From c1f46771d7c9f39e776a2c20945251ff4b9c92f7 Mon Sep 17 00:00:00 2001
From: Timothy Warren <twarren@nabancard.com>
Date: Mon, 19 Aug 2019 15:19:16 -0400
Subject: [PATCH] Render tabs as spaces

---
 kilo.c | 90 +++++++++++++++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 86 insertions(+), 4 deletions(-)

diff --git a/kilo.c b/kilo.c
index 4012d9f..1772c48 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)
 
@@ -36,12 +37,15 @@ 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;
@@ -231,6 +235,43 @@ 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));
@@ -240,6 +281,11 @@ 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++;
 }
 
@@ -311,6 +357,16 @@ void editorScroll()
 	{
 		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)
@@ -353,13 +409,18 @@ void editorDrawRows(struct abuf *ab)
 		}
 		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);
@@ -382,7 +443,8 @@ void editorRefreshScreen()
 	editorDrawRows(&ab);
 
 	char buf[32];
-	snprintf(buf, sizeof(buf), "\x1b[%d;%dH", E.cy + 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);
@@ -395,6 +457,8 @@ void editorRefreshScreen()
 
 void editorMoveCursor(int key)
 {
+	erow *row = (E.cy >= E.numrows) ? NULL : &E.row[E.cy];
+
 	switch (key)
 	{
 		case ARROW_LEFT:
@@ -402,13 +466,23 @@ void editorMoveCursor(int key)
 			{
 				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:
@@ -425,6 +499,13 @@ 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;
+	}
 }
 
 void editorProcessKeypress()
@@ -473,6 +554,7 @@ void initEditor()
 	E.cx = 0;
 	E.cy = 0;
 	E.rowoff = 0;
+	E.coloff = 0;
 	E.numrows = 0;
 	E.row = NULL;