From 6accff3cbdf26a94372bffc0935675df6912ce03 Mon Sep 17 00:00:00 2001
From: silverweed <silverweed14@proton.me>
Date: Thu, 8 Aug 2024 16:25:09 +0200
Subject: [PATCH] jumping to cluster now also sets latest page gone to

---
 src/render.cpp  |  6 ++++--
 src/rntuple.cpp | 12 ++++++++++--
 src/rntuple.h   |  5 +++--
 3 files changed, 17 insertions(+), 6 deletions(-)

diff --git a/src/render.cpp b/src/render.cpp
index 0b32b56..da32525 100644
--- a/src/render.cpp
+++ b/src/render.cpp
@@ -210,11 +210,13 @@ void viewer_jump_to_cluster(App_State &app, u64 cluster_idx)
 {
   assert(app.rndata.n_clusters > 0);
   cluster_idx = (cluster_idx + app.rndata.n_clusters) % app.rndata.n_clusters;
-
-  Page_Info_Node *page = app.rndata.clusters[cluster_idx].first_page;
+  
+  Cluster_Info &cluster = app.rndata.clusters[cluster_idx];
+  Page_Info_Node *page = cluster.first_page;
   assert(page);
 
   app.viewer.highlighted_cluster = cluster_idx;
+  app.viewer.latest_page_gone_to = cluster.first_page_idx;
   viewer_jump_to(app, page->range.start);
 }
 
diff --git a/src/rntuple.cpp b/src/rntuple.cpp
index 3fa127f..5df3546 100644
--- a/src/rntuple.cpp
+++ b/src/rntuple.cpp
@@ -96,7 +96,7 @@ void gather_ntuple_metadata(Arena *arena, RMicroFileReader &reader, const RNTupl
       
   chr::time_point start_t = chr::high_resolution_clock::now();
 
-  Cluster_Info_Node *clusters = arena_push_array<Cluster_Info_Node>(arena, descriptor.GetNActiveClusters());
+  Cluster_Info *clusters = arena_push_array<Cluster_Info>(arena, descriptor.GetNActiveClusters());
 
   // gather clusters and pages metadata
   for (const RClusterDescriptor &cluster_desc : descriptor.GetClusterIterable()) {
@@ -116,8 +116,10 @@ void gather_ntuple_metadata(Arena *arena, RMicroFileReader &reader, const RNTupl
         assert(cluster_desc.GetId() <= UINT_MAX);
         pinfo->cluster_id = cluster_desc.GetId();
 
-        Cluster_Info_Node &cluster = clusters[pinfo->cluster_id];
+        Cluster_Info &cluster = clusters[pinfo->cluster_id];
         if (!cluster.first_page || pinfo->range.start < cluster.first_page->range.start) {
+          if (cluster.first_page)
+            cluster.first_page->is_first_in_cluster = false;
           cluster.first_page = pinfo;
           pinfo->is_first_in_cluster = true;
         }
@@ -230,6 +232,12 @@ void gather_ntuple_metadata(Arena *arena, RMicroFileReader &reader, const RNTupl
     }
     chunks_tail->range.len += pinfo->range.len;
 
+    // while we're at it, set the first_page_idx information on the page's parent cluster
+    // Note that the first page won't update its cluster's `first_page_idx` (since we loop
+    // from idx = 1) but that's fine because that idx is by definition 0.
+    if (pinfo->is_first_in_cluster)
+      clusters[pinfo->cluster_id].first_page_idx = idx;
+
     if (idx++ % GROUP_SIZE != 0)
       continue;
     
diff --git a/src/rntuple.h b/src/rntuple.h
index 167898e..3d00998 100644
--- a/src/rntuple.h
+++ b/src/rntuple.h
@@ -36,8 +36,9 @@ struct Page_Info_Chunk {
   u32 first_group;
 };
 
-struct Cluster_Info_Node {
+struct Cluster_Info {
   Page_Info_Node *first_page;
+  u64 first_page_idx; // index in the pages linked list
 };
 
 struct Cluster_Group_Info {
@@ -83,7 +84,7 @@ struct RNTuple_Data {
   u64 n_cluster_groups;
   u64 tot_page_list_size;
 
-  Cluster_Info_Node *clusters;
+  Cluster_Info *clusters;
   u64 n_clusters;
 
   Page_Info_Group *page_groups;