Modern GPU API such as Metal and Vulkan use explicit render passes
and command buffers for recording rendering commands. They don't have
global state; each render pass starts with a clean set of bound
textures, pipeline etc.
Change our GPU abstraction to better match newer API and modify our two
renderers to explicitly describe their render passes.
Signed-off-by: Elias Naur <mail@eliasnaur.com>
There's no meaningful reason to have them separate. The intention was to
enable rendering concurrent with other processing, but that's gaining
framerate at the expense of input latency and complicating ImageOp
semantics.
Signed-off-by: Elias Naur <mail@eliasnaur.com>
Both the OpenGL and the Direct3D API are stateful and gpu.GPU renders to
the render target current when Frame is called.
Modern GPU API such as Metal don't have a concept of a current render
target, and the target even changes each frame.
Add RenderTarget and add an explicit target argument to GPU.Frame as
well as the underlying driver.Device.BeginFrame.
Signed-off-by: Elias Naur <mail@eliasnaur.com>
The clear background is the most useful, and the old behaviour can
be achieved by filling the entire viewport with a white paint.ColorOp.
Signed-off-by: Elias Naur <mail@eliasnaur.com>
The CPU fallback of the compute renderer needs ReadPixels data in OpenGL
format (origin at bottom left). Unfortunately, the OpenGL driver
automatically mirrors images in the Y-axis to match the top left origin
image.RGBA.
Remove the mirroring from the driver and introduce a DownloadImage to
restore the old behaviour.
Signed-off-by: Elias Naur <mail@eliasnaur.com>
There are no longer any importers of package backend outside of
gioui.org/gpu. Move it internally, and rename it to the slightly more
specific "driver" while we're at it.
Signed-off-by: Elias Naur <mail@eliasnaur.com>
Elias Naur