custom shader: add color scheme information to uniforms #9417
Description
// 256-color ANSI palette
uniform vec4 iPalette[256]; // palette 0-255
// Core terminal colors
uniform vec4 iBackgroundColor; // background
uniform vec4 iForegroundColor; // foreground
uniform vec4 iCursorColor; // cursor-colorNote
iCursorColor already technically already exists as iCurrentCursorColor, but it behaves differently than I would expect. Currently, when using this uniform it includes the opacity from cursor-opacity baked in. This proposal adds iCursorColor as the pure, un-modified color from the colorscheme, giving shader authors both options. When using shaders to replace the cursor entirely (with cursor-opacity = 0.0), having access to the original color value is essential.