Start refactoring graphics system to have per-window backing stores.

It was fun for everyone to share a single framebuffer but it was also
kinda really awful. Let's move towards having a "GraphicsBitmap" as the
backing store for each Window.

This is going to need a lot of refactoring so let's get started.

AK/WeakPtr.h

@@ -35,7 +35,7 @@ public:
     WeakLink<T>* leakLink() { return m_link.leakRef(); }
 
 private:
-    WeakPtr(RetainPtr<WeakLink<T>>&& link) : m_link(std::move(link)) { }
+    WeakPtr(RetainPtr<WeakLink<T>>&& link) : m_link(move(link)) { }
 
     RetainPtr<WeakLink<T>> m_link;
 };

Widgets/AbstractScreen.h

@@ -2,6 +2,7 @@
 
 #include "Object.h"
 #include "Rect.h"
+#include "Size.h"
 
 class AbstractScreen : public Object {
 public:
@@ -12,6 +13,7 @@ public:
 
     static AbstractScreen& the();
 
+    Size size() const { return { width(), height() }; }
     Rect rect() const { return { 0, 0, width(), height() }; }
 
 protected:

Widgets/Button.h

@@ -2,6 +2,7 @@
 
 #include "Widget.h"
 #include <AK/AKString.h>
+#include <AK/Function.h>
 
 class Button final : public Widget {
 public:
@@ -11,7 +12,7 @@ public:
     String caption() const { return m_caption; }
     void setCaption(String&&);
 
-    std::function<void(Button&)> onClick;
+    Function<void(Button&)> onClick;
 
 private:
     virtual void paintEvent(PaintEvent&) override;

Widgets/FrameBufferSDL.cpp

@@ -1,4 +1,5 @@
 #include "FrameBufferSDL.h"
+#include "GraphicsBitmap.h"
 #include <AK/Assertions.h>
 
 FrameBufferSDL* s_the = nullptr;
@@ -57,3 +58,27 @@ void FrameBufferSDL::initializeSDL()
     SDL_UpdateWindowSurface(m_window);
 }
 
+dword* FrameBufferSDL::scanline(int y)
+{
+    return (dword*)(((byte*)m_surface->pixels) + (y * m_surface->pitch));
+}
+
+void FrameBufferSDL::blit(const Point& position, GraphicsBitmap& bitmap)
+{
+    Rect dst_rect(position, bitmap.size());
+
+    printf("blit at %d,%d %dx%d\n", dst_rect.x(), dst_rect.y(), dst_rect.width(), dst_rect.height());
+    dst_rect.intersect(rect());
+    printf("    -> intersection %d,%d %dx%d\n", dst_rect.x(), dst_rect.y(), dst_rect.width(), dst_rect.height());
+
+    for (int y = 0; y < dst_rect.height(); ++y) {
+        auto* framebuffer_scanline = scanline(position.y() + y);
+        auto* bitmap_scanline = bitmap.scanline(y);
+        memcpy(framebuffer_scanline + position.x(), bitmap_scanline, dst_rect.width() * 4);
+    }
+}
+
+void FrameBufferSDL::flush()
+{
+    SDL_UpdateWindowSurface(m_window);
+}

Widgets/FrameBufferSDL.h

@@ -3,6 +3,8 @@
 #include "AbstractScreen.h"
 #include <SDL.h>
 
+class GraphicsBitmap;
+
 class FrameBufferSDL final : public AbstractScreen {
 public:
     FrameBufferSDL(unsigned width, unsigned height);
@@ -15,6 +17,11 @@ public:
 
     static FrameBufferSDL& the();
 
+    dword* scanline(int y);
+
+    void blit(const Point&, GraphicsBitmap&);
+    void flush();
+
 private:
     void initializeSDL();
 

