This is a reland of e54d0f90
This was reverted due to a build failure as a result of a missing
virtual destructor in the widget base class.
Original change's description:
> Vulkan: Debug overlay
>
> A debug overlay system for the Vulkan backend designed with efficiency
> and runtime configurability in mind. Overlay widgets are of two
> fundamental types:
>
> - Text widgets: A single line of text with small, medium or large font.
> - Graph widgets: A bar graph of data.
>
> Built on these, various overlay widget types are defined that gather
> statistics. Five such types are defined with one widget per type as
> example:
>
> - Count: A widget that counts something. VulkanValidationMessageCount
> is an overlay widget of this type that shows the number of validation
> messages received from the validation layers.
> - Text: A generic text. VulkanLastValidationMessage is an overlay
> widget of this type that shows the last validation message.
> - PerSecond: A value that gets reset every second automatically. FPS is
> an overlay widget of this type that simply gets incremented on every
> swap().
> - RunningGraph: A graph of last N values. VulkanCommandGraphSize is an
> overlay of this type. On every vkQueueSubmit, the number of nodes in
> the command graph is accumulated. On every present(), the value is
> taken as the number of nodes for the whole duration of the frame.
> - RunningHistogram: A histogram of last N values. Input values are in
> the [0, 1] range and they are ranked to N buckets for histogram
> calculation. VulkanSecondaryCommandBufferPoolWaste is an overlay
> widget of this type. On vkQueueSubmit, the memory waste from command
> buffer pool allocations is recorded in the histogram.
>
> Overlay font is placed in libANGLE/overlay/ which gen_overlay_fonts.py
> processes to create an array of bits, which is processed at runtime to
> create the actual font image (an image with 3 layers).
>
> The overlay widget layout is defined in overlay_widgets.json which
> gen_overlay_widgets.py processes to generate an array of widgetss, each
> of its respective type, and sets their properties, such as color and
> bounding box. The json file allows widgets to align against other
> widgets as well as against the framebuffer edges.
>
> Two compute shaders are implemented to efficiently render the UI:
>
> - OverlayCull: This shader creates a bitset of Text and Graph widgets
> whose bounding boxes intersect a corresponding subgroup processed by
> OverlayDraw. This is done only when the enabled overlay widgets are
> changed (a feature that is not yet implemented) or the surface is
> resized.
> - OverlayDraw: Using the bitsets generated by OverlayCull, values that
> are uniform for each workgroup (set to be equal to hardware subgroup
> size), this shader loops over enabled widgets that can possibly
> intersect the pixel being processed and renders and blends in texts
> and graphs. This is done once per frame on present().
>
> Currently, to enable overlay widgets an environment variable is used.
> For example:
>
> $ export ANGLE_OVERLAY=FPS:VulkanSecondaryCommandBufferPoolWaste
> $ ./hello_triangle --use-angle=vulkan
>
> Possible future work:
>
> - On Android, add settings in developer options and enable widgets based
> on those.
> - Spawn a small server in ANGLE and write an application that sends
> enable/disable commands remotely.
> - Implement overlay for other backends.
>
> Bug: angleproject:3757
> Change-Id: If9c6974d1935c18f460ec569e79b41188bd7afcc
> Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1729440
> Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>
> Reviewed-by: Jamie Madill <jmadill@chromium.org>
Bug: angleproject:3757
Change-Id: I47915d88b37b6f882c686c2de13fca309a10b572
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1780897Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>
