kiloz

commit 4940f97f8cc9ad33079dec85720f8eef0f2a2a0f
parent 47ff0ed3be44c1ebe20aad21033e3e372d1c64ec
Author: Martin Ashby <martin@ashbysoft.com>
Date:   Sat, 13 Jan 2024 09:04:32 +0000

Step 70

Diffstat:
M
src/main.zig
 | 
33
+++++++++++++++++++++++----------

1 file changed, 23 insertions(+), 10 deletions(-)
diff --git a/src/main.zig b/src/main.zig
@@ -36,10 +36,11 @@ const EditorState = struct {
     a: std.mem.Allocator,
     screen_buf: std.ArrayListUnmanaged(u8) = .{},
     termios_orig: std.os.linux.termios = undefined,
-    screenrows: u16 = 0,
-    screencols: u16 = 0,
-    cx: u16 = 10,
-    cy: u16 = 10,
+    screenrows: usize = 0,
+    screencols: usize = 0,
+    cx: usize = 0,
+    cy: usize = 0,
+    rowoff: usize = 0,
     erow: []ERow = &[_]ERow{},
 
     fn init(a: std.mem.Allocator) EditorState {
@@ -226,6 +227,8 @@ fn clearScreen() void {
 }
 
 fn editorRefreshScreen(es: *EditorState) !void {
+    editorScroll(es);
+
     // Use a buffer to avoid multiple write() calls to the actual terminal device
     // Reduces rendering artifacts / flickering
     es.screen_buf.clearRetainingCapacity();
@@ -235,7 +238,7 @@ fn editorRefreshScreen(es: *EditorState) !void {
     //try wtr.writeAll("\x1b[2J");    // J clear 2 whole screen
     try wtr.writeAll("\x1b[H"); // Reset cursor (to 1:1)
     try editorDrawRows(es, wtr);
-    try std.fmt.format(wtr, "\x1b[{};{}H", .{ es.cy + 1, es.cx + 1 }); // Move the cursor to our stored position
+    try std.fmt.format(wtr, "\x1b[{};{}H", .{ es.cy - es.rowoff + 1, es.cx + 1 }); // Move the cursor to our stored position
     try wtr.writeAll("\x1b[?25h"); // Show the cursor again
     try std.io.getStdOut().writeAll(es.screen_buf.items);
 }
@@ -246,7 +249,8 @@ fn editorDrawRows(es: *const EditorState, wtr: anytype) !void {
 
         var lw = limitedWriter(wtr, es.screencols); // Never write more than we have columns
         const wtr2 = lw.writer();
-        if (y >= es.erow.len) {
+        const filerow = y + es.rowoff;
+        if (filerow >= es.erow.len) {
             if (es.erow.len == 0 and y == es.screenrows / 3) {
                 const welcome_msg = try std.fmt.allocPrint(es.a, "Kilo editor -- version {s}", .{version}); // TODO don't allocate every time...
                 defer es.a.free(welcome_msg);
@@ -259,7 +263,7 @@ fn editorDrawRows(es: *const EditorState, wtr: anytype) !void {
                 try wtr2.writeAll("~");
             }
         } else {
-            try wtr2.writeAll(es.erow[y]);
+            try wtr2.writeAll(es.erow[filerow]);
         }
 
         if (y < es.screenrows-1) {
@@ -268,6 +272,15 @@ fn editorDrawRows(es: *const EditorState, wtr: anytype) !void {
     }
 }
 
+fn editorScroll(es: *EditorState) void {
+    if (es.cy < es.rowoff) {
+        es.rowoff = es.cy;
+    }
+    if (es.cy >= es.rowoff + es.screenrows) {
+        es.rowoff = es.cy - es.screenrows + 1;
+    }
+}
+
 //// Input
 
 fn editorProcessKeyPress(es: *EditorState) !void {
@@ -294,7 +307,7 @@ fn editorMoveCursor(key: editorKey, es: *EditorState) !void {
             if (es.cy > 0) es.cy -= 1;
         },
         .ARROW_DOWN => {
-            if (es.cy < (es.screenrows - 1)) es.cy += 1;
+            if (es.cy < es.erow.len) es.cy += 1;
         },
         .ARROW_LEFT => {
             if (es.cx > 0) es.cx -= 1;
@@ -303,10 +316,10 @@ fn editorMoveCursor(key: editorKey, es: *EditorState) !void {
             if (es.cx < (es.screencols - 1)) es.cx += 1;
         },
         .PAGE_UP => {
-            es.cy = 0;
+            es.cy = std.math.sub(usize, es.cy, es.screenrows) catch 0;
         },
         .PAGE_DOWN => {
-            es.cy = es.screenrows-1;
+            es.cy = @min(es.cy+es.screenrows, es.erow.len-1);
         },
         .HOME => {
             es.cx = 0;