Window Options & the OS

App(...) takes these options, which are the window's.

Option	Default	What it does
dpi_scaling	True	Scales the window by the screen's density, so a 16-pixel size is the same size on every screen. False draws in device pixels.
present_mode	"vsync"	How frames reach the screen: vsync paces frames to the display, low_latency shows the newest frame at once, at the cost of drawing as fast as it can while something animates.
transparent	False	A window with no background of its own: what is not drawn shows the desktop. Fixed when the window opens. app.transparent_active says whether the platform could.
blur_behind	False	The OS blurs the desktop behind a transparent window.
click_through	False	Presses fall through the window to what is under it.
ripple	"nodes"	How a press ripple is drawn: nodes grows a circle per press and lets the engine animate it; shader draws up to three at once with one fill shader (soft edges, one node per clickable thing), moved a frame at a time.
focus_ring	"solid"	The ring around a keyboard-focused node: solid is one colour; gradient is a sweep through secondary, primary and tertiary that turns once every three seconds (standing still when motion is reduced). tre does not animate a gradient border, so Python sets the angle 30 times a second while a ring shows.
glyph_cache	False	Keeps the shapes of letters between frames: less work for a lot of text.
system_fonts	False	Lets a font family that isn't registered be found among the system's.

app.scale_factor is the current density. A platform that can't do an option says so, naming it.

Less motion, more contrast

Operating systems let users ask for less animation and for more contrast. An app follows both unless told otherwise: App(reduced_motion="system", high_contrast="system") is the default, True or False fixes the setting, and app.set_reduced_motion(...) and app.set_high_contrast(...) change it later.

• Reduced motion: animations take no time, so things are where they are going at once, and indicators that would repeat for ever (the indeterminate progress bar and spinner, the loading indicator) stay still.
• High contrast: the theme is made again at the highest contrast level of Material 3's palette, so text and outlines stand out, and the app re-themes at once, as it does for dark mode. It follows the OS as the user turns it on and off.

app.reduced_motion and app.high_contrast are what the app is doing now. For your own animations, tesserae.motion.duration(window, ms) is ms, or 0 when motion is reduced.

Spring easing

An animation's easing can be a spring: Theme.easing("spring"), or Theme.spring(bounce) with a bounce from -1 to 1 (above 0 overshoots). The duration is the spring's period, and it runs until it settles:

node.animate("scale", 1.0, 300, easing=Theme.spring(0.3))

What a frame costs

app.frame_stats() says what the frames cost (frames, last, and recent: the frame rate and the mean, 95th percentile and maximum of the frame time). app.profile_nodes = True measures each node's drawing too, and app.start_trace("trace.json") / app.stop_trace() record every frame for Perfetto. app.stats_handle() is an object another thread can read the stats from.

For a quick look, app.stats_overlay = True shows the frame rate and time in the window's corner, and running with TESSERAE_STATS=1 in the environment turns it on for a run from the terminal:

TESSERAE_STATS=1 python app.py