ui::testing::OffscreenCapture¶

Header: winui/testing/OffscreenCapture.hpp.

Renders a laid-out Window to a Bitmap with the same renderer an on-screen window uses, with no native window and no GPU. The pixel golden tests capture through it.

Draws into a software bitmap with grayscale text anti-aliasing, so output is stable run to run and independent of the monitor. Lay the window out with measurer() first so text metrics match what capture() paints. On a platform the library has no renderer for, ok() is false and every capture is an empty bitmap. Not copyable.

Example:

ui::testing::OffscreenCapture d2d;
REQUIRE(d2d.ok());

ui::Window window;
window.set_content(ui::Button{.text = "Hello"});
const ui::Size client{200, 60};
window.layout(client, d2d.measurer());

const ui::Bitmap image = d2d.capture(window, client, ui::Theme::light().colors().background);
REQUIRE(image.width() == 200);

OffscreenCapture¶

OffscreenCapture()

Sets up the renderer; check ok() afterwards.

~OffscreenCapture¶

~OffscreenCapture()

Releases the renderer's resources.

OffscreenCapture¶

OffscreenCapture(const OffscreenCapture&) = delete

Not copyable: owns renderer resources.

operator=¶

OffscreenCapture& operator=(const OffscreenCapture&) = delete

Not copyable: owns renderer resources.

ok¶

bool ok() const

True if the renderer was set up and capture() can draw.

measurer¶

const TextMeasurer& measurer() const

The text measurer the renderer uses. Lay the window out with it so text metrics match what capture() paints. Owned by this object; valid for its lifetime.

capture¶

Bitmap capture(const Window& window, Size client, const Color& background = colors::White)

Renders an already laid-out window at client pixels (1 DIP == 1 px) to an RGBA image, over background. Pass the theme's window background, since Fluent fills are translucent. Returns an empty image if the renderer is not ok().

capture_changes¶

Bitmap capture_changes(Window& window, Size client, const Color& background = colors::White)

capture() the way a window repaints. Over what the last capture of the same size left, only the areas Window::take_damage() reports are cleared and drawn again, and the whole image the first time. A test of the partial repaint checks that the result matches a full capture().