Add a simple spray fill tool

Could do with some more tweaking no doubt, and it'd be nice to have a
circular spray, but this is better than nothing.

Applications/PaintBrush/SprayTool.cpp

@@ -0,0 +1,69 @@
+#include "SprayTool.h"
+#include "PaintableWidget.h"
+#include <AK/Queue.h>
+#include <AK/SinglyLinkedList.h>
+#include <LibGUI/GPainter.h>
+#include <SharedGraphics/GraphicsBitmap.h>
+#include <stdio.h>
+
+SprayTool::SprayTool()
+{
+    m_timer.on_timeout = [=]() {
+        paint_it();
+    };
+    m_timer.set_interval(200);
+}
+
+SprayTool::~SprayTool()
+{
+}
+
+static double nrand()
+{
+    return double(rand()) / double(RAND_MAX);
+}
+
+void SprayTool::paint_it()
+{
+    GPainter painter(m_widget->bitmap());
+    auto& bitmap = m_widget->bitmap();
+    ASSERT(bitmap.format() == GraphicsBitmap::Format::RGB32);
+    m_widget->update();
+    const double radius = 15;
+    for (int i = 0; i < 100 + (nrand() * 800); i++) {
+        const int minX = m_last_pos.x() - radius;
+        const int minY = m_last_pos.y() - radius;
+        const int xpos = minX + (radius * 2 * nrand());
+        const int ypos = minY + (radius * 2 * nrand());
+        if (xpos < 0 || xpos >= bitmap.width())
+            continue;
+        if (ypos < 0 || ypos >= bitmap.height())
+            continue;
+        bitmap.set_pixel<GraphicsBitmap::Format::RGB32>(xpos, ypos, m_color);
+    }
+}
+
+void SprayTool::on_mousedown(GMouseEvent& event)
+{
+    if (!m_widget->rect().contains(event.position()))
+        return;
+
+    m_color = m_widget->color_for(event);
+    m_last_pos = event.position();
+    m_timer.start();
+    paint_it();
+}
+
+void SprayTool::on_mousemove(GMouseEvent& event)
+{
+    m_last_pos = event.position();
+    if (m_timer.is_active()) {
+        paint_it();
+        m_timer.restart(m_timer.interval());
+    }
+}
+
+void SprayTool::on_mouseup(GMouseEvent&)
+{
+    m_timer.stop();
+}