(In reply to Nicolas Silva [:nical] from comment #2) > Without going through the steps in comment 0 (just running a local build on x11 with webrender enabled), I see gdk_window_set_opaque_region being called. Is this specific to a certain configuration? Yes, it's getting called but it does not have the desired effect - I don't think it's specific to a configuration, it certainly applies to default settings (I also tested with and without title bar). AFAICS the problem is that GTK also calls `gdk_window_set_opaque_region ` internally, directly unsetting the region again - and I think the problem is that we don't call it the way it's intended by GTK (we don't seem to follow the docs). I'm planning to look into this again until the weekend, just so you know.
Bug 1617002 Comment 3 Edit History
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(In reply to Nicolas Silva [:nical] from comment #2) > Without going through the steps in comment 0 (just running a local build on x11 with webrender enabled), I see gdk_window_set_opaque_region being called. Is this specific to a certain configuration? Yes, it's getting called but it does not have the desired effect - I don't think it's specific to a configuration, it certainly applies to default settings (I also tested with and without title bar). AFAICS the problem is that GTK also calls `gdk_window_set_opaque_region ` internally, directly unsetting the region again - and I think the problem is that we don't call it the way it's intended by GTK (we don't seem to follow the docs). I'm planning to look into this again until the weekend, just so you know. P.S.: I also assume this affects all DEs (as I think it's a wrong handling of GTK), but didn't test yet