From 758de9577dcf3ff912c794dc4dffa13e138ffd41 Mon Sep 17 00:00:00 2001
From: Jean-Marc Lasgouttes <lasgouttes@lyx.org>
Date: Fri, 31 Mar 2017 18:50:14 +0200
Subject: [PATCH] Improve drawing of math roots (\sqrt and \root)

This is preliminary work to make roots look more like in TeX output:

* correct font size for root order

* set minimum size of the root from the max ascent descent of the
  font. This is what TeX does.

* fix drawing, and in particular horizontal size.

More needs to be done, in particular:

* handle zooming and dpi correctly by removing hardcoded pixel values.

* factor the code for the two types of roots in one.
---
 src/mathed/InsetMathRoot.cpp | 40 ++++++++++++++++++++++++++----------
 src/mathed/InsetMathSqrt.cpp | 11 +++++++---
 2 files changed, 37 insertions(+), 14 deletions(-)

diff --git a/src/mathed/InsetMathRoot.cpp b/src/mathed/InsetMathRoot.cpp
index f61db16e8f..db8954f8c2 100644
--- a/src/mathed/InsetMathRoot.cpp
+++ b/src/mathed/InsetMathRoot.cpp
@@ -15,6 +15,7 @@
 
 #include "MathData.h"
 #include "MathStream.h"
+#include "MathSupport.h"
 
 #include "Cursor.h"
 #include "LaTeXFeatures.h"
@@ -42,27 +43,44 @@ Inset * InsetMathRoot::clone() const
 void InsetMathRoot::metrics(MetricsInfo & mi, Dimension & dim) const
 {
 	Changer dummy = mi.base.changeEnsureMath();
-	cellsMetrics(mi);
-	Dimension const & dim0 = cell(0).dimension(*mi.base.bv);
-	Dimension const & dim1 = cell(1).dimension(*mi.base.bv);
-	dim.asc = max(dim0.ascent()  + 5, dim1.ascent())  + 2;
-	dim.des = max(dim0.descent() - 5, dim1.descent()) + 2;
-	dim.wid = dim0.width() + dim1.width() + 10;
+	Dimension dim0;
+	{
+		Changer script = mi.base.font.changeStyle(LM_ST_SCRIPTSCRIPT);
+		cell(0).metrics(mi, dim0);
+		// make sure that the dim is high enough for any character
+		Dimension fontDim;
+		math_font_max_dim(mi.base.font, fontDim.asc, fontDim.des);
+		dim0 += fontDim;
+	}
+
+	Dimension dim1;
+	cell(1).metrics(mi, dim1);
+	// make sure that the dim is high enough for any character
+	Dimension fontDim;
+	math_font_max_dim(mi.base.font, fontDim.asc, fontDim.des);
+	dim1 += fontDim;
+
+	dim.asc = max(dim0.ascent()  + 5, dim1.ascent()) + 1;
+	dim.des = max(dim0.descent() - 5, dim1.descent());
+	dim.wid = dim0.width() + dim1.width() + 4;
 }
 
 
 void InsetMathRoot::draw(PainterInfo & pi, int x, int y) const
 {
 	Changer dummy = pi.base.changeEnsureMath();
+	Dimension const dim = dimension(*pi.base.bv);
+	int const a = dim.ascent();
+	int const d = dim.descent();
 	Dimension const & dim0 = cell(0).dimension(*pi.base.bv);
 	int const w = dim0.width();
 	// the "exponent"
-	cell(0).draw(pi, x, y - 5 - dim0.descent());
+	{
+		Changer script = pi.base.font.changeStyle(LM_ST_SCRIPTSCRIPT);
+		cell(0).draw(pi, x, y + (d - a)/2 - dim0.descent());
+	}
 	// the "base"
-	cell(1).draw(pi, x + w + 8, y);
-	Dimension const dim = dimension(*pi.base.bv);
-	int const a = dim.ascent();
-	int const d = dim.descent();
+	cell(1).draw(pi, x + w + 4, y);
 	int xp[4];
 	int yp[4];
 	pi.pain.line(x + dim.width(), y - a + 1,
diff --git a/src/mathed/InsetMathSqrt.cpp b/src/mathed/InsetMathSqrt.cpp
index 4505d70567..d11dac084c 100644
--- a/src/mathed/InsetMathSqrt.cpp
+++ b/src/mathed/InsetMathSqrt.cpp
@@ -14,6 +14,7 @@
 
 #include "MathData.h"
 #include "MathStream.h"
+#include "MathSupport.h"
 
 #include "LaTeXFeatures.h"
 #include "MetricsInfo.h"
@@ -39,9 +40,13 @@ void InsetMathSqrt::metrics(MetricsInfo & mi, Dimension & dim) const
 {
 	Changer dummy = mi.base.changeEnsureMath();
 	cell(0).metrics(mi, dim);
-	dim.asc += 4;
-	dim.des += 2;
-	dim.wid += 12;
+	// make sure that the dim is high enough for any character
+	Dimension fontDim;
+	math_font_max_dim(mi.base.font, fontDim.asc, fontDim.des);
+	dim += fontDim;
+	// Some room for the decoration
+	dim.asc += 1;
+	dim.wid += 7;
 }
 
 
-- 
2.39.2