Fix Windows transparency behavior to support fully-opaque regions #1621
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@Osspial Does this look ok? (Note: I rebased this onto the latest master revision and Android tests are failing now, but looking at the CI logs, this is happening for other builds too and doesn't have anything to do with my patch, which is Windows-only anyway.) |
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@Osspial, @kchibisov: I rebased this again onto the latest master and the tests look good again. Just let me know if there's anything I need to change so that this can merge. Thanks! |
msiglreith
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msiglreith
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Oct 13, 2020
This patch removes an unneeded workaround for transparent windows on the Windows platform. In addition, it simplifies a couple of related API calls: * Remove the `CreateRectRgn` call, since we want the entire window's region to have blur behind it, and `DwnEnableBlurBehindWindow` does that by default. * Remove the `color_key` for `SetLayeredWindowAttributes`, since it's not used (we're not passing `winuser::LWA_COLORKEY` to the flags).
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@msiglreith Ok, I updated my branch and moved the relnote to the right section (and rephrased it a bit so it's less hard to understand). Thanks for taking a look! |
This was referenced Dec 31, 2020
msiglreith
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Feb 17, 2021
* Restore the ability to have fully transparent windows on Windows Besides its original purpose, commit 6343059 "Fix Windows transparency behavior to support fully-opaque regions (#1621)" also included some changes considered cleanups, one of them was: * Remove the `CreateRectRgn` call, since we want the entire window's region to have blur behind it, and `DwnEnableBlurBehindWindow` does that by default. But the original code actually disabled the blur effect for the whole window by creating an empty region for it, because that allows for the window to be truely fully transparent. With the blur effect in place, the areas meant to be transparent either blur the things behind it (until Windows 8) or are darkened (since Windows 8). This also means that on Windows 8 and newer, the resulting colors are darker than intended in translucent areas when the blur effect is enabled. This restores the behaviour from winit <0.24 and fixes #1814. Arguably, one might want to expose the ability to control the blur region, but that is outside the scope of this commit. * Remove useless WS_EX_LAYERED from transparent windows on Windows `WS_EX_LAYERED` is not supposed to be used in combination with `CS_OWNDC`. In winit, as it is currently used, `WS_EX_LAYERED` actually has no effect at all. The only relevant call is to `SetLayeredWindowAttributes`, which is required to make the window visible at all with `WS_EX_LAYERED` set, but is called with full opacity, i.e. there's no transparency involved at all. The actual transparency is already achieved by using `DwmEnableBlurBehindWindow`, so `WS_EX_LAYERED` and the call to `SetLayeredWindowAttributes` can both be removed.
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cargo fmthas been run on this branchCHANGELOG.mdif knowledge of this change could be valuable to userscargo docbuilds successfullyThis PR is primarily here to fix a downstream bug (alacritty/alacritty#1927). Testing the transparency feature out on Windows (both via
examples/transparency.rsand with a build of alacritty), I was unable to reproduce the issue described in the old comment in this code. I suppose it's possible that this only manifests on some configurations though (for completeness, I'm testing on a Windows 10 environment, though I cross-compiled things on a Linux box using GNU tools). To be on the safe side, it might make sense for other people with access to a Windows environment to double check that this doesn't regress anything.In addition, I removed a couple of redundant bits in the Windows API calls (see the description below).
Original commit message follows:
This patch removes an unneeded workaround for transparent windows on the Windows platform. In addition, it simplifies a couple of related API calls:
CreateRectRgncall, since we want the entire window's region to have blur behind it, andDwnEnableBlurBehindWindowdoes that by default.color_keyforSetLayeredWindowAttributes, since it's not used (we're not passingwinuser::LWA_COLORKEYto the flags).