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The default canvas size is 300x150 pixels. If the element or document we are trying to screenshot for the WebDriver is not at least that size, then we will create a canvas that is wider or taller than the actual element we are painting, resulting in a bunch of transparent pixels falling off the end. This fixes 14 WPT css/CSS2/floats tests that we run in CI, and presumably a ton of other reftests in the WPT test suite.
81 lines
3.4 KiB
C++
81 lines
3.4 KiB
C++
/*
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* Copyright (c) 2022, Tim Flynn <trflynn89@serenityos.org>
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#include <AK/Optional.h>
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#include <LibGfx/Bitmap.h>
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#include <LibGfx/Rect.h>
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#include <LibWeb/DOM/Document.h>
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#include <LibWeb/DOM/ElementFactory.h>
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#include <LibWeb/HTML/AnimationFrameCallbackDriver.h>
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#include <LibWeb/HTML/BrowsingContext.h>
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#include <LibWeb/HTML/HTMLCanvasElement.h>
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#include <LibWeb/HTML/TagNames.h>
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#include <LibWeb/HTML/TraversableNavigable.h>
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#include <LibWeb/HTML/Window.h>
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#include <LibWeb/Namespace.h>
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#include <LibWeb/Page/Page.h>
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#include <LibWeb/Platform/EventLoopPlugin.h>
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#include <LibWeb/WebDriver/Error.h>
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#include <LibWeb/WebDriver/Screenshot.h>
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namespace Web::WebDriver {
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// https://w3c.github.io/webdriver/#dfn-encoding-a-canvas-as-base64
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static Response encode_canvas_element(HTML::HTMLCanvasElement& canvas)
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{
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// FIXME: 1. If the canvas element’s bitmap’s origin-clean flag is set to false, return error with error code unable to capture screen.
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// 2. If the canvas element’s bitmap has no pixels (i.e. either its horizontal dimension or vertical dimension is zero) then return error with error code unable to capture screen.
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if (canvas.bitmap()->width() == 0 || canvas.bitmap()->height() == 0)
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return Error::from_code(ErrorCode::UnableToCaptureScreen, "Captured screenshot is empty"sv);
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// 3. Let file be a serialization of the canvas element’s bitmap as a file, using "image/png" as an argument.
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// 4. Let data url be a data: URL representing file. [RFC2397]
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auto data_url = canvas.to_data_url("image/png"sv, {});
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// 5. Let index be the index of "," in data url.
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auto index = data_url.find_byte_offset(',');
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VERIFY(index.has_value());
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// 6. Let encoded string be a substring of data url using (index + 1) as the start argument.
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auto encoded_string = MUST(data_url.substring_from_byte_offset(*index + 1));
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// 7. Return success with data encoded string.
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return JsonValue { move(encoded_string) };
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}
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// Common animation callback steps between:
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// https://w3c.github.io/webdriver/#take-screenshot
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// https://w3c.github.io/webdriver/#take-element-screenshot
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Response capture_element_screenshot(Painter const& painter, Page& page, DOM::Element& element, Gfx::IntRect& rect)
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{
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Optional<Response> encoded_string_or_error;
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element.document().window().animation_frame_callback_driver().add([&](auto) {
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auto viewport_rect = page.top_level_traversable()->viewport_rect();
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rect.intersect(page.enclosing_device_rect(viewport_rect).to_type<int>());
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auto canvas_element = DOM::create_element(element.document(), HTML::TagNames::canvas, Namespace::HTML).release_value_but_fixme_should_propagate_errors();
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auto& canvas = verify_cast<HTML::HTMLCanvasElement>(*canvas_element);
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// FIXME: Handle DevicePixelRatio in HiDPI mode.
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MUST(canvas.set_width(rect.width()));
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MUST(canvas.set_height(rect.height()));
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if (!canvas.create_bitmap(rect.width(), rect.height())) {
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encoded_string_or_error = Error::from_code(ErrorCode::UnableToCaptureScreen, "Unable to create a screenshot bitmap"sv);
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return;
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}
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painter(rect, *canvas.bitmap());
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encoded_string_or_error = encode_canvas_element(canvas);
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});
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Platform::EventLoopPlugin::the().spin_until([&]() { return encoded_string_or_error.has_value(); });
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return encoded_string_or_error.release_value();
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}
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}
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