package render import ( "fmt" "math" "git.kirsle.net/apps/doodle/src/events" ) // Engine is the interface for the rendering engine, keeping SDL-specific stuff // far away from the core of Doodle. type Engine interface { Setup() error // Poll for events like keypresses and mouse clicks. Poll() (*events.State, error) GetTicks() uint32 WindowSize() (w, h int) // Present presents the current state to the screen. Present() error // Clear the full canvas and set this color. Clear(Color) DrawPoint(Color, Point) DrawLine(Color, Point, Point) DrawRect(Color, Rect) DrawBox(Color, Rect) DrawText(Text, Point) error ComputeTextRect(Text) (Rect, error) // Texture caching. NewBitmap(filename string) (Texturer, error) Copy(t Texturer, src, dst Rect) // Delay for a moment using the render engine's delay method, // implemented by sdl.Delay(uint32) Delay(uint32) // Tasks that the Setup function should defer until tear-down. Teardown() Loop() error // maybe? } // Texturer is a stored image texture used by the rendering engine while // abstracting away its inner workings. type Texturer interface { Size() Rect } // Rect has a coordinate and a width and height. type Rect struct { X int32 Y int32 W int32 H int32 } // NewRect creates a rectangle of size `width` and `height`. The X,Y values // are initialized to zero. func NewRect(width, height int32) Rect { return Rect{ W: width, H: height, } } func (r Rect) String() string { return fmt.Sprintf("Rect<%d,%d,%d,%d>", r.X, r.Y, r.W, r.H, ) } // Point returns the rectangle's X,Y values as a Point. func (r Rect) Point() Point { return Point{ X: r.X, Y: r.Y, } } // Bigger returns if the given rect is larger than the current one. func (r Rect) Bigger(other Rect) bool { // TODO: don't know why this is ! return !(other.X < r.X || // Lefter other.Y < r.Y || // Higher other.W > r.W || // Wider other.H > r.H) // Taller } // Intersects with the other rectangle in any way. func (r Rect) Intersects(other Rect) bool { // Do a bidirectional compare. compare := func(a, b Rect) bool { var corners = []Point{ NewPoint(b.X, b.Y), NewPoint(b.X, b.Y+b.H), NewPoint(b.X+b.W, b.Y), NewPoint(b.X+b.W, b.Y+b.H), } for _, pt := range corners { if pt.Inside(a) { return true } } return false } return compare(r, other) || compare(other, r) || false } // IsZero returns if the Rect is uninitialized. func (r Rect) IsZero() bool { return r.X == 0 && r.Y == 0 && r.W == 0 && r.H == 0 } // Add another rect. func (r Rect) Add(other Rect) Rect { return Rect{ X: r.X + other.X, Y: r.Y + other.Y, W: r.W + other.W, H: r.H + other.H, } } // Add (or subtract) a point to move the rect. This is usually the method you // want to use: negative Point values will subtract the rect's position. func (r Rect) AddPoint(other Point) Rect { return Rect{ X: r.X + other.X, Y: r.Y + other.Y, W: r.W, H: r.H, } } // SubtractPoint is the inverse of AddPoint. Use this only if you need to // invert the Point being added. func (r Rect) SubtractPoint(other Point) Rect { return Rect{ X: r.X - other.X, Y: r.Y - other.Y, W: r.W, H: r.H, } } // Text holds information for drawing text. type Text struct { Text string Size int Color Color Padding int32 PadX int32 PadY int32 Stroke Color // Stroke color (if not zero) Shadow Color // Drop shadow color (if not zero) FontFilename string // Path to *.ttf file on disk } func (t Text) String() string { return fmt.Sprintf(`Text<"%s" %dpx %s>`, t.Text, t.Size, t.Color) } // IsZero returns if the Text is the zero value. func (t Text) IsZero() bool { return t.Text == "" && t.Size == 0 && t.Color == Invisible && t.Padding == 0 && t.Stroke == Invisible && t.Shadow == Invisible } // Common color names. var ( Invisible = Color{} White = RGBA(255, 255, 255, 255) Grey = RGBA(153, 153, 153, 255) Black = RGBA(0, 0, 0, 255) SkyBlue = RGBA(0, 153, 255, 255) Blue = RGBA(0, 0, 255, 255) DarkBlue = RGBA(0, 0, 153, 255) Red = RGBA(255, 0, 0, 255) DarkRed = RGBA(153, 0, 0, 255) Green = RGBA(0, 255, 0, 255) DarkGreen = RGBA(0, 153, 0, 255) Cyan = RGBA(0, 255, 255, 255) DarkCyan = RGBA(0, 153, 153, 255) Yellow = RGBA(255, 255, 0, 255) DarkYellow = RGBA(153, 153, 0, 255) Magenta = RGBA(255, 0, 255, 255) Purple = RGBA(153, 0, 153, 255) Pink = RGBA(255, 153, 255, 255) ) // IterLine is a generator that returns the X,Y coordinates to draw a line. // https://en.wikipedia.org/wiki/Digital_differential_analyzer_(graphics_algorithm) func IterLine(x1, y1, x2, y2 int32) chan Point { generator := make(chan Point) go func() { var ( dx = float64(x2 - x1) dy = float64(y2 - y1) ) var step float64 if math.Abs(dx) >= math.Abs(dy) { step = math.Abs(dx) } else { step = math.Abs(dy) } dx = dx / step dy = dy / step x := float64(x1) y := float64(y1) for i := 0; i <= int(step); i++ { generator <- Point{ X: int32(x), Y: int32(y), } x += dx y += dy } close(generator) }() return generator } // IterLine2 works with two Points rather than four coordinates. func IterLine2(p1 Point, p2 Point) chan Point { return IterLine(p1.X, p1.Y, p2.X, p2.Y) }