Widgets/GraphicsBitmap.cpp

@@ -0,0 +1,25 @@
+#include "GraphicsBitmap.h"
+#include <AK/kmalloc.h>
+
+RetainPtr<GraphicsBitmap> GraphicsBitmap::create(const Size& size)
+{
+    return adopt(*new GraphicsBitmap(size));
+}
+
+GraphicsBitmap::GraphicsBitmap(const Size& size)
+    : m_size(size)
+{
+    m_data = (byte*)kmalloc(size.width() * size.height() * 4);
+}
+
+GraphicsBitmap::~GraphicsBitmap()
+{
+    kfree(m_data);
+}
+
+dword* GraphicsBitmap::scanline(int y)
+{
+    unsigned pitch = m_size.width() * 4;
+    return (dword*)(((byte*)m_data) + (y * pitch));
+}
+

Widgets/GraphicsBitmap.h

@@ -0,0 +1,23 @@
+#pragma once
+
+#include "Size.h"
+#include <AK/Retainable.h>
+#include <AK/RetainPtr.h>
+
+class GraphicsBitmap : public Retainable<GraphicsBitmap> {
+public:
+    static RetainPtr<GraphicsBitmap> create(const Size&);
+    ~GraphicsBitmap();
+
+    dword* scanline(int y);
+
+    Size size() const { return m_size; }
+    int width() const { return m_size.width(); }
+    int height() const { return m_size.height(); }
+
+private:
+    explicit GraphicsBitmap(const Size&);
+
+    Size m_size;
+    byte* m_data { nullptr };
+};

Widgets/Makefile

@@ -11,6 +11,7 @@ VFS_OBJS = \
     FrameBufferSDL.o \
     EventLoop.o \
     EventLoopSDL.o \
+    Rect.o \
     Object.o \
     Widget.o \
     RootWidget.o \
@@ -28,6 +29,7 @@ VFS_OBJS = \
     ListBox.o \
     TextBox.o \
     MsgBox.o \
+    GraphicsBitmap.o \
     test.o
 
 OBJS = $(AK_OBJS) $(VFS_OBJS)

Widgets/Painter.cpp

@@ -11,28 +11,18 @@ Painter::Painter(Widget& widget)
     : m_widget(widget)
     , m_font(&widget.font())
 {
-    if (auto* window = widget.window()) {
-        m_translation = window->position();
+    m_target = widget.backing();
+    ASSERT(m_target);
+    m_window = widget.window();
     m_translation.moveBy(widget.relativePosition());
-    } else {
-        m_translation.setX(widget.x());
-        m_translation.setY(widget.y());
-    }
-
     m_clipRect.setWidth(AbstractScreen::the().width());
     m_clipRect.setHeight(AbstractScreen::the().height());
 }
 
 Painter::~Painter()
 {
-    int rc = SDL_UpdateWindowSurface(FrameBufferSDL::the().window());
-    ASSERT(rc == 0);
-}
-
-static dword* scanline(int y)
-{
-    auto& surface = *FrameBufferSDL::the().surface();
-    return (dword*)(((byte*)surface.pixels) + (y * surface.pitch));
+    if (m_window)
+        m_window->did_paint();
 }
 
 void Painter::fillRect(const Rect& rect, Color color)
@@ -41,7 +31,7 @@ void Painter::fillRect(const Rect& rect, Color color)
     r.moveBy(m_translation);
 
     for (int y = max(r.top(), m_clipRect.top()); y < min(r.bottom(), m_clipRect.bottom()); ++y) {
-        dword* bits = scanline(y);
+        dword* bits = m_target->scanline(y);
         for (int x = max(r.left(), m_clipRect.left()); x < min(r.right(), m_clipRect.right()); ++x) {
             bits[x] = color.value();
         }
@@ -54,7 +44,7 @@ void Painter::drawRect(const Rect& rect, Color color)
     r.moveBy(m_translation);
 
     for (int y = max(r.top(), m_clipRect.top()); y < min(r.bottom(), m_clipRect.bottom()); ++y) {
-        dword* bits = scanline(y);
+        dword* bits = m_target->scanline(y);
         if (y == r.top() || y == (r.bottom() - 1)) {
             for (int x = max(r.left(), m_clipRect.left()); x < min(r.right(), m_clipRect.right()); ++x) {
                 bits[x] = color.value();
@@ -74,7 +64,7 @@ void Painter::xorRect(const Rect& rect, Color color)
     r.moveBy(m_translation);
 
