[librsvg: 2/11] Add links to overview.md, and the example program

[Marge Bot <marge-bot src gnome org>]

commit ce88488dbd3df47f0bd9477dfe1ed893f50d14c8
Author: Federico Mena Quintero <federico gnome org>
Date:   Thu Mar 10 14:04:53 2022 -0600

    Add links to overview.md, and the example program
    
    Fixes #828
    
    Part-of: <https://gitlab.gnome.org/GNOME/librsvg/-/merge_requests/674>

 doc/overview.md | 95 +++++++++++++++++++++++++++++++++++++++++++++------------
 1 file changed, 76 insertions(+), 19 deletions(-)
---
diff --git a/doc/overview.md b/doc/overview.md
index 302226c6c..07e42eca7 100644
--- a/doc/overview.md
+++ b/doc/overview.md
@@ -26,44 +26,45 @@ are the following:
 
 Librsvg's API is divided into two main parts: one for loading SVG data
 and one for rendering it. In the *loading stage*, you create an
-`RsvgHandle` object from SVG data, which can come from a file or from a
-stream of bytes. In the *rendering stage*, you take an `RsvgHandle` and
+[class@Rsvg.Handle] object from SVG data, which can come from a file or from a
+stream of bytes. In the *rendering stage*, you take an [class@Rsvg.Handle] and
 ask it to render itself to a Cairo context.
 
 ## Loading
 
-`RsvgHandle` is an object that represents SVG data in memory. Your program
-creates an `RsvgHandle` from an SVG file, or from a memory buffer that
-contains SVG data, or in the most general form, from a GIO stream that
+[class@Rsvg.Handle] is an object that represents SVG data in memory. Your program
+creates an [class@Rsvg.Handle] from an SVG file, or from a memory buffer that
+contains SVG data, or in the most general form, from a [class@Gio.InputStream] that
 will provide SVG data.  At this stage you can get either I/O errors or
-parsing errors. If loading completes successfully, the `RsvgHandle` will
+parsing errors. If loading completes successfully, the [class@Rsvg.Handle] will
 be ready for rendering.
 
-Generally you should use `rsvg_handle_new_from_gfile_sync()` or
-`rsvg_handle_new_from_stream_sync()` to load an SVG document into an
-`RsvgHandle`. There are other convenience functions to load an SVG
-document, but these two functions let one set the "base file" and the
-`RsvgHandleFlags` in a single call.
+Generally you should use [ctor@Rsvg.Handle.new_from_gfile_sync] or
+[ctor@Rsvg.Handle.new_from_stream_sync] to load an SVG document into
+an [class@Rsvg.Handle]. There are other convenience functions to load
+an SVG document, but these two functions let one set the "[base
+file](class.Handle.html#the-base-file-and-resolving-references-to-external-files)"
+and the [flags@Rsvg.HandleFlags] in a single call.
 
 ## Rendering
 
-Once you have an SVG image loaded into an `RsvgHandle`, you can render it
+Once you have an SVG image loaded into an [class@Rsvg.Handle], you can render it
 to a Cairo context any number of times, or to different Cairo contexts,
 as needed. As a convenience, you can pick a single element in the SVG by
 its `id` attribute and render only that element; this is so that
 sub-elements can be extracted conveniently out of a larger SVG.
 
-Generally you should use `rsvg_handle_render_document()` to render the
+Generally you should use [method@Rsvg.Handle.render_document] to render the
 whole SVG document at any size you choose into a Cairo context.
 
 ## Example: simple loading and rendering
 
 The following program loads `hello.svg`, renders it scaled to fit within
-640x480 pixels, and writes a `hello.png` file.
+640×480 pixels, and writes a `hello.png` file.
 
 Note the following:
 
-* `rsvg_handle_render_document()` will scale the document
+* [method@Rsvg.Handle.render_document] will scale the document
    proportionally to fit the viewport you specify, and it will center
    the image within that viewport.
 
@@ -72,8 +73,64 @@ Note the following:
   transparent. If you wish to have a specific background, fill the
   viewport area yourself before rendering the SVG.
 
+```c
+/* gcc -Wall -g -O2 -o load-and-render load-and-render.c `pkg-config --cflags --libs rsvg-2.0` */
+
+#include <stdlib.h>
+#include <librsvg/rsvg.h>
+
+#define WIDTH 640
+#define HEIGHT 480
+
+int
+main (void)
+{
+  /* First, load an SVG document into an RsvgHandle */
+
+  GError *error = NULL;
+  GFile *file = g_file_new_for_path ("hello.svg");
+  RsvgHandle *handle = rsvg_handle_new_from_gfile_sync (file, RSVG_HANDLE_FLAGS_NONE, NULL, &error);
+
+  if (!handle)
+    {
+      g_printerr ("could not load: %s", error->message);
+      exit (1);
+    }
+
+  /* Create a Cairo image surface and a rendering context for it */
+
+  cairo_surface_t *surface = cairo_image_surface_create (CAIRO_FORMAT_ARGB32, WIDTH, HEIGHT);
+  cairo_t *cr = cairo_create (surface);
+
+  /* Render the handle scaled proportionally into that whole surface */
+
+  RsvgRectangle viewport = {
+    .x = 0.0,
+    .y = 0.0,
+    .width = WIDTH,
+    .height = HEIGHT,
+  };
+
+  if (!rsvg_handle_render_document (handle, cr, &viewport, &error))
+    {
+      g_printerr ("could not render: %s", error->message);
+      exit (1);
+    }
+
+  /* Write a PNG file */
+
+  if (cairo_surface_write_to_png (surface, "hello.png") != CAIRO_STATUS_SUCCESS)
+    {
+      g_printerr ("could not write output file");
+      exit (1);
+    }
+
+  /* Free our memory and we are done! */
+
+  cairo_destroy (cr);
+  cairo_surface_destroy (surface);
+  g_object_unref (handle);
+  g_object_unref (file);
+  return 0;
+}
 ```
-FIXME: include load-and-render.c here
-```
-            
-