decoration: configurable graphical effects, added to a particle

CMakeLists.txt

@@ -25,6 +25,7 @@ pkg_check_modules(UDEV REQUIRED libudev)                 # Module/battery
 add_executable(f00bar
   bar.c bar.h
   config.c config.h
+  decoration.h
   font.c font.h
   log.c log.h
   main.c
@@ -34,6 +35,8 @@ add_executable(f00bar
   xcb.c xcb.h
   yml.c yml.h
 
+  decorations/background.c decorations/background.h
+
   particles/list.c particles/list.h
   particles/map.c particles/map.h
   particles/ramp.c particles/ramp.h

decoration.h

@@ -0,0 +1,10 @@
+#pragma once
+
+#include <cairo.h>
+
+struct deco {
+    void *private;
+    void (*expose)(const struct deco *deco, cairo_t *cr,
+                   int x, int y, int width, int height);
+    void (*destroy)(struct deco *deco);
+};

decorations/background.c

@@ -0,0 +1,39 @@
+#include "background.h"
+
+#include <stdlib.h>
+
+struct private {
+    struct rgba color;
+};
+
+static void
+destroy(struct deco *deco)
+{
+    struct private *d = deco->private;
+    free(d);
+    free(deco);
+}
+
+static void
+expose(const struct deco *deco, cairo_t *cr, int x, int y, int width, int height)
+{
+    const struct private *d = deco->private;
+    cairo_set_source_rgba(
+        cr, d->color.red, d->color.green, d->color.blue, d->color.alpha);
+    cairo_rectangle(cr, x, y, width, height);
+    cairo_fill(cr);
+}
+
+struct deco *
+deco_background(struct rgba color)
+{
+    struct private *priv = malloc(sizeof(*priv));
+    priv->color = color;
+
+    struct deco *deco = malloc(sizeof(*deco));
+    deco->private = priv;
+    deco->expose = &expose;
+    deco->destroy = &destroy;
+
+    return deco;
+}

decorations/background.h

@@ -0,0 +1,6 @@
+#pragma once
+
+#include "../color.h"
+#include "../decoration.h"
+
+struct deco *deco_background(struct rgba color);