Improve the looks of a wave line by draw it with bezier curves

This adds drawing the wave line (typically used to underline the
wrongly spelled words) with bezier curves. Previously the wave
lines were drawn with drawing pixels, which didn't look that good,
especially on HiDPI display, so the looks of wave lines now is
therefor much better.

The creation of the wave line as a polygon has been added to the
basegfx module, so it can be reused if needed.

In addition, everytime we draw the waveline, we have to enable
antialiasing, to have a much better quality of the curves. By
default the antialiasing is disabled for some reason.

This also adds ScopedStates.hxx file which currently includes
ScopedAntialiasing, which sets the antialiasing to a certain state
for the time the object is in scope, and then sets it back to the
original state.

Change-Id: I4b866fc5d69725eb7f6f78a1acf4176b1205aa73
Reviewed-on: https://gerrit.libreoffice.org/74810
Tested-by: Jenkins
Reviewed-by: Tomaž Vajngerl <quikee@gmail.com>

2 files changed, 54 insertions, 1 deletions

diff --git a/basegfx/Library_basegfx.mk b/basegfx/Library_basegfx.mk
index 4a89d4995583..8ba2fb7cb32c 100644
--- a/basegfx/Library_basegfx.mk
+++ b/basegfx/Library_basegfx.mk
@@ -39,7 +39,7 @@ $(eval $(call gb_Library_add_exception_objects,basegfx,\
     basegfx/source/matrix/b2dhommatrixtools \
     basegfx/source/matrix/b3dhommatrix \
     basegfx/source/matrix/b3dhommatrixtools \
-	basegfx/source/numeric/ftools \
+    basegfx/source/numeric/ftools \
     basegfx/source/point/b2dpoint \
     basegfx/source/point/b2ipoint \
     basegfx/source/point/b3dpoint \
@@ -58,6 +58,7 @@ $(eval $(call gb_Library_add_exception_objects,basegfx,\
     basegfx/source/polygon/b3dpolygontools \
     basegfx/source/polygon/b3dpolypolygon \
     basegfx/source/polygon/b3dpolypolygontools \
+    basegfx/source/polygon/WaveLine \
     basegfx/source/range/b2dpolyrange \
     basegfx/source/range/b2drange \
     basegfx/source/range/b2drangeclipper \
diff --git a/basegfx/source/polygon/WaveLine.cxx b/basegfx/source/polygon/WaveLine.cxx
new file mode 100644
index 000000000000..8385cef7be1b
--- /dev/null
+++ b/basegfx/source/polygon/WaveLine.cxx
@@ -0,0 +1,52 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/*
+ * This file is part of the LibreOffice project.
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ *
+ */
+
+#include <basegfx/polygon/WaveLine.hxx>
+#include <basegfx/point/b2dpoint.hxx>
+
+namespace basegfx
+{
+BASEGFX_DLLPUBLIC B2DPolygon createWaveLinePolygon(basegfx::B2DRectangle const& rRectangle)
+{
+    basegfx::B2DPolygon aPolygon;
+
+    double fWaveHeight = rRectangle.getHeight();
+    // Wavelength depends on the wave height so it looks nice
+    double fHalfWaveLength = fWaveHeight + 1.0;
+    double fWaveAmplitude = fWaveHeight / 2.0;
+
+    double fLastX = rRectangle.getMinX();
+    double fBaseY = rRectangle.getMinY() + fWaveAmplitude;
+    double fDirection = 1.0;
+
+    // In quadratic bezier the curve is 1/2 of the control height
+    // so we need to compensate for that.
+    double fHeightCompensation = 2.0;
+
+    aPolygon.append(basegfx::B2DPoint(fLastX, fBaseY));
+
+    for (double fI = fHalfWaveLength; fI <= rRectangle.getWidth(); fI += fHalfWaveLength)
+    {
+        basegfx::B2DPoint aPoint(fLastX + fHalfWaveLength, fBaseY);
+        basegfx::B2DPoint aControl(fLastX + (fHalfWaveLength / 2.0),
+                                   fBaseY + fDirection * fWaveAmplitude * fHeightCompensation);
+
+        aPolygon.appendQuadraticBezierSegment(aControl, aPoint);
+
+        fLastX = aPoint.getX(); // next iteration
+        fDirection *= -1.0; // fDirection iterates between 1 and -1
+    }
+
+    return aPolygon;
+}
+
+} // end of namespace basegfx
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */