[writan/format] add image support [visual-snow] add visual example

TODO.org

@@ -1,12 +1,9 @@
 Writan:
- - Image support.
  - Additional error handling in the formatter.
  - Remove extraneous <p> tags in output.
 
 Pages:
  - Add a category theory page (more general, math).
- - Improve visual snow page with graphic examples.
 
 Orphan pages:
- - Visual snow
  - Emacs

format.c

@@ -1,3 +1,4 @@
+#include <ctype.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <stdint.h>
@@ -277,6 +278,29 @@ emit_blockquote(FILE *input, FILE *output)
     fprintf(output, "</blockquote>\n");
 }
 
+void
+emit_image(FILE *input, FILE *output)
+{
+    char buf[80];
+    char *bufptr = buf;
+
+    for(;;) {
+        char c = fgetc(input);
+        if (isspace(c))
+            break;
+        else if (c == EOF)
+            die("EOF encountered while parsing image filename.");
+        else
+            *(bufptr++) = c;
+    }
+
+    *bufptr = '\0';
+
+    fprintf(output, "<img src=\"../resources/img/%s\" />", buf);
+
+    fseek(input, -1L, SEEK_CUR);
+}
+
 /* main formatter */
 void
 format(FILE *input, FILE *output)
@@ -298,6 +322,21 @@ format(FILE *input, FILE *output)
                 fprintf(output, "<p>");
             emit_link(input, output);
         }
+        else if (c == '$') { /* maybe image */
+            char buf[5];
+            size_t i;
+            for (i = 0; i < 4; i++)
+                buf[i] = fgetc(input);
+            buf[i] = '\0';
+
+            if (!strcmp(buf, "img ")) {
+                emit_image(input, output);
+            }
+            else {
+                fseek(input, -4L, SEEK_CUR);
+                emit_sanitized_char(c, output);
+            }
+        }
         else if (c == '_') {
             fprintf(output, "%s", em_tags[in_em]);
             in_em = !in_em;
@@ -360,7 +399,6 @@ main(int argc, char *argv[])
     format(in, out);
     write_file(out, "resources/footer.html");
 
-
     fclose(in);
     fclose(out);
 }

resources/txt/writan-example.txt

@@ -34,3 +34,8 @@ You can inline ``code`` blocks.
 > multiple lines.
 
 One can mark emphasis by surrounding a word with _underscores_.
+
+An image is embedded like follows. The filename is expanded to
+resources/img/image-file.png.
+
+$img image-file.png

site-src/c.wtn

@@ -111,6 +111,6 @@ Casts to ``void*`` are implicit in C, so do not explicitly cast pointers to
 
 Indentation is done with 4 spaces.
 
-I do not ``typedef`` my structs.
+I do not ``typedef`` my structs nor my enums.
 
 Everything is named in snake case with all lower case letters.

site-src/visual-snow.wtn

@@ -1,5 +1,7 @@
 * Visual snow
 
+$img visual-snow.gif
+
 Visual snow is a visual impairment which makes those affected see black, white
 or coloured semi-transparent dots in part of or the whole visual field. The
 effect tends to be more prevalent at lower light levels. Additional symptoms

site-src/writan.wtn

@@ -5,7 +5,7 @@ only has a few distinct formatting rules.
 
 It uses the file extension ".wtn".
 
-To get an overview over how it works, take a look at the {../resources/writan-example.txt
+To get an overview over how it works, take a look at the {../resources/txt/writan-example.txt
 example document}.
 
 {https://tildegit.org/opfez/codex/branch/master/format.c Source code of the