LibDraw: Introduce (formerly known as SharedGraphics.)

Instead of LibGUI and WindowServer building their own copies of the drawing
and graphics code, let's it in a separate LibDraw library.

This avoids building the code twice, and will encourage better separation
of concerns. :^)

Libraries/LibDraw/Painter.h

@@ -0,0 +1,97 @@
+#pragma once
+
+#include "Color.h"
+#include "Point.h"
+#include "Rect.h"
+#include "Size.h"
+#include <AK/AKString.h>
+#include <LibDraw/TextAlignment.h>
+#include <LibDraw/TextElision.h>
+
+class CharacterBitmap;
+class GlyphBitmap;
+class GraphicsBitmap;
+class Font;
+
+class Painter {
+public:
+    explicit Painter(GraphicsBitmap&);
+    ~Painter();
+    void fill_rect(const Rect&, Color);
+    void fill_rect_with_gradient(const Rect&, Color gradient_start, Color gradient_end);
+    void draw_rect(const Rect&, Color, bool rough = false);
+    void draw_bitmap(const Point&, const CharacterBitmap&, Color = Color());
+    void draw_bitmap(const Point&, const GlyphBitmap&, Color = Color());
+    void set_pixel(const Point&, Color);
+    void draw_line(const Point&, const Point&, Color, int thickness = 1);
+    void draw_scaled_bitmap(const Rect& dst_rect, const GraphicsBitmap&, const Rect& src_rect);
+    void blit(const Point&, const GraphicsBitmap&, const Rect& src_rect, float opacity = 1.0f);
+    void blit_dimmed(const Point&, const GraphicsBitmap&, const Rect& src_rect);
+    void blit_tiled(const Point&, const GraphicsBitmap&, const Rect& src_rect);
+    void blit_offset(const Point&, const GraphicsBitmap&, const Rect& src_rect, const Point&);
+    void blit_scaled(const Rect&, const GraphicsBitmap&, const Rect&, float, float);
+    void draw_text(const Rect&, const StringView&, const Font&, TextAlignment = TextAlignment::TopLeft, Color = Color::Black, TextElision = TextElision::None);
+    void draw_text(const Rect&, const StringView&, TextAlignment = TextAlignment::TopLeft, Color = Color::Black, TextElision = TextElision::None);
+    void draw_glyph(const Point&, char, Color);
+    void draw_glyph(const Point&, char, const Font&, Color);
+
+    const Font& font() const { return *state().font; }
+    void set_font(const Font& font) { state().font = &font; }
+
+    enum class DrawOp {
+        Copy,
+        Xor
+    };
+    void set_draw_op(DrawOp op) { state().draw_op = op; }
+    DrawOp draw_op() const { return state().draw_op; }
+
+    void add_clip_rect(const Rect& rect);
+    void clear_clip_rect();
+    Rect clip_rect() const { return state().clip_rect; }
+
+    void translate(int dx, int dy) { state().translation.move_by(dx, dy); }
+    void translate(const Point& delta) { state().translation.move_by(delta); }
+
+    Point translation() const { return state().translation; }
+
+    GraphicsBitmap* target() { return m_target.ptr(); }
+
+    void save() { m_state_stack.append(m_state_stack.last()); }
+    void restore()
+    {
+        ASSERT(m_state_stack.size() > 1);
+        m_state_stack.take_last();
+    }
+
+protected:
+    void set_pixel_with_draw_op(u32& pixel, const Color&);
+    void fill_rect_with_draw_op(const Rect&, Color);
+    void blit_with_alpha(const Point&, const GraphicsBitmap&, const Rect& src_rect);
+    void blit_with_opacity(const Point&, const GraphicsBitmap&, const Rect& src_rect, float opacity);
+    void draw_pixel(const Point&, Color, int thickness = 1);
+
+    void draw_text_line(const Rect&, const StringView&, const Font&, TextAlignment, Color, TextElision);
+
+    struct State {
+        const Font* font;
+        Point translation;
+        Rect clip_rect;
+        DrawOp draw_op;
+    };
+
+    State& state() { return m_state_stack.last(); }
+    const State& state() const { return m_state_stack.last(); }
+
+    Rect m_clip_origin;
+    NonnullRefPtr<GraphicsBitmap> m_target;
+    Vector<State, 4> m_state_stack;
+};
+
+class PainterStateSaver {
+public:
+    explicit PainterStateSaver(Painter&);
+    ~PainterStateSaver();
+
+private:
+    Painter& m_painter;
+};