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Fix broken windows boot logo(and customize)

Posted: Fri May 24, 2019 11:27 am
by dygkset
when boot EFI windows bootloader(bootmgfw.efi) read BGRT(boot graphics resource table) form acpi table
BGRT contain address of Bitmap image(usually motherboard vender logo)
So when BGRT and right bitmap image data is exist then Windows efi bootloader draw that image instead of windows default boot logo

Like this
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Boot moarl.png (12.33 KiB) Viewed 313 times
But some of you see like these when chainload windows form Clover bootloader
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black.png (2.95 KiB) Viewed 313 times
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borken ratio.png (6.38 KiB) Viewed 313 times
First one caused by wrong status value in BGRT

second one caused by wrong offset value in BGRT
UEFI set offset value to bgrt offset calculate based on low res boot screen
clover reset resolution to higher but offset inside BGRT does not changed…

you can fix it by using this UEFI application
https://github.com/Metabolix/HackBGRT
to me it works find thanks to Metabolix…
it provide BGRT offset, status, modifi and load custom BMP file


attached moded clover r4934(bootx64.efi) file is ‘hackBGRT’ merged clover r4934
with this version of clover you can use hackBGRT by setting clover custom boot logo setting in
GUI->custom entry->custom boot logo
I think some of you fill more convenient in this way….
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clover_config.png (1.7 MiB) Viewed 313 times
Set like this
Empty = just fix offset and status value for motherboard logo
Apple = remove BGRT for ‘windows default logo’
\EFI\CLOVER\filename.png = load custom png logo

When entry type is EFI_windows then your order processed by hackBGRT
Else it just work vanilla r4934