     for (int y = max(r.top(), m_clipRect.top()); y < min(r.bottom(), m_clipRect.bottom()); ++y) {
-        dword* bits = scanline(y);
+        dword* bits = m_target->scanline(y);
         if (y == r.top() || y == (r.bottom() - 1)) {
             for (int x = max(r.left(), m_clipRect.left()); x < min(r.right(), m_clipRect.right()); ++x) {
                 bits[x] ^= color.value();
@@ -96,7 +86,7 @@ void Painter::drawBitmap(const Point& p, const CBitmap& bitmap, Color color)
         int y = point.y() + row;
         if (y < m_clipRect.top() || y >= m_clipRect.bottom())
             break;
-        dword* bits = scanline(y);
+        dword* bits = m_target->scanline(y);
         for (unsigned j = 0; j < bitmap.width(); ++j) {
             int x = point.x() + j;
             if (x < m_clipRect.left() || x >= m_clipRect.right())
@@ -143,7 +133,7 @@ void Painter::drawPixel(const Point& p, Color color)
     point.moveBy(m_translation);
     if (!m_clipRect.contains(point))
         return;
-    scanline(point.y())[point.x()] = color.value();
+    m_target->scanline(point.y())[point.x()] = color.value();
 }
 
 void Painter::drawLine(const Point& p1, const Point& p2, Color color)
@@ -162,7 +152,7 @@ void Painter::drawLine(const Point& p1, const Point& p2, Color color)
         if (point1.y() > point2.y())
             std::swap(point1, point2);
         for (int y = max(point1.y(), m_clipRect.top()); y <= min(point2.y(), m_clipRect.bottom()); ++y)
-            scanline(y)[x] = color.value();
+            m_target->scanline(y)[x] = color.value();
         return;
     }
 
@@ -176,7 +166,7 @@ void Painter::drawLine(const Point& p1, const Point& p2, Color color)
             return;
         if (point1.x() > point2.x())
             std::swap(point1, point2);
-        auto* pixels = scanline(point1.y());
+        auto* pixels = m_target->scanline(point1.y());
         for (int x = max(point1.x(), m_clipRect.left()); x <= min(point2.x(), m_clipRect.right()); ++x)
             pixels[x] = color.value();
         return;
@@ -193,7 +183,7 @@ void Painter::drawLine(const Point& p1, const Point& p2, Color color)
 
     int y = point1.y();
     for (int x = point1.x(); x <= point2.x(); ++x) {
-        scanline(y)[x] = color.value();
+        m_target->scanline(y)[x] = color.value();
         error += deltaError;
         if (error >= 0.5) {
             y = (double)y + yStep;

Widgets/Painter.h

@@ -7,8 +7,10 @@
 #include <AK/AKString.h>
 
 class CBitmap;
+class GraphicsBitmap;
 class Font;
 class Widget;
+class Window;
 
 class Painter {
 public:
@@ -32,6 +34,7 @@ private:
     Widget& m_widget;
     const Font* m_font;
     Point m_translation;
-
     Rect m_clipRect;
+    RetainPtr<GraphicsBitmap> m_target;
+    Window* m_window { nullptr };
 };

Widgets/Rect.cpp

@@ -0,0 +1,21 @@
+#include "Rect.h"
+#include <AK/StdLibExtras.h>
+
+void Rect::intersect(const Rect& other)
+{
+    int l = max(left(), other.left());
+    int r = min(right(), other.right());
+    int t = max(top(), other.top());
+    int b = min(bottom(), other.bottom());
+
+    if (l >= r || t >= b) {
+        m_location = { };
+        m_size = { };
+        return;
+    }
+
+    m_location.setX(l);
+    m_location.setY(t);
+    m_size.setWidth(r - l);
+    m_size.setHeight(b - t);
+}

