From d815f4615662b3b9525a05363a06bf25907c4315 Mon Sep 17 00:00:00 2001
From: Moritz Bunkus <mo@bunkus.online>
Date: Sat, 13 Nov 2021 20:30:55 +0100
Subject: [PATCH] GUI: headers: calculate top level pages on the fly, no
 caching

Part of the implementation of #3227.
---
 .../header_editor/page_model.cpp              | 34 +++++++++++--------
 src/mkvtoolnix-gui/header_editor/page_model.h |  3 +-
 src/mkvtoolnix-gui/header_editor/tab.cpp      |  6 ++--
 3 files changed, 23 insertions(+), 20 deletions(-)

diff --git a/src/mkvtoolnix-gui/header_editor/page_model.cpp b/src/mkvtoolnix-gui/header_editor/page_model.cpp
index 4c01063a0..312bbe6bf 100644
--- a/src/mkvtoolnix-gui/header_editor/page_model.cpp
+++ b/src/mkvtoolnix-gui/header_editor/page_model.cpp
@@ -53,8 +53,6 @@ PageModel::appendPage(PageBase *page,
   page->setItems(newItems);
 
   m_pages[pageId] = page;
-  if (!parentIdx.isValid())
-    m_topLevelPages << page;
 }
 
 bool
@@ -66,10 +64,6 @@ PageModel::deletePage(PageBase *page) {
   m_pages.remove(pageId);
   delete page;
 
-  auto idx = m_topLevelPages.indexOf(page);
-  if (-1 != idx)
-    m_topLevelPages.removeAt(idx);
-
   return true;
 }
 
@@ -83,23 +77,36 @@ PageModel::pages()
   return pages;
 }
 
-QList<PageBase *> const &
+QList<PageBase *>
 PageModel::topLevelPages()
   const {
-  return m_topLevelPages;
+  auto rootItem = invisibleRootItem();
+
+  QList<PageBase *> pages;
+  pages.reserve(rootItem->rowCount());
+
+  for (int row = 0, numRows = rootItem->rowCount(); row < numRows; ++row) {
+    auto topLevelItem = rootItem->child(row);
+    auto pageId       = topLevelItem->data(Util::HeaderEditorPageIdRole).value<int>();
+
+    pages << m_pages[pageId];
+  }
+
+  return pages;
 }
 
 QList<PageBase *>
 PageModel::allExpandablePages()
   const {
-  auto pages = m_topLevelPages;
+  auto allTopLevelPages = topLevelPages();
+  auto expandablePages  = allTopLevelPages;
 
-  for (auto const &page : m_topLevelPages)
+  for (auto const &page : allTopLevelPages)
     for (auto const &subPage : page->m_children)
       if (dynamic_cast<TopLevelPage *>(subPage))
-        pages << static_cast<TopLevelPage *>(subPage);
+        expandablePages << static_cast<TopLevelPage *>(subPage);
 
-  return pages;
+  return expandablePages;
 }
 
 void
@@ -110,7 +117,6 @@ PageModel::reset() {
     delete page;
 
   m_pages.clear();
-  m_topLevelPages.clear();
 
   removeRows(0, rowCount());
 
@@ -120,7 +126,7 @@ PageModel::reset() {
 QModelIndex
 PageModel::validate()
   const {
-  for (auto page : m_topLevelPages) {
+  for (auto page : topLevelPages()) {
     auto result = page->validate();
     if (result.isValid())
       return result;
diff --git a/src/mkvtoolnix-gui/header_editor/page_model.h b/src/mkvtoolnix-gui/header_editor/page_model.h
index d2f552a81..2fcf0a49f 100644
--- a/src/mkvtoolnix-gui/header_editor/page_model.h
+++ b/src/mkvtoolnix-gui/header_editor/page_model.h
@@ -16,7 +16,6 @@ class PageModel: public QStandardItemModel {
   Q_OBJECT
 protected:
   QHash<int, PageBase *> m_pages;
-  QList<PageBase *> m_topLevelPages;
   int m_pageId{};
   QModelIndex m_lastSelectedIdx;
 
@@ -30,7 +29,7 @@ public:
   bool deletePage(PageBase *page);
 
   QList<PageBase *> pages() const;
-  QList<PageBase *> const &topLevelPages() const;
+  QList<PageBase *> topLevelPages() const;
   QList<PageBase *> allExpandablePages() const;
 
   void reset();
diff --git a/src/mkvtoolnix-gui/header_editor/tab.cpp b/src/mkvtoolnix-gui/header_editor/tab.cpp
index a52afd516..90df34332 100644
--- a/src/mkvtoolnix-gui/header_editor/tab.cpp
+++ b/src/mkvtoolnix-gui/header_editor/tab.cpp
@@ -407,8 +407,7 @@ Tab::title()
 
 PageBase *
 Tab::hasBeenModified() {
-  auto &pages = m_model->topLevelPages();
-  for (auto const &page : pages) {
+  for (auto const &page : m_model->topLevelPages()) {
     auto modifiedPage = page->hasBeenModified();
     if (modifiedPage)
       return modifiedPage;
@@ -476,8 +475,7 @@ Tab::determineTrackUIDChanges() {
 
 void
 Tab::doModifications() {
-  auto &pages = m_model->topLevelPages();
-  for (auto const &page : pages)
+  for (auto const &page : m_model->topLevelPages())
     page->doModifications();
 
   pruneEmptyMastersForAllTracks();