Change scroll behaviour of timeline

This requires Qt 5.9 (to calculate overshoot).
The default scroll behaviour of list views has far too much inertia.
This should make scrolling feel more like scrolling the other scroll
areas of nheko.

.travis.yml

@@ -43,8 +43,8 @@ matrix:
           env:
               - CXX_COMPILER=g++-8
               - C_COMPILER=gcc-8
-              - QT_VERSION=58
-              - QT_PKG=58
+              - QT_VERSION=592
+              - QT_PKG=59
               - USE_BUNDLED_BOOST=1
               - USE_BUNDLED_CMARK=1
               - USE_BUNDLED_JSON=1

README.md

@@ -89,7 +89,7 @@ sudo port install nheko
 
 ### Build Requirements
 
-- Qt5 (5.8 or greater). Qt 5.7 adds support for color font rendering with
+- Qt5 (5.9 or greater). Qt 5.7 adds support for color font rendering with
   Freetype, which is essential to properly support emoji, 5.8 adds some features
   to make interopability with Qml easier.
 - CMake 3.15 or greater. (Lower version may work, but may break boost linking)
@@ -132,7 +132,7 @@ sudo pacman -S qt5-base \
 ##### Gentoo Linux
 
 ```bash
-sudo emerge -a ">=dev-qt/qtgui-5.7.1" media-libs/fontconfig
+sudo emerge -a ">=dev-qt/qtgui-5.9.0" media-libs/fontconfig
 ```
 
 ##### Ubuntu (e.g 14.04)

resources/qml/TimelineView.qml

-import QtQuick 2.6
+import QtQuick 2.9
 import QtQuick.Controls 2.1
 import QtQuick.Layouts 1.2
 import QtGraphicalEffects 1.0
@@ -46,6 +46,29 @@ Item {
 
 			model: timelineManager.timeline
 
+			boundsBehavior: Flickable.StopAtBounds
+
+			onVerticalOvershootChanged: contentY = contentY - verticalOvershoot
+
+			MouseArea {
+				anchors.fill: parent
+				acceptedButtons: Qt.NoButton
+				propagateComposedEvents: true
+				z: -1
+				onWheel: {
+					if (wheel.angleDelta != 0) {
+						chat.contentY = chat.contentY - wheel.angleDelta.y
+						if (wheel.angleDelta.y > 0 && chat.contentY > chat.contentHeight - chat.height)
+							chat.contentY = chat.contentHeight - chat.height
+						else if (wheel.angleDelta < 0 && chat.contentY < 0)
+							chat.contentY = 0
+						wheel.accepted = true
+						chat.forceLayout()
+						chat.updatePosition()
+					}
+				}
+			}
+
 			onModelChanged: {
 				if (model) {
 					currentIndex = model.currentIndex