FontEditor: Add undo and redo commands

Userland/Applications/FontEditor/UndoGlyph.h

@@ -0,0 +1,65 @@
+/*
+ * Copyright (c) 2021, the SerenityOS developers
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <LibGUI/Command.h>
+#include <LibGUI/UndoStack.h>
+#include <LibGfx/BitmapFont.h>
+
+class UndoGlyph : public RefCounted<UndoGlyph> {
+public:
+    explicit UndoGlyph(const size_t code_point, const Gfx::BitmapFont& font)
+        : m_code_point(code_point)
+        , m_font(font)
+    {
+    }
+    RefPtr<UndoGlyph> save_state() const
+    {
+        auto state = adopt(*new UndoGlyph(m_code_point, *m_font));
+        auto glyph = font().glyph(m_code_point).glyph_bitmap();
+        for (int x = 0; x < glyph.width(); x++)
+            for (int y = 0; y < glyph.height(); y++)
+                state->m_bits[x][y] = glyph.bit_at(x, y);
+        return state;
+    }
+    void restore_state(const UndoGlyph& state) const
+    {
+        auto bitmap = font().glyph(state.m_code_point).glyph_bitmap();
+        for (int x = 0; x < bitmap.width(); x++)
+            for (int y = 0; y < bitmap.height(); y++)
+                bitmap.set_bit_at(x, y, state.m_bits[x][y]);
+    }
+    void set_code_point(size_t point) { m_code_point = point; }
+    void set_font(Gfx::BitmapFont& font) { m_font = font; }
+    const Gfx::BitmapFont& font() const { return *m_font; }
+
+private:
+    size_t m_code_point;
+    RefPtr<Gfx::BitmapFont> m_font;
+    u8 m_bits[32][36] = {};
+};
+
+class GlyphUndoCommand : public GUI::Command {
+public:
+    GlyphUndoCommand(UndoGlyph& glyph)
+        : m_state(glyph.save_state())
+        , m_undo_glyph(glyph)
+    {
+    }
+    virtual void undo() override
+    {
+        m_undo_glyph.restore_state(*m_state);
+    }
+    virtual void redo() override
+    {
+        undo();
+    }
+
+private:
+    RefPtr<UndoGlyph> m_state;
+    UndoGlyph& m_undo_glyph;
+};