Enable mercator-to-screen projection in GLSL

With this change, all the geo-to-screen conversion,
and the triangulation operations for geo polylines
and geo polygon are performed either at set time
or in the shader.
A separate bounding box geometry is processed
in the old way to provide a correct QtQuick Item
geometry, that can be used for nesting mouse areas,
performing translations, input event delivery, etc.

With this approach, performance are improved by more
than one order of magnitude in average, but complex
geometries will of course benefit more.

It also adds correct rendering support for polygons
with holes, previously only rendered correctly
by the MapboxGL plugin.

The polyline shader has basic miter joins. The miter is
skipped if the angle is too sharp to avoid complicating
the implementation.
This shader introduces some glitches when the polyline
is minified, for which the real fix is to
have LOD for the geometry, and render simplified
geometries at low zoom levels (added in a subsequent patch).

Note: this approach, at least in its current implementation,
does not support enabling layers on individual items, only
on the Map element.

Task-number: QTBUG-49303
Task-number: QTBUG-38459
Change-Id: I0c2dc0bf364d32f74ca7c4014f6d66e6219c8ae4
Reviewed-by: Alexandru Croitor <alexandru.croitor@qt.io>

1 files changed, 180 insertions, 0 deletions

diff --git a/src/location/declarativemaps/qdeclarativegeomapitemutils.cpp b/src/location/declarativemaps/qdeclarativegeomapitemutils.cpp
new file mode 100644
index 00000000..e2774559
--- /dev/null
+++ b/src/location/declarativemaps/qdeclarativegeomapitemutils.cpp
@@ -0,0 +1,180 @@
+/****************************************************************************
+**
+** Copyright (C) 2020 Paolo Angelelli <paolo.angelelli@gmail.com>
+** Copyright (C) 2020 The Qt Company Ltd.
+** Contact: http://www.qt.io/licensing/
+**
+** This file is part of the QtLocation module of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL3$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see http://www.qt.io/terms-conditions. For further
+** information use the contact form at http://www.qt.io/contact-us.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 3 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPLv3 included in the
+** packaging of this file. Please review the following information to
+** ensure the GNU Lesser General Public License version 3 requirements
+** will be met: https://www.gnu.org/licenses/lgpl.html.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 2.0 or later as published by the Free
+** Software Foundation and appearing in the file LICENSE.GPL included in
+** the packaging of this file. Please review the following information to
+** ensure the GNU General Public License version 2.0 requirements will be
+** met: http://www.gnu.org/licenses/gpl-2.0.html.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include "qdeclarativegeomapitemutils_p.h"
+#include <QtPositioning/private/qdoublevector3d_p.h>
+#include <QtPositioning/private/qdoublematrix4x4_p.h>
+#include <QtPositioning/QGeoCoordinate>
+#include <QPointF>
+#include <QMatrix4x4>
+#include <QPainterPath>
+#include <QPainterPathStroker>
+#include <QtGui/private/qvectorpath_p.h>
+#include <QtGui/private/qtriangulatingstroker_p.h>
+#include <QtGui/private/qtriangulator_p.h>
+#include <QtPositioning/private/qclipperutils_p.h>
+
+QT_BEGIN_NAMESPACE
+
+void QDeclarativeGeoMapItemUtils::wrapPath(const QList<QGeoCoordinate> &perimeter,
+                                           const QGeoCoordinate &geoLeftBound,
+                                           const QGeoProjectionWebMercator &p,
+                                           QList<QDoubleVector2D> &wrappedPath,
+                                           QList<QDoubleVector2D> &wrappedPathMinus1,
+                                           QList<QDoubleVector2D> &wrappedPathPlus1,
+                                           QDoubleVector2D *leftBoundWrapped)
+{
+    QList<QDoubleVector2D> path;
+    for (const QGeoCoordinate &c : perimeter)
+        path << p.geoToMapProjection(c);
+    const QDoubleVector2D leftBound = p.geoToMapProjection(geoLeftBound);
+    wrappedPath.clear();
+    wrappedPathPlus1.clear();
+    wrappedPathMinus1.clear();
+    // compute 3 sets of "wrapped" coordinates: one w regular mercator, one w regular mercator +- 1.0
+    for (int i = 0; i < path.size(); ++i) {
+        QDoubleVector2D coord = path.at(i);
+
+        // We can get NaN if the map isn't set up correctly, or the projection
+        // is faulty -- probably best thing to do is abort
+        if (!qIsFinite(coord.x()) || !qIsFinite(coord.y()))
