From 28f6c312a95ba6a2f632c7540b8b69f0f2c0ab02 Mon Sep 17 00:00:00 2001
From: Guillaume Munch <gm@lyx.org>
Date: Mon, 23 May 2016 11:38:48 +0100
Subject: [PATCH] Painter: Add a line style to disable antialiasing

It is not possible to use opacity effects (such as drawing an antialiased line
to strike diagonally through an inset), until the painter is fixed so that it
does not redraw repeatedly over the same spot (otherwise, the usual aritfacs
appear).

For now, pixellated lines are OK.
---
 src/Changes.cpp                  | 11 ++++++-----
 src/frontends/Painter.h          |  2 ++
 src/frontends/qt4/GuiPainter.cpp | 13 ++++++++-----
 3 files changed, 16 insertions(+), 10 deletions(-)

diff --git a/src/Changes.cpp b/src/Changes.cpp
index fc05d1c42a..e9191e37d8 100644
--- a/src/Changes.cpp
+++ b/src/Changes.cpp
@@ -556,9 +556,9 @@ void Change::paintCue(PainterInfo & pi, double const x1, double const y,
 		return;
 	// Calculate 1/3 height of font
 	FontMetrics const & fm = theFontMetrics(font);
-	int const y_bar = int(deleted() ? y - fm.maxAscent() / 3
-		: y + 2 * pi.base.solidLineOffset() + pi.base.solidLineThickness());
-	pi.pain.line(int(x1), y_bar, int(x2), y_bar, color(),
+	double const y_bar = deleted() ? y - fm.maxAscent() / 3
+		: y + 2 * pi.base.solidLineOffset() + pi.base.solidLineThickness();
+	pi.pain.line(int(x1), int(y_bar), int(x2), int(y_bar), color(),
 	             Painter::line_solid, pi.base.solidLineThickness());
 }
 
@@ -586,8 +586,9 @@ void Change::paintCue(PainterInfo & pi, double const x1, double const y1,
 		y = y1;
 		break;
 	}
-	pi.pain.line(int(x1), int(y2), int(x2), int(y), 
-	             color(), Painter::line_solid,
+	// we cannot use antialias since we keep drawing on the same background
+	pi.pain.line(int(x1), int(y2), int(x2), int(y),
+	             color(), Painter::line_solid_aliased,
 	             pi.base.solidLineThickness());
 }
 
diff --git a/src/frontends/Painter.h b/src/frontends/Painter.h
index b62a4e5c26..11bd24f66c 100644
--- a/src/frontends/Painter.h
+++ b/src/frontends/Painter.h
@@ -61,6 +61,8 @@ public:
 	/// possible line styles
 	enum line_style {
 		line_solid, //< solid line
+		line_solid_aliased, //< solid line, no anti-aliasing (used as a
+		                    // workaround to painting issues)
 		line_onoffdash //< dashes with spaces
 	};
 
diff --git a/src/frontends/qt4/GuiPainter.cpp b/src/frontends/qt4/GuiPainter.cpp
index 2fd2a20a7e..5762c9b958 100644
--- a/src/frontends/qt4/GuiPainter.cpp
+++ b/src/frontends/qt4/GuiPainter.cpp
@@ -82,8 +82,11 @@ void GuiPainter::setQPainterPen(QColor const & col,
 	pen.setColor(col);
 
 	switch (ls) {
-		case line_solid: pen.setStyle(Qt::SolidLine); break;
-		case line_onoffdash: pen.setStyle(Qt::DotLine); break;
+	case line_solid:
+	case line_solid_aliased:
+		pen.setStyle(Qt::SolidLine); break;
+	case line_onoffdash:
+		pen.setStyle(Qt::DotLine); break;
 	}
 
 	pen.setWidth(lw);
@@ -188,7 +191,7 @@ void GuiPainter::line(int x1, int y1, int x2, int y2,
 
 	setQPainterPen(computeColor(col), ls, lw);
 	bool const do_antialiasing = renderHints() & TextAntialiasing
-		&& x1 != x2 && y1 != y2;
+		&& x1 != x2 && y1 != y2 && ls != line_solid_aliased;
 	setRenderHint(Antialiasing, do_antialiasing);
 	drawLine(x1, y1, x2, y2);
 	setRenderHint(Antialiasing, false);
@@ -210,7 +213,7 @@ void GuiPainter::lines(int const * xp, int const * yp, int np,
 	if (np > points.size())
 		points.resize(2 * np);
 
-	bool antialias = false;
+	bool antialias = ls != line_solid_aliased;
 	for (int i = 0; i < np; ++i) {
 		points[i].setX(xp[i]);
 		points[i].setY(yp[i]);
@@ -261,7 +264,7 @@ void GuiPainter::path(int const * xp, int const * yp,
 	QColor const color = computeColor(col);
 	setQPainterPen(color, ls, lw);
 	bool const text_is_antialiased = renderHints() & TextAntialiasing;
-	setRenderHint(Antialiasing, text_is_antialiased);
+	setRenderHint(Antialiasing, text_is_antialiased && ls != line_solid_aliased);
 	drawPath(bpath);
 	if (fs != fill_none)
 		fillPath(bpath, QBrush(color));