tdf#160430: Fix glyph bounds calculation, and use basegfx::B2DRectangle

... instead of tools::Rectangle.

Several problems were there:
1. First, a horizontal bounding rectangle was calculated, with due
rounding; and then the result was rotated, and after that, rounded
again. That made the resulting rotated rectangle coordinates very
imprecise.
2. Also, ceil/floor was applied without normalization; and in case
of rotated font, that meant, that sometimes the range could be not
expanded to cover partially covered pixels, but instead collapsed.
3. The rotation to angles other than 90 degree multiples was done
incorrectly, resulting in cut off parts of characters.
4. For 90 degrees, the imprecise result of sin/cos converted 0.0
into values like 3e-16, which then could be ceil'ed up to 1.

Using B2DRectangle and its transform allows to simplify and fix
the calculations easily, and avoids premature rounding. Render of
rotated text of small size is more stable with this change.

Change-Id: Idffd74b9937feb2418ab76a8d325fdaf4ff841b7
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/165553
Tested-by: Jenkins
Reviewed-by: Tomaž Vajngerl <quikee@gmail.com>
Reviewed-by: Mike Kaganski <mike.kaganski@collabora.com>

1 files changed, 12 insertions, 12 deletions

diff --git a/vcl/source/gdi/sallayout.cxx b/vcl/source/gdi/sallayout.cxx
index af281127ba86..d1a29de327ff 100644
--- a/vcl/source/gdi/sallayout.cxx
+++ b/vcl/source/gdi/sallayout.cxx
@@ -214,12 +214,15 @@ bool SalLayout::GetOutline(basegfx::B2DPolyPolygonVector& rVector) const
     return (bAllOk && bOneOk);
 }
 
+// No need to expand to the next pixel, when the character only covers its tiny fraction
+static double trimInsignificant(double n) { return std::round(n * 1e5) / 1e5; }
+
 bool SalLayout::GetBoundRect(tools::Rectangle& rRect) const
 {
     bool bRet = false;
-    rRect.SetEmpty();
 
-    tools::Rectangle aRectangle;
+    basegfx::B2DRectangle aUnion;
+    basegfx::B2DRectangle aRectangle;
 
     basegfx::B2DPoint aPos;
     const GlyphItem* pGlyph;
@@ -230,22 +233,19 @@ bool SalLayout::GetBoundRect(tools::Rectangle& rRect) const
         // get bounding rectangle of individual glyph
         if (pGlyph->GetGlyphBoundRect(pGlyphFont, aRectangle))
         {
-            if (!aRectangle.IsEmpty())
+            if (!aRectangle.isEmpty())
             {
-                aRectangle.AdjustLeft(std::floor(aPos.getX()));
-                aRectangle.AdjustRight(std::ceil(aPos.getX()));
-                aRectangle.AdjustTop(std::floor(aPos.getY()));
-                aRectangle.AdjustBottom(std::ceil(aPos.getY()));
-
+                aRectangle.transform(basegfx::utils::createTranslateB2DHomMatrix(aPos));
                 // merge rectangle
-                if (rRect.IsEmpty())
-                    rRect = aRectangle;
-                else
-                    rRect.Union(aRectangle);
+                aUnion.expand(aRectangle);
             }
             bRet = true;
         }
     }
+    rRect = tools::Rectangle(rtl::math::approxFloor(trimInsignificant(aUnion.getMinX())),
+                             rtl::math::approxFloor(trimInsignificant(aUnion.getMinY())),
+                             rtl::math::approxCeil(trimInsignificant(aUnion.getMaxX())),
+                             rtl::math::approxCeil(trimInsignificant(aUnion.getMaxY())));
 
     return bRet;
 }