From 55b1a9be2fd9b219b019022d98b0276de86f0a79 Mon Sep 17 00:00:00 2001
From: Shubham Gupta <shubham13297@gmail.com>
Date: Wed, 26 Mar 2025 13:49:40 +0800
Subject: [PATCH] Process Key Value Pairs into ViewportDescription

Signed-off-by: Shubham Gupta <shubham13297@gmail.com>
---
 components/script/dom/htmlmetaelement.rs      | 14 ++++++--
 components/shared/compositing/lib.rs          |  1 +
 .../compositing/viewport_description.rs       | 36 +++++++++++++++++++
 3 files changed, 48 insertions(+), 3 deletions(-)

diff --git a/components/script/dom/htmlmetaelement.rs b/components/script/dom/htmlmetaelement.rs
index d1bfffa6609..8453258308d 100644
--- a/components/script/dom/htmlmetaelement.rs
+++ b/components/script/dom/htmlmetaelement.rs
@@ -2,6 +2,7 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
 
+use compositing_traits::viewport_description::ViewportDescription;
 use dom_struct::dom_struct;
 use html5ever::{LocalName, Prefix, local_name, ns};
 use js::rust::HandleObject;
@@ -62,7 +63,7 @@ impl HTMLMetaElement {
                 self.apply_referrer();
             }
             if name == "viewport" {
-                self.parse_viewport();
+                self.parse_and_send_viewport_if_necessary();
             }
         // https://html.spec.whatwg.org/multipage/#attr-meta-http-equiv
         } else if !self.HttpEquiv().is_empty() {
@@ -119,8 +120,15 @@ impl HTMLMetaElement {
     }
 
     /// <https://drafts.csswg.org/css-viewport/#parsing-algorithm>
-    fn parse_viewport(&self) {
-        let _element = self.upcast::<Element>();
+    fn parse_and_send_viewport_if_necessary(&self) {
+        // Skip processing if this isn't the top level frame
+        if !self.owner_window().is_top_level() {
+            return;
+        }
+        let element = self.upcast::<Element>();
+        if let Some(content) = element.get_attribute(&ns!(), &local_name!("content")) {
+            let _viewport = ViewportDescription::from_str(&content.value()).unwrap_or_default();
+        }
     }
 
     /// <https://html.spec.whatwg.org/multipage/#attr-meta-http-equiv-content-security-policy>
diff --git a/components/shared/compositing/lib.rs b/components/shared/compositing/lib.rs
index 67ff0046885..ee4e230fcf0 100644
--- a/components/shared/compositing/lib.rs
+++ b/components/shared/compositing/lib.rs
@@ -23,6 +23,7 @@ use webrender_api::DocumentId;
 
 pub mod display_list;
 pub mod rendering_context;
+pub mod viewport_description;
 
 use std::collections::HashMap;
 use std::sync::{Arc, Mutex};
diff --git a/components/shared/compositing/viewport_description.rs b/components/shared/compositing/viewport_description.rs
index 2418921e2c3..64f374d7b7b 100644
--- a/components/shared/compositing/viewport_description.rs
+++ b/components/shared/compositing/viewport_description.rs
@@ -5,6 +5,7 @@
 //! This module contains helpers for Viewport
 
 use std::collections::HashMap;
+use std::str::FromStr;
 
 use euclid::default::Scale;
 use serde::{Deserialize, Serialize};
@@ -18,6 +19,9 @@ pub const MAX_ZOOM: f32 = 10.0;
 /// <https://developer.mozilla.org/en-US/docs/Web/HTML/Viewport_meta_tag#initial-scale>
 pub const DEFAULT_ZOOM: f32 = 1.0;
 
+/// <https://drafts.csswg.org/css-viewport/#parsing-algorithm>
+const SEPARATORS: [char; 2] = [',', ';']; // Comma (0x2c) and Semicolon (0x3b)
+
 /// A set of viewport descriptors:
 ///
 /// <https://www.w3.org/TR/css-viewport-1/#viewport-meta>
@@ -137,3 +141,35 @@ impl ViewportDescription {
         zoom.clamp(self.minimum_scale.get(), self.maximum_scale.get())
     }
 }
+
+/// <https://drafts.csswg.org/css-viewport/#parsing-algorithm>
+///
+/// This implementation differs from the specified algorithm, but is equivalent because
+/// 1. It uses higher-level string operations to process string instead of character-by-character iteration.
+/// 2. Uses trim() operation to handle whitespace instead of explicitly handling throughout the parsing process.
+impl FromStr for ViewportDescription {
+    type Err = ViewportDescriptionParseError;
+    fn from_str(string: &str) -> Result<Self, Self::Err> {
+        if string.is_empty() {
+            return Err(ViewportDescriptionParseError::Empty);
+        }
+
+        // Parse key-value pairs from the content string
+        // 1. Split the content string using SEPARATORS
+        // 2. Split into key-value pair using "=" and trim whitespaces
+        // 3. Insert into HashMap
+        let parsed_values = string
+            .split(SEPARATORS)
+            .filter_map(|pair| {
+                let mut parts = pair.split('=').map(str::trim);
+                if let (Some(key), Some(value)) = (parts.next(), parts.next()) {
+                    Some((key.to_string(), value.to_string()))
+                } else {
+                    None
+                }
+            })
+            .collect::<HashMap<String, String>>();
+
+        Ok(Self::process_viewport_key_value_pair(parsed_values))
+    }
+}