Spreadsheet: Implement infinite-scroll for rows

Every time the scrollbar reaches the end, we append 100 more rows
(seamlessly!).
As a result of defaulting to 100 rows, we can also save with the
smallest number of rows required.
This partially deals with #4170.

5 files changed, 69 insertions, 11 deletions

diff --git a/Applications/Spreadsheet/Spreadsheet.cpp b/Applications/Spreadsheet/Spreadsheet.cpp
index 6f419bcf16..006ce2eec5 100644
--- a/Applications/Spreadsheet/Spreadsheet.cpp
+++ b/Applications/Spreadsheet/Spreadsheet.cpp
@@ -49,10 +49,10 @@ Sheet::Sheet(const StringView& name, Workbook& workbook)
 {
     m_name = name;
 
-    for (size_t i = 0; i < 20; ++i)
+    for (size_t i = 0; i < default_row_count; ++i)
         add_row();
 
-    for (size_t i = 0; i < 16; ++i)
+    for (size_t i = 0; i < default_column_count; ++i)
         add_column();
 }
 
@@ -318,7 +318,7 @@ void Sheet::copy_cells(Vector<Position> from, Vector<Position> to, Optional<Posi
 RefPtr<Sheet> Sheet::from_json(const JsonObject& object, Workbook& workbook)
 {
     auto sheet = adopt(*new Sheet(workbook));
-    auto rows = object.get("rows").to_u32(20);
+    auto rows = object.get("rows").to_u32(default_row_count);
     auto columns = object.get("columns");
     if (!columns.is_array())
         return nullptr;
@@ -326,7 +326,7 @@ RefPtr<Sheet> Sheet::from_json(const JsonObject& object, Workbook& workbook)
 
     sheet->set_name(name);
 
-    for (size_t i = 0; i < rows; ++i)
+    for (size_t i = 0; i < max(rows, (unsigned)Sheet::default_row_count); ++i)
         sheet->add_row();
 
     // FIXME: Better error checking.
@@ -421,6 +421,19 @@ RefPtr<Sheet> Sheet::from_json(const JsonObject& object, Workbook& workbook)
     return sheet;
 }
 
+Position Sheet::written_data_bounds() const
+{
+    Position bound;
+    for (auto& entry : m_cells) {
+        if (entry.key.row > bound.row)
+            bound.row = entry.key.row;
+        if (entry.key.column > bound.column)
+            bound.column = entry.key.column;
+    }
+
+    return bound;
+}
+
 JsonObject Sheet::to_json() const
 {
     JsonObject object;
@@ -433,12 +446,14 @@ JsonObject Sheet::to_json() const
             obj.set("background_color", format.background_color.value().to_string());
     };
 
+    auto bottom_right = written_data_bounds();
+
     auto columns = JsonArray();
     for (auto& column : m_columns)
         columns.append(column);
     object.set("columns", move(columns));
 
-    object.set("rows", m_rows);
+    object.set("rows", bottom_right.row);
 
     JsonObject cells;
     for (auto& it : m_cells) {
@@ -502,10 +517,12 @@ Vector<Vector<String>> Sheet::to_xsv() const
 {
     Vector<Vector<String>> data;
 
+    auto bottom_right = written_data_bounds();
+
     // First row = headers.
     data.append(m_columns);
 
-    for (size_t i = 0; i < m_rows; ++i) {
+    for (size_t i = 0; i <= bottom_right.row; ++i) {
         Vector<String> row;
         row.resize(m_columns.size());
         for (size_t j = 0; j < m_columns.size(); ++j) {
@@ -527,7 +544,7 @@ RefPtr<Sheet> Sheet::from_xsv(const Reader::XSV& xsv, Workbook& workbook)
 
     auto sheet = adopt(*new Sheet(workbook));
     sheet->m_columns = cols;
-    for (size_t i = 0; i < rows; ++i)
+    for (size_t i = 0; i < max(rows, Sheet::default_row_count); ++i)
         sheet->add_row();
 
     for (auto row : xsv) {
diff --git a/Applications/Spreadsheet/Spreadsheet.h b/Applications/Spreadsheet/Spreadsheet.h
index f9a2c5af2b..edc2c68d60 100644
--- a/Applications/Spreadsheet/Spreadsheet.h
+++ b/Applications/Spreadsheet/Spreadsheet.h
@@ -46,6 +46,9 @@ class Sheet : public Core::Object {
     C_OBJECT(Sheet);
 
 public:
+    constexpr static size_t default_row_count = 100;
+    constexpr static size_t default_column_count = 26;
+
     ~Sheet();
 
     static Optional<Position> parse_cell_name(const StringView&);
@@ -124,6 +127,9 @@ public:
 
     void copy_cells(Vector<Position> from, Vector<Position> to, Optional<Position> resolve_relative_to = {});
 
