1 files changed, 53 insertions, 28 deletions

diff --git a/src/ui.hpp b/src/ui.hpp
index 2c87d2a..414fff9 100644
--- a/src/ui.hpp
+++ b/src/ui.hpp
@@ -32,6 +32,8 @@ struct scroll_window_state {
 
   // The line at the top of the screen
   float scroll_top = 0;
+  // TODO we can probably do away when we use lazy views everywhere
+  int no_shown_items = 0;
 
   // To deal with large items
   bool large_item_mode = false;
@@ -91,7 +93,7 @@ toggle_read(rttt::active_storage<std::string, item_view_state> &&state,
 
 rttt::active_storage<std::string, item_view_state>
 mark_read(rttt::active_storage<std::string, item_view_state> &&state,
-            const std::string &id) {
+          const std::string &id) {
   if (!is_read(state, id))
     return toggle_read(std::move(state), id);
   return std::move(state);
@@ -225,7 +227,7 @@ inline bool drawHelpPopup(bool open) {
                 "/r/front, /hn/top)   ");
     ImGui::Text("    s           - toggle Messages window    ");
     ImGui::Text("    g           - go to top    ");
-    ImGui::Text("    G           - go to end    ");
+    ImGui::Text("    G           - go to bottom (of the loaded items)");
     ImGui::Text("    o/O         - open in browser    ");
     ImGui::Text("    j/k down/up - navigate items    ");
     ImGui::Text(
@@ -280,10 +282,11 @@ lineariseComments(std::vector<ItemVariant> items,
     if (result.size() >= head)
       break;
 
+    // FIXME: not loaded comments don't have an id yet, should probably treat them separately?
     auto maybe_id = try_id_string(item);
-    assert(maybe_id.has_value());
-
-    bool is_collapsed = ui::is_collapsed(item_view_states, maybe_id.value());
+    bool is_collapsed = false;
+    if (maybe_id.has_value())
+      is_collapsed = ui::is_collapsed(item_view_states, maybe_id.value());
 
     result.push_back({depth, item});
 
@@ -462,8 +465,7 @@ inline void drawItem(const ItemVariant &item, size_t id, size_t indent,
 // Draw a scrollable window of items
 template <typename T>
 scroll_window_state drawItems(
-    scroll_window_state &&state, const T &items,
-    const rttt::list_mode &list_mode,
+    scroll_window_state &&state, T &items, const rttt::list_mode &list_mode,
     rttt::active_storage<std::string, ui::item_view_state> &item_view_states) {
   size_t counter = 0;
   ImGui::SetScrollY(state.scroll_top);
@@ -473,13 +475,19 @@ scroll_window_state drawItems(
   auto it = items.begin();
   auto s_it = it;
 
+  bool passed_highlighted_item = false;
+  // Number of stories to draw below the scrollable area.
+  // Important because hackernews only loads the "viewable" items, so we need to
+  // cache some extra for smooth scroling
+  size_t draw_extra = 10;
+
   for (; it != items.end(); ++it) {
-    const auto &indent = it->first;
-    const auto &item = it->second;
+    const auto &indent = (*it).first;
+    const auto &item = (*it).second;
 
     bool isHighlighted = false;
-    if (!maybe_hid.has_value() || maybe_hid.value().empty() ||
-        maybe_hid.value() == "0") {
+
+    if (!maybe_hid.has_value()) {
       // Invalid value, so select the top one
       if (counter == 0)
         isHighlighted = true;
@@ -521,22 +529,38 @@ scroll_window_state drawItems(
                state.ui_view_mode, ui::item_view_state());
     }
 
-    if (isHighlighted &&
-        ImGui::GetCursorPosY() > state.scroll_top + ImGui::GetWindowHeight()) {
-      // Tried using IsItemVisible, but that does not seem to work with
-      // scrolling
-      state.highlighted_item_size =
-          ImGui::GetCursorPosY() - state.highlighted_item_size;
-      state.large_item_mode =
-          (state.highlighted_item_size - state.large_item_offset) >
-          ImGui::GetWindowHeight();
-      if (!state.large_item_mode) {
-        ImGui::SetScrollHereY(1.0);
-        state.scroll_top = ImGui::GetScrollY();
+    if (isHighlighted) {
+      passed_highlighted_item = true;
+      if (ImGui::GetCursorPosY() >
+          state.scroll_top + ImGui::GetWindowHeight()) {
+        // Tried using IsItemVisible, but that does not seem to work with
+        // scrolling
+        state.highlighted_item_size =
+            ImGui::GetCursorPosY() - state.highlighted_item_size;
+        state.large_item_mode =
+            (state.highlighted_item_size - state.large_item_offset) >
+            ImGui::GetWindowHeight();
+        if (!state.large_item_mode) {
+          ImGui::SetScrollHereY(1.0);
+          state.scroll_top = ImGui::GetScrollY();
+        }
       }
     }
+
     ++counter;
+
+    if (passed_highlighted_item &&
+        ImGui::GetCursorPosY() > state.scroll_top + ImGui::GetWindowHeight()) {
+      --draw_extra;
+      // Stop drawing if we have shown the highlighted_item and are outside the
+      // visible area
+      if (draw_extra == 0)
+        break;
+    }
   }
+
+  state.no_shown_items = counter;
+
   if (ImGui::IsWindowFocused()) {
     if (ImGui::IsKeyPressed('J', true) || ImGui::IsKeyPressed('K', true)) {
       auto maybe_id = try_id_string(state.highlighted_item);
@@ -556,9 +580,9 @@ scroll_window_state drawItems(
         }
       }
       if (!state.large_item_mode) {
-        if (s_it > items.begin()) {
+        if (s_it != items.begin()) {
           --s_it;
-          state.highlighted_item = s_it->second;
+          state.highlighted_item = (*s_it).second;
         }
       }
     }
@@ -574,9 +598,10 @@ scroll_window_state drawItems(
         }
       }
       if (!state.large_item_mode) {
-        if (items.size() > 0 && s_it < items.end() - 1) {
+        if (!items.empty() && s_it != items.end()) {
           ++s_it;
-          state.highlighted_item = s_it->second;
+          if (s_it != items.end())
+            state.highlighted_item = (*s_it).second;
         }
       }
     }
@@ -590,7 +615,7 @@ scroll_window_state drawItems(
     if (ImGui::IsKeyReleased('G')) {
       state.large_item_mode = false;
       state.large_item_offset = 0;
-      state.highlighted_item = items.back().second;
+      state.highlighted_item = (*(--it)).second;
     }
 
     if (ImGui::IsKeyReleased('v')) {