Add half-screen down/up scrolling

1 files changed, 14 insertions, 7 deletions

diff --git a/lib/stitched_article.ml b/lib/stitched_article.ml
index 9548e11..9df2bd6 100644
--- a/lib/stitched_article.ml
+++ b/lib/stitched_article.ml
@@ -72,14 +72,17 @@ let rec render
   in
   Common.Term.image t img;
   let content_length = Array.length content_pretty in
-  let scroll_up () =
-    let scroll = if y - content_start - scroll = 0 then max (scroll - 1) 0 else scroll in
-    render t @@ { state with pos = x, max (y - 1) content_start; scroll; output = None }
+  let scroll_up ?(amount = 1) () =
+    let scroll =
+      if y - content_start - scroll - amount < 0 then max (scroll - amount) 0 else scroll
+    in
+    render t { state with pos = x, max (y - amount) content_start; scroll; output = None }
   in
-  let scroll_down () =
-    let scroll = if y - scroll >= size_y - 1 then scroll + 1 else scroll in
-    render t
-    @@ { state with pos = x, min (y + 1) (content_length - 1); scroll; output = None }
+  let scroll_down ?(amount = 1) () =
+    let scroll = if y - scroll >= size_y - amount then scroll + amount else scroll in
+    render
+      t
+      { state with pos = x, min (y + amount) content_length; scroll; output = None }
   in
   match Common.Term.event t with
   | `End | `Key (`Escape, []) | `Key (`ASCII 'q', []) | `Key (`ASCII 'C', [ `Ctrl ]) -> ()
@@ -120,6 +123,10 @@ let rec render
       }
     in
     Input_prompt.render t input_state
+  | `Key (`ASCII 'D', [ `Ctrl ]) | `Key (`Page `Down, []) ->
+    scroll_down ~amount:(size_y / 2) ()
+  | `Key (`ASCII 'U', [ `Ctrl ]) | `Key (`Page `Up, []) ->
+    scroll_up ~amount:(size_y / 2) ()
   | `Key (`ASCII '!', []) ->
     let file_number_offset, content_line = Array.get content_pretty (y - content_start) in
     let content_line = Grep.display_type_line content_line in