Widgets/Rect.h

@@ -1,14 +1,19 @@
 #pragma once
 
 #include "Point.h"
+#include "Size.h"
 
 class Rect {
 public:
     Rect() { }
     Rect(int x, int y, int width, int height)
         : m_location(x, y)
-        , m_width(width)
-        , m_height(height)
+        , m_size(width, height)
+    {
+    }
+    Rect(const Point& location, const Size& size)
+        : m_location(location)
+        , m_size(size)
     {
     }
 
@@ -85,25 +90,33 @@ public:
 
     int x() const { return location().x(); }
     int y() const { return location().y(); }
-    int width() const { return m_width; }
-    int height() const { return m_height; }
+    int width() const { return m_size.width(); }
+    int height() const { return m_size.height(); }
 
     void setX(int x) { m_location.setX(x); }
     void setY(int y) { m_location.setY(y); }
-    void setWidth(int width) { m_width = width; }
-    void setHeight(int height) { m_height = height; }
+    void setWidth(int width) { m_size.setWidth(width); }
+    void setHeight(int height) { m_size.setHeight(height); }
 
     Point location() const { return m_location; }
+    Size size() const { return m_size; }
 
     bool operator==(const Rect& other) const
     {
         return m_location == other.m_location
-            && m_width == other.m_width
-            && m_height == other.m_height;
+            && m_size == other.m_size;
+    }
+
+    void intersect(const Rect&);
+
+    static Rect intersection(const Rect& a, const Rect& b)
+    {
+        Rect r(a);
+        r.intersect(b);
+        return a;
     }
 
 private:
     Point m_location;
-    int m_width { 0 };
-    int m_height { 0 };
+    Size m_size;
 };

Widgets/RootWidget.cpp

@@ -1,3 +1,5 @@
+#include "AbstractScreen.h"
+#include "GraphicsBitmap.h"
 #include "RootWidget.h"
 #include "Painter.h"
 #include "WindowManager.h"
@@ -5,6 +7,7 @@
 
 RootWidget::RootWidget()
 {
+    m_backing = GraphicsBitmap::create(AbstractScreen::the().size());
 }
 
 RootWidget::~RootWidget()

Widgets/RootWidget.h

@@ -2,6 +2,8 @@
 
 #include "Widget.h"
 
+class GraphicsBitmap;
+
 class RootWidget final : public Widget {
 public:
     RootWidget();
@@ -10,4 +12,8 @@ public:
 private:
     virtual void paintEvent(PaintEvent&) override;
     virtual void mouseMoveEvent(MouseEvent&) override;
+
+    virtual GraphicsBitmap* backing() override { return m_backing.ptr(); }
+
+    RetainPtr<GraphicsBitmap> m_backing;
 };

Widgets/Size.h

@@ -13,6 +13,12 @@ public:
     void setWidth(int w) { m_width = w; }
     void setHeight(int h) { m_height = h; }
 
+    bool operator==(const Size& other) const
+    {
+        return m_width == other.m_width &&
+               m_height == other.m_height;
+    }
+
 private:
     int m_width { 0 };
     int m_height { 0 };

Widgets/Widget.cpp

@@ -1,6 +1,7 @@
 #include "Widget.h"
 #include "Event.h"
 #include "EventLoop.h"
+#include "GraphicsBitmap.h"
 #include "WindowManager.h"
 #include "Window.h"
 #include "Painter.h"
@@ -155,3 +156,10 @@ void Widget::setFont(RetainPtr<Font>&& font)
     else
         m_font = std::move(font);
 }
+
+GraphicsBitmap* Widget::backing()
+{
+    if (auto* w = window())
+        return w->backing();
+    return nullptr;
+}

Widgets/Widget.h

@@ -6,8 +6,8 @@
 #include "Color.h"
 #include "Font.h"
 #include <AK/AKString.h>
-#include <functional>
 
+class GraphicsBitmap;
 class Window;
 
 class Widget : public Object {
@@ -15,7 +15,7 @@ public:
     explicit Widget(Widget* parent = nullptr);
     virtual ~Widget();
 
