This commit introduces "AtlasEngine", a new text renderer based on DxEngine.
But unlike it, DirectWrite and Direct2D are only used to rasterize glyphs.
Blending and placing these glyphs into the target view is being done using
Direct3D and a simple HLSL shader. Since this new renderer more aggressively
assumes that the text is monospace, it simplifies the implementation:
The viewport is divided into cells, and its data is stored as a simple matrix.
Modifications to this matrix involve only simple pointer arithmetic and is easy
to understand. But just like with DxEngine however, DirectWrite
related code remains extremely complex and hard to understand.
Supported features:
* Basic text rendering with grayscale AA
* Foreground and background colors
* Emojis, including zero width joiners
* Underline, dotted underline, strikethrough
* Custom font axes and features
* Selections
* All cursor styles
* Full alpha support for all colors
* _Should_ work with Windows 7
Unsupported features:
* A more conservative GPU memory usage
The backing texture atlas for glyphs is grow-only and will not shrink.
After 256MB of memory is used up (~20k glyphs) text output
will be broken until the renderer is restarted.
* ClearType
* Remaining gridlines (left, right, top, bottom, double underline)
* Hyperlinks don't get full underlines if hovered in WT
* Softfonts
* Non-default line renditions
Performance:
* Runs at up to native display refresh rate
Unfortunately the frame rate often drops below refresh rate, due us
fighting over the buffer lock with other parts of the application.
* CPU consumption is up to halved compared to DxEngine
AtlasEngine is still highly unoptimized. Glyph hashing
consumes up to a third of the current CPU time.
* No regressions in WT performance
VT parsing and related buffer management takes up most of the CPU time (~85%),
due to which the AtlasEngine can't show any further improvements.
* ~2x improvement in raw text throughput in OpenConsole
compared to DxEngine running at 144 FPS
* ≥10x improvement in colored VT output in WT/OpenConsole
compared to DxEngine running at 144 FPS
This commit introduces a new build configuration, "Fuzzing", which
enables the new address sanitizer (shipped in VS 16.9) and code
coverage over the entire solution. Only a small subset of projects
(those comprising original conhost, right now) are selected to build in
this configuration, and even then only in Fuzzing|x64.
It also adds a fuzzing-adapted build of conhost, which makes no server
connections and handles no client applications. To do this, I've
replicated a bit of the console startup routine into fuzzmain.cpp and
made up some fake data. This is the bare minimum required to boot up
Win32 interactivity (or VT interactivity!) and pretend that a process
has connected.
If we don't pretend that a process has connected, "conhost" will exit
immediately. If we don't forge the process list, conhost will exit. If
we can't provide a server handle, we can't provide a "device comm".
Minor changes were necessary to server/host such that they would accept
a preexisting "device comm". We use this new behavior to provide a
"null" one that only hangs up threads and otherwise responds to requests
successfully.
This fuzzing-adapted build links LLVM's libFuzzer, which is an excellent
coverage-based fuzzer that will produce a corpus of inputs that exercise
unique codepaths. Eventually, we can use this to generate known-"good"
inputs for anything.
I've gone ahead and added a fuzz function that yeets bytes directly into
WriteCharsLegacy, which was the original reason I went down this path.
The implementation of LLVMFuzzerTestOneInput should be replaced with
whatever you want to fuzz.
