Experiment with this once again, this time in a more forward looking
manner: move the code previously placed into eglfs's eglfs_viv backend
into its own plugin.
Move our attention to devices like the Raspberry Pi 4, where
VK_KHR_display has recently been introduced to the Mesa v3dv
backend. This is not in Mesa 20.3.3, the latest release at the time of
writing, but is available and functional when building master. This
serves as the reference system for testing the plugin, because it
looks like a fairly robust implementation.
The sole thing the plugin enables at the moment is creating a
QVulkanInstance and a QWindow with surfaceType VulkanSurface. This is
sufficient to run plain QWindow+QRhi (with QRhi::Vulkan), Qt Quick,
and Qt Quick 3D (with QSG_RHI_BACKEND=vulkan) applications.
One display and mode is chosen, by default the first in the
enumeration lists reported by the Vulkan extension. This can be
overridden with QT_VK_DISPLAY_INDEX and QT_VK_MODE_INDEX (modeled
after QT_VK_PHYSICAL_DEVICE_INDEX). The indices can be determined
based on the logs printed to the debug output. Changing the mode seems
to be working nicely with v3dv.
Multiple screen setups, where there would be more than one
VkDisplayKHR enumerated, have not been tested yet. Regardless,
multiple screens (reporting more than one QScreen, with a different
QWindow on each, eglfs style) are not currently supported. This may be
improved later (while keeping in mind that VK_KHR_display does not
have a fully-featured output management API).
Multiple (non-fullscreen) windows and especially raster windows
(QWidget) are not and will not be supported. Our single QWindow is
always forced to fullscreen.
When it comes to input, the level of support should match linuxfb and
eglfs. Note that while mouse input is fully functional, there is no
mouse cursor. (and this is unlikely to be implemented)
[ChangeLog][Platform Specific Changes][Embedded Linux] Introduced a
vkkhrdisplay platform plugin to run Vulkan-based applications in
fullscreen, without a windowing system, on systems where
VK_KHR_display and VK_KHR_display_swapchain are supported by the
Vulkan implementation.
Change-Id: I6388416f7fb2bfdc4b412a0a4971f25cc05d4668
Reviewed-by: Andy Nichols <andy.nichols@qt.io>
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