From 334743e8a7182fd7f233cbcf7c4a057700d7c7fe Mon Sep 17 00:00:00 2001
From: Mitchell Hashimoto <mitchell.hashimoto@gmail.com>
Date: Mon, 14 Nov 2022 17:41:15 -0800
Subject: [PATCH] Don't crash on huge padding, warn users if padding is absurd

---
 src/Window.zig        | 8 ++++++++
 src/config.zig        | 5 +++++
 src/renderer/size.zig | 8 ++++----
 3 files changed, 17 insertions(+), 4 deletions(-)

diff --git a/src/Window.zig b/src/Window.zig
index a96cd73fb..ad1b9b836 100644
--- a/src/Window.zig
+++ b/src/Window.zig
@@ -581,6 +581,14 @@ fn sizeCallback(window: glfw.Window, width: i32, height: i32) void {
 
     // Recalculate our grid size
     win.grid_size = win.renderer.gridSize(screen_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?", .{});
+    }
+    if (win.grid_size.rows < 2 and (win.padding.top > 0 or win.padding.bottom > 0)) {
+        log.warn("WARNING: very small terminal grid detected with padding " ++
+            "set. Is your padding reasonable?", .{});
+    }
 
     // Mail the IO thread
     _ = win.io_thread.mailbox.push(.{
diff --git a/src/config.zig b/src/config.zig
index 796894d37..d7a60753e 100644
--- a/src/config.zig
+++ b/src/config.zig
@@ -93,6 +93,11 @@ pub const Config = struct {
     /// the window border. The "x" option applies to the left and right
     /// padding and the "y" option is top and bottom. The value is in points,
     /// meaning that it will be scaled appropriately for screen DPI.
+    ///
+    /// If this value is set too large, the screen will render nothing, because
+    /// the grid will be completely squished by the padding. It is up to you
+    /// as the user to pick a reasonable value. If you pick an unreasonable
+    /// value, a warning will appear in the logs.
     @"window-padding-x": u32 = 0,
     @"window-padding-y": u32 = 0,
 
diff --git a/src/renderer/size.zig b/src/renderer/size.zig
index 51a3b135c..a96ae160e 100644
--- a/src/renderer/size.zig
+++ b/src/renderer/size.zig
@@ -48,8 +48,8 @@ pub const ScreenSize = struct {
     /// Subtract padding from the screen size.
     pub fn subPadding(self: ScreenSize, padding: Padding) ScreenSize {
         return .{
-            .width = self.width - @floatToInt(u32, padding.left + padding.right),
-            .height = self.height - @floatToInt(u32, padding.top + padding.bottom),
+            .width = self.width -| @floatToInt(u32, padding.left + padding.right),
+            .height = self.height -| @floatToInt(u32, padding.top + padding.bottom),
         };
     }
 };
@@ -71,8 +71,8 @@ pub const GridSize = struct {
     /// Update the columns/rows for the grid based on the given screen and
     /// cell size.
     pub fn update(self: *GridSize, screen: ScreenSize, cell: CellSize) void {
-        self.columns = @floatToInt(Unit, @intToFloat(f32, screen.width) / cell.width);
-        self.rows = @floatToInt(Unit, @intToFloat(f32, screen.height) / cell.height);
+        self.columns = @max(1, @floatToInt(Unit, @intToFloat(f32, screen.width) / cell.width));
+        self.rows = @max(1, @floatToInt(Unit, @intToFloat(f32, screen.height) / cell.height));
     }
 };