Update TODO list.

1 files changed, 79 insertions, 47 deletions

diff --git a/TODO.org b/TODO.org
index 4dca8f8..c117a8a 100644
--- a/TODO.org
+++ b/TODO.org
@@ -1,4 +1,48 @@
 * Tasks
+** TODO [#A] Rewrite renderer
+It is finally time to make Chickadee at least theoretically capable of
+using a graphics API other than OpenGL.  OpenGL is showing its age and
+all newer graphics APIs use a stateless render queue approach that is
+much better than OpenGL's awful global state. MacOS doesn't support
+anything past OpenGL 3 and there's already been a number of
+compatibility issues for Chickadee.  WebGPU is quickly becoming a
+thing and with Guile Hoot on the horizon it should be possible to ship
+Chickadee games in the browser that use modern graphics APIs, but the
+work to make that happen needs to start now.  So, the goal is to move
+all OpenGL code to an OpenGL backend, add support for multiple
+backends, and expose a WebGPU-like interface since the team who made
+it have already done the hard work of abstracting over Vulkan, Metal,
+and Direct3D.  When we can target the web via Hoot, our graphics
+backend will be a thin wrapper over the WebGPU JS API, more or less.
+And of course on native targets we will now have the option of using
+whatever graphics API makes the most sense.
+
+Some big subtasks here:
+- [ ] Decouple OpenGL state management from dynamic render context
+- [ ] Refactor all OpenGL calls into a single module
+- [ ] Add generic WebGPU-like graphics API
+- [ ] Implement that API for OpenGL backend
+- [ ] Update all graphics modules to use new API
+
+One big caveat is that our shading language will still be GLSL at the
+end of this, which prevents us from being truly generic.  The Seagull
+shading language project will take care of that so we can compile to
+whichever shader language our backend uses.
+
+See this for how Trial does graphics pipelines:
+https://reader.tymoon.eu/article/363
+** TODO [#A] Move game logic to its own thread
+The main thread should be reserved for running the game loop,
+processing the input queue, and processing the render queue.
+** TODO [#A] Switch from OpenAL to SDL2 audio
+I've decided that OpenAL is too high level to be a library that
+Chickadee should rely upon, since part of the goal of Chickadee is to
+implement as much as possible in Scheme and only resort to C if
+absolutely necessary.  OpenAL will also make it more difficult to ship
+games on the web using Web Audio when Hoot is ready (no I am not going
+to compile OpenAL with emscripten.)  Instead, we can use SDL2's
+cross-platform audio API and implement all the audio mixing directly
+in Scheme in a dedicated audio thread.
 ** TODO [#A] Improve error messages in sprite-batch-add!
 =sprite-batch-add!= throws an error if it is called before
 =sprite-batch-clear!= maps the GPU memory, but the error message
@@ -6,21 +50,30 @@ doesn't mean anything to users.  Also, make sure the docs explain why
 you need to clear first.  Consider renaming =sprite-batch-clear!= to
 =sprite-batch-begin!= while you're at it. Explain the difference
 between capacity and size.
-** TODO [#A] Remove allocations in hot code paths
+** TODO [#A] Bug: Bundled games don't close properly?
+The window goes black but doesn't close. Closing the window again
+actually closes it.
+** TODO [#B] Remove allocations in hot code paths
 - [ ] hash-for-each causes closure allocation in at least the shader,
   text, and audio modules
 - [ ] call-with-error-handling in (chickadee game-loop) allocates
   closures and is called twice per loop iteration.
-** TODO [#A] Bug: Vertical line rendering not working
+** TODO [#B] Bug: Vertical line rendering not working
 Vertical lines are invisible.  Not great!
-** TODO [#A] Scheme -> GLSL compiler
-Like CL's varjo but for Guile.  Start with a simple sexp -> GLSL
-serializer.
+** TODO [#B] The Seagull Shading Language
+Like CL's varjo but for Scheme!  The goal here is to stop exposing
+GLSL to users.  For one thing, GLSL sucks to write when you're a
+Lisper.  If you want to embed a shader in a Scheme module, it has to
+be in a gross multi-line string literal.  It also tightly couples
+Chickadee to OpenGL, but ideally we want to be graphics API agnostic.
+By using a Schemey shader language we get something that composes well
+with regular Scheme code while also opening up the possibility of
+targetting modern graphics APIs in the future.
 
