From faf242c49860ba627d0ea4b6af9d4ae0b76e03ba Mon Sep 17 00:00:00 2001
From: "Kartik K. Agaram" <vc@akkartik.com>
Date: Wed, 11 Aug 2021 21:58:47 -0700
Subject: [PATCH] experiment: more granular scrolling

---
 browse-slack/environment.mu | 35 +++++++++++++++++++++++++++++++++++
 1 file changed, 35 insertions(+)

diff --git a/browse-slack/environment.mu b/browse-slack/environment.mu
index 13ef1c36..c7333adf 100644
--- a/browse-slack/environment.mu
+++ b/browse-slack/environment.mu
@@ -109,6 +109,10 @@ fn render-menu screen: (addr screen) {
   draw-text-rightward-from-cursor screen, " next page  ", width, 0xf/fg, 0/bg
   draw-text-rightward-from-cursor screen, " ^b ", width, 0/fg 0xf/bg
   draw-text-rightward-from-cursor screen, " previous page  ", width, 0xf/fg, 0/bg
+  draw-text-rightward-from-cursor screen, " ^n ", width, 0/fg 0xf/bg
+  draw-text-rightward-from-cursor screen, " next (older) item  ", width, 0xf/fg, 0/bg
+  draw-text-rightward-from-cursor screen, " ^p ", width, 0/fg 0xf/bg
+  draw-text-rightward-from-cursor screen, " previous (more recent) item  ", width, 0xf/fg, 0/bg
 }
 
 fn render-item screen: (addr screen), _item: (addr item), _users: (addr array user), y: int, screen-height: int -> _/ecx: int {
@@ -173,6 +177,18 @@ fn render-item screen: (addr screen), _item: (addr item), _users: (addr array us
 }
 
 fn update-environment env: (addr environment), key: byte, items: (addr item-list) {
+  {
+    compare key, 0xe/ctrl-n
+    break-if-!=
+    next-item env, items
+    return
+  }
+  {
+    compare key, 0x10/ctrl-p
+    break-if-!=
+    previous-item env, items
+    return
+  }
   {
     compare key, 6/ctrl-f
     break-if-!=
@@ -187,6 +203,25 @@ fn update-environment env: (addr environment), key: byte, items: (addr item-list
   }
 }
 
+fn next-item _env: (addr environment), _items: (addr item-list) {
+  var env/edi: (addr environment) <- copy _env
+  var dest/eax: (addr int) <- get env, item-index
+  compare *dest, 0
+  break-if-<=
+  decrement *dest
+}
+
+fn previous-item _env: (addr environment), _items: (addr item-list) {
+  var env/edi: (addr environment) <- copy _env
+  var items/esi: (addr item-list) <- copy _items
+  var newest-item-index-a/ecx: (addr int) <- get items, newest
+  var newest-item-index/ecx: int <- copy *newest-item-index-a
+  var dest/eax: (addr int) <- get env, item-index
+  compare *dest, newest-item-index
+  break-if->=
+  increment *dest
+}
+
 fn page-down _env: (addr environment), _items: (addr item-list) {
   var env/edi: (addr environment) <- copy _env
   var items/esi: (addr item-list) <- copy _items