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Fix dynamic changing of font in Windows console on CJK codepages #771

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merged 4 commits into from
Oct 10, 2018

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SteveL-MSFT
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On Windows, the outputencoding is tied to a codepage which is tied to a font. When using a CJK locale, the default is using a raster font that can render the CJK glyphs. Previously, PSReadLine 2.0.0 was manipulating the OutputEncoding to utf8 which resulted in a visible font change in the console and the resulting rendering in the screen buffer was not correct.

The fix is to detect that a raster font is being used and not change the output encoding. Also in cases where the output encoding is already utf8, there's no need to change it.

@lzybkr
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lzybkr commented Oct 3, 2018

If PowerShell is not running in a console, this code probably won't work as expected - for example if we are running under ConPTY, so we should avoid checking the font in that case.

I think you can check this easily enough by calling GetFileType on the file handle from STD_INPUT_HANDLE. If the return value is not FILE_TYPE_CHAR, then we can skip calling checking the font.

private static bool IsHandleRedirected(bool stdin)
{
var handle = GetStdHandle((uint)(stdin ? StandardHandleId.Input : StandardHandleId.Output));

// If handle is not to a character device, we must be redirected:
int fileType = GetFileType(handle);
if ((fileType & FILE_TYPE_CHAR) != FILE_TYPE_CHAR)
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Per the documentation, GetFileType() returns a single value and is not flags.

PSReadLine/ReadLine.cs Outdated Show resolved Hide resolved
@lzybkr lzybkr merged commit 1d8dd4a into PowerShell:master Oct 10, 2018
@SteveL-MSFT SteveL-MSFT deleted the outputencoding-rasterfont branch October 10, 2018 16:27
lzybkr added a commit that referenced this pull request Dec 3, 2018
The original fix in #771 resulted in essentially never setting the UTF8
output encoding because it only tested the fixed width bit on the font
family, but every console font is fixed width.

The proper fix appears to be testing that all 4 lower bits in FontFamily
are not set.

Fix #823
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2 participants