Bug 1708403 - Make resetting of scroll position for drawSnapshot opt-in. r=mstange,kmag

Differential Revision: https://phabricator.services.mozilla.com/D117613

browser/extensions/screenshots/background/takeshot.js

@@ -40,6 +40,7 @@ this.takeshot = (function() {
         height: pos.height,
       };
       options.rect = rectangle;
+      options.resetScrollPosition = true;
 
       // To avoid creating extremely large images (which causes
       // performance problems), we set the devicePixelRatio to 1.

devtools/server/actors/utils/capture-screenshot.js

@@ -118,7 +118,8 @@ async function captureScreenshot(args, browsingContext) {
       const snapshot = await browsingContext.currentWindowGlobal.drawSnapshot(
         rect,
         actualRatio,
-        "rgb(255,255,255)"
+        "rgb(255,255,255)",
+        args.fullpage
       );
 
       const fileScale = args.fileScale || actualRatio;

dom/canvas/test/test_drawSnapshot_fixed.html

@@ -43,7 +43,7 @@
     // be visually in the middle of the root scroll frame, but should still be at the
     // top of the snapshot (since snapshots with a rect are taken relative to the document).
     var rect = new window.DOMRect(0, 0, 500, 2000);
-    let image = await SpecialPowers.snapshotContext(window, rect, "rgb(255, 255, 255)");
+    let image = await SpecialPowers.snapshotContext(window, rect, "rgb(255, 255, 255)", true);
     testWrapCx.drawImage(image, 0, 0);
 
     var refCanvas = make_canvas();

dom/chrome-webidl/WindowGlobalActors.webidl

@@ -128,6 +128,10 @@ interface WindowGlobalParent : WindowContext {
    * @param scale The scale to render the window at. Use devicePixelRatio
    * to have comparable rendering to the OS.
    * @param backgroundColor The background color to use.
+   * @param resetScrollPosition If true, temporarily resets the scroll position
+   * of the root scroll frame to 0, such that position:fixed elements are drawn
+   * at their initial position. This parameter only takes effect when passing a
+   * non-null rect.
    *
    * This API can only be used in the parent process, as content processes
    * cannot access the rendering of out of process iframes. This API works
@@ -136,7 +140,8 @@ interface WindowGlobalParent : WindowContext {
   [Throws]
   Promise<ImageBitmap> drawSnapshot(DOMRect? rect,
                                     double scale,
-                                    UTF8String backgroundColor);
+                                    UTF8String backgroundColor,
+                                    optional boolean resetScrollPosition = false);
 
   /**
    * Fetches the securityInfo object for this window. This function will

dom/ipc/WindowGlobalParent.cpp

@@ -930,7 +930,7 @@ void WindowGlobalParent::PermitUnload(std::function<void(bool)>&& aResolver) {
 
 already_AddRefed<mozilla::dom::Promise> WindowGlobalParent::DrawSnapshot(
     const DOMRect* aRect, double aScale, const nsACString& aBackgroundColor,
-    mozilla::ErrorResult& aRv) {
+    bool aResetScrollPosition, mozilla::ErrorResult& aRv) {
   nsIGlobalObject* global = GetParentObject();
   RefPtr<Promise> promise = Promise::Create(global, aRv);
   if (NS_WARN_IF(aRv.Failed())) {
@@ -949,6 +949,8 @@ already_AddRefed<mozilla::dom::Promise> WindowGlobalParent::DrawSnapshot(
   if (!aRect) {
     // If no explicit Rect was passed, we want the currently visible viewport.
     flags = gfx::CrossProcessPaintFlags::DrawView;
+  } else if (aResetScrollPosition) {
+    flags = gfx::CrossProcessPaintFlags::ResetScrollPosition;
   }
 
   if (!gfx::CrossProcessPaint::Start(this, aRect, (float)aScale, color, flags,

dom/ipc/WindowGlobalParent.h

@@ -160,7 +160,7 @@ class WindowGlobalParent final : public WindowContext,
 
   already_AddRefed<mozilla::dom::Promise> DrawSnapshot(
       const DOMRect* aRect, double aScale, const nsACString& aBackgroundColor,
-      mozilla::ErrorResult& aRv);
+      bool aResetScrollPosition, mozilla::ErrorResult& aRv);
 
   already_AddRefed<Promise> GetSecurityInfo(ErrorResult& aRv);
 

dom/media/systemservices/video_engine/tab_capturer.cc

@@ -178,7 +178,7 @@ void TabCapturer::CaptureFrameNow() {
     // XXX This would be more efficient if it returned a MozPromise, and
     // even more if we used CrossProcessPaint directly and returned a surface.
     RefPtr<dom::Promise> promise =
-        wgp->DrawSnapshot(nullptr, 1.0, "white"_ns, IgnoreErrors());
+        wgp->DrawSnapshot(nullptr, 1.0, "white"_ns, false, IgnoreErrors());
     if (!promise) {
       return;
     }

gfx/ipc/CrossProcessPaint.cpp

@@ -122,8 +122,10 @@ PaintFragment PaintFragment::Record(dom::BrowsingContext* aBc,
   RenderDocumentFlags renderDocFlags = RenderDocumentFlags::None;
   if (!(aFlags & CrossProcessPaintFlags::DrawView)) {
     renderDocFlags = (RenderDocumentFlags::IgnoreViewportScrolling |
-                      RenderDocumentFlags::ResetViewportScrolling |
                       RenderDocumentFlags::DocumentRelative);
+    if (aFlags & CrossProcessPaintFlags::ResetScrollPosition) {
+      renderDocFlags |= RenderDocumentFlags::ResetViewportScrolling;
+    }
   }
 
   // Perform the actual rendering

gfx/ipc/CrossProcessPaint.h

@@ -43,6 +43,7 @@ class CrossProcessPaint;
 enum class CrossProcessPaintFlags {
   None = 0,
   DrawView = 1 << 1,
+  ResetScrollPosition = 1 << 2,
 };
 
 MOZ_MAKE_ENUM_CLASS_BITWISE_OPERATORS(CrossProcessPaintFlags)

toolkit/components/extensions/parent/ext-tabs-base.js

@@ -132,8 +132,20 @@ class TabBase {
     let scale = options?.scale || win.devicePixelRatio;
     let rect = options?.rect && win.DOMRect.fromRect(options.rect);
 
+    // We only allow mozilla addons to use the resetScrollPosition option,
+    // since it's not standardized.
+    let resetScrollPosition = false;
+    if (!context.extension.restrictSchemes) {
+      resetScrollPosition = !!options?.resetScrollPosition;
+    }
+
     let wgp = this.browsingContext.currentWindowGlobal;
-    let image = await wgp.drawSnapshot(rect, scale * zoom, "white");
+    let image = await wgp.drawSnapshot(
+      rect,
+      scale * zoom,
+      "white",
+      resetScrollPosition
+    );
 
     let doc = Services.appShell.hiddenDOMWindow.document;
     let canvas = doc.createElement("canvas");

toolkit/components/extensions/schemas/extension_types.json

@@ -45,6 +45,11 @@
             "type": "number",
             "optional": true,
             "description": "The scale of the resulting image.  Defaults to <code>devicePixelRatio</code>."
+          },
+          "resetScrollPosition": {
+            "type": "boolean",
+            "optional": true,
+            "description": "If true, temporarily resets the scroll position of the document to 0. Only takes effect if rect is also specified."
           }
         }
       },