kcms/nightcolor: hide preview message after scroll manipulation

Currently, if you interact with one of the color temperature sliders
by scrolling, the preview message and full-screen color tint are
activated but never deactivated. This is because the deactivation only
happens in an `onPressedChanged` handler, but with a scroll, there is no
change to the `pressed` property's status, so it never fires and hence
the message and overlay never disappear.

This commit fixes that by using a timer to hide them that only triggers
when a slider is manipulated using a scroll.

BUG: 458675
FIXED-IN: 5.26

kcms/nightcolor/package/contents/ui/main.qml

@@ -43,6 +43,16 @@ KCM.SimpleKCM {
         root.locator.destroy();
     }
 
+    function startPreview(value) {
+        previewMessage.state = "visible"
+        cA.preview(value)
+    }
+
+    function stopPreview() {
+        previewMessage.state = "invisible"
+        cA.stopPreview()
+    }
+
     Connections {
         target: kcm.nightColorSettings
         function onActiveChanged() {
@@ -70,6 +80,12 @@ KCM.SimpleKCM {
         }
     }
 
+    Timer {
+        id: previewMessageTimer
+        interval: Kirigami.Durations.humanMoment
+        onTriggered: stopPreview()
+    }
+
     ColumnLayout {
         spacing: 0
 
@@ -186,14 +202,21 @@ KCM.SimpleKCM {
 
                     onMoved: {
                         kcm.nightColorSettings.dayTemperature = value
-                        previewMessage.state = "visible"
                         previewMessage.text = i18n("This is what day color temperature will look like when active.")
-                        cA.preview(value)
+                        root.startPreview(value)
+
+                        // This can fire for scroll events; in this case we need
+                        // to use a timer to make the preview message disappear, since
+                        // we can't make it disappear in the onPressedChanged handler
+                        // since there is no press
+                        if (!pressed) {
+                            previewMessageTimer.restart()
+                        }
                     }
-
                     onPressedChanged: {
-                        previewMessage.state = "invisible"
-                        cA.stopPreview()
+                        if (!pressed) {
+                            root.stopPreview()
+                        }
                     }
 
                     KCM.SettingStateBinding {
@@ -239,14 +262,21 @@ KCM.SimpleKCM {
 
                     onMoved: {
                         kcm.nightColorSettings.nightTemperature = value
-                        previewMessage.state = "visible"
                         previewMessage.text = i18n("This is what night color temperature will look like when active.")
-                        cA.preview(value)
+                        root.startPreview(value)
+
+                        // This can fire for scroll events; in this case we need
+                        // to use a timer to make the preview message disappear, since
+                        // we can't make it disappear in the onPressedChanged handler
+                        // since there is no press
+                        if (!pressed) {
+                            previewMessageTimer.restart()
+                        }
                     }
-
                     onPressedChanged: {
-                        previewMessage.state = "invisible"
-                        cA.stopPreview()
+                        if (!pressed) {
+                            root.stopPreview()
+                        }
                     }
 
                     KCM.SettingStateBinding {