[panel] Fix dragging panel to resize for top and right panels

Previously, dragging up or right was always required to increase the
value of the spinbox and hance increase the thickness of the panel.
This makes sense for bottom and left panels, but is inverted for top
and right panels.

This commit reverses the stepSize when using a top or right panel, which
has the result that you can now always drag the SpinBox in the direction
of where you want the panel to resize no matter which screen edge the
panel is on.

BUG: 429063
FIXED-IN: 5.20.4


(cherry picked from commit b62ed146)

desktoppackage/contents/configuration/panelconfiguration/ToolBar.qml

@@ -119,7 +119,11 @@ Item {
 
             from: 20 // below this size, the panel is mostly unusable
             to: PlasmaCore.Types.LeftEdge || panel.location === PlasmaCore.Types.RightEdge ? panel.screenToFollow.geometry.width / 2 : panel.screenToFollow.geometry.height / 2
-            stepSize: 2
+
+            // When the panel is on the top or left, we need to reverse the drag
+            // and scroll directions so people can drag and scroll towards the
+            // center of the screen
+            stepSize: panel.location === PlasmaCore.Types.TopEdge || panel.location === PlasmaCore.Types.RightEdge ? -2 : 2
 
             value: panel.thickness
             onValueModified: {