[Qt] Fix map aspect ratio

Take QGuiApplication::devicePixelRatio() in consideration when resizing
the map.

Fixes #4889.

platform/qt/app/mapwindow.cpp

@@ -149,13 +149,16 @@ void MapWindow::initializeGL()
 
 void MapWindow::resizeGL(int w, int h)
 {
-    m_map.resize(QSize(w, h));
+    QSize size(w, h);
+#if QT_VERSION >= 0x050000
+    size /= qApp->devicePixelRatio();
+#endif
+    m_map.resize(size);
+    glViewport(0, 0, size.width(), size.height());
 }
 
 void MapWindow::paintGL()
 {
-    glViewport(0, 0, width(), height());
-
     m_frameDraws++;
     m_map.render();
 }

platform/qt/src/qmapboxgl.cpp

@@ -11,7 +11,12 @@
 #include <mbgl/util/geo.hpp>
 #include <mbgl/util/traits.hpp>
 
+#if QT_VERSION >= 0x050000
+#include <QGuiApplication>
+#else
 #include <QCoreApplication>
+#endif
+
 #include <QImage>
 #include <QMapboxGL>
 #include <QMargins>
@@ -636,8 +641,12 @@ QMapboxGLPrivate::~QMapboxGLPrivate()
 
 float QMapboxGLPrivate::getPixelRatio() const
 {
+#if QT_VERSION >= 0x050000
+    return qApp->devicePixelRatio();
+#else
     // FIXME: Should handle pixel ratio.
     return 1.0;
+#endif
 }
 
 std::array<uint16_t, 2> QMapboxGLPrivate::getSize() const

platform/qt/src/qquickmapboxglrenderer.cpp

@@ -3,6 +3,7 @@
 #include <QMapboxGL>
 #include <QQuickMapboxGL>
 
+#include <QGuiApplication>
 #include <QSize>
 #include <QOpenGLFramebufferObject>
 #include <QOpenGLFramebufferObjectFormat>
@@ -27,7 +28,7 @@ QQuickMapboxGLRenderer::~QQuickMapboxGLRenderer()
 
 QOpenGLFramebufferObject* QQuickMapboxGLRenderer::createFramebufferObject(const QSize &size)
 {
-    m_map->resize(size);
+    m_map->resize(size / qApp->devicePixelRatio());
 
     QOpenGLFramebufferObjectFormat format;
     format.setAttachment(QOpenGLFramebufferObject::CombinedDepthStencil);