diff --git a/src/Window.zig b/src/Window.zig
index ad1b9b836..23f2a563c 100644
--- a/src/Window.zig
+++ b/src/Window.zig
@@ -79,8 +79,10 @@ io: termio.Impl,
 io_thread: termio.Thread,
 io_thr: std.Thread,
 
-/// The dimensions of the grid in rows and columns.
+/// All the cached sizes since we need them at various times.
+screen_size: renderer.ScreenSize,
 grid_size: renderer.GridSize,
+cell_size: renderer.CellSize,
 
 /// Explicit padding due to configuration
 padding: renderer.Padding,
@@ -262,6 +264,9 @@ pub fn create(alloc: Allocator, app: *App, config: *const Config) !*Window {
     });
     errdefer font_group.deinit(alloc);
 
+    // Pre-calculate our initial cell size ourselves.
+    const cell_size = try renderer.CellSize.init(alloc, font_group);
+
     // Convert our padding from points to pixels
     const padding_x = (@intToFloat(f32, config.@"window-padding-x") * x_dpi) / 72;
     const padding_y = (@intToFloat(f32, config.@"window-padding-y") * y_dpi) / 72;
@@ -279,6 +284,7 @@ pub fn create(alloc: Allocator, app: *App, config: *const Config) !*Window {
             .explicit = padding,
             .balance = config.@"window-padding-balance",
         },
+        .window_mailbox = .{ .window = self, .app = app.mailbox },
     });
     errdefer renderer_impl.deinit();
     renderer_impl.background = .{
@@ -298,13 +304,16 @@ pub fn create(alloc: Allocator, app: *App, config: *const Config) !*Window {
         .width = window_size.width,
         .height = window_size.height,
     };
-    const grid_size = renderer_impl.gridSize(screen_size);
+    const grid_size = renderer.GridSize.init(
+        screen_size.subPadding(padding),
+        cell_size,
+    );
 
     // Set a minimum size that is cols=10 h=4. This matches Mac's Terminal.app
     // but is otherwise somewhat arbitrary.
     try window.setSizeLimits(.{
-        .width = @floatToInt(u32, renderer_impl.cell_size.width * 10),
-        .height = @floatToInt(u32, renderer_impl.cell_size.height * 4),
+        .width = @floatToInt(u32, cell_size.width * 10),
+        .height = @floatToInt(u32, cell_size.height * 4),
     }, .{ .width = null, .height = null });
 
     // Create the cursor
@@ -371,7 +380,9 @@ pub fn create(alloc: Allocator, app: *App, config: *const Config) !*Window {
         .io = io,
         .io_thread = io_thread,
         .io_thr = undefined,
+        .screen_size = screen_size,
         .grid_size = grid_size,
+        .cell_size = cell_size,
         .padding = padding,
         .config = config,
 
@@ -569,18 +580,22 @@ fn sizeCallback(window: glfw.Window, width: i32, height: i32) void {
         };
     };
 
-    const screen_size: renderer.ScreenSize = .{
-        .width = px_size.width,
-        .height = px_size.height,
-    };
-
     const win = window.getUserPointer(Window) orelse return;
 
     // TODO: if our screen size didn't change, then we should avoid the
     // overhead of inter-thread communication
 
+    // Save our screen size
+    win.screen_size = .{
+        .width = px_size.width,
+        .height = px_size.height,
+    };
+
     // Recalculate our grid size
-    win.grid_size = win.renderer.gridSize(screen_size);
+    win.grid_size = renderer.GridSize.init(
+        win.screen_size.subPadding(win.padding),
+        win.cell_size,
+    );
     if (win.grid_size.columns < 5 and (win.padding.left > 0 or win.padding.right > 0)) {
         log.warn("WARNING: very small terminal grid detected with padding " ++
             "set. Is your padding reasonable?", .{});
@@ -594,7 +609,7 @@ fn sizeCallback(window: glfw.Window, width: i32, height: i32) void {
     _ = win.io_thread.mailbox.push(.{
         .resize = .{
             .grid_size = win.grid_size,
-            .screen_size = screen_size,
+            .screen_size = win.screen_size,
             .padding = win.padding,
         },
     }, .{ .forever = {} });
@@ -1386,10 +1401,10 @@ fn cursorPosCallback(
     //
 
     // the boundary point at which we consider selection or non-selection
-    const cell_xboundary = win.renderer.cell_size.width * 0.6;
+    const cell_xboundary = win.cell_size.width * 0.6;
 
     // first xpos of the clicked cell
-    const cell_xstart = @intToFloat(f32, win.mouse.left_click_point.x) * win.renderer.cell_size.width;
+    const cell_xstart = @intToFloat(f32, win.mouse.left_click_point.x) * win.cell_size.width;
     const cell_start_xpos = win.mouse.left_click_xpos - cell_xstart;
 
     // If this is the same cell, then we only start the selection if weve
@@ -1464,7 +1479,7 @@ fn posToViewport(self: Window, xpos: f64, ypos: f64) terminal.point.Viewport {
     return .{
         .x = if (xpos < 0) 0 else x: {
             // Our cell is the mouse divided by cell width
-            const cell_width = @floatCast(f64, self.renderer.cell_size.width);
+            const cell_width = @floatCast(f64, self.cell_size.width);
             const x = @floatToInt(usize, xpos / cell_width);
 
             // Can be off the screen if the user drags it out, so max
@@ -1473,7 +1488,7 @@ fn posToViewport(self: Window, xpos: f64, ypos: f64) terminal.point.Viewport {
         },
 
         .y = if (ypos < 0) 0 else y: {
-            const cell_height = @floatCast(f64, self.renderer.cell_size.height);
+            const cell_height = @floatCast(f64, self.cell_size.height);
             const y = @floatToInt(usize, ypos / cell_height);
             break :y @min(y, self.io.terminal.rows - 1);
         },
diff --git a/src/renderer/Options.zig b/src/renderer/Options.zig
index c313d91c6..38789f1c7 100644
--- a/src/renderer/Options.zig
+++ b/src/renderer/Options.zig
@@ -2,6 +2,7 @@
 
 const font = @import("../font/main.zig");
 const renderer = @import("../renderer.zig");
+const Window = @import("../Window.zig");
 
 /// The font group that should be used.
 font_group: *font.GroupCache,
@@ -9,6 +10,10 @@ font_group: *font.GroupCache,
 /// Padding options for the viewport.
 padding: Padding,
 
+/// The mailbox for sending the window messages. This is only valid
+/// once the thread has started and should not be used outside of the thread.
+window_mailbox: Window.Mailbox,
+
 pub const Padding = struct {
     // Explicit padding options, in pixels. The windowing thread is
     // expected to convert points to pixels for a given DPI.