imgui/imgui.odin

package imgui

import "core:container/queue"
import "core:log"

import "microui"

MAX_DRAW_COMMANDS :: #config(IMGUI_MAX_DRAW_COMMANDS, 512 * 1024)

// TODO: SS - Consider not having 'microui' as a seperate package and instead have it (and other backends) in the 'imgui' package directly.

IMGUI_BACKEND_MICROUI :: #config(IMGUI_BACKEND_MICROUI, false)

when IMGUI_BACKEND_MICROUI {
    Context_Backend :: microui.Context
}

Context :: struct {
    backend: ^Context_Backend,

    draw_commands: queue.Queue(Draw_Command),
    input: Input,
}

Input :: struct {
    mouse_state: Mouse_State,
}

Mouse_Button_State :: enum {
    Up,
    Pressed,
    Down,
    Released,
}

Mouse_State :: struct {
    pos_x, pos_y: u16,
    left, middle, right: Mouse_Button_State,
}

Draw_Command :: struct {
    color: [4]u8,
    type: Draw_Command_Type,
}

Draw_Command_Type :: union {
    Draw_Command_Rect,
}

Draw_Command_Rect :: struct {
    x, y, width, height: u16,
}

Rect :: struct {
    x, y, width, height: u16,
}

init :: proc(ctx: ^Context) -> bool {
    assert(ctx != nil)
    assert(ctx.backend == nil)

    backend, err := new(Context_Backend)
    if err != .None {
        log.errorf("Failed to allocate space for the backend. Error: %v", err)
        return false
    }
    ctx.backend = backend

    ok := false

    when IMGUI_BACKEND_MICROUI {
        ok = microui.init(ctx.backend)
    }

    if !ok {
        free(backend)
        return false
    }

    queue_err := queue.init(&ctx.draw_commands, MAX_DRAW_COMMANDS)
    if queue_err != .None {
        free(backend)
        log.errorf("Failed to allocate space for the queue of imgui draw-commands. Error: %v", queue_err)
        return false
    }

    return true
}

set_input :: proc(ctx: ^Context, input: Input) {
    ctx.input = input
}

begin :: proc(ctx: ^Context) {
    assert(ctx != nil)
    assert(ctx.backend != nil)

    when IMGUI_BACKEND_MICROUI {
        input: microui.Input
        input.mouse_x = ctx.input.mouse_state.pos_x
        input.mouse_y = ctx.input.mouse_state.pos_y

        if ctx.input.mouse_state.left == .Pressed {
            input.mouse_buttons_pressed += { .LEFT }
        }
        else if ctx.input.mouse_state.left == .Released {
            input.mouse_buttons_released += { .LEFT }
        }

        if ctx.input.mouse_state.middle == .Pressed {
            input.mouse_buttons_pressed += { .MIDDLE }
        }
        else if ctx.input.mouse_state.middle == .Released {
            input.mouse_buttons_released += { .MIDDLE }
        }

        if ctx.input.mouse_state.right == .Pressed {
            input.mouse_buttons_pressed += { .RIGHT }
        }
        else if ctx.input.mouse_state.right == .Released {
            input.mouse_buttons_released += { .RIGHT }
        }

        microui.begin(ctx.backend, input)
    }
}

end :: proc(ctx: ^Context) {
    assert(ctx != nil)
    assert(ctx.backend != nil)
    
    when IMGUI_BACKEND_MICROUI {
        microui.end(ctx.backend)
    }
}

begin_window :: proc(ctx: ^Context, title: string, rect: Rect) -> bool {
    assert(ctx != nil)

    when IMGUI_BACKEND_MICROUI {
        return microui.begin_window(ctx.backend, title, microui.Rect {
            x = i32(rect.x),
            y = i32(rect.y),
            w = i32(rect.width),
            h = i32(rect.height),
        })
    }

    return false
}

end_window :: proc(ctx: ^Context) {
    assert(ctx != nil)

    when IMGUI_BACKEND_MICROUI {
        microui.end_window(ctx.backend)
    }
}

button :: proc(ctx: ^Context, title: string) -> bool {
    when IMGUI_BACKEND_MICROUI {
        return microui.button(ctx.backend, title)
    }

    return false
}

collect :: proc(ctx: ^Context) { // TODO: SS - Come up with a better name. Adds commands from backend to queue in ctx.
    assert(ctx != nil)

    // TODO: SS - Reduce code-repetition if possible. MicroUI asks to be "popped"/iterated like this, apparently.

    when IMGUI_BACKEND_MICROUI {
        last_cmd: ^microui.Command = nil
        for {
            dc: Draw_Command
            dc.type = nil

            cmd := microui.pop_draw_command(ctx.backend, last_cmd)
            if cmd == nil {
                break
            }
            
            last_cmd = cmd

            #partial switch &v in &cmd.variant {
                // case ^microui.Command_Jump: {} // Internal.
                // case ^microui.Command_Clip: {
                // }
                // case ^microui.Command_Icon: {
                // }
                case ^microui.Command_Rect: {
                    assert(v.rect.x >= 0)
                    assert(v.rect.y >= 0)
                    assert(v.rect.w >= 0)
                    assert(v.rect.h >= 0)

                    dc.color = {
                        v.color.r,
                        v.color.g,
                        v.color.b,
                        v.color.a,
                    }
                    dc.type = Draw_Command_Rect {
                        x = u16(v.rect.x),
                        y = u16(v.rect.y),
                        width = u16(v.rect.w),
                        height = u16(v.rect.h),
                    }
                }
                // case ^microui.Command_Text: {
                // }
            }

            if dc.type != nil {
                queue.push_back(&ctx.draw_commands, dc)
            }
        }
    }
}

pop_draw_command :: proc(ctx: ^Context, out_draw_command: ^Draw_Command) -> bool {
    assert(ctx != nil)
    assert(out_draw_command != nil)

    out_draw_command^ = {}

    elem, ok := queue.pop_front_safe(&ctx.draw_commands)
    if !ok {
        return false
    }
    
    out_draw_command^ = elem
    return true
}

shutdown :: proc(ctx: ^Context) {
    assert(ctx != nil)
    assert(ctx.backend != nil)

    when IMGUI_BACKEND_MICROUI {
        microui.shutdown(ctx.backend)
    }

    free(ctx.backend)
    ctx.backend = nil

    queue.destroy(&ctx.draw_commands)
}