+            return;
+
+        const bool isPointLessThanUnwrapBelowX = (coord.x() < leftBound.x());
+        // unwrap x to preserve geometry if moved to border of map
+        if (isPointLessThanUnwrapBelowX)
+            coord.setX(coord.x() + 1.0);
+
+        QDoubleVector2D coordP1(coord.x() + 1.0, coord.y());
+        QDoubleVector2D coordM1(coord.x() - 1.0, coord.y());
+
+        wrappedPath.append(coord);
+        wrappedPathPlus1.append(coordP1);
+        wrappedPathMinus1.append(coordM1);
+    }
+    if (leftBoundWrapped)
+        *leftBoundWrapped = leftBound;
+}
+
+void QDeclarativeGeoMapItemUtils::wrapPath(const QList<QGeoCoordinate> &perimeter,
+                                           const QGeoCoordinate &geoLeftBound,
+                                           const QGeoProjectionWebMercator &p,
+                                           QList<QDoubleVector2D> &wrappedPath,
+                                           QDoubleVector2D *leftBoundWrapped)
+{
+    QList<QDoubleVector2D> path;
+    for (const QGeoCoordinate &c : perimeter)
+        path << p.geoToMapProjection(c);
+    const QDoubleVector2D leftBound = p.geoToMapProjection(geoLeftBound);
+    wrapPath(path, leftBound,wrappedPath);
+    if (leftBoundWrapped)
+        *leftBoundWrapped = leftBound;
+}
+
+void QDeclarativeGeoMapItemUtils::wrapPath(const QList<QDoubleVector2D> &path,
+                                           const QDoubleVector2D &geoLeftBound,
+                                           QList<QDoubleVector2D> &wrappedPath)
+{
+    wrappedPath.clear();
+    // compute 3 sets of "wrapped" coordinates: one w regular mercator, one w regular mercator +- 1.0
+    for (int i = 0; i < path.size(); ++i) {
+        QDoubleVector2D coord = path.at(i);
+
+        // We can get NaN if the map isn't set up correctly, or the projection
+        // is faulty -- probably best thing to do is abort
+        if (!qIsFinite(coord.x()) || !qIsFinite(coord.y()))
+            return;
+
+        const bool isPointLessThanUnwrapBelowX = (coord.x() < geoLeftBound.x());
+        // unwrap x to preserve geometry if moved to border of map
+        if (isPointLessThanUnwrapBelowX)
+            coord.setX(coord.x() + 1.0);
+
+        wrappedPath.append(coord);
+    }
+}
+
+void QDeclarativeGeoMapItemUtils::clipPolygon(const QList<QDoubleVector2D> &wrappedPath, const QGeoProjectionWebMercator &p, QList<QList<QDoubleVector2D> > &clippedPaths, QDoubleVector2D *leftBoundWrapped, const bool closed)
+{
+    // 2) Clip bounding box
+    clippedPaths.clear();
+    const QList<QDoubleVector2D> &visibleRegion = p.projectableGeometry();
+    if (visibleRegion.size()) {
+        c2t::clip2tri clipper;
+        clipper.addSubjectPath(QClipperUtils::qListToPath(wrappedPath), closed);
+        clipper.addClipPolygon(QClipperUtils::qListToPath(visibleRegion));
+        Paths res = clipper.execute(c2t::clip2tri::Intersection, QtClipperLib::pftEvenOdd, QtClipperLib::pftEvenOdd);
+        clippedPaths = QClipperUtils::pathsToQList(res);
+
+        if (leftBoundWrapped) {
+            // 2.1) update srcOrigin_ and leftBoundWrapped with the point with minimum X
+            QDoubleVector2D lb(qInf(), qInf());
+            for (const QList<QDoubleVector2D> &path: clippedPaths)
+                for (const QDoubleVector2D &p: path)
+                    if (p.x() < lb.x() || (p.x() == lb.x() && p.y() < lb.y()))
+                        // y-minimization needed to find the same point on polygon and border
+                        lb = p;
+
+            if (qIsInf(lb.x())) // e.g., when the polygon is clipped entirely
+                return;
+
+            // 2.2) Prevent the conversion to and from clipper from introducing tiny negative offsets which,
+            //      in turn will make the geometry wrap around.
+            lb.setX(qMax(leftBoundWrapped->x(), lb.x()));
+
+            *leftBoundWrapped = lb;
+            // srcOrigin_ = p.mapProjectionToGeo(p.unwrapMapProjection(lb));
+        }
+    } else {
+        clippedPaths.append(wrappedPath);
+    }
+}
+
+void QDeclarativeGeoMapItemUtils::projectBbox(const QList<QDoubleVector2D> &clippedBbox, const QGeoProjectionWebMercator &p, QPainterPath &projectedBbox)
+{
+    projectedBbox = QPainterPath(); // clear() is added in 5.13..
+    for (int i = 0; i < clippedBbox.size(); ++i) {
+        QDoubleVector2D point = p.wrappedMapProjectionToItemPosition(clippedBbox.at(i));
+        if (i == 0)
+            projectedBbox.moveTo(point.toPointF());
+        else
+            projectedBbox.lineTo(point.toPointF());
+    }
+    projectedBbox.closeSubpath();
+}
+
+QT_END_NAMESPACE