From a8a6ed667d0f9fe747a86bd8607f875e097e3af5 Mon Sep 17 00:00:00 2001 From: Kenny Levinsen Date: Fri, 1 May 2020 17:20:41 +0200 Subject: Simplify repaint scheduling documentation The current documentation for repaint scheduling is very technical and somewhat confusing. Closes: https://github.com/swaywm/sway/issues/4769 --- sway/sway-output.5.scd | 37 +++++++++++++------------------------ sway/sway.5.scd | 24 ++++++++++++++++-------- 2 files changed, 29 insertions(+), 32 deletions(-) diff --git a/sway/sway-output.5.scd b/sway/sway-output.5.scd index a95cfaa2..69f529fe 100644 --- a/sway/sway-output.5.scd +++ b/sway/sway-output.5.scd @@ -117,22 +117,17 @@ must be separated by one space. For example: (ie. blank the screen but keep workspaces as-is), one can set DPMS to off. *output* max_render_time off| - When set to a positive number of milliseconds, enables delaying output - rendering to reduce latency. The rendering is delayed in such a way as - to leave the specified number of milliseconds before the next - presentation for rendering. - - The output rendering normally takes place immediately after a - presentation (vblank, buffer flip, etc.) and the frame callbacks are - sent to surfaces immediately after the rendering to give surfaces the - most time to draw their next frame. This results in slightly below 2 - frames of latency between the surface rendering and committing new - contents, and the contents being shown on screen, on average. When the - output rendering is delayed, the frame callbacks are sent immediately - after presentation, and the surfaces have a small timespan (1 / - (refresh rate) - max_render_time) to render and commit new contents to - be shown on the next presentation, resulting in below 1 frame of - latency. + Controls when sway composites the output, as a positive number of + milliseconds before the next display refresh. A smaller number leads to + fresher composited frames and lower perceived input latency, but if set too + low, sway may not finish compositing in time for display refresh, leading to + delayed frames. + + When set to off, sway composites immediately after display refresh, + maximizing time available for compositing. + + To adjust when applications are instructed to render, see *max_render_time* + in *sway*(5). To set this up for optimal latency: . Launch some _full-screen_ application that renders continuously, like @@ -140,14 +135,8 @@ must be separated by one space. For example: . Start with *max_render_time 1*. Increment by *1* if you see frame drops. - To achieve even lower latency, see the *max_render_time* surface - property in *sway*(5). - - Note that this property has an effect only on backends which report the - presentation timestamp and the predicted output refresh rate—the DRM - and the Wayland backends. Furthermore, under the Wayland backend the - optimal max_render_time value may vary based on the parent compositor - rendering timings. + This setting only has an effect on Wayland and DRM backends, as support for + presentation timestamps and predicted output refresh rate is required. *output* adaptive_sync on|off Enables or disables adaptive synchronization (often referred to as Variable diff --git a/sway/sway.5.scd b/sway/sway.5.scd index bbcc94e2..febf749f 100644 --- a/sway/sway.5.scd +++ b/sway/sway.5.scd @@ -186,21 +186,29 @@ set|plus|minus Cycles the layout mode of the focused container through a list of layouts. *max_render_time* off| - Works together with *output max_render_time* to reduce the latency even - further by delaying the frame callbacks sent to a surface. When set to - a positive number of milliseconds, delays the frame callback in such a - way that the surface has the specified number of milliseconds to render - and commit new contents before being sampled by the compositor for the - next presentation. See *max_render_time* in *sway-output*(5) for - further details. + Controls when the relevant application is told to render this window, as a + positive number of milliseconds before the next time sway composites the + output. A smaller number leads to fresher rendered frames being composited + by sway and lower perceived input latency, but if set too low, the + application may not finish rendering before sway composites the output, + leading to delayed frames. + + When set to off, the relevant application is told to render this window + immediately after display refresh. How much time is left for rendering + before sway composites the output at that point depends on the output + *max_render_time* setting. To set this up for optimal latency: - . Set up *output max_render_time*. + . Set up *output max_render_time* (see *sway-output*(5)). . Put the target application in _full-screen_ and have it continuously render something. . Start by setting *max_render_time 1*. If the application drops frames, increment by *1*. + This setting only has an effect if a per-output *max_render_time* is in + effect on the output the window is currently on. See *sway-output*(5) for + further details. + *move* left|right|up|down [ px] Moves the focused container in the direction specified. If the container, the optional _px_ argument specifies how many pixels to move the container. -- cgit v1.2.3