hdr display

[Pierre Jasmin]

is there a simple way to detect hdr display so our fltk grey panel does not turn to white?

[Gonzalo Garramuño]

El 10/7/25 a las 12:09, Pierre Jasmin escribió:

> is there a simple way to detect hdr display so our fltk grey panel

> does not turn to white? --
What platform are you on?

--
ggar...@gmail.com

[Pierre Jasmin]

windows., linux and mac

on linux a lot of users on rocky

[Gonzalo Garramuño]

El 10/7/25 a las 12:36, Pierre Jasmin escribió:
> windows, mac and linux
>
As HDR  is too new, you will probably have to delve into each platform's
API.

Regarding linux, not sure if there will be a consensus across
compositors or Wayland itself.  Manolo, who is our FLTK's Wayland guy
may have some more info.  For now, the recommended approach is to parse
the monitor's EDID information directly and reverse engineer it.  You
can check the macOS info that does the same, albeit not sure if the
monitors will be compatible.

WARNING! Untested Windows code:

    bool is_hdr_display_active()
    {
        IDXGIFactory6* factory = nullptr;
        CreateDXGIFactory1(IID_PPV_ARGS(&factory));

        IDXGIAdapter1* adapter = nullptr;
        for (UINT i = 0;
             factory->EnumAdapters1(i, &adapter) !=
DXGI_ERROR_NOT_FOUND; ++i)
        {
            IDXGIOutput* output = nullptr;
            if (SUCCEEDED(adapter->EnumOutputs(0, &output)))
            {
                IDXGIOutput6* output6 = nullptr;
                if
(SUCCEEDED(output->QueryInterface(IID_PPV_ARGS(&output6))))
                {
                    DXGI_OUTPUT_DESC1 desc;
                    output6->GetDesc1(&desc);

                    // Check for HDR support
                    if (desc.ColorSpace ==
DXGI_COLOR_SPACE_RGB_FULL_G2084_NONE_P2020 ||
                        desc.ColorSpace ==
DXGI_COLOR_SPACE_RGB_FULL_G10_NONE_P709)
                    {
                        std::cout << "HDR is active on display.\n";
                        output6->Release();
                        output->Release();
                        adapter->Release();
                        factory->Release();
                        return true;
                    }

                    output6->Release();
                }
                output->Release();
            }
            adapter->Release();
        }
        factory->Release();
        return false;
    }


macOS (semi-tested code):

#import <Foundation/Foundation.h>
#import <IOKit/graphics/IOGraphicsLib.h>
#import <IOKit/IOKitLib.h>
#import <CoreGraphics/CoreGraphics.h>
#import <iostream>
#import <vector>
#import <string>
#import <cstring>
#import <iostream>

// Parse EDID to detect HDR static metadata support
bool parseEDIDForHDR(const uint8_t* edid, size_t length) {
    if (length < 128) return false;

    uint8_t numExtensions = edid[126];
    const uint8_t* ext = edid + 128;

    for (int i = 0; i < numExtensions && (ext + 128 <= edid + length);
++i) {
        if (ext[0] == 0x02 && ext[1] == 0x03) {  // CTA-861 Extension Block
            uint8_t dtdStart = ext[2];
            if (dtdStart == 0 || dtdStart > 127) dtdStart = 127;

            for (int j = 4; j < dtdStart - 4;) {
                uint8_t tag = (ext[j] & 0xE0) >> 5;
                uint8_t len = ext[j] & 0x1F;
                if (tag == 0x07 && ext[j + 1] == 0x06) {
                    std::cout << "→ HDR static metadata block found in
EDID\n";
                    return true;
                }
                j += len + 1;
            }
        }
        ext += 128;
    }

    return false;
}

bool displaySupportsHDR(CGDirectDisplayID cgDisplayID) {
    io_iterator_t iter;
    io_service_t service = 0;

    CFMutableDictionaryRef match = IOServiceMatching("IODisplayConnect");
    if (IOServiceGetMatchingServices(kIOMasterPortDefault, match,
&iter) != KERN_SUCCESS)
        return false;

    while ((service = IOIteratorNext(iter))) {
        CFDictionaryRef info = IODisplayCreateInfoDictionary(service,
kIODisplayOnlyPreferredName);
        if (!info) {
            IOObjectRelease(service);
            continue;
        }

        CFNumberRef vendorRef = (CFNumberRef)CFDictionaryGetValue(info,
CFSTR(kDisplayVendorID));
        CFNumberRef productRef =
(CFNumberRef)CFDictionaryGetValue(info, CFSTR(kDisplayProductID));

        uint32_t vendor = 0, product = 0;
        if (vendorRef) CFNumberGetValue(vendorRef, kCFNumberIntType,
&vendor);
        if (productRef) CFNumberGetValue(productRef, kCFNumberIntType,
&product);

        CFRelease(info);

        // Match against CoreGraphics display info
        uint32_t cgVendor = CGDisplayVendorNumber(cgDisplayID);
        uint32_t cgProduct = CGDisplayModelNumber(cgDisplayID);

        if (vendor == cgVendor && product == cgProduct) {
            CFDataRef edid =
(CFDataRef)IORegistryEntryCreateCFProperty(service,
CFSTR("IODisplayEDID"), kCFAllocatorDefault, 0);
            bool result = false;

            if (edid) {
                const UInt8* bytes = CFDataGetBytePtr(edid);
                CFIndex length = CFDataGetLength(edid);
                result = parseEDIDForHDR(bytes, length);
                CFRelease(edid);
            }

            IOObjectRelease(service);
            IOObjectRelease(iter);
            return result;
        }

        IOObjectRelease(service);
    }

    IOObjectRelease(iter);
    return false;
}


--
ggar...@gmail.com

[Pierre Jasmin]

thank you - 

[Gonzalo Garramuño]

> El 10/7/25 a las 13:00, Pierre Jasmin escribió:
>> thank you -
>>
You are welcome.

Can you share with me the Linux pipeline that is giving you HDR (gfx
card, Wayland compositor and monitor)?
If this is your company's privileged information, I understand.

--
Gonzalo Garramuño
ggar...@gmail.com

[Gonzalo Garramuño]

On 7/10/25 1:56 PM, Gonzalo Garramuño wrote:
>
> Can you share with me the Linux pipeline that is giving you HDR (gfx
> card, Wayland compositor and monitor)?
> If this is your company's privileged information, I understand.
>

I apologize for putting you in the spotlight.  This message was meant to
be private.

--
Gonzalo Garramuño
ggar...@gmail.com