Respond to resize events properly

Previously, we used to not respond to resize events. Additionally,
resizing the window would cause flickering to appear in the area where
painting would happen. This patch fixes both of those issues.

src/Window.cpp

@@ -28,19 +28,32 @@ bool Window::spawn_window() {
     m_x_display = dsp;
 
     int screen = DefaultScreen(dsp);
-    Drawable da = XCreateSimpleWindow(dsp, DefaultRootWindow(dsp), 0, 0, m_current_geometry.get_width(), m_current_geometry.get_height(), 0, 0, 0);
+    Drawable da = XCreateWindow(
+        dsp,
+        DefaultRootWindow(dsp),
+        0,
+        0,
+        m_current_geometry.get_width(),
+        m_current_geometry.get_height(),
+        0,
+        0,
+        CopyFromParent,
+        CopyFromParent,
+        0,
+        NULL
+    );
 
     XSelectInput(dsp, da, ButtonPressMask | ButtonReleaseMask | KeyPressMask | PointerMotionMask | StructureNotifyMask | ExposureMask);
     XMapWindow(dsp, da);
 
-    auto cairo_xlib_surface = Cairo::XlibSurface::create(
+    m_xlib_surface = Cairo::XlibSurface::create(
         dsp,
         da,
         DefaultVisual(dsp, screen),
         get_current_geometry().get_width(),
         get_current_geometry().get_height()
     );
-    auto cairo_context = Cairo::Context::create(cairo_xlib_surface);
+    auto cairo_context = Cairo::Context::create(m_xlib_surface);
 
     m_painter.set_cairo(cairo_context);
 
@@ -78,9 +91,25 @@ void Window::run(bool block) {
                 dispatch_full_repaint();
                 break;
             }
+            case ConfigureNotify: {
+                if (e.xconfigure.width != m_current_geometry.get_width() || e.xconfigure.height != m_current_geometry.get_height()) {
+                    m_xlib_surface->set_size(e.xconfigure.width, e.xconfigure.height);
+                    m_current_geometry.set_width(e.xconfigure.width);
+                    m_current_geometry.set_height(e.xconfigure.height);
+                    // if we have a main widget, we are going to have to resize it as well
+                    if (m_main_widget) {
+                        m_main_widget->get_current_geometry().set_width(m_current_geometry.get_width());
+                        m_main_widget->get_current_geometry().set_height(m_current_geometry.get_height());
+                    }
+                    dispatch_full_repaint();
+                }
+                break;
+            }
             case Expose: {
+                if (e.xexpose.count == 0) {
                     auto box = Box(e.xexpose.x, e.xexpose.y, e.xexpose.width, e.xexpose.height);
                     dispatch_repaint_on_box(std::move(box));
+                }
                 break;
             }
             case MotionNotify: {

src/Window.hpp

@@ -4,6 +4,7 @@
 #include "Widget.hpp"
 #include "Painter.hpp"
 #include <X11/Xlib.h>
+#include <cairomm/xlib_surface.h>
 
 namespace Raven {
 
@@ -14,6 +15,7 @@ private:
     Box m_current_geometry { 0, 0, 800, 600 };
     Painter m_painter {};
     std::shared_ptr<TopLevelStyles> m_top_level_styles = std::make_shared<TopLevelStyles>(this);
+    Cairo::RefPtr<Cairo::XlibSurface> m_xlib_surface { nullptr };
 
     Display *m_x_display { nullptr };
 public: