From 1a5dd5dcc3d9e0e2195c0323f2ba62956f205591 Mon Sep 17 00:00:00 2001
From: Tyrel Souza <923113+tyrelsouza@users.noreply.github.com>
Date: Thu, 21 Oct 2021 00:54:25 -0400
Subject: [PATCH] tabstops

---
 README.md |  3 ++
 tted.c    | 87 +++++++++++++++++++++++++++++++++++++++++++++++++++----
 2 files changed, 84 insertions(+), 6 deletions(-)

diff --git a/README.md b/README.md
index bace049..f994af7 100644
--- a/README.md
+++ b/README.md
@@ -2,3 +2,6 @@ Tyrel's Text Editor
 
 
 https://viewsourcecode.org/snaptoken/kilo/04.aTextViewer.html#vertical-scrolling
+https://viewsourcecode.org/snaptoken/kilo/04.aTextViewer.html#horizontal-scrolling
+https://viewsourcecode.org/snaptoken/kilo/04.aTextViewer.html#tabs-and-the-cursor
+https://viewsourcecode.org/snaptoken/kilo/04.aTextViewer.html#scrolling-with-page-up-and-page-down
diff --git a/tted.c b/tted.c
index 035ada6..c2380e2 100644
--- a/tted.c
+++ b/tted.c
@@ -16,6 +16,7 @@
 /** defines */
 #define TTED_VERSION "0.0.1"
 #define CTRL_KEY(k) ((k) & 0x1f)
+#define TTED_TAB_STOP 8
 
 enum editorKey {
     ARROW_LEFT = 1000,
@@ -33,12 +34,16 @@ enum editorKey {
 /** data */
 typedef struct erow {
     int size;
+    int rsize;
     char *chars;
+    char *render;
 } erow;
 
 struct editorConfig {
     int cx, cy;
+    int rx;
     int rowoff;
+    int coloff;
     int screenrows;
     int screencols;
     int numrows;
@@ -168,6 +173,43 @@ int getWindowSize(int *rows, int *cols) {
 }
 
 /** Row operations */
+int editorRowCxToRx(erow *row, int cx) {
+    int rx = 0;
+    int j;
+    for (j=0; j < cx; j++){
+        if (row->chars[j] == '\t') {
+            rx += (TTED_TAB_STOP -1) - (rx % TTED_TAB_STOP);
+        }
+        rx++;
+    }
+    return rx;
+}
+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*(TTED_TAB_STOP - 1) + 1);
+
+    int idx = 0;
+    for (j = 0; j < row->size; j++) {
+        if (row->chars[j] == '\t') {
+            row->render[idx++] = ' ';
+            while (idx % TTED_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));
 
@@ -176,6 +218,9 @@ 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++;
 }
 
@@ -221,11 +266,23 @@ void abFree(struct abuf *ab) {
 
 /** output */
 void editorScroll() {
-    if (E.cy < E.rowoff){
+    E.rx = 0;
+    if (E.cy < E.numrows){
+        E.rx = editorRowCxToRx(&E.row[E.cy], E.cx);
+    }
+
+
+    if (E.cy < E.rowoff) {
         E.rowoff = E.cy;
     }
     if (E.cy >= E.rowoff + E.screenrows) {
-        E.rowoff = E.cy - E.screenrows +1;
+        E.rowoff = E.cy - E.screenrows + 1;
+    }
+    if (E.rx < E.coloff) {
+        E.coloff = E.rx;
+    }
+    if (E.rx >= E.coloff + E.screencols) {
+        E.coloff = E.rx - E.screencols + 1;
     }
 }
 
@@ -250,9 +307,10 @@ void editorDrawRows(struct abuf *ab) {
                 abAppend(ab, "~", 1);
             }
         } else { // draw buffer
-            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; // truncate if further than columns
-            abAppend(ab, E.row[filerow].chars, len);
+            abAppend(ab, &E.row[filerow].render[E.coloff], len);
         }
 
         abAppend(ab, "\x1b[K", 3);
@@ -271,7 +329,7 @@ void editorRefreshScreen() {
     editorDrawRows(&ab);
 
     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.rx - E.coloff) + 1);
     abAppend(&ab, buf, strlen(buf));
     abAppend(&ab, "\x1b[?25h", 6);
 
@@ -282,15 +340,23 @@ 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:
@@ -304,6 +370,13 @@ void editorMoveCursor(int key) {
             }
             break;
     }
+
+    // Snap cursor
+    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() {
@@ -343,7 +416,9 @@ void editorProcessKeypress() {
 void initEditor() {
     E.cx = 0;
     E.cy = 0;
+    E.rx = 0;
     E.rowoff = 0;
+    E.coloff = 0;
     E.numrows = 0;
     E.row = NULL;
     if (getWindowSize(&E.screenrows, &E.screencols) == -1) die("getWindowSize");