From be9284e4efd921b940f68db46ed49ce7f5df162d Mon Sep 17 00:00:00 2001
From: casey langen <casey.langen@gmail.com>
Date: Thu, 8 Dec 2016 20:25:17 -0800
Subject: [PATCH] Fixed a really old bug in ListWindow where you could scroll
 past the last item if items in the viewport were of heterogenous size.

---
 src/musikbox/cursespp/ListWindow.cpp | 42 ++++++++++++++++++++++++++++
 src/musikbox/cursespp/ListWindow.h   |  2 ++
 2 files changed, 44 insertions(+)

diff --git a/src/musikbox/cursespp/ListWindow.cpp b/src/musikbox/cursespp/ListWindow.cpp
index 116a93b86..d11db91de 100755
--- a/src/musikbox/cursespp/ListWindow.cpp
+++ b/src/musikbox/cursespp/ListWindow.cpp
@@ -118,6 +118,39 @@ void ListWindow::OnInvalidated() {
     this->Invalidated(this, this->GetSelectedIndex());
 }
 
+bool ListWindow::IsSelectedItemCompletelyVisible() {
+    IScrollAdapter& adapter = this->GetScrollAdapter();
+    ScrollPos spos = this->GetScrollPosition();
+
+    size_t first = spos.firstVisibleEntryIndex;
+    size_t last = first + spos.visibleEntryCount - 1;
+
+    if (last <= spos.logicalIndex) {
+        /* get the height of all the visible items combined. */
+        int sum = 0;
+        for (size_t i = first; i <= spos.logicalIndex; i++) {
+            sum += adapter.GetEntry(this, i)->GetLineCount();
+        }
+
+        int delta = this->GetContentHeight() - sum;
+
+        /* special case -- the last item in the adapter is selected
+        and the heights match exactly -- we're at the end! */
+        if (delta == 0 && last == adapter.GetEntryCount() - 1) {
+            return true;
+        }
+
+        /* compare the visible height to the actual content
+        height. if the visible items are taller, and th selected
+        item is the last one, it means it's partially obscured. */
+        if (delta <= 0) {
+            return false;
+        }
+    }
+
+    return true;
+}
+
 void ListWindow::ScrollDown(int delta) {
     IScrollAdapter& adapter = this->GetScrollAdapter();
 
@@ -137,7 +170,16 @@ void ListWindow::ScrollDown(int delta) {
         }
 
         this->SetSelectedIndex(newIndex);
+
         this->ScrollTo(drawIndex);
+
+        /* when scrolling down it's possible for the last item to be
+        the selection, and partially obscured. if we hit this case, we
+        just continue scrolling until the selected item is completely
+        visible to the user. */
+        while (!IsSelectedItemCompletelyVisible()) {
+            this->ScrollTo(++drawIndex);
+        }
     }
 }
 
diff --git a/src/musikbox/cursespp/ListWindow.h b/src/musikbox/cursespp/ListWindow.h
index 947a31aba..53bdf48d1 100755
--- a/src/musikbox/cursespp/ListWindow.h
+++ b/src/musikbox/cursespp/ListWindow.h
@@ -81,6 +81,8 @@ namespace cursespp {
             virtual IScrollAdapter::ScrollPosition& GetMutableScrollPosition();
 
         private:
+            virtual bool IsSelectedItemCompletelyVisible();
+
             IScrollAdapter* adapter;
             IScrollAdapter::ScrollPosition scrollPosition;
             size_t selectedIndex;