showimage/showimage.odin

package showimage

import "core:os"
import "core:strings"
import rl "vendor:raylib"

tex: ^rl.Texture
zoom: f32 = 1
offset: [2]f32

main :: proc() {
	rl.InitWindow(800, 600, "showimage")
	rl.SetWindowState({ .WINDOW_RESIZABLE })
	rl.SetTargetFPS(60)

	if len(os.args) > 1 {
		path := os.args[1]
		if strings.has_prefix(path, "file://") {
			path, _ = strings.substring_from(path, 7)
		}
		tex = new_clone(rl.LoadTexture(strings.clone_to_cstring(path)))
		if tex.id <= 0 { return }
		reset_zoom()
	}

	for !rl.WindowShouldClose() {
		scroll := rl.GetMouseWheelMove()
		if scroll > 0 {
			change_zoom(zoom)
		} else if scroll < 0 {
			change_zoom(-zoom / 2)
		}
		if rl.IsMouseButtonDown(rl.MouseButton.LEFT) {
			offset += rl.GetMouseDelta()
		}
		if rl.IsMouseButtonPressed(rl.MouseButton.RIGHT) {
			offset = 0
			reset_zoom()
		}
		rl.BeginDrawing()
			rl.ClearBackground({50, 50, 50, 255})
			if tex != nil {
				rl.DrawTextureEx(tex^, offset, 0, zoom, rl.WHITE)
			}
		rl.EndDrawing()
	}
	rl.CloseWindow()
}

change_zoom :: proc(delta: f32) {
	mouse_pos := rl.GetMousePosition()
	zoom_pos := (mouse_pos - offset) / zoom
	zoom += delta
	offset = mouse_pos - zoom_pos * zoom
}

zoom_to_power :: proc(size: i32, max: i32) -> i32 {
	fit: i32 = 2
	for fit * size < max {
		fit *= 2
	}
	return fit / 2
}

reset_zoom :: proc() {
	zoom = f32(min(
		zoom_to_power(tex.width, rl.GetRenderWidth()),
		zoom_to_power(tex.height, rl.GetRenderHeight()),
	))
}