From e6af7abbd8b9d6ca07fb51c9cf1dc6128e7b17d6 Mon Sep 17 00:00:00 2001
From: meh <no-reply@pathscale.com>
Date: Mon, 31 Aug 2026 16:30:28 +0700
Subject: [PATCH] fix(capture): honour the capture viewport environment
 variables

`scripts/render-check.sh` has documented and exported CHUZZ_CAPTURE_WIDTH and
CHUZZ_CAPTURE_HEIGHT since it was written, and the capture entry point read
neither: it passed a literal 1440 by 960. Every capture was that size whatever
the caller asked for, and a run at another width produced a byte-identical
tree, which is how this surfaced.

That matters now because captures are about to be compared against a reference
browser. Two engines laying the same page out at different widths disagree on
every percentage width, every centred box and every responsive breakpoint, so
an unhonoured viewport turns a diff into noise that reads exactly like a
rendering fault.

Only CHUZZ_CAPTURE_SCALE was wired up, so the fix follows its shape.
---
 apps/chuzz/src/capture.rs    | 23 +++++++++++++++++++++++
 apps/chuzz/src/tauri_main.rs |  5 +++--
 2 files changed, 26 insertions(+), 2 deletions(-)

diff --git a/apps/chuzz/src/capture.rs b/apps/chuzz/src/capture.rs
index 7fd9ae79..1d8b0c92 100644
--- a/apps/chuzz/src/capture.rs
+++ b/apps/chuzz/src/capture.rs
@@ -45,6 +45,29 @@ fn capture_scale() -> f32 {
         .unwrap_or(1.0)
 }
 
+/// CSS pixel size to lay the page out at. Defaults to 1440 by 960.
+///
+/// A capture is only comparable against a reference browser when both laid the
+/// page out at the same width: every responsive breakpoint, every percentage
+/// width and every centred box moves with it. These were exported by
+/// `scripts/render-check.sh` and read by nothing, so a run at another size
+/// silently produced the default and the resulting diff was all viewport and
+/// no signal.
+pub fn capture_viewport() -> (u32, u32) {
+    fn dimension(name: &str, fallback: u32) -> u32 {
+        std::env::var(name)
+            .ok()
+            .and_then(|value| value.parse().ok())
+            .filter(|pixels: &u32| *pixels > 0)
+            .unwrap_or(fallback)
+    }
+
+    (
+        dimension("CHUZZ_CAPTURE_WIDTH", 1440),
+        dimension("CHUZZ_CAPTURE_HEIGHT", 960),
+    )
+}
+
 /// Which colour scheme to render at. Defaults to dark.
 ///
 /// A site that respects `prefers-color-scheme` is a different page in each, so
diff --git a/apps/chuzz/src/tauri_main.rs b/apps/chuzz/src/tauri_main.rs
index 148c97d5..25654530 100644
--- a/apps/chuzz/src/tauri_main.rs
+++ b/apps/chuzz/src/tauri_main.rs
@@ -186,10 +186,11 @@ fn main() {
             .enable_all()
             .build()
             .expect("capture needs a tokio runtime");
+        let (width, height) = capture::capture_viewport();
         let result = runtime.block_on(capture::capture(
             &url,
-            1440,
-            960,
+            width,
+            height,
             std::path::Path::new(&output),
         ));
         match result {