 Goals:
 - Scheme-like syntax
 - Embeddable within Scheme source files
-- Compiles to GLSL during regular Guile compilation
+- Compiles to GLSL (for now)
 - Clean interface for passing data from Scheme to shaders
 - Implicit returns in tail position (no 'return' keyword)
 - Everything is an expression
@@ -28,8 +81,7 @@ Goals:
 - Understands built-in shader stage variables
   - See: https://www.khronos.org/opengl/wiki/Built-in_Variable_(GLSL)
 - Macros
-- Nested functions if they are hoistable (no free variables aka not
-  closures)
+- Nested functions if they don't form closures
 - Shader libraries for reusing and composing code
 
 #+BEGIN_SRC scheme
@@ -43,45 +95,37 @@ Goals:
 
   (define (sprite-fragment (vec2 )))
 #+END_SRC
-
-** TODO [#A] Ditch the readline dependency
+** TODO [#B] Uniform buffers
+Need some way to support these while falling back to the current, slow
+way that is compatible with OpenGL 2.1.
+** TODO [#B] Ditch the readline dependency
 Figure out how to get back to using Guile's built-in REPL for
 =chickadee play= so the custom can go away.  Readline is hard to make
 work in an async manner.
-** TODO [#B] Bundled games don't close properly?
-The window goes black but doesn't close. Closing the window again
-actually closes it.
-** TODO [#B] REPL meta-command for rendering to an image file
-=,render-image= or something. Use a throwaway framebuffer to render
-arbitrary stuff to a texture and then save it as a PNG.
 ** TODO [#B] Bug: Framebuffer stencil issues
 Render a vector path to a framebuffer and you'll notice that the first
 filled path doesn't show up.  Why is this??
 ** TODO [#B] Framebuffer multisampling
 Requires creating multisampled texture.
-** TODO [#B] Multiple threads
-SDL2 operates on the main thread, so that will control the game loop
-and rendering.  OpenAL is already using its own thread for audio.  So,
-what's needed is another thread for managing game state and some
-number of generic worker threads to offload things like loading data
-from the file system.  Of course, this complicates things
-significantly, so the API will have to be carefully designed to do all
-the thread synchronization right so the user doesn't have to think
-about it.  Should I add a dependency on guile-fibers??
 
-** TODO [#B] Texture fills for vector paths
-** TODO [#B] Even-odd rule fills for vector paths
-Right now only the non-zero rule is supported.
-** TODO [#B] Add shear transformations to vector paths
-** TODO [#B] Dashed lines for stroked vector paths
-** TODO [#B] Mitered corners for stroked vector paths
-** TODO [#B] Text rendering for vector paths
 ** TODO [#B] Add screenshots to manual
-** TODO [#B] Improve particle system
+** TODO [#C] Add shear transformations to vector paths
+** TODO [#C] Dashed lines for stroked vector paths
+** TODO [#C] Mitered corners for stroked vector paths
+** TODO [#C] Even-odd rule fills for vector paths
+Right now only the non-zero rule is supported.
+** TODO [#C] Reverse winding order for vector paths
+** TODO [#C] Text rendering for vector paths
+** TODO [#C] Texture fills for vector paths
+** TODO [#C] Improve particle system
 Allow more settings to be modified.  Add angular velocity.
 Auto-expand to hold all particles rather than setting a hard cap
 upfront.
-** TODO [#B] Support loading fonts from system font cache
+** TODO [#C] Support loading fonts from system font cache
+** TODO [#C] REPL meta-command for rendering to an image file
+=,render-image= or something. Use a throwaway framebuffer to render
+arbitrary stuff to a texture and then save it as a PNG.
+
 ** TODO [#C] Rename array-list-size to array-list-length
 ** TODO [#C] Bug: Bounding boxes for stroked paths are too small
 Not sure how to fix right now but the bounding boxes are too small
@@ -89,25 +133,13 @@ because they only account for the points within a path, not the
 thickness of the line, the length of the miters in a polyline, or the
 end caps.
 ** TODO [#C] Shader cache in ~/.cache/chickadee?
-** TODO [#C] Switch from OpenAL to custom Scheme mixer
-I've decided that OpenAL is too high level to be a library that
-Chickadee should rely upon, since part of the goal of Chickadee is to
-implement as much as possible in Scheme and only resort to C if
-absolutely necessary.  Instead, we can use SDL2's cross-platform audio
-API and implement all the audio mixing directly in Scheme.
 ** TODO [#C] Binary bundles for MacOS
-** TODO [#C] GPU pipeline data structure
-Like this: https://reader.tymoon.eu/article/363
 ** TODO [#C] 2D physics simulation
 Add bindings for the chipmunk library or implement a rigid body
 simulator in Scheme.
 ** TODO [#C] Multiplayer networking
 Take a look at Xelf's UDP networking code and https://gafferongames.com/categories/building-a-game-network-protocol/
-** TODO [#C] Render command queue processing
-To replace existing immediate mode rendering
-** TODO [#C] Uniform buffers
-Need some way to support these while falling back to the current, slow
-way that is compatible with OpenGL 2.1.
+
 ** TODO [#C] Signed distance field font rendering
 ** TODO [#C] Physically-based ambient lighting
 The PBR shader currently does image based ambient lighting in a very