fix: integer overflow crash when screen w * h > max(u16)

src/InternalScreen.zig

@@ -47,7 +47,7 @@ mouse_shape: MouseShape = .default,
 /// sets each cell to the default cell
 pub fn init(alloc: std.mem.Allocator, w: u16, h: u16) !InternalScreen {
     var screen = InternalScreen{
-        .buf = try alloc.alloc(InternalCell, w * h),
+        .buf = try alloc.alloc(InternalCell, @as(usize, @intCast(w)) * h),
     };
     for (screen.buf, 0..) |_, i| {
         screen.buf[i] = .{
@@ -87,7 +87,7 @@ pub fn writeCell(
         // height out of bounds
         return;
     }
-    const i = (row * self.width) + col;
+    const i = (@as(usize, @intCast(row)) * self.width) + col;
     assert(i < self.buf.len);
     self.buf[i].char.clearRetainingCapacity();
     self.buf[i].char.appendSlice(cell.char.grapheme) catch {

src/Screen.zig

@@ -33,7 +33,7 @@ pub fn init(alloc: std.mem.Allocator, winsize: Winsize, unicode: *const Unicode)
     const w = winsize.cols;
     const h = winsize.rows;
     const self = Screen{
-        .buf = try alloc.alloc(Cell, w * h),
+        .buf = try alloc.alloc(Cell, @as(usize, @intCast(w)) * h),
         .width = w,
         .height = h,
         .width_pix = winsize.x_pixel,
@@ -53,7 +53,7 @@ pub fn writeCell(self: *Screen, col: u16, row: u16, cell: Cell) void {
     if (col >= self.width or
         row >= self.height)
         return;
-    const i = (row * self.width) + col;
+    const i = (@as(usize, @intCast(row)) * self.width) + col;
     assert(i < self.buf.len);
     self.buf[i] = cell;
 }
@@ -62,7 +62,7 @@ pub fn readCell(self: *const Screen, col: u16, row: u16) ?Cell {
     if (col >= self.width or
         row >= self.height)
         return null;
-    const i = (row * self.width) + col;
+    const i = (@as(usize, @intCast(row)) * self.width) + col;
     assert(i < self.buf.len);
     return self.buf[i];
 }

src/Vaxis.zig

@@ -315,7 +315,7 @@ pub fn queueRefresh(self: *Vaxis) void {
 /// draws the screen to the terminal
 pub fn render(self: *Vaxis, tty: AnyWriter) !void {
     defer self.refresh = false;
-    assert(self.screen.buf.len == self.screen.width * self.screen.height); // correct size
+    assert(self.screen.buf.len == @as(usize, @intCast(self.screen.width)) * self.screen.height); // correct size
     assert(self.screen.buf.len == self.screen_last.buf.len); // same size
 
     // Set up sync before we write anything
@@ -353,7 +353,7 @@ pub fn render(self: *Vaxis, tty: AnyWriter) !void {
     if (self.caps.kitty_graphics)
         try tty.writeAll(ctlseqs.kitty_graphics_clear);
 
-    var i: u16 = 0;
+    var i: usize = 0;
     while (i < self.screen.buf.len) {
         const cell = self.screen.buf[i];
         const w: u16 = blk: {

src/Window.zig

@@ -198,16 +198,16 @@ pub fn fill(self: Window, cell: Cell) void {
         self.screen.width < self.x_off or
         self.screen.height < self.y_off)
         return;
-    const first_row: u16 = @intCast(@max(self.y_off, 0));
+    const first_row: usize = @intCast(@max(self.y_off, 0));
     if (self.x_off == 0 and self.width == self.screen.width) {
         // we have a full width window, therefore contiguous memory.
         const start = @min(first_row * self.width, self.screen.buf.len);
-        const end = @min(start + (self.height * self.width), self.screen.buf.len);
+        const end = @min(start + (@as(usize, @intCast(self.height)) * self.width), self.screen.buf.len);
         @memset(self.screen.buf[start..end], cell);
     } else {
         // Non-contiguous. Iterate over rows an memset
-        var row: u16 = first_row;
-        const first_col: u16 = @max(self.x_off, 0);
+        var row: usize = first_row;
+        const first_col: usize = @max(self.x_off, 0);
         const last_row = @min(self.height + self.y_off, self.screen.height);
         while (row < last_row) : (row += 1) {
             const start = @min(first_col + (row * self.screen.width), self.screen.buf.len);

src/widgets/terminal/Screen.zig

@@ -95,7 +95,7 @@ csi_u_flags: vaxis.Key.KittyFlags = @bitCast(@as(u5, 0)),
 /// sets each cell to the default cell
 pub fn init(alloc: std.mem.Allocator, w: u16, h: u16) !Screen {
     var screen = Screen{
-        .buf = try alloc.alloc(Cell, w * h),
+        .buf = try alloc.alloc(Cell, @as(usize, @intCast(w)) * h),
         .scrolling_region = .{
             .top = 0,
             .bottom = h - 1,