: https://gerrit.libreoffice.org/63031
Tested-by: Jenkins
Reviewed-by: Jan Holesovsky <kendy@collabora.com>

6 files changed, 71 insertions, 18 deletions

diff --git a/comphelper/source/misc/lok.cxx b/comphelper/source/misc/lok.cxx
index 0641e01660ab..2f6a2c151370 100644
--- a/comphelper/source/misc/lok.cxx
+++ b/comphelper/source/misc/lok.cxx
@@ -37,6 +37,9 @@ static bool g_bLocalRendering(false);
 
 static LanguageTag g_aLanguageTag("en-US", true);
 
+/// Scaling of the cairo canvas painting for hi-dpi or zooming in Calc.
+static double g_fDPIScale(1.0);
+
 void setActive(bool bActive)
 {
     g_bActive = bActive;
@@ -77,6 +80,16 @@ bool isDialogPainting()
     return g_bDialogPainting;
 }
 
+void setDPIScale(double fDPIScale)
+{
+    g_fDPIScale = fDPIScale;
+}
+
+double getDPIScale()
+{
+    return g_fDPIScale;
+}
+
 void setTiledAnnotations(bool bTiledAnnotations)
 {
     g_bTiledAnnotations = bTiledAnnotations;
diff --git a/desktop/source/lib/init.cxx b/desktop/source/lib/init.cxx
index 202bf279f153..7ea6316f9e26 100644
--- a/desktop/source/lib/init.cxx
+++ b/desktop/source/lib/init.cxx
@@ -2126,7 +2126,20 @@ static void doc_paintTile(LibreOfficeKitDocument* pThis,
         return;
     }
 
-#if defined(UNX) && !defined(MACOSX)
+#if defined(UNX) && !defined(MACOSX) && !defined(ENABLE_HEADLESS)
+
+    // Painting of zoomed or hi-dpi spreadsheets is special, we actually draw
+    // everything at 100%, and only set cairo's scale factor accordingly, so
+    // that everything is painted bigger or smaller.  This is different to
+    // what Calc's internal scaling would do - because that one is trying to
+    // fit the lines between cells to integer multiples of pixels.
+    comphelper::ScopeGuard dpiScaleGuard([]() { comphelper::LibreOfficeKit::setDPIScale(1.0); });
+    if (doc_getDocumentType(pThis) == LOK_DOCTYPE_SPREADSHEET)
+    {
+        double fDPIScaleX = (nCanvasWidth * 3840.0) / (256.0 * nTileWidth);
+        assert(fabs(fDPIScaleX - ((nCanvasHeight * 3840.0) / (256.0 * nTileHeight))) < 0.0001);
+        comphelper::LibreOfficeKit::setDPIScale(fDPIScaleX);
+    }
 
 #if defined(IOS)
     CGContextRef cgc = CGBitmapContextCreate(pBuffer, nCanvasWidth, nCanvasHeight, 8, nCanvasWidth*4, CGColorSpaceCreateDeviceRGB(), kCGImageAlphaNoneSkipFirst | kCGImageByteOrder32Little);
diff --git a/include/comphelper/lok.hxx b/include/comphelper/lok.hxx
index 7fb4d5a04800..a2b7eb02bef3 100644
--- a/include/comphelper/lok.hxx
+++ b/include/comphelper/lok.hxx
@@ -59,6 +59,10 @@ COMPHELPER_DLLPUBLIC void setTiledPainting(bool bTiledPainting);
 COMPHELPER_DLLPUBLIC bool isDialogPainting();
 /// Set if we are painting the dialog.
 COMPHELPER_DLLPUBLIC void setDialogPainting(bool bDialogPainting);
+/// Set the DPI scale for rendering for hi-dpi displays.  Used also for zoom in Calc.
+COMPHELPER_DLLPUBLIC void setDPIScale(double fDPIScale);
+/// Get the DPI scale for rendering for hi-dpi displays.  Used also for zoom in Calc.
+COMPHELPER_DLLPUBLIC double getDPIScale();
 /// Set if we want no annotations rendering
 COMPHELPER_DLLPUBLIC void setTiledAnnotations(bool bTiledAnnotations);
 /// Check if annotations rendering is turned off
diff --git a/sc/source/ui/unoobj/docuno.cxx b/sc/source/ui/unoobj/docuno.cxx
index ef5aca3f7950..255e1a4ef3f4 100644
--- a/sc/source/ui/unoobj/docuno.cxx
+++ b/sc/source/ui/unoobj/docuno.cxx
@@ -992,12 +992,12 @@ bool ScModelObj::isMimeTypeSupported()
     return EditEngine::HasValidData(aDataHelper.GetTransferable());
 }
 
