initial

strokes.go

@@ -0,0 +1,95 @@
+package main
+
+import (
+	"errors"
+	color_lib "image/color"
+
+	"github.com/hajimehoshi/ebiten/v2"
+	"github.com/hajimehoshi/ebiten/v2/vector"
+)
+
+type Vec2 struct {
+    x, y float32
+}
+
+func cursorPosition() Vec2 {
+    x, y := ebiten.CursorPosition()
+    return Vec2{
+        x: float32(x),
+        y: float32(y),
+    }
+}
+
+type stroke struct {
+    points []Vec2
+    width float32
+    color color_lib.Color
+}
+
+func (s *stroke) appendIfMoved(point Vec2) {
+    if len(s.points) != 0 {
+        lastPoint := s.points[len(s.points)-1]
+        if lastPoint.x == point.x && lastPoint.y == point.y {
+            return
+        }
+
+    }
+    s.points = append(s.points, point)
+}
+
+func (s *stroke) drawLast(screen *ebiten.Image) error {
+    if s.color == nil {
+        return errors.New("stroke has nil color")
+    }
+
+    if len(s.points) == 0 {
+        return nil
+    }
+
+    from := s.points[len(s.points)-1]
+    vector.DrawFilledCircle(screen, from.x, from.y, s.width/2, s.color, true)
+
+    if len(s.points) == 1 {
+        return nil
+    }
+
+    to := s.points[len(s.points)-2]
+    vector.StrokeLine(
+        screen,
+        from.x,
+        from.y,
+        to.x,
+        to.y,
+        s.width,
+        s.color,
+        true,
+    )
+    vector.DrawFilledCircle(screen, to.x, to.y, s.width/2, s.color, true)
+
+    return nil
+}
+
+func (s *stroke) draw(screen *ebiten.Image) error {
+    if s.color == nil {
+        return errors.New("stroke has nil color")
+    }
+
+    from := s.points[0]
+    vector.DrawFilledCircle(screen, from.x, from.y, s.width/2, s.color, true)
+    for _, to := range s.points[1:] {
+        vector.StrokeLine(
+            screen,
+            from.x,
+            from.y,
+            to.x,
+            to.y,
+            s.width,
+            s.color,
+            true,
+        )
+        vector.DrawFilledCircle(screen, to.x, to.y, s.width/2, s.color, true)
+        from = to
+    }
+
+    return nil
+}