Fix issue where look-ahead scanline adjustments could get too high and cause monitors to dance

gnome/src/virtualmonitorsactor.js

@@ -562,9 +562,9 @@ export const VirtualMonitorEffect = GObject.registerClass({
 
             // project the vector onto a flat surface, return it's vertical position relative to the vertical fov, where 0.0 is 
             // the top and 1.0 is the bottom. vectors that project outside the vertical range of the display will have values 
-            // outside this range.
+            // outside this range, but capped
             float vectorToScanline(float fovVerticalRadians, vec3 v) {
-                return 1.0 - (-v.y / (tan(fovVerticalRadians / 2.0) * v.z) + 1.0) / 2.0;
+                return clamp(1.0 - (-v.y / (tan(fovVerticalRadians / 2.0) * v.z) + 1.0) / 2.0, -0.5, 1.5);
             }
         `;