-    virtual void event(Event&);
+    virtual void event(Event&) override;
     virtual void paintEvent(PaintEvent&);
     virtual void showEvent(ShowEvent&);
     virtual void hideEvent(HideEvent&);
@@ -83,6 +83,8 @@ public:
     const Font& font() const { return *m_font; }
     void setFont(RetainPtr<Font>&&);
 
+    virtual GraphicsBitmap* backing();
+
 private:
     Window* m_window { nullptr };
 

Widgets/Window.cpp

@@ -32,7 +32,7 @@ void Window::setTitle(String&& title)
     if (m_title == title)
         return;
 
-    m_title = std::move(title);
+    m_title = move(title);
     WindowManager::the().notifyTitleChanged(*this);
 }
 
@@ -42,6 +42,7 @@ void Window::setRect(const Rect& rect)
         return;
     auto oldRect = m_rect;
     m_rect = rect;
+    m_backing = GraphicsBitmap::create(m_rect.size());
     WindowManager::the().notifyRectChanged(*this, oldRect, m_rect);
 }
 
@@ -95,6 +96,11 @@ void Window::event(Event& event)
     return Object::event(event);
 }
 
+void Window::did_paint()
+{
+    WindowManager::the().did_paint(*this);
+}
+
 bool Window::isActive() const
 {
     return WindowManager::the().activeWindow() == this;

Widgets/Window.h

@@ -2,6 +2,7 @@
 
 #include "Object.h"
 #include "Rect.h"
+#include "GraphicsBitmap.h"
 #include <AK/AKString.h>
 #include <AK/WeakPtr.h>
 
@@ -50,6 +51,10 @@ public:
 
     void close();
 
+    GraphicsBitmap* backing() { return m_backing.ptr(); }
+
+    void did_paint();
+
 private:
     String m_title;
     Rect m_rect;
@@ -57,5 +62,7 @@ private:
     bool m_isBeingDragged { false };
 
     WeakPtr<Widget> m_focusedWidget;
+
+    RetainPtr<GraphicsBitmap> m_backing;
 };
 

Widgets/WindowManager.cpp

@@ -5,6 +5,7 @@
 #include "AbstractScreen.h"
 #include "TerminalWidget.h"
 #include "EventLoop.h"
+#include "FrameBufferSDL.h"
 
 extern TerminalWidget* g_tw;
 
@@ -131,6 +132,17 @@ void WindowManager::repaint()
     handlePaintEvent(*make<PaintEvent>());
 }
 
+void WindowManager::did_paint(Window& window)
+{
+    auto& framebuffer = FrameBufferSDL::the();
+    framebuffer.blit({ 0, 0 }, *m_rootWidget->backing());
+    for (auto* window : m_windows) {
+        ASSERT(window->backing());
+        framebuffer.blit(window->position(), *window->backing());
+    }
+    framebuffer.flush();
+}
+
 void WindowManager::removeWindow(Window& window)
 {
     if (!m_windows.contains(&window))
@@ -239,7 +251,6 @@ void WindowManager::processMouseEvent(MouseEvent& event)
             return;
         }
     }
-
 }
 
 void WindowManager::handlePaintEvent(PaintEvent& event)
@@ -255,6 +266,14 @@ void WindowManager::handlePaintEvent(PaintEvent& event)
 
     for (auto* window : m_windows)
         window->event(event);
+
+    auto& framebuffer = FrameBufferSDL::the();
+    framebuffer.blit({ 0, 0 }, *m_rootWidget->backing());
+    for (auto* window : m_windows) {
+        ASSERT(window->backing());
+        framebuffer.blit(window->position(), *window->backing());
+    }
+    framebuffer.flush();
 }
 
 void WindowManager::event(Event& event)

Widgets/WindowManager.h

@@ -29,6 +29,8 @@ public:
 
     bool isVisible(Window&) const;
 
+    void did_paint(Window&);
+
     void repaint();
 
 private: