From 0a8cb732901531a9a88d9e5567477101c804628b Mon Sep 17 00:00:00 2001
From: Aaron Fischer <aaron.fischer@marbis.net>
Date: Mon, 1 Oct 2018 17:03:40 +0200
Subject: [PATCH] Add tabs

---
 kilo.c | 62 ++++++++++++++++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 58 insertions(+), 4 deletions(-)

diff --git a/kilo.c b/kilo.c
index bf0bbca..8666576 100644
--- a/kilo.c
+++ b/kilo.c
@@ -17,6 +17,7 @@
 /*** defines ***/
 
 #define KILO_VERSION "0.0.1"
+#define KILO_TAB_STOP 8
 
 #define CTRL_KEY(k) ((k) & 0x1f)
 
@@ -37,12 +38,15 @@ enum editorKey {
 
 typedef struct erow {
   int size;
+  int rsize;
   char *chars;
+  char *render;
 } erow;
 
 struct editorConfig {
   int cx, cy;
   int rowoff;
+  int coloff;
   int screenrows;
   int screencols;
   int numrows;
@@ -171,6 +175,29 @@ int getWindowSize(int *rows, int *cols) {
 
 /*** row operations ***/
 
+void editorUpdateRow(erow *row) {
+  int tabs = 0;
+  int j;
+  for (j=0; j<row->size; j++) {
+    if (row->chars[j] == '\t') tabs++;
+  }
+
+  free(row->render);
+  row->render = malloc(row->size + tabs*(KILO_TAB_STOP-1) + 1);
+
+  int idx = 0;
+  for (j=0; j<row->size; j++) {
+    if (row->chars[j] == '\t') {
+      row->render[idx++] = ' ';
+      while (idx%KILO_TAB_STOP != 0) row->render[idx++] = ' ';
+    } else {
+      row->render[idx++] = row->chars[j];
+    }
+  }
+  row->render[idx] = '\0';
+  row->rsize = idx;
+}
+
 void editorAppendRow(char *s, size_t len) {
   E.row = realloc(E.row, sizeof(erow) * (E.numrows +1));
 
@@ -179,6 +206,11 @@ void editorAppendRow(char *s, size_t len) {
   E.row[at].chars = malloc(len + 1);
   memcpy(E.row[at].chars, s, len);
   E.row[at].chars[len] = '\0';
+
+  E.row[at].rsize = 0;
+  E.row[at].render = NULL;
+  editorUpdateRow(&E.row[at]);
+
   E.numrows++;
 }
 
@@ -230,6 +262,12 @@ void editorScroll() {
   if (E.cy >= E.rowoff + E.screenrows) {
     E.rowoff = E.cy - E.screenrows + 1;
   }
+  if (E.cx < E.coloff) {
+    E.coloff = E.cx;
+  }
+  if (E.cx >= E.coloff + E.screencols) {
+    E.coloff = E.cx - E.screencols + 1;
+  }
 }
 
 void editorDrawRows(struct abuf *ab) {
@@ -253,9 +291,10 @@ void editorDrawRows(struct abuf *ab) {
         abAppend(ab, "~", 1);
       }
     } else {
-      int len = E.row[filerow].size;
+      int len = E.row[filerow].rsize - E.coloff;
+      if (len < 0) len = 0;
       if (len > E.screencols) len = E.screencols;
-      abAppend(ab, E.row[filerow].chars, len);
+      abAppend(ab, &E.row[filerow].render[E.coloff], len);
     }
 
     abAppend(ab, "\x1b[K", 3); // Erase one line
@@ -277,7 +316,7 @@ void editorRefreshScreen() {
 
   // Update cursor position
   char buf[32];
-  snprintf(buf, sizeof(buf), "\x1b[%d;%dH", (E.cy - E.rowoff) + 1, E.cx + 1);
+  snprintf(buf, sizeof(buf), "\x1b[%d;%dH", (E.cy - E.rowoff) + 1, (E.cx - E.coloff) + 1);
   abAppend(&ab, buf, strlen(buf));
 
   abAppend(&ab, "\x1b[?25h", 6); // Show cursor
@@ -289,15 +328,23 @@ void editorRefreshScreen() {
 /*** input ***/
 
 void editorMoveCursor(int key) {
+  erow *row = (E.cy >= E.numrows) ? NULL : &E.row[E.cy];
+
   switch (key) {
     case ARROW_LEFT:
       if (E.cx != 0) {
         E.cx--;
+      } else if (E.cy > 0) {
+        E.cy--;
+        E.cx = E.row[E.cy].size;
       }
       break;
     case ARROW_RIGHT:
-      if (E.cx != E.screencols -1) {
+      if (row && E.cx < row->size) {
         E.cx++;
+      } else if (row && E.cx == row->size) {
+        E.cy++;
+        E.cx = 0;
       }
       break;
     case ARROW_UP:
@@ -311,6 +358,12 @@ void editorMoveCursor(int key) {
       }
       break;
   }
+
+  row = (E.cy >= E.numrows) ? NULL : &E.row[E.cy];
+  int rowlen = row ? row->size : 0;
+  if (E.cx > rowlen) {
+    E.cx = rowlen;
+  }
 }
 
 
@@ -356,6 +409,7 @@ void initEditor() {
   E.cx = 0;
   E.cy = 0;
   E.rowoff = 0;
+  E.coloff = 0;
   E.numrows = 0;
   E.row = NULL;