Reduce InstanceData footprint

The InstanceData type in the rendering subsystem was previously 16
floats which occupied a total of 64 bytes per instance. This meant that
for every character or background cell drawn, 64 bytes were sent to the
GPU. In the case of a 400x100 cell grid, a total of 2.5MB would be sent.

This patch reduces InstanceData's size to 26 bytes, a 60% improvement!
Using the above example for comparison, a worst case of 1MB would be
transferred.

The motivation for this patch comes from macOS. Once the terminal grid
would reach a certain size, performance experienced a sharp and dramatic
drop (render times would go from ~3ms to ~16ms). I don't want to
speculate too much on the underlying issue, but suffice it to say that
this patch alleviates the problem in my testing.

1 files changed, 1 insertions, 0 deletions

diff --git a/Cargo.toml b/Cargo.toml
index 4709ea67..5191de04 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -33,6 +33,7 @@ clap = "2.20"
 fnv = "1.0.5"
 unicode-width = "0.1.4"
 arraydeque = "0.2"
+half = "1.0"
 clippy = { version = "0.0.104", optional = true }
 
 [target.'cfg(any(target_os = "linux", target_os = "freebsd", target_os="dragonfly", target_os="openbsd"))'.dependencies]