UI: Increase Gizmo 3D Part Hit Size For Pens

Gizmos that contain 3D parts, like the rounded lines of the "Rotate"
gizmo, have a fairly small hit size that make it hard to grab with a
tablet pen. This PR just increases the radius around the pointer
position while using a pen.

Pull Request: https://projects.blender.org/blender/blender/pulls/136847

source/blender/windowmanager/gizmo/intern/wm_gizmo_map.cc

@@ -716,10 +716,19 @@ static wmGizmo *gizmo_find_intersected_3d(bContext *C,
                                   });
     GPU_framebuffer_bind(depth_read_fb);
 
+    const wmWindow *win = CTX_wm_window(C);
+    /* How much this gizmo is bigger or smaller than default. */
+    const float gizmo_ratio = float(U.gizmo_size) / 75.0f;
+    /* Wider test area for tablet pens. */
+    const int test_min = ((win->event_last_handled->tablet.active) ? 6.0f : 4.0f) * UI_SCALE_FAC *
+                         gizmo_ratio;
+    const int test_max = ((win->event_last_handled->tablet.active) ? 12.0f : 10.0f) *
+                         UI_SCALE_FAC * gizmo_ratio;
+
     const int hotspot_radii[] = {
-        int(3 * U.pixelsize),
+        test_min,
         /* This runs on mouse move, careful doing too many tests! */
-        int(10 * U.pixelsize),
+        test_max,
     };
     for (int i = 0; i < ARRAY_SIZE(hotspot_radii); i++) {
       hit = gizmo_find_intersected_3d_intern(