Week 4 of Gateware: End of the First Month

     Well, here we are at the end of the month. Much learned, but still far more to learn. The problem we were having with the MacOS crashing last week was that the CMake code we were using to link the Vulkan SDK was outdated and since then, CMake has built-in support for linking with newer Vulkan SDK's, so we just needed to update that bit of code to get it working. So after that was done, it was finally compiling, but it was now crashing on the VulkanSurface tests.

    So in the newer Vukan SDK's for MacOS, they force the extension "VK_KHR_PORTABIITY_subset" to be enabled. This extension allows for applications to exist on non-conformant platforms and since MoltenVK isn't fully conformant, this extension needs to be enabled. And just for those who don't know (like me up until two weeks ago), MoltenVK is needed so that Vulkan can can map to Apple's Metal graphics framework. To opt-in to this extension, you need to modify the VkInstanceCreateInfo by adding the VK_INSTANCE_CREATE_ENUMERATE_PROTABILITY_BIT_KHR bit to the flag parameters and add the VK_KHR_PORTABILITY_ENUMERATE_EXTENSION_NAME extension to the ppEnabledExtensionNames array along with incrementing the enabledExtensionCount variable. Links and a screenshot of this information will be posted below.
Link: https://vulkan.lunarg.com/doc/sdk/1.3.243.0/mac/getting_started.html

While this is a very simple thing to implement in an ordinary application, Gateware is no ordinary application and took a bit more finessing. 

    GVulkanSurface uses a file called GVulkanSurface_core to implement the majority of the VulkanSurface implementation and thus makes the OS-specific files much smaller. But since our VkInstanceCreateInfo is in the core file, we can't just make all those changes there since Linux and Windows are comformant platforms and would cause another crashing error. So instead, after the original VkInstanceCreateInfo is created and setup, we have a new function called "PlatformOverrideInstanceCreate," which allows us to pass in the VkInstanceCreateInfo, along with some of its original variables to be cleaned up later, and then modify them all in the function to opt-in to the extension. We then of course had to include dummy versions of this function into the Linux and Windows version of VulkanSurface so that the function can still be called on other Operating Sytems.

    Since this extension only exists on newer versions of Vulkan, we aren't able to get Gateware to compile on older SDK's with the new Mac implementation. With this said, we will be dropping support for Vulkan SDK's on MacOS older than 1.3.216.

    Since we have been doing a lot of updating on the Mac side of things, we are also trying to update our Mac testing machines to the latest MacOS that they can support, which is Monterey. However, this has caused a previously discovered bug to pop up again. GWindow causes crashing on Monterey (and likely other newer MacOS's as well). While we aren't entirely certain what the problem is, we believe it has something to do with multi-threading. I wasn't really able to discover anything new with this issue, just tried to understand what was already found and made. I would like to return and try to fix this problem later on before I graduate, but we'll see when we get there. For now, this is the link to the issue in GitLab. https://gitlab.com/gateware-development/gsource/-/issues/229.