Spreadsheet: Highlight the source causing an exception in red

This commit makes the cell editor highlight the likely source of the
exception in red.

Applications/Spreadsheet/CellSyntaxHighlighter.cpp

@@ -53,6 +53,19 @@ void CellSyntaxHighlighter::rehighlight(Gfx::Palette palette)
         false,
         false,
         nullptr);
+
+    if (m_cell && m_cell->exception()) {
+        auto range = m_cell->exception()->source_ranges().first();
+        GUI::TextRange text_range { { range.start.line - 1, range.start.column }, { range.end.line - 1, range.end.column - 1 } };
+        m_editor->document().spans().prepend({ text_range,
+            Color::Black,
+            Color::Red,
+            false,
+            false,
+            false,
+            nullptr });
+    }
+    m_editor->update();
 }
 
 CellSyntaxHighlighter::~CellSyntaxHighlighter()

Applications/Spreadsheet/CellSyntaxHighlighter.h

@@ -26,6 +26,7 @@
 
 #pragma once
 
+#include "Cell.h"
 #include <LibGUI/JSSyntaxHighlighter.h>
 #include <LibGUI/SyntaxHighlighter.h>
 
@@ -37,6 +38,10 @@ public:
     virtual ~CellSyntaxHighlighter() override;
 
     virtual void rehighlight(Gfx::Palette) override;
+    void set_cell(const Cell* cell) { m_cell = cell; }
+
+private:
+    const Cell* m_cell { nullptr };
 };
 
 }

Applications/Spreadsheet/SpreadsheetWidget.cpp

@@ -142,6 +142,7 @@ void SpreadsheetWidget::setup_tabs(NonnullRefPtrVector<Sheet> new_sheets)
                     update();
                 };
                 m_cell_value_editor->set_enabled(true);
+                static_cast<CellSyntaxHighlighter*>(const_cast<GUI::SyntaxHighlighter*>(m_cell_value_editor->syntax_highlighter()))->set_cell(&cell);
                 return;
             }
 
@@ -169,9 +170,11 @@ void SpreadsheetWidget::setup_tabs(NonnullRefPtrVector<Sheet> new_sheets)
                 }
             };
             m_cell_value_editor->set_enabled(true);
+            static_cast<CellSyntaxHighlighter*>(const_cast<GUI::SyntaxHighlighter*>(m_cell_value_editor->syntax_highlighter()))->set_cell(cells.first());
         };
         m_selected_view->on_selection_dropped = [&]() {
             m_cell_value_editor->set_enabled(false);
+            static_cast<CellSyntaxHighlighter*>(const_cast<GUI::SyntaxHighlighter*>(m_cell_value_editor->syntax_highlighter()))->set_cell(nullptr);
             m_cell_value_editor->set_text("");
             m_current_cell_label->set_enabled(false);
             m_current_cell_label->set_text("");