Nav: Fixed navigating outside of current scrolling bounds (bug from 0cc20fca83) (#323)

+ spaces

imgui.cpp

@@ -1920,7 +1920,18 @@ static bool NavScoreItem(ImRect cand)
         return false;
 
     const ImRect& curr = g.NavScoringRectScreen; // Current modified source rect (NB: we've applied Max.x = Min.x in NavUpdate() to inhibit the effect of having lots of items with varied width)
-    window->ClipRect.Clip(cand);
+
+    // We perform scoring on items bounding box clipped by their parent window on the other axis (clipping on our movement axis would give us equal scores for all clipped items)
+    if (g.NavMoveDir == ImGuiNavDir_Left || g.NavMoveDir == ImGuiNavDir_Right)
+    {
+        cand.Min.y = ImClamp(cand.Min.y, window->ClipRect.Min.y, window->ClipRect.Max.y);
+        cand.Max.y = ImClamp(cand.Max.y, window->ClipRect.Min.y, window->ClipRect.Max.y);
+    }
+    else
+    {
+        cand.Min.x = ImClamp(cand.Min.x, window->ClipRect.Min.x, window->ClipRect.Max.x);
+        cand.Max.x = ImClamp(cand.Max.x, window->ClipRect.Min.x, window->ClipRect.Max.x);
+    }
 
     // Compute distance between boxes
     // FIXME-NAVIGATION: Introducing various biases toward typical imgui uses cases, but we don't have any rigorous proof of their effect now.