> If window chrome is not scaled, and since web content could already have a default zoom set, what is the aim of this toggle right now?
Optimally this setting should have no visual effect at all (or things should be minimally sharper in some cases). The main goal is to improve performance by reducing overdraw.
Short example: on a 1920x1080 screen at 125%, without this setting Firefox (or any Wayland app without support for the protocol) would draw a buffer of 3072x1728 (= 1536*2 x 864*2 = 1920/1.25*2 x 1080/1.25*2) in fullscreen mode, which then gets scaled down to 1920x1080 by the compositor. With this protocol the buffer size would be 1920x1080. That's roughly 60% less pixels to be drawn per full redraw.
Bug 1849109 Comment 19 Edit History
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> If window chrome is not scaled, and since web content could already have a default zoom set, what is the aim of this toggle right now?
Optimally this setting should have no visual effect at all (or things should be minimally sharper in some cases). The main goal is to improve performance by reducing overdraw.
Short example: on a 1920x1080 screen at 125%, without this setting Firefox (or any Wayland app without support for the protocol) would draw a buffer of 3072x1728 (= 1536 * 2 x 864 * 2 = 1920/1.25 * 2 x 1080/1.25 * 2) in fullscreen mode, which then gets scaled down to 1920x1080 by the compositor. With this protocol the buffer size would be 1920x1080. That's roughly 60% less pixels to be drawn per full redraw.