vkdto

Vulkan Dynamic Text Overlay - Heavily based on mesa overlay

Status

This software is highly experimental and not ready for any use apart development.

How to build

Have packages build-essential and libvulkan-dev installed, then execute make - this should be enough.

How to use

Compile the shared object, then copy vkdto.x86_64.json in /usr/share/vulkan/implicit_layer.d/. Once done, open the file /usr/share/vulkan/implicit_layer.d/vkdto.x86_64.json with any text editor, and amend the "library_path" : "/home/ema/tmp/vkdto/vkdto.so" line with where you compiled your vkdto.so. For example if you build and move your vkdto.so under /usr/lib/vkdto.so, then that line should be "library_path" : "/usr/lib/vkdto.so".

Once done, execute your application with VKDTO_HUD=1 and VKDTO_FILE=<update file here> to start the overlay have it working.

How does vkdto work

vkdto works by constantly loading a wchar_t encoded file (specified with VKDTO_FILE=<update file here>) and displaying it's content using a (ideally monospace) system font (it tries to load Ubuntu font currently). Once the wchar_t file is fully loaded, it will display its content via Vulkan overlay (using ImGui) on the top-left of the screen.

vkdto also supports some meta characters to define some attributes such as text color, inverted text color/background and bold font; see the file hashtext_fmt.h for the binary definitions. For example, to print some text green, the meta characters should be used as follows:

Some normal text here <GREEN_ON>my green text<GREEN_OFF> some other text...

And all of this should be encoded as a wchar_t.

Furthermore, the # character is the escape charcater, hence when needing to print such character, one should write two of those. As example:

This is a hash: ##

Will result in: This is a hash #

Another important constraint is that vkdto required sizeof(uint32_t) == sizeof(wchar_t) hence should work ok on Linux, alas not on Windows.

vkdto options

It is possible to specify further options (such as overlay position, font size, ...). In order to do so, one has to export the environment variable VKDTO_OPT=(options string) where (options string) is defined as follows:

<param>=<value>:<param>=<value>:...

An example could be VKDTO_OPT="pos=tc:font_size=15.6". Paramaters/values can be as follows:

• pos - overlay position
  Can have following values tl, tc, tr for top-left, top-center and top-right and also bl, bc, br for the same but bottom
• font_size - font size
  A floating point value can be specified for the font size in pixels
• margin - overlay margin
  A floating point value can be specified to set the margin gap between the window borders and the overlay
• alpha - transparency
  A floating point value controlling overall transparency (1.0 fully opaque, 0.0 fully transparent)

vkdto debug log

A debug log mechanism has been added; for now a very small number of functions/logic is traced; in order to enable this debug log, export the environment variable VKDTO_DEBUG_LOG=<log filename>.