feat: Query screen size and store it in global state.

kilo.c

@@ -1,9 +1,11 @@
 /*** includes ***/
 
+#include <asm-generic/ioctls.h>
 #include <ctype.h>
 #include <errno.h>
 #include <stdio.h>
 #include <stdlib.h>
+#include <sys/ioctl.h>
 #include <termios.h>
 #include <unistd.h>
 
@@ -14,6 +16,8 @@
 /*** data ***/
 
 struct editorConfig {
+    int screenrows;
+    int screencols;
     struct termios orig_termios;
 };
 
@@ -67,10 +71,22 @@ char editorReadKey() {
     return c;
 }
 
+int getWindowSize(int *rows, int *cols) {
+    struct winsize ws;
+
+    if (ioctl(STDOUT_FILENO, TIOCGWINSZ, &ws) == -1 || ws.ws_col == 0) {
+        return -1;
+    }
+
+    *rows = ws.ws_row;
+    *cols = ws.ws_col;
+    return 0;
+}
+
 /*** output ***/
 
 void editorDrawRows() {
-    for (int y = 0; y < 24; y++) {
+    for (int y = 0; y < E.screenrows; y++) {
         write(STDOUT_FILENO, "~\r\n", 3);
     }
 }
@@ -105,8 +121,15 @@ void editorProcessKeypress() {
 
 /*** init ***/
 
+void initEditor() {
+    if (getWindowSize(&E.screenrows, &E.screencols) == -1) {
+        die("getWindowSize");
+    }
+}
+
 int main() {
     enableRawMode();
+    initEditor();
 
     while(1) {
         editorRefreshScreen();