Improve window scroll

karlseguin · karlseguin · commit 15b64d5a2589 · 2025-10-01T18:41:56.000+08:00
scroll alias for scrollTo

add get_scrollX and get_scrollY, along with their aliases: pageXOffset and
pageYOffset. These always return 0, unless scroll or scrollTo are called.
diff --git a/src/browser/html/window.zig b/src/browser/html/window.zig
@@ -68,6 +68,8 @@ pub const Window = struct {
     performance: Performance,
     screen: Screen = .{},
     css: Css = .{},
+    scroll_x: u32 = 0,
+    scroll_y: u32 = 0,
     onload_callback: ?Function = null,
 
     pub fn create(target: ?[]const u8, navigator: ?Navigator) !Window {
@@ -388,12 +390,20 @@ pub const Window = struct {
         const Opts = struct {
             top: i32,
             left: i32,
-            behavior: []const u8,
+            behavior: []const u8 = "",
         };
     };
-    pub fn _scrollTo(self: *Window, opts: ScrollToOpts, y: ?u32) !void {
-        _ = opts;
-        _ = y;
+    pub fn _scrollTo(self: *Window, opts: ScrollToOpts, y: ?i32) !void {
+        switch (opts) {
+            .x => |x| {
+                self.scroll_x = @intCast(@max(x, 0));
+                self.scroll_y = @intCast(@max(0, y orelse 0));
+            },
+            .opts => |o| {
+                self.scroll_y = @intCast(@max(0, o.top));
+                self.scroll_x = @intCast(@max(0, o.left));
+            },
+        }
 
         {
             const scroll_event = try parser.eventCreate();
@@ -417,6 +427,28 @@ pub const Window = struct {
             );
         }
     }
+    pub fn _scroll(self: *Window, opts: ScrollToOpts, y: ?i32) !void {
+        // just an alias for scrollTo
+        return self._scrollTo(opts, y);
+    }
+
+    pub fn get_scrollX(self: *const Window) u32 {
+        return self.scroll_x;
+    }
+
+    pub fn get_scrollY(self: *const Window) u32 {
+        return self.scroll_y;
+    }
+
+    pub fn get_pageXOffset(self: *const Window) u32 {
+        // just an alias for scrollX
+        return self.get_scrollX();
+    }
+
+    pub fn get_pageYOffset(self: *const Window) u32 {
+        // just an alias for scrollY
+        return self.get_scrollY();
+    }
 
     // libdom's document doesn't have a parent, which is correct, but
     // breaks the event bubbling that happens for many events from
diff --git a/src/tests/window/window.html b/src/tests/window/window.html
@@ -1,6 +1,6 @@
 <!DOCTYPE html>
 <script src="../testing.js"></script>
-<body></body>
+<body style=height:4000px;width:4000px></body>
 <script id=aliases>
   testing.expectEqual(window, window.self);
   testing.expectEqual(window, window.parent);
@@ -82,12 +82,41 @@
 <script id=scroll>
   let scroll = false;
   let scrollend = false
+
   window.addEventListener('scroll', () => {scroll = true});
   document.addEventListener('scrollend', () => {scrollend = true});
   window.scrollTo(0, 0);
+  testing.expectEqual(0, scrollX);
+  testing.expectEqual(0, pageXOffset);
+  testing.expectEqual(0, scrollY);
+  testing.expectEqual(0, pageYOffset);
 
   testing.expectEqual(true, scroll);
   testing.expectEqual(true, scrollend);
+
+  window.scrollTo(10, 20);
+  testing.expectEqual(10, scrollX);
+  testing.expectEqual(10, pageXOffset);
+  testing.expectEqual(20, scrollY);
+  testing.expectEqual(20, pageYOffset);
+
+  window.scrollTo(-10, -20);
+  testing.expectEqual(0, scrollX);
+  testing.expectEqual(0, pageXOffset);
+  testing.expectEqual(0, scrollY);
+  testing.expectEqual(0, pageYOffset);
+
+  window.scrollTo({top: 30, left: 40});
+  testing.expectEqual(40, scrollX);
+  testing.expectEqual(40, pageXOffset);
+  testing.expectEqual(30, scrollY);
+  testing.expectEqual(30, pageYOffset);
+
+  window.scrollTo({top: -30, left: -40});
+  testing.expectEqual(0, scrollX);
+  testing.expectEqual(0, pageXOffset);
+  testing.expectEqual(0, scrollY);
+  testing.expectEqual(0, pageYOffset);
 </script>
 
 <script id=queueMicroTask>
