Migrate i3 rendering to cairo.

This patch migrates all decoration rendering of i3 to cairo. Using the
compile switch CAIRO_SUPPORT, rendering can be switched back to the
previous XCB behavior, just like with the previous migration to cairo
in i3bar.

This patch also fixes a bug in draw_util.c where copying one surface
to another would use incorrect coordinates if the source coordinates
are not 0, 0.

Furthermore, this patch implicitly fixes some minor issues in the
decoration rendering which would be ignored previously due to the fact
that errors would only show up in the event queue, but not cause the
rendering code path to crash. One example is zero-height pixmaps which
are not allowed. Using cairo, these would cause i3 to instantly segfault,
so this patch avoids this.

Lastly, this patch annotates other issues found but not fixed in this patch
using TODO comments, e.g., the zero-height check not working correctly
and the comment that it should probably work the same way for zero-width
pixmaps.

relates to #1278

include/libi3.h

@@ -513,6 +513,8 @@ typedef struct surface_t {
     /* A classic XCB graphics context. */
     xcb_gcontext_t gc;
 
+    xcb_visualtype_t *visual_type;
+
     int width;
     int height;
 
@@ -530,13 +532,20 @@ typedef struct surface_t {
  * Initialize the surface to represent the given drawable.
  *
  */
-void draw_util_surface_init(surface_t *surface, xcb_drawable_t drawable, int width, int height);
+void draw_util_surface_init(xcb_connection_t *conn, surface_t *surface, xcb_drawable_t drawable,
+                            xcb_visualtype_t *visual, int width, int height);
+
+/**
+ * Resize the surface to the given size.
+ *
+ */
+void draw_util_surface_set_size(surface_t *surface, int width, int height);
 
 /**
  * Destroys the surface.
  *
  */
-void draw_util_surface_free(surface_t *surface);
+void draw_util_surface_free(xcb_connection_t *conn, surface_t *surface);
 
 /**
  * Parses the given color in hex format to an internal color representation.
@@ -545,6 +554,8 @@ void draw_util_surface_free(surface_t *surface);
  */
 color_t draw_util_hex_to_color(const char *color);
 
+color_t draw_util_colorpixel_to_color(uint32_t colorpixel);
+
 /**
  * Draw the given text using libi3.
  * This function also marks the surface dirty which is needed if other means of
@@ -559,17 +570,17 @@ void draw_util_text(i3String *text, surface_t *surface, color_t fg_color, color_
  * surface as well as restoring the cairo state.
  *
  */
-void draw_util_rectangle(surface_t *surface, color_t color, double x, double y, double w, double h);
+void draw_util_rectangle(xcb_connection_t *conn, surface_t *surface, color_t color, double x, double y, double w, double h);
 
 /**
  * Clears a surface with the given color.
  *
  */
-void draw_util_clear_surface(surface_t *surface, color_t color);
+void draw_util_clear_surface(xcb_connection_t *conn, surface_t *surface, color_t color);
 
 /**
  * Copies a surface onto another surface.
  *
  */
-void draw_util_copy_surface(surface_t *src, surface_t *dest, double src_x, double src_y,
+void draw_util_copy_surface(xcb_connection_t *conn, surface_t *src, surface_t *dest, double src_x, double src_y,
                             double dest_x, double dest_y, double width, double height);