+    /// Gives the bottom-right corner of the smallest bounding box containing all the written data.
+    Position written_data_bounds() const;
+
 private:
     explicit Sheet(Workbook&);
     explicit Sheet(const StringView& name, Workbook&);
diff --git a/Applications/Spreadsheet/SpreadsheetModel.cpp b/Applications/Spreadsheet/SpreadsheetModel.cpp
index 58ac126095..5cc55acf08 100644
--- a/Applications/Spreadsheet/SpreadsheetModel.cpp
+++ b/Applications/Spreadsheet/SpreadsheetModel.cpp
@@ -170,6 +170,7 @@ void SheetModel::set_data(const GUI::ModelIndex& index, const GUI::Variant& valu
 void SheetModel::update()
 {
     m_sheet->update();
+    did_update(UpdateFlag::DontInvalidateIndexes);
 }
 
 }
diff --git a/Applications/Spreadsheet/SpreadsheetView.cpp b/Applications/Spreadsheet/SpreadsheetView.cpp
index dfb718182d..7361258cc0 100644
--- a/Applications/Spreadsheet/SpreadsheetView.cpp
+++ b/Applications/Spreadsheet/SpreadsheetView.cpp
@@ -35,6 +35,7 @@
 #include <LibGUI/Menu.h>
 #include <LibGUI/ModelEditingDelegate.h>
 #include <LibGUI/Painter.h>
+#include <LibGUI/ScrollBar.h>
 #include <LibGUI/TableView.h>
 #include <LibGfx/Palette.h>
 
@@ -57,17 +58,40 @@ void SpreadsheetView::EditingDelegate::set_value(const GUI::Variant& value)
     StringModelEditingDelegate::set_value("");
 }
 
+void InfinitelyScrollableTableView::did_scroll()
+{
+    TableView::did_scroll();
+    auto& vscrollbar = vertical_scrollbar();
+    if (vscrollbar.is_visible() && vscrollbar.value() == vscrollbar.max()) {
+        if (on_reaching_vertical_end)
+            on_reaching_vertical_end();
+    }
+}
+
+void SpreadsheetView::update_with_model()
+{
+    m_table_view->model()->update();
+    m_table_view->update();
+}
+
 SpreadsheetView::SpreadsheetView(Sheet& sheet)
     : m_sheet(sheet)
 {
     set_layout<GUI::VerticalBoxLayout>().set_margins({ 2, 2, 2, 2 });
-    m_table_view = add<GUI::TableView>();
+    m_table_view = add<InfinitelyScrollableTableView>();
     m_table_view->set_grid_style(GUI::TableView::GridStyle::Both);
     m_table_view->set_cursor_style(GUI::TableView::CursorStyle::Item);
     m_table_view->set_edit_triggers(GUI::AbstractView::EditTrigger::EditKeyPressed | GUI::AbstractView::AnyKeyPressed | GUI::AbstractView::DoubleClicked);
     m_table_view->set_tab_key_navigation_enabled(true);
     m_table_view->row_header().set_visible(true);
     m_table_view->set_model(SheetModel::create(*m_sheet));
+    m_table_view->on_reaching_vertical_end = [&]() {
+        for (size_t i = 0; i < 100; ++i) {
+            auto index = m_sheet->add_row();
+            m_table_view->set_column_painting_delegate(index, make<TableCellPainter>(*m_table_view));
+        };
+        update_with_model();
+    };
 
     set_focus_proxy(m_table_view);
 
@@ -107,8 +131,7 @@ SpreadsheetView::SpreadsheetView(Sheet& sheet)
 
         if (on_selection_changed) {
             on_selection_changed(move(selected_positions));
-            m_table_view->model()->update();
-            m_table_view->update();
+            update_with_model();
         };
     };
 
diff --git a/Applications/Spreadsheet/SpreadsheetView.h b/Applications/Spreadsheet/SpreadsheetView.h
index 93a3c83acc..09bcb59251 100644
--- a/Applications/Spreadsheet/SpreadsheetView.h
+++ b/Applications/Spreadsheet/SpreadsheetView.h
@@ -79,6 +79,15 @@ private:
     }
 };
 
+class InfinitelyScrollableTableView : public GUI::TableView {
+    C_OBJECT(InfinitelyScrollableTableView)
+public:
+    Function<void()> on_reaching_vertical_end;
+
+private:
+    virtual void did_scroll() override;
+};
+
 class SpreadsheetView final : public GUI::Widget {
     C_OBJECT(SpreadsheetView);
 
@@ -100,6 +109,8 @@ private:
     virtual void hide_event(GUI::HideEvent&) override;
     virtual void show_event(GUI::ShowEvent&) override;
 
+    void update_with_model();
+
     SpreadsheetView(Sheet&);
 
     class EditingDelegate final : public GUI::StringModelEditingDelegate {
@@ -143,7 +154,7 @@ private:
     };
 
     NonnullRefPtr<Sheet> m_sheet;
-    RefPtr<GUI::TableView> m_table_view;
+    RefPtr<InfinitelyScrollableTableView> m_table_view;
     RefPtr<GUI::Menu> m_cell_range_context_menu;
 };