support Github style code formatting (#121)

Signed-off-by: Namhyung Kim <namhyung@gmail.com>

include/markdown.h

@@ -48,6 +48,7 @@ enum line_bitmask {
     IS_QUOTE,
     IS_CODE,
     IS_TILDE_CODE,
+    IS_GFM_CODE,
     IS_HR,
     IS_UNORDERED_LIST_1,
     IS_UNORDERED_LIST_2,

include/parser.h

@@ -59,5 +59,6 @@ int prev_blank(cstring_t *text, int i);
 int next_blank(cstring_t *text, int i);
 int next_word(cstring_t *text, int i);
 int next_nontilde(cstring_t *text, int i);
+int next_nonbacktick(cstring_t *text, int i);
 
 #endif // !defined( PARSER_H )

sample.md

@@ -115,8 +115,8 @@ at least as many or more ~ for closing.
 becomes
 
 ~~~ {.numberLines}
-int main(int argc, char \*argv[]) {
-    printf("%s\\n", "Hello world!");
+int main(int argc, char *argv[]) {
+    printf("%s\n", "Hello world!");
 }
 ~~~~~~~~~~~~~~~~~~
 
@@ -127,6 +127,30 @@ will be ignored
 
 -> # Supported markdown formatting <-
 
+You can also use [github](https://guides.github.com/features/mastering-markdown/#GitHub-flavored-markdown) flavored markdown's
+code block. Use at least three backticks to open
+and at least as many or more backticks for closing.
+
+\```
+\int main(int argc, char \*argv[]) {
+\    printf("%s\\n", "Hello world!");
+\}
+\```
+
+becomes
+
+```
+int main(int argc, char *argv[]) {
+    printf("%s\n", "Hello world!");
+}
+```
+
+Language hint will be ignored
+
+-------------------------------------------------
+
+-> # Supported markdown formatting <-
+
 Quotes are auto-detected by preceding *>*.
 
 Multiple *>* are interpreted as nested quotes.

src/parser.c

@@ -158,7 +158,8 @@ deck_t *markdown_load(FILE *input, int noexpand) {
                 slide = next_slide(slide);
                 sc++;
 
-            } else if(CHECK_BIT(bits, IS_TILDE_CODE) &&
+            } else if((CHECK_BIT(bits, IS_TILDE_CODE) ||
+		       CHECK_BIT(bits, IS_GFM_CODE)) &&
                       CHECK_BIT(bits, IS_EMPTY)) {
                 // remove tilde code markers
                 (text->reset)(text);
@@ -400,6 +401,7 @@ int markdown_analyse(cstring_t *text, int prev) {
     static int unordered_list_level = 0;
     static int unordered_list_level_offset[] = {-1, -1, -1, -1};
     static int num_tilde_characters = 0;
+    static int num_backticks = 0;
 
     int i = 0;      // increment
     int bits = 0;   // markdown bits
@@ -447,6 +449,27 @@ int markdown_analyse(cstring_t *text, int prev) {
         return bits;
     }
 
+    // IS_GFM_CODE
+    if (wcsncmp(text->value, L"```", 3) == 0) {
+        int backticks_in_line = next_nonbacktick(text, 0);
+        if (backticks_in_line >= num_backticks) {
+            if (num_backticks > 0) {
+                num_backticks = 0;
+            } else {
+                num_backticks = backticks_in_line;
+            }
+            SET_BIT(bits, IS_EMPTY);
+            SET_BIT(bits, IS_GFM_CODE);
+            return bits;
+        }
+    }
+
+    if (num_backticks > 0) {
+        SET_BIT(bits, IS_CODE);
+        SET_BIT(bits, IS_GFM_CODE);
+        return bits;
+    }
+
     // IS_STOP
     if((offset < CODE_INDENT || !CHECK_BIT(prev, IS_CODE)) &&
        (!wcsncmp(&text->value[offset], L"<br>", 4) ||
@@ -831,3 +854,10 @@ int next_nontilde(cstring_t *text, int i) {
     return i;
 }
 
+int next_nonbacktick(cstring_t *text, int i) {
+    while ((i < text->size) && text->value[i] == L'`')
+        i++;
+
+    return i;
+}
+

src/viewer.c

@@ -656,7 +656,8 @@ void add_line(WINDOW *window, int y, int x, line_t *line, int max_cols, int colo
     // IS_CODE
     if(CHECK_BIT(line->bits, IS_CODE)) {
 
-        if (!CHECK_BIT(line->bits, IS_TILDE_CODE)) {
+        if (!CHECK_BIT(line->bits, IS_TILDE_CODE) &&
+            !CHECK_BIT(line->bits, IS_GFM_CODE)) {
             // set static offset for code
             offset = CODE_INDENT;
         }