[gtk/matthiasc/for-master: 3/4] gsk: Avoid long lines in serialized nodes

[Matthias Clasen <matthiasc src gnome org>]

commit 8845cd2e9d9a297d10da9ca02772441276a845e5
Author: Matthias Clasen <mclasen redhat com>
Date:   Sat Oct 3 09:45:28 2020 -0400

    gsk: Avoid long lines in serialized nodes
    
    When encoding big blobs of data in base64,
    insert newlines. Base64 allows it, CSS allows
    it, so not need to make GtkTextView struggle
    with multi-megabyte lines.

 gsk/gskrendernodeparser.c | 71 ++++++++++++++++++++++++++++++++++++++++-------
 1 file changed, 61 insertions(+), 10 deletions(-)
---
diff --git a/gsk/gskrendernodeparser.c b/gsk/gskrendernodeparser.c
index c07b749bf6..320f74a13c 100644
--- a/gsk/gskrendernodeparser.c
+++ b/gsk/gskrendernodeparser.c
@@ -2202,10 +2202,57 @@ cairo_destroy_array (gpointer array)
   g_byte_array_free (array, TRUE);
 }
 
+static void
+append_escaping_newlines (GString    *str,
+                          const char *string)
+{
+  gsize len;
+
+  do {
+    len = strcspn (string, "\n");
+    g_string_append_len (str, string, len);
+    string += len;
+    g_string_append (str, "\\\n");
+    string++;
+  } while (*string);
+}
+
+/* like g_base64 encode, but breaks lines
+ * in CSS-compatible way
+ */
+static char *
+base64_encode_with_linebreaks (const guchar *data,
+                               gsize         len)
+{
+  gsize max;
+  char *out;
+  int state = 0, outlen;
+  int save = 0;
+
+  g_return_val_if_fail (data != NULL || len == 0, NULL);
+
+  /* We can use a smaller limit here, since we know the saved state is 0,
+     +1 is needed for trailing \0, also check for unlikely integer overflow */
+  g_return_val_if_fail (len < ((G_MAXSIZE - 1) / 4 - 1) * 3, NULL);
+
+  max = (len / 3 + 1) * 4 + 1;
+  max += 2 * (max / 76);
+
+  out = g_malloc (max);
+
+  outlen = g_base64_encode_step (data, len, TRUE, out, &state, &save);
+  outlen += g_base64_encode_close (TRUE, out + outlen, &state, &save);
+  out[outlen] = '\0';
+
+  return out;
+}
+
 static void
 render_node_print (Printer       *p,
                    GskRenderNode *node)
 {
+  char *b64;
+
   switch (gsk_render_node_get_node_type (node))
     {
     case GSK_CONTAINER_NODE:
@@ -2518,7 +2565,6 @@ render_node_print (Printer       *p,
         GdkTexture *texture = gsk_texture_node_get_texture (node);
         cairo_surface_t *surface;
         GByteArray *array;
-        char *b64;
 
         start_node (p, "texture");
         append_rect_param (p, "bounds", &node->bounds);
@@ -2526,13 +2572,15 @@ render_node_print (Printer       *p,
         surface = gdk_texture_download_surface (texture);
         array = g_byte_array_new ();
         cairo_surface_write_to_png_stream (surface, cairo_write_array, array);
-        b64 = g_base64_encode (array->data, array->len);
 
         _indent (p);
-        g_string_append_printf (p->str, "texture: url(\"data:image/png;base64,%s\");\n", b64);
+        g_string_append (p->str, "texture: url(\"data:image/png;base64,");
+        b64 = base64_encode_with_linebreaks (array->data, array->len);
+        append_escaping_newlines (p->str, b64);
+        g_free (b64);
+        g_string_append (p->str, "\");\n");
         end_node (p);
 
-        g_free (b64);
         g_byte_array_free (array, TRUE);
         cairo_surface_destroy (surface);
       }
@@ -2828,7 +2876,6 @@ render_node_print (Printer       *p,
       {
         cairo_surface_t *surface = gsk_cairo_node_peek_surface (node);
         GByteArray *array;
-        char *b64;
 
         start_node (p, "cairo");
         append_rect_param (p, "bounds", &node->bounds);
@@ -2837,12 +2884,14 @@ render_node_print (Printer       *p,
           {
             array = g_byte_array_new ();
             cairo_surface_write_to_png_stream (surface, cairo_write_array, array);
-            b64 = g_base64_encode (array->data, array->len);
 
             _indent (p);
-            g_string_append_printf (p->str, "pixels: url(\"data:image/png;base64,%s\");\n", b64);
-
+            g_string_append (p->str, "pixels: url(\"data:image/png;base64,");
+            b64 = base64_encode_with_linebreaks (array->data, array->len);
+            append_escaping_newlines (p->str, b64);
             g_free (b64);
+            g_string_append (p->str, "\");\n");
+
             g_byte_array_free (array, TRUE);
 
 #ifdef CAIRO_HAS_SCRIPT_SURFACE
@@ -2856,10 +2905,12 @@ render_node_print (Printer       *p,
 
                 if (cairo_script_from_recording_surface (script, surface) == CAIRO_STATUS_SUCCESS)
                   {
-                    b64 = g_base64_encode (array->data, array->len);
                     _indent (p);
-                    g_string_append_printf (p->str, "script: url(\"data:;base64,%s\");\n", b64);
+                    g_string_append (p->str, "script: url(\"data:;base64,");
+                    b64 = base64_encode_with_linebreaks (array->data, array->len);
+                    append_escaping_newlines (p->str, b64);
                     g_free (b64);
+                    g_string_append (p->str, "\");\n");
                   }
 
                 /* because Cairo is stupid and writes to the device after we finished it,