1 files changed, 97 insertions, 0 deletions
diff --git a/src/Geometry.cxx b/src/Geometry.cxx
new file mode 100644
index 000000000..68ce1f628
--- /dev/null
+++ b/src/Geometry.cxx
@@ -0,0 +1,97 @@
+// Scintilla source code edit control
+/** @file Geometry.cxx
+ ** Helper functions for geometric calculations.
+ **/
+// Copyright 2020 by Neil Hodgson <neilh@scintilla.org>
+// The License.txt file describes the conditions under which this software may be distributed.
+
+#include <cmath>
+
+#include <algorithm>
+
+#include "Geometry.h"
+
+namespace Scintilla {
+
+PRectangle Clamp(PRectangle rc, Edge edge, XYPOSITION position) noexcept {
+	switch (edge) {
+	case Edge::left:
+		return PRectangle(std::clamp(position, rc.left, rc.right), rc.top, rc.right, rc.bottom);
+	case Edge::top:
+		return PRectangle(rc.left, std::clamp(position, rc.top, rc.bottom), rc.right, rc.bottom);
+	case Edge::right:
+		return PRectangle(rc.left, rc.top, std::clamp(position, rc.left, rc.right), rc.bottom);
+	case Edge::bottom:
+	default:
+		return PRectangle(rc.left, rc.top, rc.right, std::clamp(position, rc.top, rc.bottom));
+	}
+}
+
+PRectangle Side(PRectangle rc, Edge edge, XYPOSITION size) noexcept {
+	switch (edge) {
+	case Edge::left:
+		return PRectangle(rc.left, rc.top, std::min(rc.left + size, rc.right), rc.bottom);
+	case Edge::top:
+		return PRectangle(rc.left, rc.top, rc.right, std::min(rc.top + size, rc.bottom));
+	case Edge::right:
+		return PRectangle(std::max(rc.left, rc.right - size), rc.top, rc.right, rc.bottom);
+	case Edge::bottom:
+	default:
+		return PRectangle(rc.left, std::max(rc.top, rc.bottom - size), rc.right, rc.bottom);
+	}
+}
+
+Interval Intersection(Interval a, Interval b) noexcept {
+	const XYPOSITION leftMax = std::max(a.left, b.left);
+	const XYPOSITION rightMin = std::min(a.right, b.right);
+	// If the result would have a negative width. make empty instead.
+	const XYPOSITION rightResult = (rightMin >= leftMax) ? rightMin : leftMax;
+	return { leftMax, rightResult };
+}
+
+PRectangle Intersection(PRectangle rc, Interval horizontalBounds) noexcept {
+	const Interval intersection = Intersection(HorizontalBounds(rc), horizontalBounds);
+	return PRectangle(intersection.left, rc.top, intersection.right, rc.bottom);
+}
+
+Interval HorizontalBounds(PRectangle rc) noexcept {
+	return { rc.left, rc.right };
+}
+
+XYPOSITION PixelAlign(XYPOSITION xy, int pixelDivisions) noexcept {
+	return std::round(xy * pixelDivisions) / pixelDivisions;
+}
+
+XYPOSITION PixelAlignFloor(XYPOSITION xy, int pixelDivisions) noexcept {
+	return std::floor(xy * pixelDivisions) / pixelDivisions;
+}
+
+Point PixelAlign(const Point &pt, int pixelDivisions) noexcept {
+	return Point(
+		     std::round(pt.x * pixelDivisions) / pixelDivisions,
+		     std::round(pt.y * pixelDivisions) / pixelDivisions);
+}
+
+PRectangle PixelAlign(const PRectangle &rc, int pixelDivisions) noexcept {
+	// Move left and right side to nearest pixel to avoid blurry visuals.
+	// The top and bottom should be integers but floor them to make sure.
+	// `pixelDivisions` is commonly 1 except for 'retina' displays where it is 2.
+	// On retina displays, the positions should be moved to the nearest device
+	// pixel which is the nearest half logical pixel.
+	return PRectangle(
+		std::round(rc.left * pixelDivisions) / pixelDivisions,
+		PixelAlignFloor(rc.top, pixelDivisions),
+		std::round(rc.right * pixelDivisions) / pixelDivisions,
+		PixelAlignFloor(rc.bottom, pixelDivisions));
+}
+
+PRectangle PixelAlignOutside(const PRectangle &rc, int pixelDivisions) noexcept {
+	// Move left and right side to extremes (floor(left) ceil(right)) to avoid blurry visuals.
+	return PRectangle(
+		std::floor(rc.left * pixelDivisions) / pixelDivisions,
+		std::floor(rc.top * pixelDivisions) / pixelDivisions,
+		std::ceil(rc.right * pixelDivisions) / pixelDivisions,
+		std::floor(rc.bottom * pixelDivisions) / pixelDivisions);
+}
+
+}