From 13419f434fb841964e71a1095d2f59002eabbcfd Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?L=C3=A9a=20Saviot?= <lea.saviot@numworks.com>
Date: Wed, 19 Dec 2018 15:16:00 +0100
Subject: [PATCH] [apps/shared] Memoize in
 StorageFuncListCtrl::indexFromCumulatedHeight

---
 ...storage_expression_model_list_controller.h |  6 ++-
 .../storage_function_list_controller.cpp      | 37 +++++++++++++++++++
 .../shared/storage_function_list_controller.h |  1 +
 3 files changed, 42 insertions(+), 2 deletions(-)

diff --git a/apps/shared/storage_expression_model_list_controller.h b/apps/shared/storage_expression_model_list_controller.h
index 21116c000..063bcbf73 100644
--- a/apps/shared/storage_expression_model_list_controller.h
+++ b/apps/shared/storage_expression_model_list_controller.h
@@ -35,14 +35,16 @@ protected:
   virtual StorageExpressionModelStore * modelStore() = 0;
   virtual InputViewController * inputController() = 0;
   EvenOddMessageTextCell m_addNewModel;
-private:
+protected:
   // Memoization
   static constexpr int k_memoizedCellHeightsCount = 5;
+private:
+  // Memoization
+  static constexpr int k_resetedMemoizedValue = -1;
   static_assert(StorageExpressionModelListController::k_memoizedCellHeightsCount == 5, "Wrong array size in initialization of StorageExpressionModelListController::m_memoizedCellHeight.");
   static_assert(StorageExpressionModelListController::k_memoizedCellHeightsCount % 2 == 1, "StorageExpressionModelListController::k_memoizedCellHeightsCount should be odd to be able to compute the middle element.");
   void resetMemoization();
   virtual KDCoordinate notMemoizedCumulatedHeightFromIndex(int j) = 0;
-  static constexpr int k_resetedMemoizedValue = -1;
   KDCoordinate m_memoizedCellHeight[k_memoizedCellHeightsCount];
   KDCoordinate m_cumulatedHeightForSelectedIndex;
 };
diff --git a/apps/shared/storage_function_list_controller.cpp b/apps/shared/storage_function_list_controller.cpp
index a555a4c76..d15d10f8f 100644
--- a/apps/shared/storage_function_list_controller.cpp
+++ b/apps/shared/storage_function_list_controller.cpp
@@ -4,6 +4,7 @@
 namespace Shared {
 
 static inline int max(int x, int y) { return x > y ? x : y; }
+static inline int min(int x, int y) { return x < y ? x : y; }
 
 StorageFunctionListController::StorageFunctionListController(Responder * parentResponder, ButtonRowController * header, ButtonRowController * footer, I18n::Message text) :
   StorageExpressionModelListController(parentResponder, text),
@@ -81,6 +82,42 @@ int StorageFunctionListController::indexFromCumulatedWidth(KDCoordinate offsetX)
   }
 }
 
+int StorageFunctionListController::indexFromCumulatedHeight(KDCoordinate offsetY) {
+  if (offsetY == 0) {
+    return 0;
+  }
+
+  /* We use memoization to speed up this method: if offsetY is "around" the
+   * memoized cumulatedHeightForIndex, we can compute its value easily by
+   * adding/substracting memoized row heights. */
+
+  int currentSelectedRow = selectedRow();
+  int rowsCount = numberOfRows();
+  if (rowsCount <= 1 || currentSelectedRow < 1) {
+    return TableViewDataSource::indexFromCumulatedHeight(offsetY);
+  }
+
+  KDCoordinate currentCumulatedHeight = cumulatedHeightFromIndex(currentSelectedRow);
+  if (offsetY > currentCumulatedHeight) {
+    int iMax = min(k_memoizedCellHeightsCount/2 + 1, rowsCount - currentSelectedRow);
+    for (int i = 0; i < iMax; i++) {
+      currentCumulatedHeight+= rowHeight(currentSelectedRow + i);
+      if (offsetY <= currentCumulatedHeight) {
+        return currentSelectedRow + i;
+      }
+    }
+  } else {
+    int iMax = min(k_memoizedCellHeightsCount/2, currentSelectedRow);
+    for (int i = 1; i <= iMax; i++) {
+      currentCumulatedHeight-= rowHeight(currentSelectedRow-i);
+      if (offsetY > currentCumulatedHeight) {
+        return currentSelectedRow - i;
+      }
+    }
+  }
+  return TableViewDataSource::indexFromCumulatedHeight(offsetY);
+}
+
 int StorageFunctionListController::typeAtLocation(int i, int j) {
   if (isAddEmptyRow(j)){
     return i + 2;
diff --git a/apps/shared/storage_function_list_controller.h b/apps/shared/storage_function_list_controller.h
index c47644ad1..c8e21fb30 100644
--- a/apps/shared/storage_function_list_controller.h
+++ b/apps/shared/storage_function_list_controller.h
@@ -26,6 +26,7 @@ public:
   KDCoordinate cumulatedWidthFromIndex(int i) override;
   KDCoordinate cumulatedHeightFromIndex(int j) override;
   int indexFromCumulatedWidth(KDCoordinate offsetX) override;
+  int indexFromCumulatedHeight(KDCoordinate offsetY) override;
   int typeAtLocation(int i, int j) override;
   HighlightCell * reusableCell(int index, int type) override;
   int reusableCellCount(int type) override;