[ruby/reline] Use appropriate dialog height and reduce screen pushup

problem
(https://github.com/ruby/reline/pull/542)

* Provide preferred_dialog_height for dialog positioning

* Fix rendering test

2 files changed, 11 insertions, 1 deletions

diff --git a/lib/reline.rb b/lib/reline.rb
index a128d7347d..fd70ffc9d0 100644
--- a/lib/reline.rb
+++ b/lib/reline.rb
@@ -260,7 +260,7 @@ module Reline
         pos: cursor_pos_to_render,
         contents: result,
         scrollbar: true,
-        height: 15,
+        height: [15, preferred_dialog_height].min,
         bg_color: 46,
         pointer_bg_color: 45,
         fg_color: 37,
diff --git a/lib/reline/line_editor.rb b/lib/reline/line_editor.rb
index b6304bc040..2e84ca4d0c 100644
--- a/lib/reline/line_editor.rb
+++ b/lib/reline/line_editor.rb
@@ -562,6 +562,16 @@ class Reline::LineEditor
       @line_editor.instance_variable_get(:@screen_size).last
     end
 
+    def screen_height
+      @line_editor.instance_variable_get(:@screen_size).first
+    end
+
+    def preferred_dialog_height
+      rest_height = @line_editor.instance_variable_get(:@rest_height)
+      scroll_partial_screen = @line_editor.instance_variable_get(:@scroll_partial_screen) || 0
+      [cursor_pos.y - scroll_partial_screen, rest_height, (screen_height + 6) / 5].max
+    end
+
     def completion_journey_data
       @line_editor.instance_variable_get(:@completion_journey_data)
     end