added base class for screen savers

ScreensaverPlugin.cpp

@@ -0,0 +1,56 @@
+//
+// ScreensaverPlugin.cpp
+// tmp
+//
+// Created by Bob Polis at 2020-10-26
+// Copyright (c) 2020 SwiftCoder. All rights reserved.
+//
+
+#include "ScreensaverPlugin.hpp"
+
+ScreensaverPlugin::ScreensaverPlugin(cairo_t* context, const cairo_rectangle_t& rect)
+    : _c {context}, _r {rect}, _x_dist {rect.x, rect.width}, _y_dist {rect.y, rect.height} {
+
+}
+
+void ScreensaverPlugin::make_black() {
+    cairo_set_source_rgb(_c, 0, 0, 0);
+    cairo_rectangle(_c, 0, 0, _r.width, _r.height);
+    cairo_fill(_c);
+}
+
+cairo_rectangle_t ScreensaverPlugin::random_rect() {
+    cairo_rectangle_t rect;
+    double v1, v2;
+    v1 = random_x();
+    v2 = random_x();
+    if (v1 < v2) {
+        rect.x = v1;
+        rect.width = v2 - v1;
+    } else {
+        rect.x = v2;
+        rect.width = v1 - v2;
+    }
+    v1 = random_y();
+    v2 = random_y();
+    if (v1 < v2) {
+        rect.y = v1;
+        rect.height = v2 - v1;
+    } else {
+        rect.y = v2;
+        rect.height = v1 - v2;
+    }
+    return rect;
+}
+
+double ScreensaverPlugin::random_x() {
+    return _x_dist(_eng);
+}
+
+double ScreensaverPlugin::random_y() {
+    return _y_dist(_eng);
+}
+
+double ScreensaverPlugin::random01() {
+    return _01_dist(_eng);
+}

ScreensaverPlugin.hpp

@@ -0,0 +1,39 @@
+//
+// ScreensaverPlugin.hpp
+// screensaver
+//
+// Created by Bob Polis at 2020-10-26
+// Copyright (c) 2020 SwiftCoder. All rights reserved.
+//
+
+#ifndef _ScreensaverPlugin_H_
+#define _ScreensaverPlugin_H_
+
+#include <cairo/cairo.h>
+#include <random>
+
+class ScreensaverPlugin {
+    public:
+        ScreensaverPlugin(cairo_t* context, const cairo_rectangle_t& rect);
+        virtual ~ScreensaverPlugin() = default;
+
+        virtual void draw_frame() = 0;
+        virtual int fps() const = 0;
+
+    protected:
+        cairo_t* _c;
+        cairo_rectangle_t _r;
+        std::random_device _dev;
+        std::default_random_engine _eng {_dev()};
+        std::uniform_real_distribution<> _01_dist {};
+        std::uniform_real_distribution<> _x_dist;
+        std::uniform_real_distribution<> _y_dist;
+
+        void make_black();
+        cairo_rectangle_t random_rect();
+        double random_x();
+        double random_y();
+        double random01();
+};
+
+#endif // _ScreensaverPlugin_H_