-void ScModelObj::setClientZoom(int nTilePixelWidth_, int nTilePixelHeight_, int nTileTwipWidth_, int nTileTwipHeight_)
+void ScModelObj::setClientZoom(int /*nTilePixelWidth_*/, int /*nTilePixelHeight_*/, int /*nTileTwipWidth_*/, int /*nTileTwipHeight_*/)
 {
-    mnTilePixelWidth = nTilePixelWidth_;
-    mnTilePixelHeight = nTilePixelHeight_;
-    mnTileTwipWidth = nTileTwipWidth_;
-    mnTileTwipHeight = nTileTwipHeight_;
+    mnTilePixelWidth = 256;
+    mnTilePixelHeight = 256;
+    mnTileTwipWidth = mnTilePixelWidth * TWIPS_PER_PIXEL;
+    mnTileTwipHeight = mnTilePixelHeight * TWIPS_PER_PIXEL;
 }
 
 OUString ScModelObj::getRowColumnHeaders(const tools::Rectangle& rRectangle)
diff --git a/sc/source/ui/view/gridwin4.cxx b/sc/source/ui/view/gridwin4.cxx
index e74c18125a45..542a4c6283c6 100644
--- a/sc/source/ui/view/gridwin4.cxx
+++ b/sc/source/ui/view/gridwin4.cxx
@@ -32,6 +32,7 @@
 
 #include <LibreOfficeKit/LibreOfficeKitEnums.h>
 #include <comphelper/lok.hxx>
+#include <comphelper/scopeguard.hxx>
 #include <sfx2/lokhelper.hxx>
 
 #include <svx/svdview.hxx>
@@ -1109,17 +1110,30 @@ void ScGridWindow::PaintTile( VirtualDevice& rDevice,
     // coords only, and avoid all the SetMapMode()'s.
     // Similarly to Writer, we should set the mapmode once on the rDevice, and
     // not care about any zoom settings.
-
-    Fraction aFracX(long(nOutputWidth * TWIPS_PER_PIXEL), nTileWidth);
-    Fraction aFracY(long(nOutputHeight * TWIPS_PER_PIXEL), nTileHeight);
-
-    // page break zoom, and aLogicMode in ScViewData
+    //
+    // But until that happens, we actually draw everything at 100%, and only
+    // set cairo's scale factor accordingly, so that everything is painted
+    // bigger or smaller.  This is different to what Calc's internal scaling
+    // would do - because that one is trying to fit the lines between cells to
+    // integer multiples of pixels.
+    //
+    // See also desktop/source/lib/init.cxx for details, where we have to set
+    // the stuff accorndingly for the VirtualDevice creation.
+
+    // page break zoom, and aLogicMode in ScViewData - hardcode that 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);
 
-    const double fTilePosXPixel = static_cast<double>(nTilePosX) * nOutputWidth / nTileWidth;
-    const double fTilePosYPixel = static_cast<double>(nTilePosY) * nOutputHeight / nTileHeight;
-    const double fTileBottomPixel = static_cast<double>(nTilePosY + nTileHeight) * nOutputHeight / nTileHeight;
-    const double fTileRightPixel = static_cast<double>(nTilePosX + nTileWidth) * nOutputWidth / nTileWidth;
+    // Cairo scales for us, we have to compensate for that, otherwise we are
+    // painting too far away
+    const double fDPIScale = comphelper::LibreOfficeKit::getDPIScale();
+
+    const double fTilePosXPixel = static_cast<double>(nTilePosX) * nOutputWidth / (nTileWidth * fDPIScale);
+    const double fTilePosYPixel = static_cast<double>(nTilePosY) * nOutputHeight / (nTileHeight * fDPIScale);
+    const double fTileBottomPixel = static_cast<double>(nTilePosY + nTileHeight) * nOutputHeight / (nTileHeight * fDPIScale);
+    const double fTileRightPixel = static_cast<double>(nTilePosX + nTileWidth) * nOutputWidth / (nTileWidth * fDPIScale);
 
     SCTAB nTab = pViewData->GetTabNo();
     ScDocument* pDoc = pViewData->GetDocument();
diff --git a/vcl/headless/svpvd.cxx b/vcl/headless/svpvd.cxx
index 4172fc383744..875f22a5d7fc 100644
--- a/vcl/headless/svpvd.cxx
+++ b/vcl/headless/svpvd.cxx
@@ -25,6 +25,7 @@
 #include <headless/svpgdi.hxx>
 
 #include <basegfx/vector/b2ivector.hxx>
+#include <comphelper/lok.hxx>
 
 #include <cairo.h>
 
@@ -90,9 +91,17 @@ bool SvpSalVirtualDevice::SetSizeUsingBuffer( long nNewDX, long nNewDY,
         {
 #if CAIRO_VERSION >= CAIRO_VERSION_ENCODE(1, 14, 0)
             double fXScale, fYScale;
-            cairo_surface_get_device_scale(m_pRefSurface, &fXScale, &fYScale);
-            nNewDX *= fXScale;
-            nNewDY *= fYScale;
+            if (comphelper::LibreOfficeKit::isActive())
+            {
+                // Force scaling of the painting
+                fXScale = fYScale = comphelper::LibreOfficeKit::getDPIScale();
+            }
+            else
+            {
+                cairo_surface_get_device_scale(m_pRefSurface, &fXScale, &fYScale);
+                nNewDX *= fXScale;
+                nNewDY *= fYScale;
+            }
 #endif
 
             m_pSurface = cairo_image_surface_create_for_data(pBuffer, CAIRO_FORMAT_ARGB32,